In 2012, the AABB’s Clinical Transfusion Medicine Committee issued 3 clinical practice guidelines regarding RBC transfusion. That are they?
- Adhere to a restrictive transfusion strategy (7 to 8 g/dL as a transfusion trigger) for hospitalized, stable patients. 2. Adhere to a restrictive transfusion strategy in hospitalized patients with preexisting cardiovascular disease and consider transfusion for patients with symptoms or with a hemoglobin level of 8 g/dL or less. 3. Transfusion decisions should be influenced by symptoms as well as hemoglobin concentration. There was high-quality evidence for recommendation #1 and moderate-quality evidence for recommendation #2.
What is contained in prothrombin complex concentrate and in activated prothrombin complex concentrate?
PCC contains vitamin K-dependent clotting factors (factors II, VII, IX, and X) (mostly unactivated forms) and proteins C and S. aPCC has higher amounts of the activated forms (factors VIIa and Xa). To prevent activation, most PCC contain heparin.
Are prothrombin complex concentrates approved for hemophilia B?
Neither PCC nor aPCC are approved for hemophilia B (factor IX deficiency) because recombinant or purified factor IX products are available. PCC is approved for congenital prothrombin or factor X deficiencies, and is used off-label for urgent reversal of warfarin over-anticoagulation. aPCC is approved for acute bleeds in hemophilia A or B and in patients with clotting factor inhibitors.
Prothrombin complex concentrates are produced by…
PCC are produced by ion-exchange chromatography from the cryoprecipitate supernatant of large plasma pools after removal of antithrombin and factor XI. Different processing techniques involving ion exchangers enable the production of either three-factor (i.e., factors II, IX and X) or four-factor (i.e., factors II, VII, IX and X) concentrates with a final overall clotting factor concentration approximately 25 times higher than in normal plasma. To prevent activation of these factors, most PCC contain heparin. PCC may also contain the natural coagulation inhibitors protein C and protein S. The PCC are standardised according to their factor IX content. All PCC undergo at least one step of viral reduction or elimination (solvent detergent treatment, nanofiltration, etc.).
Dabigatran (Pradaxa) is an alternative to warfarin FDA approved 10/2010 for patients with atrial fibrillation. Currently there is no reversal medication available. If there is bleeding, the recommendation is ___. If there is severe bleeding or CNS bleeding, the recommendation is ___.
If there is bleeding, the recommendation is to give plasma. If there is severe bleeding or CNS bleeding, the recommendation is to give plasma and Novo-7.
At UTMCK, all factor concentrates are stored in and dispensed from the pharmacy. The only non-blood product in our blood bank is ___.
At UTMCK, all factor concentrates are stored in and dispensed from the pharmacy. The only non-blood product in our blood bank is Rh IG.
3-factor PCCs and 4-factor PCCs.
All prothrombin complex concentrates contain factors II, VII, IX, but some products contain no or very little FVII. PCCs with normal amounts of VII are known as 4-factor PCCs while the products without VII are 3-factor PCCs. In the United States, two 3-factor PCCs are available (Bebulin VH, Profilnine, Profilnine SD), and one 4-factor PCC is available (Proplex T).
FFP vs. PCC for emergency anticoagulation reversal for warfarin.
FFP contains normal levels of all the coagulation factors while PCCs contain factors II, IX and X with variable amounts of factor VII in a concentrated form. PCCs are virally inactivated and can be given in a small volume without the need to thaw the product first. FFP however, has to be thawed before use, must be blood group specific and because it needs to be given at a dose of at least 10–15 mL/kg, it risks precipitating volume overload in the recipients who are often frail and elderly. Some guidelines recommend PCCs over FFP because of their more rapid administration and complete INR correction.
In UTMCK massive transfusion protocol, how many units of RBCs are in each cooler?
4 units RBCs per cooler. After 3 coolers, there is no need to crossmatch additional units, since 8-10 units RBCs is considered complete blood volume replacement.
All platelet units at UTMCK are (whole blood derived/apheresis derived).
All platelet units at UTMCK are apheresis derived.
For platelet apheresis donation, single dose aspirin or piroxicam use is a __ day deferral, daily aspirin or piroxicam use is a __ day deferral, and clopidogrel and ticlopidine use is a __ day deferral.
For platelet apheresis donation, single dose aspirin or piroxicam use is a 2 day deferral, daily aspirin or piroxicam use is a 14 day deferral, and clopidogrel and ticlopidine use is a 14 day deferral.
Patients undergoing cardiopulmonary bypass may have platelet dysfunction due to ___.
Patients undergoing cardiopulmonary bypass may have platelet dysfunction due to activation of platelets during the procedure. Because of this pump effect, post-bypass platelet transfusion is based upon clinical findings rather than platelet counts.
What two conditions are absolute contraindications for platelet transfusion, and what condition is a strong relative contraindication?
Absolute contraindications: TTP and HIT. Immune thrombocytopenia (idiopathic thrombocytopenic purpura and post-transfusion purpura) are strong relative contraindications; Do not transfuse unless severe thrombocytopenia with life-threatening bleeding; Large numbers of units may be needed due to rapid immune destruction.
Can platelets be transfused with an IV pump?
The use of an IV pump is contraindicated for transfusion in most circumstances because the platelets could become activated, depending upon the pump type and FDA clearances. At UTMCK, since only some of our pumps are FDA approved for platelet transfusion and it could cause confusion, nursing policy is that IV pumps are not to be used for platelet transfusion.
What is the #1 cause of transfusion-related deaths?
Are FFP, FP24, and 5-day cold plasma considered equivalent blood products?
Generally yes, except that FP24 and 5-day cold plasma should not be used for replacement of Factor V or Factor VIII. However, selective Factor V deficiency is rare, occuring in ~1/million and the general population and is not associated with a bleeding tendency; also, Factor VIII concentrate is an available product, and cryoprecipitate can be used if factor concentrate is unavailable. So FFP, FP24, and 5-day cold plasma are basically equivalent blood products.
At UTMCK, we use FP24 or 5-day cold plasma instead of FFP for all uses except for ___.
At UTMCK, we use FP24 or 5-day cold plasma instead of FFP for all uses except for the NICU, for preparation of red cells for exchange transfusion, and for therapeutic apheresis.
Place the following blood types in decreasing order of amount of H antigen: A1, A2, A1B, A2B, B, O.
What lectin is used to distinguish A1 from A2 RBCs?
Dolichos biflorus lectin is used to distinguish A1 from A2, as it will agglutinate A1 but not A2 RBCs.
In ABO blood types, there are at least __ different A subgroup alleles and ___ B subgroup alleles, as well as __ different O alleles.
In ABO blood types, there are at least 41 different A subgroup alleles and 18 B subgroup alleles, as well as 61 different O alleles. This heterogeneity makes ABO typing with DNA technologies complicated. In addition, the same genotype gives rise to different phenotypes even within families, which further adds to the complexity.
The Rh system has at least (#) antigens, most notably (5).
The Rh system has at least 45 antigens, most notably C, c, E, and e antigens, which are carried on the RhCE protein encoded by the RHCE gene, and the D antigen on the RhD protein encoded by the RHD gene. The RHCE and RHD genes are 96% homologous and are adjacent to one another on chromosome 1.
What are the Rh null and Rh mod phenotypes?
The Rh antigens are carried on hydrophobic 12-pass transmembrane proteins. The RhAG protein does not carry Rh antigens, but is important for bringing the RhD and RhCE proteins to the membrane. Lack of RhAG results in the absence of Rh antigen expression (Rh null phenotype) or marked reduction of Rh antigen expression (Rh mod phenotype).
What are the regular and amorph types of Rh-null?
Rh-null RBCs lack expression of Rh antigens, are stomatocytic and spherocytic, and affected individuals have variable degrees of anemia. The regulator type is caused by mutations in the RHAG gene so they have no Rh or RhAG proteins, and the amorph type is caused by mutations in the RHCE gene on a deleted RHD background so they have no Rh proteins and reduced RhAG proteins.
Anti-D, anti-c, anti-C, anti-e, and anti-E Rh antibodies. Which cause severe HDFN and which cause no or mild HDFN?
Anti-D and anti-c can cause severe HDFN, while anti-C, anti-e, and anti-E usually cause no or mild HDFN.
In blood donor deferral durations for history of recent vaccination, some live attenuated viral and bacterial vaccines are a 2 week deferral, while others are a 4 week deferral. What vaccines fall into these 2 categories?
2 week deferral: Measles (rubeola), mumps, polio (Sabin/oral), typhoid (oral), yellow fever. 4 week deferral: German measles (rubella), chickenpox (Varicella zoster).
What are donation intervals for whole blood, 2-unit RBC, infrequent plasmapheresis, and plasma-, platelet-, or leukapheresis?
> or =56 days after whole blood donation. > or=112 days after 2-unit RBC donation. > or=28 days after infrequent plasmapheresis. > or =2 days after plasma-, platelet-, or leukapheresis.
Blood donation is deferred if a patient is currently pregnant or has been pregnant within the last __ weeks.
Blood donation is deferred if a patient is currently pregnant or has been pregnant within the last 6 weeks.
For testing blood donors, list the infectious diseases that fall into each of the following 3 categories: Tests are available but may not detect early-stage or window-period infections. Tests are available but not used in all donor centers. No licensed laboratory tests are available for blood donor screening.
Tests are available but may not detect early-stage or window-period infections: Chagas disease. Hepatitis (HBV, HCV). HIV-1,-2. HTLV, types I and II. West Nile Virus. Tests are available but not used in all donor centers: HIV group O. No licensed laboratory tests are available for blood donor screening: Babesiosis. CJD. Variant CJD. Malaria.
What is Evans syndrome?
Evans syndrome is an autoimmune disease in which an individual’s antibodies attack their own RBCs and platelets. Both of these events may occur simultaneously or one may follow on from the other. Its overall pathology resembles a combination of autoimmune hemolytic anemia and ITP. The diagnosis is made upon blood tests to confirm not only hemolytic anemia and idiopathic thrombocytopenic purpura, but also a positive DAT and an absence of any known underlying etiology. Other antibodies may occur directed against neutrophils and lymphocytes, and “immunopancytopenia” has been suggested as a better term for this syndrome. Initial treatment is with glucocorticoid corticosteroids or IVIg, a procedure that is also used in ITP cases. Although the majority of cases initially respond well to treatment, relapses are not uncommon and immunosuppressive drugs are subsequently used. Splenectomy is effective in some cases, but relapses are not uncommon. The only prospect for a permanent cure is allogeneic HSCT.
What are the compositions of the RBC additive solutions CPD, CPDA-1, and AS-1, and the outdates for products with these additive solutions?
CPD: citrate, sodium phosphate, dextrose; 21 days. CPDA-1: citrate, sodium phosphate, dextrose, adenine; 35 days. AS-1: dextrose, sodium phosphate, adenine, mannitol, sodium chloride; 42 days.
Random donor platelets must contain as least ___ of platelets, while pheresis platelets must contain at least ___ platelets.
Random donor platelets must contain as least 5x10^10 of platelets, while pheresis platelets must contain at least 3x10^11 platelets.
Irradiated RBCs, for the prevention of GVHD, are good for __ days post-irradiation, or the original outdate, whichever comes first.
Irradiated RBCs, for the prevention of GVHD, are good for 28 days post-irradiation, or the original outdate, whichever comes first.
When plasma is separated from platelet concentrate, it must be placed into an __ C or colder freezer within __ hours of blood collection to make FFP. It expires in __ years. After thawing it expires in __ hours.
When plasma is separated from platelet concentrate, it must be placed into an -18 C or colder freezer within 8 hours of blood collection to make FFP. It expires in 1 year. After thawing it expires in 24 hours.
The degree of leukoreduction depends on the goal. If meant to prevent febrile reactions, the unit must contain <__ WBCs.
The degree of leukoreduction depends on the goal. If meant to prevent febrile reactions, the unit must contain <5x10^6 WBCs.
What are 4 definitions of “massive transfusion?”
Transfusion of an amount of blood equal to the patient’s blood volume in 24 hours. Transfusion of 10+ units of blood in 24 hours. Transfusion of 50% of blood volume in 3 hours. Transfusion to replace blood loss of over 150 mL/min.
What RBCs can you give if… 1. Blood is needed now (30 min.
- Uncrossmatched group O neg. May start out with O pos if male or older female during emergencies. 2. Uncrossmatched ABO group and Rh type specific. 3. Crossmatched ABO group and Rh type specific. *Use all possible means to give D-negative blood to childbearing age and younger females. *When D-negative blood is used, be prepared to switch to D-positive blood if massive use depletes inventory.
The half-life of RhIG is ___.
The half-life of RhIG is ~25 days. However, it can be detected for as long as 6 months.
Platelet refractoriness is the inability to respond to platelet transfusion with a significant qualitative increase in platelet count. Are immune or nonimmune causes more frequent?
Nonimmune causes outweigh immune causes. Nonimmune causes include: fever, splenomegaly, DIC, bleeding (?), drugs (such as amphotericin). Immune causes include anti-HLA and/or anti-platelet antibodies.
Pink-top blood collection tubes are used in immunohematology for ABO grouping, Rh typing, and antibody screening. These tubes have a special cross-match label for information required by ___.
Pink tubes are used in immunohematology for ABO grouping, Rh typing, and antibody screening. These tubes have a special cross-match label for information required by the American Association of Blood Banks (AABB) and approved by the U.S. Food and Drug Administration (FDA) for blood bank collections.
Leukocyte reduction of blood components reduces the risk of what 3 things?
Leukocyte reduction of blood components reduces alloimmunization to human leukocyte antigens, cytomegalovirus transmission, and febrile reactions.
Failure to respond to platelet transfusion may be due to what 3 general categories of causes? Give examples within each category as well.
Failure to respond to platelet transfusion may be due to immune causes (human leukocyte antigens or platelet-specific antibodies), nonimmune clinical causes (bleeding, splenomegaly, disseminated intravascular coagulation, medications), or product-specific causes (ABO incompatibility, age of component).
Plasma transfusion is generally indicated for what conditions/situations?
Plasma transfusion is generally indicated for coagulation factor deficiency, disseminated intravascular coagulation, dilutional coagulopathy, urgent warfarin reversal, and thrombotic thrombocytopenic purpura.
Blood centers and transfusion services (collectively known as ___) are regulated by ___.
Blood centers and transfusion services (collectively known as blood establishments) are regulated by the FDA. All blood establishments must be registered with the FDA, and blood centers that manufacture blood components must be licensed. Criteria for the acceptability of blood donors, performance of pretransfusion testing, manufacture of blood components, donor infectious disease testing, and evaluation and reporting of adverse events associated with transfusion are all defined by the FDA. Blood establishments are subject to periodic unannounced inspections by the FDA.
There are rare circumstances under which directed donation may be desirable. What circumstances?
These include rare blood group compatibility requirements and limitations of donor exposure for patients with long-term expected transfusion requirements such as aplastic anemia. In cases of neonatal alloimmune thrombocytopenia, collection of maternal platelets may be the best way of providing compatible antigen-negative platelets. In the past, donor-specific transfusion was utilized in kidney transplantation. However, with current immunosuppressive regimens, the value of donor-specific transfusion in prolonging renal graft survival is questionable.
What are vital signs requirements for allogeneic blood donation?
BP less than or equal to 180/100. Pulse 50-100 bpm without pathologic irregularities; <50 acceptable is an otherwise healthy athlete. Temp less than or equal to 37.5 C.
What infectious disease risks are an indefinite deferral from allogeneic blood donation?
Viral hepatitis after 11th birthday. Positive test for hepatitis B surface antigen. Repeat reactive test for anti-HBc on more than one occasion. Clinical or laboratory evidence of HCV, HTLV, or HIV infection by current FDA regulations. Previous donation associated with hepatitis, HIV, or HTLV transmission. Behavioral risk factors for HIV infection according to current FDA guidance. History of babesiosis or Chagas’ disease. Stigma of parenteral drug use. Injection of nonprescription drugs. Risk of vCJD according to current FDA guidelines.
What infectious disease risks are a 12-month deferral from allogeneic blood donation?
Mucous membrane exposure to blood. Nonsterile skin or needle penetration. Sexual contact with an individual with a confirmed positive test for hepatitis B surface antigen. Sexual contact with an individual with viral hepatitis. Sexual contact with an individual with HIV infection or at higher risk for HIV infection. Incarceration in a correctional institution for longer than 72 consecutive hours. History of syphilis or gonorrhea.
The maximum allowable storage time for RBCs is defined by ___.
The maximum allowable storage time for RBCs is defined by the requirement for recovery of 70% of transfused cells 24 hours after transfusion.
Plasma may be stored in the liquid state at __–__° C, or it may be frozen for extended preservation. In the liquid state at refrigerator temperatures, there is loss of labile clotting factors, particularly factor __ and factor __. Fresh frozen plasma (FFP) is separated from the RBCs and is placed at __ C within __ hours of collection. Plasma frozen within 24 hours after phlebotomy (FP24) is manufactured similarly to FFP but may not be frozen for up to 24 hours after collection. Frozen plasma may be stored for up to 1 year at __ C or lower. Before transfusion, both FFP and FP24 are thawed at __ C and must be transfused within __ hours. Thawed plasma not used within 24 hours may be relabeled as “Thawed Plasma.” Thawed plasma can be kept at refrigerator temperatures for up to __ days, while adequate levels of factors __ and __ are maintained.
Plasma may be stored in the liquid state at 1°–6° C, or it may be frozen for extended preservation. In the liquid state at refrigerator temperatures, there is loss of labile clotting factors, particularly factor VIII and factor V. Fresh frozen plasma (FFP) is separated from the RBCs and is placed at −18° C within 8 hours of collection. Plasma frozen within 24 hours after phlebotomy (FP24) is manufactured similarly to FFP but may not be frozen for up to 24 hours after collection. Frozen plasma may be stored for up to 1 year at −18° C or lower. Before transfusion, both FFP and FP24 are thawed at 37° C and must be transfused within 24 hours. Thawed plasma not used within 24 hours may be relabeled as “Thawed Plasma.” Thawed plasma can be kept at refrigerator temperatures for up to 5 days, while adequate levels of factors V and VIII are maintained.
Do granulocyte units for transfusion need to be ABO compatible with the recipient?
Yes. Granulocyte units contain a substantial number of RBCs and must be ABO compatible with the recipient.
Why is prestorage leukocyte reduction favored over poststorage leukocyte reduction?
Both methods are effective for removing leukocytes. However, prestorage leukocyte reduction has the advantage of preventing accumulation of leukocyte-derived biological response modifiers, particularly cytokines, which may cause adverse reactions. In addition, filtration at the time of manufacture allows for better process control.
To be considered leukocyte reduced, blood components must be prepared by a method known to reduce the total number of residual leukocytes to fewer than ___ per unit for RBC and fewer than ___ for whole blood–derived PC.
To be considered leukocyte reduced, blood components must be prepared by a method known to reduce the total number of residual leukocytes to fewer than 5 × 106 per unit for RBC and fewer than 8.3 × 105 for whole blood–derived PC.
Why is irradiation not equivalent to leukocyte reduction?
Irradiation causes chromosomal damage, which prevents replication of transfused lymphocytes in the recipient. However, irradiated cells are immunogenic. Thus, irradiation is not equivalent to leukocyte reduction.
What is the minimum radiation dose for preparation of irradiated blood components?
The minimum dose is 25 Gy delivered to the center of the blood container and no less than 15 Gy to the periphery.
Red blood cells can be stored in the frozen state after addition of a cryoprotective agent, such as glycerol. Frozen RBCs can be stored in mechanical freezers or liquid nitrogen for up to ___. Frozen units are thawed rapidly at __ C, then the cryoprotective agent must be removed by progressive addition of washing solutions with decreasing osmolality. After deglycerolization, red cells can be stored for up to ___ at __–__ C if processed by an open method, or up to ___ if processed by a closed method. The main use of frozen RBCs is to ___.
Red blood cells can be stored in the frozen state after addition of a cryoprotective agent, such as glycerol. Frozen RBCs can be stored in mechanical freezers or liquid nitrogen for up to 10 years. Frozen units are thawed rapidly at 37 C, then the cryoprotective agent must be removed by progressive addition of washing solutions with decreasing osmolality. After deglycerolization, red cells can be stored for up to 1 day at 1–6 C if processed by an open method, or up to 14 days if processed by a closed method. The main use of frozen RBCs is to maintain an inventory of rare antigen-negative units.
2010 blood donor infectious disease testing required entities.
Hep B surface antigen (EIA). Hep B core antibody (EIA). Hep C virus antibody (EIA). HIV-1 and HIV-2 antibodies (EIA) (combined HIV p24 antigen, HIV-1 antibodies, and HIV-2 antibodies acceptable). HTLV-I and HTLV-II antibodies (EIA). Trypanosoma cruzi antibodies (EIA). Serologic test for syphilis. Hep C RNA (NAT). HIV RNA (NAT). West Nile virus DNA (NAT).
What are medications that are cause for deferral of allogeneic blood donation, and what are the deferral periods?
Finasteride, isotretinoin—defer 1 month after last dose. Dutasteride—defer 6 months after last dose. Acitretin—defer 3 years after last dose. Etretinate—defer indefinitely. Bovine insulin manufactured in the United Kingdom—defer indefinitely. Ingestion of medications that irreversibly inhibit platelet function (aspirin) within 36 hours of donation precludes use of donor as sole source of platelets.
In what situations is directed donation contraindicated?
Donation of any plasma-containing blood component from a mother to her child is particularly problematic because the formation of human leukocyte antigens (HLA) antibodies to fetal antigens is common in pregnancy, and transfusion of such antibodies can precipitate transfusion-related acute lung injury (see later). Transfusions from close relatives should be avoided in recipients of hematopoietic progenitor cell transplants because of the risk of immunization to HLA and other histocompatibility antigens, which may endanger graft survival.
What is a computer cross-match?
An alternative to a major cross-match performed between recipient serum or plasma and donor RBCs for ensurance of ABO compatibility is the so-called computer cross-match. This is applicable when at least two determinations of the recipient’s ABO group have been made, at least one on a current sample, and there are no unexpected antibodies. A validated computer system can then ensure that issued blood complements are ABO compatible.
What are desirable rates of infusion for blood products?
The desirable rate of administration depends on the patient’s blood volume, cardiac status, and hemodynamic state. Except for urgent resuscitation, the transfusion should be started slowly (approximately 2 mL/minute for the first 15 minutes). The patient should be carefully observed for the first 15 minutes of infusion because severe reactions such as hemolysis, anaphylaxis, or sepsis may manifest after a small volume has entered the circulation. Subsequently, the administration rate may be increased. In general, it is desirable to complete a red cell transfusion within 2 hours and a platelet or plasma transfusion within 30–60 minutes. Any transfusion should be completed within 4 hours of initiation. Patients at risk of volume overload may require slower administration. If the total administration time exceeds 4 hours, smaller-volume blood components should be provided. When high flow rates are required, such as in some resuscitation or surgical situations, a pressure infusion device may be used. When such devices are used, care must be taken to avoid mechanical hemolysis or air embolism.
In general, it is desirable to complete a red cell transfusion within __ hours and a platelet or plasma transfusion within __ -__ minutes. Any transfusion should be completed within __ hours of initiation.
In general, it is desirable to complete a red cell transfusion within 2 hours and a platelet or plasma transfusion within 30–60 minutes. Any transfusion should be completed within 4 hours of initiation.
List general guidelines for red cell transfusion.
Symptomatic anemia in a euvolemic patient. Acute blood loss of >15% of estimated blood volume. Preoperative Hb 500 mL. Hb <60%.
List general guidelines for platelet transfusion.
In bleeding associated with platelet dysfunction, or thrombocytopenic bleeding associated with coagulopathy, there is no single transfusion threshold, and therapy must be guided by the patient’s clinical condition. Otherwise, transfusion thresholds in the case of thrombocytopenia due to decreased production are as follows: Stable patient - platelet count <100,000/µL.
Platelet transfusion in ITP is (not/relatively/absolutely) contraindicated.
The platelet transfusion is relatively contraindicated in immune thrombocytopenic purpura. In this setting, posttransfusion platelet survival is extremely brief, and platelet transfusion is indicated only if there is severe hemorrhage.
Transfusion of one apheresis platelet unit, or an equivalent pool of whole blood–derived platelet concentrates, can typically be expected to raise the platelet count of an adult by ___–___/µL.
Transfusion of one apheresis platelet unit, or an equivalent pool of whole blood–derived platelet concentrates, can typically be expected to raise the platelet count of an adult by 20,000–40,000/µL.
A platelet corrected count increment of >___ at 1 hour or >___ at 24 hours generally indicates a successful transfusion.
A CCI >7500 at 1 hour or a CCI >4500 at 24 hours generally indicates a successful transfusion.
What is the formula for the platelet corrected count increment?
In assessing platelet transfusion effectiveness, it is useful to take into account dose and body size by calculating the CCI. CCI = (Platelet count increment x Body surface area in m^2) / Number of platelets transfused (x10^11).
How can obtaining a platelet count within 1 hour of completing a platelet transfusion be helpful in distinguishing immune from nonimmune causes of platelet refractoriness?
Typically, immune refractoriness will result in an inadequate platelet increment when measured at 1 hour. Typically, nonimmune refractoriness will manifest as an adequate CCI at 1 hour but shortened survival time, so that the platelet count by 24 hours may be back to baseline.
List the guidelines for plasma transfusion.
Coagulation factor deficiency, factor concentrate unavailable. Dilutional coagulopathy. Hemorrhage in liver disease. DIC. Coumadin reversal. TTP. Acute trauma resuscitation.
Standard coagulation tests such as PT and APTT are commonly used to assess the need for plasma transfusion; however, these tests are poorly predictive of bleeding risk. In general, if the PT and APTT are less than ___ times the midpoint of the reference range, no benefit will be obtained from plasma transfusion. If the INR is used, in general, no benefit will be derived from plasma transfusion if it is less than ___, although for nervous system and retinal hemorrhage, plasma may be reasonably used unless the INR is less than ___.
Standard coagulation tests such as PT and APTT are commonly used to assess the need for plasma transfusion; however, these tests are poorly predictive of bleeding risk. In general, if the PT and APTT are less than 1.5 times the midpoint of the reference range, no benefit will be obtained from plasma transfusion. If the INR is used, in general, no benefit will be derived from plasma transfusion if it is less than 1.5, although for nervous system and retinal hemorrhage, plasma may be reasonably used unless the INR is less than 1.3.
For maximal hemostatic effect, when should plasma be transfused in relation to the time of the invasive procedure? For a bleeding patient, how often may plasma transfusion have to be repeated to maintain adequate coagulation factor levels? In general, what dose of plasma per kilogram is needed to achieve hemostasis?
For maximal hemostatic effect, plasma should be transfused immediately before an invasive procedure is performed. For the bleeding patient, plasma transfusion may have to be repeated every 3–4 hours to maintain adequate coagulation factor levels. In general, a dose of 10–20 mL per kilogram is necessary to achieve a hemostatic effect.
List the guidelines for cryoprecipitate transfusion.
Factor VIII deficiency, factor concentrate unavailable. von Willebrand disease, factor concentrate unavailable. Hypofibrinogenemia. Factor XIII deficiency. Uremic bleeding (DDAVP preferred). Topical fibrin sealant (commercial product preferred).
Exchange transfusion of the neonate for hyperbilirubinemia is usually indicated if the total bilirubin is greater than ___ mg/dL.
Exchange transfusion of the neonate for hyperbilirubinemia is usually indicated if the total bilirubin is greater than 25 mg/dL. A two-blood volume exchange is typically used, which can be expected to reduce the total bilirubin by 25% and the fetal red cell mass by about 70%.
List the guidelines for neonatal transfusion of RBCs, plasma, and platelets.
For RBC transfusion: Hct 35% or mechanical ventilation with MAP >6 cm H2O. Hct <100,000/µL in unstable premature infant.
Patients with deficiency of ___ or ___ can develop antibodies against them and have anaphylactic transfusion reactions.
Patients with deficiency of IgA or haptoglobin can develop antibodies against them and have anaphylactic transfusion reactions.
Acute hemolytic transfusion reactions, by definition, present within ___ of transfusion.
Acute hemolytic transfusion reactions, by definition, present within 24 hours of transfusion, while delayed hemolytic transfusion reactions occur at least 24 hours after transfusion of the offending unit. The time from transfusion to diagnosis of a DHTR is variable. Most patients present within the first 2 weeks after receiving the transfusion. However, clinical DHTR may be recognized more than 6 weeks later.
How long after transfusion do delayed hemolytic transfusion reactions occur?
Delayed hemolytic transfusion reactions occur at least 24 hours after transfusion of the offending unit. The time from transfusion to diagnosis of a DHTR is variable. Most patients present within the first 2 weeks after receiving the transfusion. However, clinical DHTR may be recognized more than 6 weeks later.
What is the most common general cause of delayed hemolytic transfusion reactions?
Almost all DHTRs are due to an anamnestic response to a red cell antigen to which the patient has previously made an antibody, the concentration of which was too low to detect in pretransfusion testing. Rarely, a DHTR may be due to primary alloimmunization to a red cell antigen.
Intravascular hemolysis is more common in (acute/delayed) hemolytic transfusion reactions.
Intravascular hemolysis is much more common in acute hemolytic reactions than is extravascular hemolysis. In delayed hemolytic reactions, hemolysis is typically extravascular, but intravascular hemolysis may occur also.
What are FDA approved methods for detection of bacterial contamination of platelets?
AABB standards require that blood banks and transfusion services have methods to detect and limit bacterial contamination of platelets. FDA approved methods include culture, measurement of oxygen consumption, and rapid qualitative immunoassay. Measurements of pH or glucose and inspection for “swirling” have been used as indicators of contamination but are not sufficiently sensitive to meet current AABB standards.
List the absolute indications and probable indications for irradiation of blood components for prevention of TA-GVHD.
Absolute indications: Congenital cellular immunodeficiency. Hematopoietic progenitor cell transplantation. Hodgkin lymphoma. Granulocyte transfusions. Intrauterine transfusions (IUTs). Transfusion to neonates who have received IUT. Transfusions from biological relatives. Chemotherapy with purine analogs (fludarabine). Probable indications: Low-birthweight infants (<1200 g). Hematologic malignancies other than Hodgkin lymphoma. HLA-matched platelet concentrates. High-dose chemotherapy, radiation therapy, and/or aggressive immunotherapy.
List the controversial indications and situations where irradiation is not indicated.
Controversial indications: Solid organ transplantation. Large-volume or exchange transfusion of infants who did not receive IUT. Aplastic anemia. Absolute lymphopenia (Absolute lymphocyte count <500/mL). Situations where irradiation is not indicated: HIV infection. Hemophilia. Small-volume transfusion of term infants who did not receive IUT. Elderly patients. Typical dose immunosuppressive therapy (other than purine analogs). Immunocompetent surgical patients. Pregnancy. Red cell membrane, metabolic, or hemoglobin disorders (e.g., thalassemia, SCD).
True or false. Humoral immunodeficiencies are a risk factor for TA-GVHD.
False. Patients with with marked cellular immunodeficiencies are at risk of TA-GVHD. These include congenital cellular immunodeficiencies (DiGeorge syndrome, severe combined immunodeficiency syndrome), immaturity of the immune system (intrauterine transfusions, very-low-birthweight infants), disease-associated immunodeficiencies (Hodgkin lymphoma), and therapy-associated cellular immunodeficiencies (hematopoietic progenitor cell transplantation, fludarabine treatment). Humoral immunodeficiencies, such as common variable immunodeficiency (CVID), are not a risk factor for GVHD.
True or false. HIV infection is a risk factor for TA-GVHD.
False. HIV infection, although it may cause marked T cell dysfunction, does not increase the risk of TA-GVHD.
In what situation may a patient with normal immunity be at risk for TA-GVHD?
Patients with normal immunity may be at risk of TA-GVHD if the recipient is homozygous for an HLA haplotype and the donor is heterozygous but shares one haplotype. In this case, recipient lymphocytes are unable to recognize transfused lymphocytes as foreign, but transfused cells see recipient cells as foreign. This is most likely to occur with donations from close (first- or second-degree) relatives but may also occur owing to chance, particularly in populations that are relatively homogeneous.
How long after transfusion does TA-GVHD usually manifest? What are characteristic physical findings? Mortality?
TA-GVHD typically manifests 2–50 days after transfusion. Characteristic findings include rash, diarrhea, fever, liver dysfunction, and pancytopenia. Mortality is greater than 90%, with most patients dying of infection.
What is thought to be the cause of transfusion-associated hypotension?
The cause of transfusion-associated hypotension has not been established definitively. However, the condition is most likely due to the release of bradykinin through activation of the contact pathway of coagulation. Some reactions have been associated with angiotensin-converting enzyme (ACE) inhibitor drugs in the recipient and/or the use of leukocyte reduction filters. ACE is the major enzyme that breaks down bradykinin in the circulation. Some filters, particularly those with a net-negative surface charge, appear to cause activation of kallikrein and cleavage of high molecular weight kininogen, which results in the release of bradykinin. However, there is variability because not all such filtered units show activation.
What measures can be taken to prevent transfusion-associated circulatory overload in at-risk pateints?
Blood should be transfused slowly. Although a transfusion usually should be completed within 4 hours, the duration may be extended if medically indicated. If longer than 6 hours is required, however, alternative strategies should be considered. Small volumes can be transfused with adequate time between transfusions to allow for diuresis. To avoid additional donor exposures, a unit can be split using sterile technique and a portion retained in the blood bank for later transfusion. Units can also be concentrated by plasma removal. A diuretic can be administered before or during the transfusion.
What are the 2010 risk estimates for per-unit risk of transfusion-associated infectious disease transmission for: HIV, HBV, HCV, HTLV-I/II, and West Nile virus?
HIV - 1:1,467,000. HBV - 1:280,000-1:357,000. HCV - 1:1,149,000. HTLV-I/II - 1:641,000-1:1,900,000. West Nile virus - ~1:7,000,000.
Approximately __% of blood donors are CMV seropositive, although the estimated risk of transmission by a seropositive transfusion is about __%.
Approximately 50% of blood donors are CMV seropositive, although the estimated risk of transmission by a seropositive transfusion is about 1%.
List the top 12 most immunogenic clinically important blood group antigens and their relative potencies (approximate percentage of persons negative for a specific antigen who, if transfused with one unit of corresponding antigen-positive blood, would develop antibodies to that specific antigen).
D - 0.70. K - 0.10. C - 0.041. E - 0.0338. k - 0.030. e - 0.0112. Fya - 0.0046. C - 0.0022. Jka - 0.0014. S - 0.0008. Jkb - 0.0006. s - 0.0006.
What are the top 3 most immunogenic clinically important blood group antigens and their relative potencies (approximate percentage of persons negative for a specific antigen who, if transfused with one unit of corresponding antigen-positive blood, would develop antibodies to that specific antigen).
D - 0.70. K - 0.10. C - 0.041.
True or false. All Ig classes (M, G, A, D, and E) can have kappa or lambda light chains.
What are the valencies (Ag binding) for the 5 Ig classes?
IgG: 2. IgM: 5 (valency of 10 can be seen with very small haptens). IgA: 2-4. IgD: 1. IgE: 1.
True or false. Babesia species are capable of surviving in refrigerated red blood cells.
Intravascular RBC hemolysis is usually caused by antibodies directed against the ABO antigens. In what other rare situations can there be intravascular hemolysis?
Rarely, other IgM blood group antibodies, as well as some complement-fixing IgG antibodies (e.g., anti-Kidd antibodies), can induce intravascular hemolysis.
Which Ig class causes the majority of extravascular hemolysis?
IgG antibodies cause the majority of extravascular hemolysis via the RE system, which removes complement-coated RBCs.
What are the steps in the complement pathway that occur in extravascular hemolysis?
IgG antibodies cause the majority of extravascular hemolysis via the RE system. When IgG antibodies bind RBCs and activate complement, complement regulatory proteins generally stop the activation process at the C3/C4 level. RBC-bound C3b is degraded to iC3b, which is enzymatically inactive, by factor I and factor H. iC3b is further degraded to C3c and C3dg by factor I and CR1, a cofactor and C3b/C4b receptor. Initially, C3b/iC3b-coated RBCs are rapidly sequestered in the liver by monocytes and macrophages, which have receptors for C3b. A portion of the RBCs sequestered in the liver are immobilized and destroyed by phagocytosis with a half-life of about 2 minutes. Within 15–20 minutes, however, destruction slows, and many of the cells escape extravascular destruction through the action of the complement regulatory protein, factor I, as previously described. C3dg, the iC3b fragment produced by factor I cleavage, remains attached to RBCs but has no enzymatic or opsonic properties. As a result, sequestered C3dg-coated RBCs are released back into the circulation and survive normally. In the circulation, C3dg is cleaved, leaving C3d attached to the RBC membrane.
Clinically significant blood group antibodies are typically of what Ig type?
The majority of clinically significant blood group antibodies are IgG or IgM, although occasionally an IgA antibody is encountered.
More than __ erythrocyte antigens have been reported in the literature and have been organized into __ blood group systems by the International Society of Blood Transfusion (ISBT).
More than 700 erythrocyte antigens have been reported in the literature and have been organized into 30 blood group systems by the International Society of Blood Transfusion (ISBT).
What are the frequencies in the US population of blood groups O, A, B, and AB among Caucasians, Blacks, Native Americans, and Asians?
Group O: 45%, 49%, 79%, 40%. Group A: 40%, 27%, 16%, 28%. Group B: 11%, 20%, 4%, 27%. Group AB: 4%, 4%, <1%, 5%.
Compare the two blood group A subtypes, A1 and A2, for the following: reaction with diluted anti-A, reaction with Dolichos biflorus lectin, presence of anti-A1 in serum, N-acetyl-galactosaminyltransferase activity, and number of antigen sites.
Reaction with diluted anti-A: ++++; ++. Reaction with Dolichos biflorus (anti-A1) lectin: ++++; 0. Presence of anti-A1 in serum: No; 1-8%. N-acetyl-galactosaminyltransferase activity: Normal activity, optimal at pH 6; Decreased activity, optimal at pH 7. Number of antigen sites: A1 adult - 1,000,000; A2 adult - 250,000; A1 newborn - 310,000; A2 newborn - 140,000.
Briefly describe cis-AB, B[A], and acquired B blood phenotypes.
Anomalous ABO expression can be inherited (cis-AB, B[A]) or acquired (acquired B). In the cis-AB phenotype, A and B antigens are synthesized by the same enzyme and are inherited as a single, autosomal dominant allele. Likewise, the B(A) phenotype, an autosomal dominant phenotype characterized by trace A antigen expression on group B RBCs, is due to synthesis of A antigen by the B-gene enzyme. The acquired B phenotype, on the other hand, is an acquired enzymatic modification of group A1 red cells in vivo. The acquired B phenotype usually occurs in the setting of bacterial infection or cancer and reflects enzymatic deacetylation of group A antigen to form a B-like antigen on RBCs. The cis-AB, B(A), and acquired B phenotypes are usually detected because of discrepancies in ABO typing.
On what chromosome is the ABO gene locus and what does it encode for?
The ABO gene locus is located on chromosome 9q34 and encodes the A and B glycosyltransferases The gene is large, spanning 18kb, and contains seven exons, although exons 6 and 7 encode the majority of the active enzyme. The product of the ABO gene is a 41-kD, 353 amino acid type II transmembrane glycoprotein.
Blood groups A and B. How similar are the A gene glycosyltransferase and the B gene glycosyltransferase, and how similar are the product antigens?
Comparison of A and B enzymes shows nearly 98% identity, differing by four key amino acids at residues 176, 235, 266, and 268. Biochemically, the A and B antigens are very similar, differing only by the presence of an N-acetyl group.
ABO antibodies are weak or absent in the sera of newborns until ___ months of age. Adult levels of ABO antibodies are reached by ___ years of age and decrease only slightly with advancing age.
ABO antibodies are weak or absent in the sera of newborns until 3–6 months of age. Adult levels of ABO antibodies are reached by 5–10 years of age and decrease only slightly with advancing age.
What are 2 non-antibody and 2 general categories of antibody causes of TRALI?
Bioactive lipids and CD40L are 2 non-antibody causes of TRALI. Bioactive lipids such as lysophosphatylcholine accumulate during the storage of cellular blood products and can prime neutrophils. CD40L levels increase in stored platelets and can prime neutrophils. HLA class I and II antibodies and HNA (Human Neutrophil Antigens) antibodies are also causes.
List the blood groups A1, A2, A1B, A2B, B, and O in decreasing order of reactivity with anti-H.
O > A2 > B > A2B > A1 > A1B.
M and N antigens are fairly evenly distributed in both blacks and Caucasians, with approximately 25% of donors homozygous for M or N antigen. In contrast, the S antigen is nearly twice as frequent in (blacks/Caucasians).
M and N antigens are fairly evenly distributed in both blacks and Caucasians, with approximately 25% of donors homozygous for M or N antigen. In contrast, the S antigen is nearly twice as frequent in Caucasians (57%) as in black people (30%). In a minority (
What are the 3 major null phenotypes present in the MNS blood group system?
Three major null phenotypes are present in the MNSs system: U−, Mk, and En (a−). The U− phenotype is the most common and is observed exclusively in blacks. In S−s−U− individuals, complete loss or a recombination of glycophorin B occurs, leading to altered expression of S/s and U antigens. The MkMk phenotype lacks all MNSs antigens, including En(a), as the result of recombination and deletion of glycophorins A and B (GYPA and GYPB). The En (a−) phenotype is the result of recombination between glycophorin A and B genes to form a Lepore-type A-B hybrid (exons A1-B2-B5) lacking most of glycophorin A (GYPA).
Biochemistry of the MNS blood group system.
The M/N antigens reside on GYPA (CD235A), a major RBC membrane glycoprotein. In the membrane, GYPA is present as a dimer, usually in association with Band 3, the erythrocyte anion exchanger. Structurally, GYPA is a 31-kD, 131 amino acid, type 1 glycoprotein composed of a large, 72 amino acid extracellular domain, a transmembrane domain, and a short cytoplasmic tail. The M and N antigens reside on the extreme amino-terminus of GYPA. The S/s and U antigens reside on GYPB, a related RBC glycoprotein. GYPB (CD235B) is a 20-kD, 72 amino acid glycoprotein composed of a large, extracellular N-terminal domain containing 11 O-linked glycans. Although GYPB shares considerable homology with GYPA at the amino-terminus, GYPB is smaller, lacking both an N-glycan and a cytoplasmic tail. The S/s epitope is located at amino acid 29.
MNS blood group system. Are antibodies against M and N naturally occuring? Ig isotype? detected at room temp/body temp? show dosage? affected by enzyme treatment? clinical significance?
Antibodies against M and N antigens are naturally occurring antibodies of IgM isotype, usually detected as room temperature saline agglutinins. Anti-M and anti-N may show dosage, reacting more weakly with heterozygous (M/N) cells than with homozygous (M/M or N/N) cells. Because the M and N antigens reside on GYPA, the reactivity of anti-M and anti-N is destroyed by pretreatment of RBCs with proteolytic enzymes or neuraminidase. Some examples of anti-M and anti-N can be enhanced by acidification of serum to pH 6.5, use of an albumin diluent, or preincubation of RBCs in a glucose-containing solution. In general, anti-M and anti-N are clinically insignificant antibodies and only rarely cause hemolytic transfusion reactions or HDFN.
MNS blood group system. Are antibodies against M, N, S, s, and U naturally occuring? Ig isotype? detected at room temp/body temp? show dosage? affected by enzyme treatment? clinical significance?
Antibodies against M and N antigens are naturally occurring antibodies of IgM isotype, usually detected as room temperature saline agglutinins. Anti-M and anti-N may show dosage, reacting more weakly with heterozygous (M/N) cells than with homozygous (M/M or N/N) cells. Because the M and N antigens reside on GYPA, the reactivity of anti-M and anti-N is destroyed by pretreatment of RBCs with proteolytic enzymes or neuraminidase. Some examples of anti-M and anti-N can be enhanced by acidification of serum to pH 6.5, use of an albumin diluent, or preincubation of RBCs in a glucose-containing solution. In general, anti-M and anti-N are clinically insignificant antibodies and only rarely cause hemolytic transfusion reactions or HDFN. Unlike anti-M and anti-N, antibodies against S, s, and U antigens are always clinically significant. All are antibodies of IgG isotype, reactive at 37° C, arising from immune stimulation. Some examples of anti-S and anti-s show dosage. Enzymatic modification of RBCs with proteases, but not neuraminidase, can decrease the reactivity of some anti-S and anti-s. The reactivity of anti-U is resistant to proteolytic digestion. Anti-S, -s, and -U are causes of hemolytic transfusion reactions and HDFN.
MNS blood group system. Are antibodies against S, s, and U naturally occuring? Ig isotype? detected at room temp/body temp? show dosage? affected by enzyme treatment? clinical significance?
Unlike anti-M and anti-N, antibodies against S, s, and U antigens are always clinically significant. All are antibodies of IgG isotype, reactive at 37° C, arising from immune stimulation. Some examples of anti-S and anti-s show dosage. Enzymatic modification of RBCs with proteases, but not neuraminidase, can decrease the reactivity of some anti-S and anti-s. The reactivity of anti-U is resistant to proteolytic digestion. Anti-S, -s, and -U are causes of hemolytic transfusion reactions and HDFN.
MNS blood group system. Which is more common - anti-M or anti-N?
Clinically, anti-M is a commonly encountered antibody in the blood bank. In contrast, anti-N is distinctly uncommon, despite the fact that 25% of patients are negative for N antigen (M homozygous). The rarity of anti-N is due to the presence of ‘N’ antigen on GYPB. When observed, anti-N is usually an autoantibody, reacting with both N and ‘N’ antigens.
What is anti-Nf?
An autoantibody to N antigen in the NMS blood group system. An autoanti-N (anti-Nf) was reported in hemodialysis patients in the past, caused by the use of formaldehyde to sterilize membranes. Formaldehyde reacted with the terminal leucine on N and ‘N’ antigens, creating a neoantigen.
MNS blood group system. Generally, anti-M and anti-N are clinically insignificant antibodies. What phenotype is the exception?
In general, anti-M and anti-N are clinically insignificant antibodies and only rarely cause hemolytic transfusion reactions or HDFN. In contrast, potent hemolytic alloanti-N is observed in patients lacking GYPB (M+N−S−s− phenotype). In these patients, severe hemolytic transfusion reactions and HDFN can occur after transfusion of N+ RBCs.
What antigens does the P blood group system consist of?
P1 (renamed P1PK by the ISBT), and two members of the GLOB collection, P^k and P. Similar to the Lewis system, the P blood group antigens are glycosphingolipids.
True or false. Expression of the P1 antigen in the P blood group system can be lost with in vitro storage.
The P blood group system antigens are: P1 (renamed P1PK by the ISBT), and two members of the GLOB collection, P^k and P. On what cell types are these antigens located?
RBCs are particularly rich in P antigen, which makes up nearly 6% of the total RBC lipid. Pk and P antigens are also expressed on nonerythroid cells, including lymphocytes, platelets, plasma, kidney, lung, heart, endothelium, placenta, uroepithelium, fibroblasts, and synovium. Pk and P antigens are high-frequency antigens on most donor RBCs (>99.9%). In contrast, the P1 antigen is uniquely expressed on RBCs. ~79% of Caucasian and 94% of black donors express P1 on their RBCs.
The P1 and P2 phenotypes in the P blood group system account for >99% of donors. P1 phenotype expresses P^k, P, and P1 RBC antigens. P2 phenotype expresses P^k and P RBC antigens. What are the null and weak P phenotypes?
There are 3 null phenotypes: P1^k (expresses P1, and increased P^k RBC antigens); P2^k (expresses increased P^k RBC antigen); p (no RBC antigens). There are 2 weak phenotypes: Variant P^k (expresses increased P^k and decreased P RBC antigens); Weak P (expresses decreased P^k and decreased P RBC antigens).
P blood group system. Null phenotypes p and P^k (P1^k and P2^k), because they lack P antigen, they are resistant to what microorganism?
Clinically, the most common antibody observed in the P blood group system is anti-P1, which is detected in one quarter to two thirds of P2 donors. What Ig type? At what temperature does it react? Antibody reactivity can be eliminated by addition of what?
Anti-P1 is a naturally occurring antibody of IgM isotype and is often detected as a weak, room temperature agglutinin. Rare examples of anti-P1 are reactive at 37° C or show in vitro hemolysis. Because P1 expression varies in strength between individuals, anti-P1 may not react with all P1-positive cells tested. Anti-P1 can bind complement and may be detected in the IAT if polyspecific AHG is used. Antibody reactivity can be eliminated by prewarming sera or by adding soluble P1 substance from hydatid cyst fluid, earthworms, and bird eggs. Anti-P1 titers are often elevated in patients with hydatid cyst disease or fascioliasis (liver fluke), and in bird fanciers. Some examples of anti-P1 have I blood group specificity (anti-IP1).
In the P blood group system, is anti-P1 clinically significant?
In general, anti-P1 is not clinically significant, and its presence rarely requires transfusion of antigen-negative blood. The exception is seen in patients with an anti-P1 showing in vitro hemolysis. Because of the risk of immediate and delayed hemolytic transfusion reactions, these patients should receive P1-negative (P2), crossmatch compatible units. Anti-P1 is not a cause of HDFN.
In the P blood group system, what is auto-anti-P?
An autoantibody with anti-P specificity is seen in patients with paroxysmal cold hemoglobinuria, a clinical syndrome that may occur in children following viral infection. In PCH, autoanti-P is an IgG, biphasic hemolysin capable of binding RBCs at colder temperatures, followed by intravascular hemolysis at body temperature. This characteristic can be demonstrated in vitro in the Donath-Landsteiner test.
In the P blood group system, what is alloanti-PP1Pk?
Anti-PP1Pk (historically known as anti-Tja) is a separable mixture of anti-P, anti-P1, and anti-Pk in the sera of p individuals. These antibodies are naturally occurring and may be IgM only or IgM plus IgG (IgG3). Because anti-PP1Pk antibodies are potent hemolysins, patients can be transfused only with p RBCs.
An autoantibody with anti-___ specificity is seen in patients with paroxysmal cold hemoglobinuria, a clinical syndrome that may occur in children following viral infection.
An autoantibody with anti-P specificity is seen in patients with paroxysmal cold hemoglobinuria, a clinical syndrome that may occur in children following viral infection.
Several P blood group antigens are receptors for microbial pathogens. Give examples.
The P blood group antigen is the receptor for parvovirus B19. Pk can bind HIV and may confer resistance to HIV infection. The P1 and Pk antigens are receptors for shiga toxins, produced by Shigella dysenteriae and enterohemorrhagic Escherichia coli (EHEC) strains. In addition to gastroenteritis, EHEC infection is the most common cause of community-acquired hemolytic-uremic syndrome, probably reflecting toxin binding to Pk antigen on glomerular vascular endothelium and platelets. P, Pk, and LKE blood group antigens on uroepithelium are cell receptors for P-fimbriae, a bacterial adhesin and colonization factor expressed on uropathogenic E. coli strains. The Pk antigen also serves as a receptor for Streptococcus suis and Pseudomonas aeruginosa.
What 3 integral membrane proteins does the Rh complex consist of? Biochemistry of these 3 proteins?
Rh complex consists of three integral membrane proteins: RhD, RhCE, and Rh-associated glycoprotein (RhAg). RhD and RhCE are highly homologous proteins, differing by approximately 30 amino acids. Both are 30-kD, 416 amino acid multipass proteins containing 12 transmembrane domains, six extracellular loops, and a cytoplasmic amino- and carboxy-terminus. RhAg is a 45–70-kD multipass glycoprotein, evolutionarily related to RhD and RhCcEe glycoproteins. RhAg is a 409 amino acid glycoprotein with 12 transmembrane domains and a single, large N-linked carbohydrate side chain on the first extracellular loop.
The genes for RhD (RHD) and RhCE (RHCE) proteins span 65kb on chromosome ___ and share nearly 92% sequence identity. The two genes are separated by only 30kb and have opposite orientations, facing each other at their 3′ ends. The RHAG gene (RHAG) resides on chromosome ___ and shares 36% homology with the RHD and RHCE genes.
The genes for RhD (RHD) and RhCE (RHCE) proteins span 65kb on chromosome 1p34-36.1 and share nearly 92% sequence identity. The two genes are separated by only 30kb and have opposite orientations, facing each other at their 3′ ends. The RHAG gene (RHAG) resides on chromosome 6p11.1 and shares 36% homology with the RHD and RHCE genes.
On what chromosomes are these genes: RHD, RHCE, and RHAG.
RHD and RHCE are on chromosome 1. RHAG is on chromosome 6.
Approximately __% of D-positive individuals type as weak D (historically known as Du), characterized by weak or absent RBC agglutination by anti-D during routine serologic testing. In weak D individuals, the D antigen usually requires enhancement with AHG owing to a quantitative decrease in RhD protein. In these individuals, the number of RhD molecules is decreased __–__-fold, ranging from __–__ molecules per red cell.
Approximately 1% of D-positive individuals type as weak D (historically known as Du), characterized by weak or absent RBC agglutination by anti-D during routine serologic testing. In weak D individuals, the D antigen usually requires enhancement with AHG owing to a quantitative decrease in RhD protein. In these individuals, the number of RhD molecules is decreased 40–100-fold, ranging from 66–5200 molecules per red cell.
A weak D phenotype can occur with many partial D phenotypes, such as ___.
A weak D phenotype can occur with many partial D phenotypes, Ce in trans with suppression of RHD, in the Rhmod phenotype, and via autosomal recessive inheritance of two weak RHD alleles. The latter accounts for the majority of weak D phenotypes present in the general population.
What are partial D antigens?
Partial D antigens are RHD proteins with missing D epitopes. Although they type as D-positive, persons with partial D antigens can make alloanti-D antibodies reactive with allogeneic, but not autologous, RBCs. The alloanti-D produced by these individuals recognizes D-specific epitopes missing on their own RBCs. Partial D can result from missense mutations or from genetic recombination of RHD and RHCE genes.
What is the genetic basis of the Rh-negative phenotype for different racial groups?
Rh-negative (D−) occurs in approximately 15% of white donors, almost always in association with a ce/ce or rr phenotype. In most Caucasian people, D− reflects a deletion of the entire RHD gene. In blacks, D− can result from gene deletion or from inheritance of an RHD pseudogene. Nearly 60% of D-negative black people inherit a mutant RHD allele (RHψD) containing a 37–bp internal duplication, frameshift, and premature stop codon. RHD genes containing nonsense mutations and nucleotide deletions have also been reported in some D-negative Japanese and Caucasian donors.
What is the Rh null phenotype?
Extremely rare (<1 in 6 million). Rhnull erythrocytes lack all Rh antigens as a result of an apparent absence of RhD and RhCE proteins. In addition, Rhnull erythrocytes lack the high-frequency antigens Fy5 and LW and may have markedly decreased expression of S/s and U antigens. The absence of these non-Rh antigens reflects the complex topologic association of Duffy, LW, and GYPB proteins with Rh proteins on RBC membranes. Rhnull cells have structural and physiologic abnormalities, showing increased osmotic fragility and a shortened circulating half-life, often accompanied by a mild hemolytic anemia (Rh deficiency syndrome). Because Rhnull individuals can become sensitized to multiple Rh antigens, including high-frequency antigens, transfusion support can be quite difficult.
Rhnull erythrocytes lack all Rh antigens as a result of an apparent absence of RhD and RhCE proteins. In addition, Rhnull erythrocytes lack the high-frequency antigens Fy5 and LW and may have markedly decreased expression of S/s and U antigens. Why?
Rhnull erythrocytes lack all Rh antigens as a result of an apparent absence of RhD and RhCE proteins. In addition, Rhnull erythrocytes lack the high-frequency antigens Fy5 and LW and may have markedly decreased expression of S/s and U antigens. The absence of these non-Rh antigens reflects the complex topologic association of Duffy, LW, and GYPB proteins with Rh proteins on RBC membranes.
What are the Rh null amorph type and Rh null regulator type?
The Rhnull phenotype can arise from two distinct genetic backgrounds—regulator and amorph. The Rhnull-amorph type is the result of nonsense mutations in the RHCE gene in D-negative people. Because of the absence of RhD and RhCE proteins, Rhnull-amorph RBCs have reduced (but not absent) expression of RhAg protein. The Rhnull regulator type arises from mutations in RHAG.
What is the Rh mod phenotype?
Whereas Rhnull RBCs lack all Rh antigens as a result of an apparent absence of RhD and RhCE proteins, Rhmod RBCs have markedly decreased Rh and RhAg expression, detectable only by careful adsorption and elution studies. Similar to Rhnull individuals, persons with Rhmod may have laboratory evidence of Rh deficiency syndrome with a mild hemolytic anemia. Mutations in RHAG are also observed in the Rhmod phenotype.
In general, antibodies against Rh antigens are the result of immune stimulation by transfusion or pregnancy. Exceptions include ___.
In general, antibodies against Rh antigens are the result of immune stimulation by transfusion or pregnancy. Exceptions include some examples of anti-Cw and anti-E, which can be naturally occurring.
For transfusion in patients that are alloimmunized to Rh, RBC units should be negative for the Rh antigen of interest and crossmatch compatible with the recipient’s serum through the AHG phase of testing. One possible exception (where there may be a DHTR due to development of an antibody) may be ___.
For transfusion in patients that are alloimmunized to Rh, RBC units should be negative for the Rh antigen of interest and crossmatch compatible with the recipient’s serum through the AHG phase of testing. One possible exception may be R1R1 (DCe/DCe) patients who have developed anti-E alloantibodies. Because these patients are at increased risk of delayed hemolytic transfusion reactions because of the subsequent development of anti-c, many blood bankers advocate transfusing only R1R1 units to R1R1 patients.
Administration of one vial of Rh immune globulin is recommended for every __ mL whole blood or __ mL packed RBCs transfused. Rh immune globulin should be given within __ hours of exposure to prevent active immunization.
Administration of one vial of Rh immune globulin is recommended for every 30 mL whole blood or 15 mL packed RBCs transfused. Rh immune globulin should be given within 72 hours of exposure to prevent active immunization.
What can cause additional reactivity on forward typing of blood?
Acquired antigens (acquired B phenotype). Transplantation. Out-of-group transfusion. Autoagglutinins. Unwashed red cells (plasma proteins; antibody in patient’s serum to reagent constituent).
What can cause lack of expected reactivity on forward typing of blood?
Malignancy. Transplantation/transfusion (including intrauterine fetal transfusion). Neonates. Excessive soluble blood group substances.
What can cause a mixed field appearance on forward typing of blood?
Chimera (transplantation chimera; genetic chimera (twin); transfusion chimera). Fetomaternal hemorrhage. Some subgroups of A (e.g. A3 and Aend).
What are the 5 most immunogenic Rh antigens?
D is the most immunogenic Rh antigen, followed by c, E, C, and e.
How can malignancies cause lack of expected reactivity on forward typing of blood?
Some cancers, especially of GI tract, ovary, and leukemias, produce A and B-like soluble substances which react with antibodies during testing, neutralizing them. This can be corrected by thoroughly washing, then retesting.
What can cause additional reactivity on reverse typing of blood?
Extra antibodies. Transfusion (plasma components not type-specific to patient; IV Ig/albumin). Transplantation. Subgroup of a major blood type (especially subgroup of A (i.e. A2). Rouleaux (multiple myeloma; chronic inflammatory disorders).
What can cause lack of expected reactivity on reverse typing of blood?
Neonates. Elderly. Severe immunosuppression. Transplantation. Hypogammaglobulinemia. Subgroup of a major blood type.
How many antigens does the Lutheran blood group system contain? One what type of cells/tissues are Lutheran antigens expressed?
The Lutheran (Lu) blood group system contains 19 antigens including four pairs of allelic antigens and 11 high-incidence antigens. Lutheran is a minor constituent of RBC membranes, averaging only 2000–5000 molecules per cell, and can vary in strength between and within individuals. Lutheran antigens are ubiquitously expressed on several human tissues.
What are the null phenotypes of the Lutheran blood group system?
A Lu(a−b−) phenotype can occur in three settings with distinct patterns of inheritance: autosomal recessive, autosomal dominant (In[Lu]), and X-linked recessive. All are very rare.
Are the Lutheran blood group system antibodies clinically significant?
In general, Lutheran antibodies are not clinically significant and are only rarely associated with HDFN and hemolytic transfusion reactions.
What is the most common Lutheran blood group system alloantibody?
Anti-Lua is the most common Lutheran alloantibody encountered in the blood bank and is often an IgM, room temperature agglutinin. Because not all RBCs express detectable Lu antigens, anti-Lua can display mixed field agglutination. Antibodies against Lub and other Lutheran antigens are most often of IgG isotype, reacting best in the IAT. Reactivity of anti-Lua, Lub, and other Lutheran antibodies can be inhibited by pretreatment of RBCs with chymotrypsin, trypsin, 2-aminoethylisothiouronium bromide (AET), and dithiothreitol (DTT).
What are the frequencies in the US white and black populations for the Lutheran blood group system phenotypes Lu (a+b-), Lu (a+b+), and Lu (a-b+)?
Both white and black populations have the same frequencies: Lu (a+b-) 0.1%, Lu (a+b+) 6%, and Lu (a-b+) 94%.
How many antigens are in the Kell blood group system? On what cells/tissues is the Kell antigen expressed?
The Kell blood group system currently consists of 46 high- and low-frequency antigens. The Kell antigen is found on RBCs, erythroid and megakaryocyte progenitors, skeletal muscle, and testis. RBCs express approximately 2000–6000 copies of Kell protein per cell.
What are the null phenotypes in the Kell blood group system?
McLeod, which is rare; Kmod, which is rare; and K0, which is exceedingly rare.
K0 and McLeod are both Kell blood group system null phenotypes. How are they different?
K0K0 is an autosomal recessive, null phenotype that completely lacks all Kell antigens. As a consequence, these individuals can make an alloantibody to the Kell glycoprotein (anti-Ku). Unlike McLeod RBCs, K0K0 RBCs have enhanced expression of Kx antigen, present on the XK protein. Kell antigens are significantly depressed/absent on McLeod RBCs, an X-linked recessive phenotype characterized by the absence of XK protein on RBCs (Kx antigen, XK1). Because McLeod individuals lack XK and Kell proteins, these individuals can make alloantibodies directed against both proteins. As a consequence, McLeod individuals are incompatible with both Kell-positive and K0K0 RBCs.
K+k-, K+k+, K-k+, Kp(a+b-), Kp(a+b+), Kp(a-b+), Js(a+b-), Js(a+b+), Js(a-b+). For these phenotypes in the Kell blood group system, what are the frequencies of each of the US white and US black populations?
K+k-, 0.2% and rare. K+k+, 8.8% and 2%. K-k+, 91% and 98%. Kp(a+b-), rare and 0%. Kp(a+b+), 2.3% and rare. Kp(a-b+), 97.7% and 100%. Js(a+b-), 0% and 1%. Js(a+b+), rare and 19%. Js(a-b+), 100% and 80%.
What is the biochemistry of the Kell and XK proteins?
The Kell antigens reside on a 93-kD, 732 amino acid glycoprotein (CD238), possessing a short 47 amino acid amino-terminal cytosolic domain; a single transmembrane domain; and a large, 665 amino acid extracellular domain that includes the carboxy-terminus and 4-5 N-linked glycans. Overall, the molecule has a complex, folded tertiary structure due to the formation of multiple disulfide bonds. The XK protein is a 444 amino acid, nonglycosylated, multipass protein containing 10 transmembrane domains. On RBCs, the XK protein is covalently linked to the Kell protein through a disulfide bond. In the absence of XK protein (McLeod phenotype), Kell expression is decreased on RBCs, suggesting that XK protein may help transport Kell.
What is the relationship between the Kell and Gerbich blood group systems?
Gerbich-negative phenotypes have decreased Kell antigen expression. The molecular basis for this is unknown, but it is speculated that Kell and glycophorin C (Gerbich) may be near neighbors on the RBC membrane.
What is the clinical presentation of HDFN due to materal anti-Kell antibodies?
HDFN secondary to maternal anti-Kell antibodies is often characterized by reticulocytopenia, with little or no bilirubinemia. It is now known that maternal anti-Kell (anti-KEL1 or K1) directly suppresses erythroid progenitors, leading to a severe reticulocytopenic anemia in the fetus with up to 30% of affected infants presenting with fetal hydrops. Anti-K1 is present in approximately 1% of pregnancies, with HDFN affecting 40% of K1-positive infants.
What is the most common antibody against the Kell blood group system?
The most commonly encountered antibody against the Kell blood group system is anti-K1, which is second only to Rh D in immunogenicity. Antibodies against Kell antigens are of IgG isotype, arising from immune stimulation via transfusion or pregnancy, although examples of naturally occurring anti-Kell alloantibodies are known.
Why do approximately 7% of patients with X-linked chronic granulomatous disease also express a McLeod phenotype?
CGD is a functional neutrophil defect resulting in severe, recurrent, life-threatening bacterial infections. In two thirds of patients, CGD results from a deletion or mutation of the cytochrome b gene (CYBB) at Xp21.1, and the XK gene is also on Xp21.1. Because of the proximity of the CYBB and XK genes on the X chromosome, the McLeod phenotype can also be associated with CGD.
Where are Lewis antigens synthesized?
The Lewis blood group system is unusual in that the Lewis antigens are not of erythroid origin. The Lewis antigens are synthesized in the GI tract and passively adsorbed onto RBCs from a soluble pool of secreted Lewis substance in plasma. Tissues and fluids expressing Lewis include plasma, saliva, RBCs, platelets, lymphocytes, endothelium, uroepithelium, and bowel mucosa.
In what ages/races is the Le (a+b+) phenotype seen?
The Le (a+b+) phenotype is only rarely observed, usually on RBCs of very young children and some individuals of Polynesian, Japanese, or Taiwanese ancestry.
Is the Le (a-b-) phenotype more common in whites or blacks?
The Le (a−b−) phenotype is five times more common in blacks than in Caucasians.
In what ages/races is the Le (a-b-) phenotype seen?
The Le (a-b-) phenotype is 5 times more common in blacks than whites. The Le (a−b−) phenotype is also increased in neonates owing to developmentally delayed expression of the Lewis and Secretor genes. By 5 years of age, most children will express adult levels of Lewis antigens on their RBCs.
The Le (a−b−) phenotype is increased in neonates owing to developmentally delayed expression of the Lewis and Secretor genes. By __ years of age, most children will express adult levels of Lewis antigens on their RBCs.
The Le (a−b−) phenotype is increased in neonates owing to developmentally delayed expression of the Lewis and Secretor genes. By 5 years of age, most children will express adult levels of Lewis antigens on their RBCs.
For the 3 phenotypes in the Lewis blood group system, what are possible genotypes of the Le and Se genes?
Le (a+b-): Le/Le or Le/le and se/se. Le (a-b+): Le/Le or Le/le and Se/Se or Se/se. Le (a-b-): le/le and Se/se or le/le and se/se.
On what chromosome are the FUT genes located?
How does the null phenotype of the Lewis blood group system, Le (a-b-), arise?
It arises from inactivating mutations in FUT3.
What is the Le^w phenotype?
The Lewis weak phenotype. Has a Le (a-b-) RBC phenotype but the presence of Lewis-active substance in saliva. Is due to a single missense mutation in the transmembrane domain. There is normal enzyme activity but decreased Golgi retention.
Are antibodies against Le^a and Le^b antigens naturally occurring? clinically significant?
Antibodies against Le^a and Le^b antigens are naturally occurring IgM antibodies mostly detected as room temperature agglutinins. They are seldom clinically significant.
In what Lewis phenotypes can anti-Le^b and anti-Le^a be observed?
Anti-Leb can be observed in individuals of Le (a+b−) or Le (a−b−) phenotype, whereas anti-Lea is observed only in Le (a−b−) individuals. Anti-Lea is not observed in the Le (a−b+) phenotype because these individuals synthesize a small amount of Lea.
Why is anti-Le^a not observed in individuals with a Le (a-b+) phenotype?
Anti-Lea is not observed in the Le (a−b+) phenotype because these individuals synthesize a small amount of Lea.
How can pregnancy affect the Lewis phenotype Le (a-b+)?
Some Le (a−b+) women can transiently become phenotypically Le (b−), with the development of anti-Leb, during pregnancy.
Are anti-Lewis antibodies associtated with HDFN or hemolytic transfusion reactions?
They are not associated with HDFN and are only rarely associated with hemolytic transfusion reactions. For transfusion, patients with anti-Lewis antibodies reactive only at room temperature may be safely transfused with crossmatch–compatible RBCs.
Anti-Lewis antibodies are not associated with HDFN and are only rarely associated with hemolytic transfusion reactions. For the rare cases of anti-Lewis antibodies that are hemolytic in vitro, what can be done for transfusion purposes?
Rare examples of anti-Lea or anti-Leb that are hemolytic in vitro should receive antigen-negative, crossmatch–compatible RBCs. If antigen-negative blood is not available, infusion of plasma containing the soluble Lewis antigen of interest may be helpful in neutralizing or inhibiting circulating antibody before RBC transfusion.
What is the relationship between the Lewis blood group antigens and susceptibility to/resistance against particular infectious organisms?
H. pylori binds H, Leb, and Ley antigens via BabA recognition of a terminal Fucα1–2Gal epitope and appears to explain the increased incidence of ulcers and stomach cancer among blood group O secretors. A Lewis null and/or nonsecretor phenotype has also been linked with a higher incidence of recurrent Candida vaginitis and urinary tract infection. A Le (a−b−) phenotype is associated with an increased incidence of heart disease. Conversely, a nonsecretor phenotype protects against Norovirus infection.
Why is there increased incidence of ulcers and stomach cancer among blood group O secretors?
H. pylori binds H, Leb, and Ley antigens via BabA recognition of a terminal Fucα1–2Gal epitope.
How many antigens are in the Duffy blood group system?
The Duffy blood group system contains five antigens: Fya, Fyb, Fy3, Fy5, and Fy6. Fya and Fyb are autosomal codominant antigens, whereas Fy3, Fy5, and Fy6 are high-incidence antigens present on all RBCs except the Duffy null phenotype.
What blood group system antigen has a relationship to Plasmodium vivax?
P. vivax binds to the amino-terminal domain of DARC (Duffy Antigen Receptor for Chemokines)/the Duffy glycoprotein. Hence, Fy null individuals are resistant to most P. vivax strains.
What are the frequencies in white and black people for the 4 main Duffy RBC phenotypes?
Fy (a+b-): 17% and 9%. Fy (a+b+): 49% and 1%. Fy (a-b+): 34% and 22%. Fy (a-b-): very rare and 68%.
How is the molecular basis for the Fy null or Fy (a-b-) serologic phenotype different in whites and blacks?
In Caucasians, the FY gene is disrupted (FYamorph), leading to complete absence of DARC on all tissues. As a result, these individuals can make alloantibodies to all Duffy antigens, including high-incidence antigens (Fy3, Fy5). In contrast, black Fy (a−b−) individuals are homozygous for FYFy (FYB-33), a FYB variant allele that possess a point mutation in the FY gene promoter (−33T>C) that abrogates the consensus binding site for GATA-1. The latter is an erythroid transcription binding factor that regulates the expression of FY and other genes in RBCs. As a result, FY transcription is absent in RBCs but is present in endothelial and epithelial cells, which utilize other promoter enhancer elements. Because Fyb is expressed on nonerythroid cells, black Fy (a−b−) individuals do not make anti-Fyb and only rarely make anti-Fy3.
Are antibodies against the Duffy antigens clinically significant?
Antibodies against Fya, Fyb, and other Duffy antigens are clinically significant. They are associated with HDFN and both immediate and delayed hemolytic transfusion reactions. They are usually of IgG isotype, reactive at 37° C, and are detected only in the IAT.
Which is more common, anti-Fy^a or anti-Fy^b?
Clinically, anti-Fya is the most common alloantibody encountered and can be observed in Fy (a−) individuals of all races. Anti-Fyb is relatively uncommon and is observed primarily in nonblacks.
What clinical syndrome is associated with an Fy null phenotype?
In humans, no distinct clinical syndrome is associated with an Fynull phenotype; however, the Fynull phenotype has been linked to lower neutrophil counts, susceptibility to infection, renal disease, and reduced graft survival following renal transplantation.
Mycoplasma pneumoniae infection is associated with cold agglutinin disease secondary to anti-__, and infectious mononucleosis is associated with cold agglutinin disease secondary to anti-__.
Mycoplasma pneumoniae infection is associated with cold agglutinin disease secondary to anti-I, and infectious mononucleosis is associated with cold agglutinin disease secondary to anti-i.
Most hemolysis with non-ABO antibodies is extravascular, but antibodies to the ___ blood group system is associated with intravascular hemolysis (and delayed hemolytic transfusion reactions).
Most hemolysis with non-ABO antibodies is extravascular, but antibodies to the Kidd blood group system is associated with intravascular hemolysis (and delayed hemolytic transfusion reactions).
What are the 3 non-null Kidd blood group system phenotypes, and what is the frequency in US whites and blacks?
Jk (a+b-): 28% and 57%. Jk (a+b+): 49% and 34%. Jk (a-b+): 23% and 9%. All 3 of these phenotypes have positive reactions with anti-Jk3.
What are the 2 null Kidd blood group phenotypes?
The autosomal recessive Jk null (Jk (a-b-), and negative reaction with anti-Jk3) is very rare, except among Polynesians (1% or less) and Finns. In (Jk) is an autosomal dominant Jk null with very weak Kidd expression (Jk (a-b-), 0/w reaction with anti-Jk^a, 0/w reaction with anti-Jk^b, and weak reaction with anti-Jk3); this phenotype is rare.
Clinically, anti-Jk or Kidd antibodies are a common cause of hemolytic transfusion reactions, accounting for __% of all delayed hemolytic transfusion reactions and __% of those with true hemolytic sequelae.
Clinically, anti-Jk or Kidd antibodies are a common cause of hemolytic transfusion reactions, accounting for 25% of all delayed hemolytic transfusion reactions and 75% of those with true hemolytic sequelae.
Why are anti-Jk antibodies difficult to detect or identify in the blood bank?
Anti-Jk antibodies are often of low titer with weak avidity and can display dosage in vitro. Furthermore, anti-Jk antibodies are frequently transient, disappearing rapidly after immune stimulation. As a consequence, patients previously sensitized to Kidd antigens may be negative for anti-Jk antibodies in later blood samples. Following transfusion of crossmatch–compatible, Jk-positive RBCs, sensitized patients can mount a brisk anamnestic antibody response with rapid and extensive in vivo hemolysis as RBCs are cleared by extravascular and intravascular hemolysis.
Do anti-Jk antibodies cause HDFN?
Although uncommon, anti-Jk can cause a mild HDFN.
The Kidd glycoprotein is encoded by a 30-kb gene (JK, SLC14A1, UT-B) on chromosome 18q12-21. This is the same location as the ___ (61% homology), suggesting that the two genes arose by gene duplication.
The Kidd glycoprotein is encoded by a 30-kb gene (JK, SLC14A1, UT-B) on chromosome 18q12-21. This is the same location as the human HUT2/UT-A urea transporter (61% homology), suggesting that the two genes arose by gene duplication.
The Diego blood group system consists of __ antigens. __ antigens are rare, low-incidence antigens present on less than 1% of donors. The 2 high-frequency antigens are: ___ and ___.
The Diego blood group system consists of 21 antigens. 19 antigens are rare, low-incidence antigens present on less than 1% of donors. The 2 high-frequency antigens are: Di^b (ISBT DI2) and Wr^b (ISBT DI4), which are both present in >99.9% of donors.
What are the null phenotypes of the Diego blood group system?
The Diego blood group system resides on Band 3, also known as AE1. Functionally, AE1 plays a critical role in gas transport and acid-base equilibrium, as well as playing a role in the RBC cytoskeleton. Given the physiologic importance of AE1, it is not surprising that no Diego null phenotype has been described to date.
The Cartwright (Yt) blood group system consists of two autosomal codominant antigens: Yta and Ytb. Yta is a high-incidence antigen expressed by ___% of Caucasian donors. The incidence of Ytb varies by race, ranging from __% in Japanese to __% in the Mideast.
The Cartwright (Yt) blood group system consists of two autosomal codominant antigens: Yta and Ytb. Yta is a high-incidence antigen expressed by 99.8% of Caucasian donors. The incidence of Ytb varies by race, anging from 0% in Japanese to 25% in the Mideast.
The Cartwright blood group system antigens are located on ___, a β-carboxyesterase responsible for degradation of the neurotransmitter acetylcholine.
The Cartwright blood group system antigens are located on acetylcholinesterase (AChE), a β-carboxyesterase responsible for degradation of the neurotransmitter acetylcholine.
The Xg blood group system contains a single antigen, ___. Are there differences in frequency of this antigen among races/ages/genders?
The Xg blood group system contains a single antigen, Xga. As a result, only two phenotypes are known: Xga-positive and Xga-negative. Because the Xga antigen is encoded by a gene on the X chromosome, the incidence of the Xga-positive phenotype is higher among women. ~89% of women and 66% of men are Xga-positive. Because of differences in Xga-positive phenotype between men and women, most examples (>85%) of anti-Xga are observed in men. Xg appears to be specific for RBCs.
Are anti-Xg^a antibodies associated with hemolytic transfusion reactions or HDFN?
Anti-Xga is not associated with hemolytic transfusion reactions or HDFN. Anti-Xga may be immune stimulated or naturally occurring. Most examples are of IgG isotype, including some capable of activating complement.
The Scianna (Sc) blood group system contains ___ antigens. Scianna appears to be specific for what cells/tissues? Scianna antigens reside on ___, a 60–68-kD, 446 amino acid glycoprotein.
The Scianna (Sc) blood group system contains seven antigens. Scianna appears to be specific for RBCs and erythropoietic tissues. Scianna antigens reside on erythrocyte membrane-associated protein (ERMAP), a 60–68-kD, 446 amino acid glycoprotein. Similar to Lutheran, Ok, and LW proteins, ERMAP is a member of the Ig superfamily.
The Dombrock blood group system contains ___ antigens. What are the frequencies for the US white and black populations for the 3 non-null phenotypes: Do (a+b-), Do (a+b+), Do (a-b+)? Where do the Dombrock antigens reside?
The Dombrock blood group system contains seven antigens. The frequencies for the US white and black populations for the 3 non-null phenotypes: Do (a+b-) 18% and 11%, Do (a+b+) 49% and 44%, Do (a-b+) 33% and 45%. Dombrock antigens reside on an adenosine diphosphate (ADP)-ribosyltransferase (CD297), which catalyzes the transfer of ADP-ribose from nicotinamide adenine dinucleotide (NAD) to a protein acceptor.
The Donull or Gy(a−) phenotype is a rare, autosomal recessive phenotype of the Dombrock blood group system. An acquired Donull phenotype can be observed in paroxysmal nocturnal hemoglobinuria type III (PNH-III). A hematopoietic stem cell disorder, PNH III is characterized by chronic hemolysis due to an absence of all GPI-linked glycoproteins, including Dombrock, ___, and ___ antigens.
The Donull or Gy(a−) phenotype is a rare, autosomal recessive phenotype of the Dombrock blood group system. An acquired Donull phenotype can be observed in paroxysmal nocturnal hemoglobinuria type III (PNH-III). A hematopoietic stem cell disorder, PNH III is characterized by chronic hemolysis due to an absence of all GPI-linked glycoproteins, including Dombrock, Cromer, and Cartwright antigens.
An acquired Donull phenotype can be observed in what condition?
An acquired Donull phenotype can be observed in paroxysmal nocturnal hemoglobinuria type III (PNH-III). A hematopoietic stem cell disorder, PNH III is characterized by chronic hemolysis due to an absence of all GPI-linked glycoproteins, including Dombrock, Cromer, and Cartwright antigens.
Are anti-Dombrock antibodies clinically significant?
Anti-Dombrock antibodies can be clinically significant, although many examples are benign. Anti-Dombrock antibodies are capable of causing shortened RBC survival and acute and delayed hemolytic transfusion reactions. Anti-Dombrock is not associated with HDFN. Antibodies against Dombrock antigens are usually of IgG isotype, arising from immune stimulation by transfusion or pregnancy.
Why is detection of anti-Dombrock antibodies difficult?
Anti-Dombrock antibodies are commonly found in mixtures of alloantibodies and can be difficult to identify. Transfusion reactions and accelerated clearance due to anti-Dombrock antibodies can be missed in routine testing, with implicated units often testing as crossmatch–compatible, even in a full IAT crossmatch. Moreover, a posttransfusion direct antiglobulin test and eluate can be negative with no observable rise in antibody titer with time. Anti-Dombrock can deteriorate with in vitro storage, complicating pretransfusion testing. In addition, Dombrock titers may decrease over time in vivo, falling below the level of detection.
How many antigens are in the Colton blood group system? Where do the Colton blood group antigens reside?
Colton blood group system consists of two autosomal codominant antigens, Coa and Cob, and a third antigen (“TOR”). Coa is a high-incidence antigen present on 99.7% of donors. Cob is expressed by less than 11% of donors, with only 0.3% being Co (a−b+). Although very rare, a Co (a−b−) or null phenotype (Co null) is reported. The Colton blood group antigens reside on aquaporin 1 (AQP-1) or channel-forming integral protein, a water-selective membrane channel.
Are anti-Colton antibodies clinically significant?
Anti-Colton antibodies can be clinically significant: They can be associated with shortened RBC survival, hemolytic transfusion reactions, and HDFN. Antibodies to Coa and Cob are usually of the IgG isotype, resulting from immune stimulation by transfusion or pregnancy. Some examples of anti-Coa and anti-Cob are reported to bind complement.
What is the relationship of the LW blood group system to the Rh blood group system in discovery and function?
The LW, or Landsteiner-Wiener, blood group system is most important for its role in the history of the Rh blood group system. Landsteiner and Wiener originally developed antibodies against the LW antigens by immunizing rabbits with rhesus monkey red cells. The resulting “anti-Rh” antibodies were initially believed to recognize the RhD antigen; however, later investigators proved that the antibodies developed by Landsteiner and Wiener recognized a non-Rh (LW) antigen. Expression of LW antigen is dependent on RhD protein expression, with the highest expression observed on RhD-positive red cells, weaker expression on RhD-negative cells, and no expression on Rhnull erythrocytes.
How many antigens are in the LW blood group system? On what cells/tissues is LW antigen expressed? Where do the LW antigens reside?
The LW blood group system consists of two allelic antigens: LWa and LWb. LWa is a high-frequency antigen (99% of white donors). Expression of LW antigen is dependent on RhD protein expression, with the highest expression observed on RhD-positive red cells and weaker expression on RhD-negative cells. LW antigens are absent from Rhnull erythrocytes. An LW (a−b−) or null phenotype can also be seen in very rare individuals who are homozygous for a silent LW allele. The LW antigen is expressed on RBCs and placenta. The LW antigens reside on intracellular adhesion molecule type 4 (ICAM-4, CD242), a 40–47-kD type 1 glycoprotein.
Are antibodies to the LW blood group system clinically significant?
Clinically benign, anti-LW antibodies are rarely a cause of hemolytic transfusion reactions or HDFN. They usually are of IgG isotype and are detected in the IAT.
How many antigens are in the Chido/Rodgers blood group system? Are they low or high incidence? On what cells/tissues are they expressed?
The Ch/Rg blood group system contains 10 antigens, including two pairs of antithetical antigens and three conformational antigens. Most Ch/Rg antigens are high-incidence antigens (>90%). Similar to Lewis blood group antigens, Ch/Rg antigens are of plasma origin and are passively adsorbed onto RBC membranes. Ch/Rg antigens are weakly expressed on cord RBCs and some GYPA-deficient RBCs. Ch/Rg antigens are antigenic determinants on the C4d fragment of the C4 complement molecule. C4 is the product of two highly homologous genes (99% identity), C4A and C4B. In general, Chido antigens are on C4B and Rodgers antigens are on C4A.
What characteristic is in common between the Lewis blood group antigens and Chido/Rodgers blood group antigens?
Both blood group antigens are of plasma origin and are passively adsorbed onto RBC membranes.
Are antibodies against the Chido/Rodgers blood group system antigens clinically significant?
Antibodies against Ch/Rg antigens do not cause hemolytic transfusion reactions or HDFN. Rare reports have described anaphylaxis following transfusion of plasma and platelets. Anti-Ch/Rg antibodies are of IgG isotype and are usually detected with AHG.
How many antigens are in the Gerbich blood group system? On what cells/tissues are the Gerbich antigens found?
The Gerbich (Ge) blood group system contains seven antigens: three high-frequency (>99%) and four low-frequency antigens. The Gerbich glycoproteins (GPC/D) are on fetal and adult RBCs, platelets, and kidney and fetal liver.
In the Gerbich blood group system, what are the 3 autosomal recessive phenotypes associated with the loss of high-incidence Gerbich antigens?
Three autosomal recessive phenotypes are associated with the loss of high-incidence Gerbich antigens: Yus (Ge-2,3,4), Gerbich (Ge-2,-3,4), and Leach (Ge-2,-3,-4).
Gerbich antigens are decreased in patients with ___ due to protein 4.1 (an RBC cytoskeletal protein) deficiency.
Gerbich antigens are decreased in patients with hereditary elliptocytosis due to protein 4.1 (an RBC cytoskeletal protein) deficiency.
By what physiologic mechanisms does hydrops fetalis occur?
HDFN is the destruction of fetal or newborn RBCs by maternal alloantibodies specific for inherited paternal RBC antigen(s). The maternal IgG is transported across the placenta into the fetal circulation where it binds to the corresponding RBC antigen, targeting the antibody-coated RBCs for destruction by macrophages in the fetal spleen. The fetal marrow initially responds by increasing erythropoiesis and releases many of the newly produced RBCs into the circulation prematurely as nucleated precursors, leading to the term “erythroblastosis fetalis.” With worsening anemia, erythropoiesis expands to the liver and spleen, causing organ enlargement and portal hypertension. A resulting decrease in liver production of albumin leads to reduced plasma colloid osmotic pressure, generalized edema, ascites, and effusions known as “hydrops fetalis.”
Why is the HIV p24 antigen testing no longer required on donated blood?
After the introduction of testing for HIV RNA by NAT, p24 antigen testing no longer provided added benefit in reducing the risk of transfusion-transmitted HIV, and the FDA allowed discontinuation of antigen testing in the US as long as HIV NAT was being used. And also, HIV-1/HIV-2 antibody tests are performed as well.
AABB Standards requires the use of what 2 tests to test donors for HBV infection?
AABB Standards requires the use of HBsAg and anti-HBc to test donors for HBV infection.
What are the two available test methods for anti-HBc?
A solid-phase inhibition immunoassay, and a direct antiglobulin assay.
In the US, HBsAg and anti-HBc testing is required to screen blood donors for HBV. How does Japan modify this screening?
Japan, a country with moderate prevalence of HBV infection, modifies anti-HBc screening to accept donor with high amounts of anti-HBs, if also HBV NAT negative, because presence of anti-HBs in the absence of detectable HBV usually signifies a resolved infection and absence of circulating virus.
AABB Standards requires the use of what 2 tests to test donors for HCV infection?
AABB Standards requires the use of anti-HCV and HCV RNA NAT to test donors for HCV infection.
What is the primary screening test for anti-HCV when testing blood donors? What is done when this is positive?
A third-generation antiglobulin EIA is the primary screening test for antibodies to HCV. If the initial EIA is positive, the test is repeated. If the second EIA is “repeat reactive,” a confirmatory/supplemental test is performed, which is currently a recombinant immunoblot assay (RIBA) against HCV antigens, which is FDA-approved for supplemental testing.
In screening blood donors for anti-HCV, EIAs are performed. For donors that have “repeat reactive” EIA, a confirmatory/supplemental test is performed, which is currently a recombinant immunoblot assay (RIBA) against HCV antigens, which is FDA-approved for supplemental testing. What is done when the RIBA is positive and what is done when it is negative?
A donor with a reactive RIBA is permanently deferred from donating and is considered to be infected with HCV. Of EIA repeatedly reactive donors, 37% have a non-reactive or indeterminate RIBA test result and are rarely infectious for HCV. Whether or not the RIBA is reactive, if a blood donor is repeatedly reactive for anti-HCV by EIA, the donation cannot be used for transfusion. However, a donor who has a non-reactive RIBA and reactive EIA (without HCV NAT positivity) can be considered for re-entry by application to the FDA.
What are the 2 commercially available, FDA-approved HCV NAT procedures used for screening blood donors?
A PCR test performed on RNA tested by chemical methods on mini-pools of 16-24 donor blood samples; and a transcription-mediated amplification (TMA) test on nucleic acid preparations in a solid phase (probe-capture) method, also performed on mini-pools of donor samples. Both test methods are sensitive and specific and perform equally well in identifying HCV RNA.
What testing type, timing and algorithm is used for screening blood donors for West Nile virus?
A minipool NAT is done, with a recommended trigger for implementing individual NAT when two presumed viremic donors (PVD; defined as an initial reactive donor that repeats on the original sample) occur within a 7-day period; MP-NAT is resumed after 7 days without PVD donations or ongoing regional activity, or at the medical director’s direction.
Screening blood donors for West Nile virus is done by NAT. What is the confirmatory test?
WNV infectivity of the donor is confirmed by either repeat NAT reactivity on a follow-up sample, or IgM and IgG antibody reactivity with neutralization testing on either the original (index) sample or a follow-up sample.
How is HTLV screened for in blood donors?
The FDA has approved the use of EIAs which detect both HTLV-1 and -2 antibodies. These tests typically use viral lysates as the capture reagent, and adherent donor antibodies are identified with an antiglobulin conjugate. There are no licensed confirmatory or supplemental tests for the HTLV-1/2 EIAs. One approach to supplemental testing to confirm a reactive anti-HTLV test is to repeat the test using an alternate manufacturer’s EIA. Western blot and radioimmunoprecipitation (RIPA) tests are available.
Blood donors are screened for HTLV-1 and -2 antibodies by EIA. What is the confirmatory test for a positive screening EIA?
There are no licensed confirmatory or supplemental tests for the HTLV-1/2 EIAs. One approach to supplemental testing to confirm a reactive anti-HTLV test is to repeat the test using an alternate manufacturer’s EIA. Western blot and radioimmunoprecipitation (RIPA) tests are available.
What are the 3 indications for leukoreduction of blood products, 2 potential indications, and 1 controversial indication?
Indications: Decreasing incidence of febrile non-hemolytic transfusion reactions. Decreasing incidence of HLA alloimmunization. Decreasing CMV transmission. Potential indications: Decreasing other HHV (i.e. EBV, HHV-6, HHV-7, HHV-8) transfusion transmitted infections. Possible decrease in transmission of prion disease. Controversial indication: Decreasing TRIM (Transfusion-Related ImmunoModulation).
In the US, the requirements for leukoreduction of RBCs and apheresis platelets are ___ leukocytes per product, and for whole blood derived platelets is ___ leukocytes per product. At least __% of the products sampled must meet this specification.
In the US, the requirements for leukoreduction of RBCs and apheresis platelets are less than 5 x 10^6 leukocytes per product, and for whole blood derived platelets is less than 0.83 x 10^6 leukocytes per product.. At least 95% of the products sampled must meet this specification.
Bedside leukoreduction is contraindicated in patients on what drug, because it can induce hypotensive episodes?
Patients on ACE inhibitors may have severe hypotensive episodes due to bradykinin activation, which is not observed for pre-storage leukoreduction.
The rosette test can detect a fetomaternal hemorrhage of approximately __ mL or more.
The rosette test can detect a fetomaternal hemorrhage of approximately 10 mL or more.
Rosette test. If there is insufficient or no washing before adding the indicator red blood cells, there can be a false (positive/negative) result. If the mother is a weak D phenotype, there can be a false (positive/negative) result. If the fetus is weak D phenotype, there can be a false (positive/negative) result.
Rosette test. If there is insufficient or no washing before adding the indicator red blood cells, there can be a false positive result because excess unbound anti-D reagent is still present. If the mother is a weak D phenotype, there can be a false positive result because she may type as negative even though she is actually positive, and the test needs to have a D- mother and a D+ fetus to work as it should. If the fetus is weak D phenotype, there can be a false negative result because the weak D may not be enough to bind the anti-D reagent. In this last situation, if a baby initially types as D-, weak D testing is done, and if weak D is positive, go straight to a Kleihauer-Betke test instead of doing a rosette test.
In the Kleihauer-Betke test, what is the formula?
(Fetal cells x Maternal blood volume) / Total cells counted = Fetal hemorrhage in mL. Maternal blood volume is calculated from 70 mL/kg or assumed to be 5000 mL if weight is not known. Total cells counted is always 2000. The result is divided by 30 (b/c one dose of RhIG (30 ug) covers 30 mL of whole blood). The resulting number is then rounded down if the number to the right of the decimal point is less than 5, then 1 is added to give the total vials/doses of RhIG. The resulting number is rounded up if the number to the right of the decimal point is 5 or more, then 1 is added to give the total vials/doses of RhIG.
For the rosette test, what is the phenotype of the indicator red blood cells?
They are ficin enzyme treated cDE, R2R2 red blood cells.
RBCs used for freezing are collected in CPD or CPDA-1, and stored as liquid whole blood or RBC products. These RBCs must be frozen within __ days of collection.
RBCs used for freezing are collected in CPD or CPDA-1, and stored as liquid whole blood or RBC products. These RBCs must be frozen within 6 days of collection.
RBCs used for freezing are collected in CPD or CPDA-1, and stored as liquid whole blood or RBC products. These RBCs must be frozen within 6 days of collection. If RBC products need to be frozen and are older than 6 days, what must be done?
They must first be rejuvenated with a FDA-approved solution (contain pyruvate, inosine, phosphate, and adenine; restores levels of ATP and 2,3-DPG to that of a freshly-drawn unit) and then frozen.
FDA-approved RBC product rejuvenation solutions contain pyruvate, inosine, phosphate, and adenine, which restores levels of ATP and 2,3-DPG to that of a freshly-drawn unit. RBC products can be rejuvenated up to __ days after expiration.
FDA-approved RBC product rejuvenation solutions contain pyruvate, inosine, phosphate, and adenine, which restores levels of ATP and 2,3-DPG to that of a freshly-drawn unit. RBC products can be rejuvenated up to 3 days after expiration.
For washed RBC products and washed platelet products: What solution(s) are they washed with? What % loss of product is there? Outdate?
RBC products can be washed with 1-2 liters of normal saline. Washing can result in loss of up to 20% of the RBC mass of the product. Washed products must be used within 24 hours, as they are washed in an open system. Platelets can be washed with normal saline, saline buffered with ACD-A or citrate, or platelet storage solutions. Washing results in ~33% loss of the platelets. Washed platelets must be used within 4 hours.
What are indications for washed blood products?
Prevention of recurrent severe allergic/anaphylactic transfusion reactions. Neonatal alloimmune thrombocytopenia. Large-volume or rapid transfusion into neonates and small children. Irradiated RBC products. Patients with T-activation. Washing of RBC products for patients with paroxysmal nocturnal hemoglobinuria used to be advocated, but is no longer recommended.
Using washed blood products for prevention of recurrent severe allergic/anaphylactic transfusion reactions. How does it work?
Anaphylactic reactions can be secondary to anti-IgA; to prevents these reactions in the future, IgA deficient products can be used, or, (more readily available) deglycerolized and/or washed RBC products can be used to remove the IgA in the product. Deglycerolized and/or washed RBCs can also be used to prevent recurrent severe allergic/anaphylactoid/anaphylactic reactions not secondary to anti-IgA, by removing residual plasma proteins.
Neonatal alloimmune thrombocytopenia (NAIT) is secondary to maternal alloantibodies, usually ___, against the platelet antigen in the fetus or neonate.
Neonatal alloimmune thrombocytopenia (NAIT) is secondary to maternal alloantibodies, usually anti-HPA-1a, against the platelet antigen in the fetus or neonate.
In neonatal alloimmune thrombocytopenia, maternal platelets are serologically compatible and are therefore a potential source of platelets for transfusion to the fetus/neonate. What must be done to the maternal platelets before transfusion?
Prior to transfusion the maternal platelets must be washed to remove the antibody against the fetal/neonatal platelet antigen contained within the maternal plasma, and irradiated to prevent TA-GVHD.
Why are washed RBC products indicated for large volume (>25 mL/kg) or rapid transfusion in neonates and small children?
Washing may be used to remove potassium, anticoagulant-preservative solution (particularly additive solutions) and other substances in the supernatant in RBC products. This decreases the risk of hyperkalemia and cardiac arrhythmias. Volume reduction can achieve the same goal.
Unlike HDFN caused by anti-D, HDFN caused by anti-K uniquely produces suppression of fetal ___, in addition to hemolysis.
Unlike HDFN caused by anti-D, HDFN caused by anti-K uniquely produces suppression of fetal erythropoiesis, in addition to hemolysis.
Which causes more severe HDFN, IgG1 or IgG3?
IgG1 is associated with more severe disease because it is transported across the placenta earlier and in larger amounts than IgG3.
Before the development of color Doppler US, the severity of HDFN was usually monitored by ___.
Before the development of color Doppler US, the severity of HDFN was usually monitored by amniocentesis, typically performed with US guidance, to follow the level of bilirubin in amniotic fluid. The aspirated amniotic fluid is protected from light and tested by a scanning spectrophhotometer for the change in fluid optical density at 450 nm, which is proportional to the bilirubin concentration. The delta OD 450 is then plotted on a graph according to gestational age. The graph is divided into zones that correspond to severity disease.
Amniotic fluid analysis for bilirubin does not correlate well with the degree of fetal anemia in HDFN in mothers with ___ system antibodies. For these patients, middle cerebral artery peak systolic velocity and/or cordocentesis is indicated.
Amniotic fluid analysis for bilirubin does not correlate well with the degree of fetal anemia in HDFN in mothers with Kell system antibodies. For these patients, middle cerebral artery peak systolic velocity and/or cordocentesis is indicated.
If it becomes necessary to distinguish passively administered RhIG from the anti-D formed by alloimmunization, what can be done?
RhIG is entirely IgG, whereas active immunization produces an antibody response with an IgM component. Thus, anti-D produced by the mother can often be detected in saline phase and completely or partially inactivated by 2-mercaptoethanol or DTT treatment, whereas RhIG cannot. Additionally, passively acquired anti-D rarely achieves a titer above 4.
What is the mechanism of action of RhIG?
The mechanism of action has not been completely elucidated. Previously, RhIG was thought to work by a simple clearance mechanism, but now it is thought that more is involved at the molecular level. RhIG is thought to work, in part, by inhibition of the normal antibody-mediated immune response that creates anti-D antibodies. Administration of anti-D antibody in RhIG coats any fetal RBC, disallowing production of active maternal anti-D antibodies. D-positive red cells may be opsonized by RhIG and removed by macrophages, which release cytokines that result in immunomodulation. The number of IgG molecules known to prevent immunization is much fewer than the D antigen sites on red cells.
Which is the more common cause of HDFN, ABO incompatibility or D incompatibility?
With the widespread use of RhIG, ABO incompatibility has become the most common cause of HDFN. D incompatibility is more severe, though.
In the US, what is the platelet antigen most commonly implicated in fetal and neonatal alloimmune thrombocytopenia (FNAIT)?
HPA-1a, formerly known as P1 A1, accounts for ~80% of cases. HPA-5b accounts for ~10%, HPA-1b accounts for ~4%, HPA-3a accounts for 2%, and 6% is by other antibodies.
Do RBCs have HLA class I antigens?
The immature nucleated red cell also has class I antigens on its surface, but as the RBC matures the expression of class I antigens is diminished. Remnants of class I HLA antigens on red blood cells are also known as Bennet-Goodspeed (Bg) antigens. The antigens are listed with their corresponding class I HLA designation: Bga – HLA-B7, Bgb – HLA-B17, Bgc – HLA –A28.
On what cell types are HLA class II antigens expressed?
HLA class II antigens are selectively expressed by dendritic cells, macrophages, B-lymphocytes, and activated T-cells that function in antigen processing and self versus non-self recognition.
How many antigens are in the Cromer blood group system? Where is the Cromer antigen and on what cell/tissue types is it expressed?
The Cromer system (Cr/CROM) contains 15 antigens. Cromer antigens are present on DAF (CD55), which is widely expressed on tissues and in secretions.
Are antibodies to the Cromer blood group system clinically significant?
The clinical significance of anti-Cromer antibodies is variable. In some individuals, anti-Cromer antibodies are associated with decreased RBC survival and HTRs. Cromer antibodies do not cause HDFN owing to adsorption of antibodies by DAF (Cromer antigens are present on DAF (CD55)) on trophoblast epithelium.
CD55/DAF, where the Cromer blood group system antigens are located, protects cells from complement by promoting the decay of what two C3 convertases?
C4b2a and C3bBb.
The Cromer blood group system antigens are present on DAF (CD55), which is widely expressed on tissues and in secretions. For what microorganisms is CD55 a receptor for?
Echovirus, coxsackie B virus, and uropathogenic and intestinal E. coli strains bearing Afa/Dr and X adhesins.
How many antigens are in the Knops blood group system? On what cells/tissues is the antigen present? Where does Knops reside? Are Knops antibodies clinically significant?
The Knops blood group contains 10-12 antigens. Knops antigens are present on adult and cord RBCs, neutrophils, B lymphocytes, and dendritic cells. Knops resides on complement receptor 1 (CR1, CD35). Knops antibodies are clinically insignificant.
How many antigens are in the Indian blood group system? On what glycoprotein are the Indian antigens present? Are antibodies against the Indian antigens clinically significant?
The Indian (IN) blood group contains 2 autosomal codominant antigens: In^a (IN1) and In^b (IN2). Three additional high-incidence antigens are known: IN3, IN4, and AnWj. The Indian antigens are present on CD44, a ubiquitous glycoprotein on many cell membranes. Antibodies against the Indian antigens can be clinically significant, with shortened RBC survival and transfusion reactions. They are not associated with HDFN.
How many antigens are in the OK blood group system? On what protein is it found?
The OK system contains a single high-frequency antigen, Ok^a, which resides on CD147. Anti-Ok^a is rare and has been described only in Japan.
How many antigens are in the RAPH blood group system? On what protein is it found?
The RAPH blood group system contains a single antigen, RAPH or MER2, located on CD151 or tetraspanin (TM4). In the cell membrane, tetraspanins are associated with integrins and are implicated in cell adhesion, tumor metastasis, and signaling.
How many antigens are in the JMH blood group system? On what protein is it found? Are anti-JMH antibodies clinically significant?
The JMH (John Milton Hagen) system contains 6 high-incidence antigens and can vary in strength between individuals. JMH is carried on CD108 (SEMA-L), a semaphorin glycoprotein. Anti-JMH antibodies are of IgG isotype and can be naturally occurring. They do not cause HTRs or HDFN.
The I blood group system. What are the antigens and how are they biochemically related? How do the antigen expressions change with age of the person? On what cells/tissues are the antigens present?
The I blood group system contains two biosynthetically related antigens: I and i. The biosynthetic precursor to I antigen, the i antigen, is strongly expressed on cord cells because of developmental delays in the enzyme responsible for I antigen synthesis. By 3 months of age, there is a perceptible decrease in i antigen, accompanied by increased I antigen, with an adult I+i− phenotype by 18–24 months of age. Both I and i antigens are ubiquitously expressed on glycolipids and glycoproteins on red cells and other tissues.
The i antigen from the I blood group system is normally present only in children. In what conditions/situations do adults have increased i antigen?
The iadult phenotype is a rare, autosomal recessive phenotype found in <1/10,000 donors. In Asia, the iadult phenotype can be associated with congenital cataracts. i antigen is also observed on cord RBCs and reticulocytes and in megaloblastic anemia, leukemia, and chronic hemolytic states as a sign of stressed erythropoiesis. Elevated i antigen is also observed in HEMPAS (hereditary erythroblastic multinuclearity with positive acidified-serum test), a congenital dyserythropoietic anemia.
How are the i and I antigens formed?
Type 2 chain oligosaccharides, both i and I antigens, terminate in a Galβ1→4GlcNAc or lactosaminyl epitope and differ only in complexity and multivalency. The i antigen is a linear oligosaccharide containing at least two successive lactosamine epitopes. The I antigen is derived from i antigen by the action of a β1–6 N-acetylglucosaminyltransferase, a first step in the synthesis of large, branched multivalent complex polylactosamines. Both i and I can be further modified by other glycosyltransferases to yield ABH, LeX, and related antigens.
Antibodies to the I blood group system. What Ig isotype? Auto and alloantibodies?
Anti-I and anti-i are antibodies of IgM isotype, reactive at room temperature. Autoantibodies to I are relatively common and are usually low-titered cold agglutinins. Some anti-I can have IH specificity, reacting stronger with group O and A2 RBC. Although generally benign, hemolysis secondary to high-titered anti-I is observed in cold autoimmune hemolytic anemia (CAIHA). CAIHA can occur in the setting of malignancy and occasionally infection (e.g., Mycoplasma pneumoniae). These antibodies display high thermal amplitude, often agglutinating RBCs at temperatures of 30°–34° C. In contrast, alloanti-I is relatively rare and is found as a naturally occurring antibody in iadult individuals.
Despite the common occurrence of major maternal-fetal ABO incompatibility, severe HDFN due to ABO incompatibility is rare (0.04%). How is the developmental delay in I antigen synthesis thought to be protective?
It is hypothesized that the developmental delay in I antigen synthesis may play a protective role against HDFN-ABO by minimizing the number of ABH antigens expressed on fetal red cells. This is supported by parallel increases in I and ABH during the first 2 years of life.
The GIL blood group system. How many antigens are in the system? On what protein is the antigen carried? Is anti-GIL clinially significant?
The GIL blood group system contains one high-incidence antigen, GIL (100% donors). GIL is carried by aquaglyceroporin (AQP-3), a member of the major intrinsic protein family of water channels. Anti-GIL is associated with hemolytic transfusion reactions. No reports have described clinical HDFN due to anti-GIL despite a positive DAT. Anti-GIL is usually of IgG isotype, reactive at 37° C and enhanced with AHG.
Which 2 blood group system antigens are located on aquaporins?
GIL is on AQP-3, and Colton is on AQP1.
Rouleaux formation or “pseudoagglutination.” In what conditions/situations is it seen and how do they cause the rouleaux formation?
Patients with multiple myeloma, Waldenström’s macroglobulinemia, and hyperviscosity syndromes have high concentrations of abnormal serum proteins that change the net surface charge on the RBC membrane. The cells thus cluster together in clumps that resemble macroscopic hemagglutination. Plasma expanders, such as dextran and hydroxyethyl starch, as well as some intravenous X-ray contrast materials can also cause rouleaux formation.
Patients with multiple myeloma, Waldenström’s macroglobulinemia, and hyperviscosity syndromes have high concentrations of abnormal serum proteins that change the net surface charge on the RBC membrane that can result in rouleaux formation or “pseudoagglutination”. How can the rouleaux formation be differentiated from true agglutination?
Rouleaux can be differentiated from true agglutination by direct microscopy (1) by the classical “stacked-coin” formation in rouleaux, and (2) by the loss of rouleaux after washing and resuspension in saline.
The presence of ___ and ___ in cord blood is responsible for the nonspecific agglutination that can be seen in cord blood samples contaminated with Wharton’s jelly.
The presence of hyaluronic acid and albumin in cord blood is responsible for the nonspecific agglutination that can be seen in cord blood samples contaminated with Wharton’s jelly.
In immunohematology procedures, IgM antibodies are often referred to as direct agglutinins, and IgG antibodies are referred to as indirect agglutinins. Why?
IgM antibodies can facilitate the second stage of hemagglutination because of their large diameter (35 nm) and multivalency, which allows them to span the distance between two adjacent RBCs in solution. Because of their innate agglutinating ability, IgM antibodies are frequently referred to as direct agglutinins. Most IgG antibodies, on the other hand, are considerably smaller (14 nm) and are unable to induce visible agglutination without the assistance of secondary enhancing reagents. Thus, IgG antibodies are commonly referred to as indirect agglutinins.
Currently, three methods are available for evaluating visual hemagglutination reactions: Tube testing, column aggutination (gel technology), and solid-phase technology. What type of gel is used for the column agglutination?
Column agglutination or gel technology utilizes a dextran acrylamide gel microtube prepared by the manufacturer.
What is the difference between direct and indirect antiglobulin tests?
The AHG test is also called the Coombs’ test. When the test is used to detect antibodies or complement bound to RBCs in vivo, it is called the direct antiglobulin test (DAT). When the test is used to detect the reaction of antibody and RBCs in vitro after an appropriate incubation phase, it is called the indirect antiglobulin test (IAT). The red cell antibody screen is an example of an IAT.
Used in the blood bank, what is polyspecific AHG composed of?
At present, the most commonly used polyspecific AHG reagents consist of rabbit polyclonal anti-IgG blended with murine monoclonal antibodies to C3b and C3d complement components. Conventional polyspecific (also called broad-spectrum) AHG contains polyclonal IgG antibodies to the spectrum of human IgG subclasses and the C3 complement cleavage products C3b and C3d. Some anti-C4b and anti-C4d activity may also be present. However, most manufacturers adsorb out anti-C4 activity from their polyspecific AHG reagents because it has been shown that in vitro complement activation by clinically insignificant cold agglutinins results in much more C4d than C3d binding.
IgG antibodies used in AHG reagents in the blood bank. Why can they potentially cross-react with IgA or IgM light chains?
Because immunization against IgG will also produce anti–light chain antibodies in a polyclonal response, one should remember that polyclonal antiglobulin sera may cross-react with IgA or IgM light chains unless the manufacturer specifies that the anti-IgG component is heavy chain specific.
What are 4 applications of the direct antiglobulin test and 4 applications of the indirect antiglobulin test in the blood bank?
DAT: Investigation of HTR. Diagnosis of HDFN. Diagnosis of AIHA. Investigation of drug-induced hemolysis. IAT: Antibody detection (or antibody screen). Antibody identification. Crossmatching. Red cell antigen typing.
What are the “check cells” in antibody screening panel, DATs, and IATs?
Quality control cells for the antiglobulin test are referred to as check cells, Coombs’ control cells, and sensitized cells. In a true-negative test, free active antiglobulin reagent should remain. Control cells, sensitized with IgG and/or C3, are added to all negative tests and centrifuged. Hemagglutination of check cells confirms both the presence and the reactivity of the AHG reagent, thus validating a negative test result. If the control cells fail to agglutinate in any tube, the tests must be repeated because they are invalid and may have yielded false-negative results.
Although the antihuman globulin test is extremely sensitive, a negative test does not exclude the possible presence of antibodies on RBCs. How can that happen?
It is estimated that 200–500 IgG or C3 molecules bound per cell are required for detection by antiglobulin antibodies. A negative reaction can occur with small quantities of bound IgG and C3. In addition, AHG sera may possess greater activity against some subclasses of IgG than against others. Consequently, certain AHG sera may produce negative results with RBCs coated by a particular IgG subclass.
Although serum has traditionally been the preferred specimen for compatibility testing in the blood bank, plasma is increasingly used owing to newer testing technologies. What are problems that can arise in conventional antiglobulin testing techniques when using plasma instead of serum?
Problems with plasma in conventional antiglobulin techniques are primarily technical. Plasma can be associated with small fibrin clots which can trap RBCs and resemble agglutination. Fibrin may also trap serum and cause neutralization of AHG reagent if not removed before washing. Finally, plasma can enhance rouleaux formation if fibrinogen levels are particularly high.
Age of sample for pretransfusion compatibility testing. According to AABB Standards, a pretransfusion specimen for testing and red cell transfusion is valid for __ hours. After __ hours, a new sample must be drawn. In elective surgery patients, some facilities will extend the age of a preoperative sample up to 1 month provided that the patient meets what 4 criteria?
Age of sample for pretransfusion compatibility testing. According to AABB Standards, a pretransfusion specimen for testing and red cell transfusion is valid for 72 hours. After 72 hours, a new sample must be drawn. In elective surgery patients, some facilities will extend the age of a preoperative sample up to 1 month provided that the patient (1) has a negative antibody screen, (2) has no history of clinically significant antibodies, (3) is not pregnant, and (4) has not been transfused within the preceding 3 months.
Sample storage for pretransfusion compatibility testing. AABB Standards require that all pretransfusion samples be stored at 1°–6° C for at least __ days after testing is completed, along with ___.
Sample storage for pretransfusion compatibility testing. AABB Standards require that all pretransfusion samples be stored at 1°–6° C for at least 7 days after testing is completed, along with at least one representative segment from each of the donor units crossmatched on the recipient. The purpose of this is to ensure that repeat or additional testing of the donor or patient may be performed later if the patient experiences a delayed hemolytic reaction or other adverse effect of transfusion.
How is the abbreviated crossmatch AKA immediate spin crossmatch performed?
The serologic test to detect ABO incompatibility commonly consists of an immediate spin protocol employing a 3%–5% saline suspension of donor RBCs prepared from an integral segment taken from the selected donor unit. Cells usually are washed once to remove any anticoagulant or plasma protein that could interfere with the testing. A drop of donor cell suspension is mixed with recipient serum, centrifuged immediately, and examined for hemolysis and/or agglutination.
When is an antiglobulin crossmatch performed?
If the pretransfusion antibody screen detects a clinically significant antibody, or a check of patient records indicates that such antibodies have been detected previously, a major or long crossmatch must be performed. In the antiglobulin crossmatch, compatibility between recipient serum and donor red cells is tested by the antiglobulin method that is routinely used by the laboratory.
In the blood bank, serum can be pretreated with sulfhydryl reagents such as 2-mercaptoethanol (2-ME) or dithiothreitol (DTT) for what purpose?
As a special technique in antibody identification. Sulfhydryl reagents destroy the pentameric structure of agglutinating IgM antibodies, effectively bypassing cold reactive autoantibodies and alloantibodies to allow for detection of underlying IgG alloantibodies.
What HLA loci are present on platelets?
Platelets only have HLA-A, HLA-B, and HLA-C antigens, which are all part of the HLA class I structure. In routine clinical practice, only HLA-A and HLA-B are generally considered when the transfusion service is matching platelets in immune refractory patients.
What methods are used in HLA typing for compatible platelets?
A number of methods are utilized in HLA typing for compatible platelets (primarily patient lymphocytes are used in testing because of the increased density of the class I HLA antigens), including: Anti-Human Globulin augmented Complement Dependent lymphoCytotoxicity Assay (AHG-CDC) – Antibodies against the HLA antigen will fix complement and cause lysis, visualized with a supravital stain. ELISA – Purified HLA gene products are adsorbed to the plate wells. Flow cytometry – Fluorescent markers identify cell surface antigens.
In the blood bank, what is an antibody identification technique performed on serum that is useful in cases of WAIHA?
Serum adsorption. Adsorb serum antibodies with autologous cells, selected allogeneic cells, or rabbit erythrocyte stroma (REST) at appropriate temperature for reactivity of antibody. This physically removes broadly reactive autoantibodies or alloantibodies from serum by reacting with absorbing cells to allow for detection of underlying IgG antibodies—particularly useful in cases of WAIHA.
Serum adsorption is an antibody identification technique performed in the blood bank. How is it done?
Adsorb serum antibodies with autologous cells, selected allogeneic cells, or rabbit erythrocyte stroma (REST) at appropriate temperature for reactivity of antibody. This physically removes broadly reactive autoantibodies or alloantibodies from serum by reacting with absorbing cells to allow for detection of underlying IgG antibodies. May be combined with elution in complicated cases involving identification of multiple antibodies.
In the blood bank, how does the prewarming technique help antibody identification?
When prewarming, keep all test components (test tubes, cells, serum, saline) at 37° C prior to testing; use monospecific anti-IgG AHG reagents. This technique bypasses reactivity of cold autoagglutinins or alloagglutinins of limited titer and thermal amplitude—prevents direct agglutination of test cells and/or in vitro complement activation in antibody detection and identification tests.
How can enzyme treatment in some cases help with identification of antibodies in the blood bank?
Eliminates some antibody reactivity by destroying corresponding antigen structures—MNS, Duffy, Ch/Rg; may be easier to pick out different specificities in a serum containing multiple antibodies. Enhances sensitization, agglutination, and/or hemolysis by other antibodies—Rh, Kidd, many IgM blood group antibodies; may allow for easier identification of weakly reactive antibodies.
What is ZZAP?
A reagent used in the blood bank that is a combination of DTT (dithiothreitol) and cysteine-activated papain. It is used to remove immunoglobulins and complement from the surface of red blood cells, commonly when evaluating a potential autoantibody. It also deactivates a multitude of RBC surface antigens.
How is ZZAP used in the blood bank?
For adsorption purposes, aliquots of washed, packed red cells are incubated with ZZAP at 37° C. Cells are then washed with large volumes of saline to remove ZZAP. The combination of DTT and enzymes destroys coating of IgG autoantibodies. The removal of autoantibodies from patient cells provides free antigen sites for adsorption of autoantibody from the serum. ZZAP also destroys antigens from some blood group systems.
Hemagglutination inhibition is a serum procedure used in the blood bank for eliminating antibody reactivity. How is the technique performed?
Hemagglutination inhibition is used to neutralize selected blood group antibodies with their corresponding antigen found in soluble form in human saliva, serum, or other body fluids, as well as in substances in nature. The identity of a suspected antibody is confirmed if it no longer agglutinates antigen-positive reagent cells after addition of soluble antigen. Hemagglutination inhibition may be particularly useful when working with a serum specimen containing multiple specificities.
Hemagglutination inhibition is used to neutralize selected blood group antibodies with their corresponding antigen found in soluble form in human saliva, serum, or other body fluids, as well as in substances in nature. For the soluble substances ABH, Le^a, Le^b, P1, Sd^a, Ch, Rg, and I, what is the source of soluble antigen used in the technique?
ABH, Le^a, Le^b: secretor saliva. P1: hydatid cyst fluid or pigeon eggs. Sd^a: human or guinea pig urine. Ch, Rg: plasma from Ch/Rg (+) individuals. I: human milk.
Which blood group antigens are destroyed by enzyme treatment?
Fya, Fyb, M, N, HTLA- Ch/Rg, JMH, Pr, Xga.
Which blood group antigens are variably affected by enzyme treatment, and which blood group is usually unaffected?
Variably affected: Lua, Lub, S, s, Yta, Ytb. Usually unaffected: Kell.
Which blood group antigens are enhanced by enzyme treatment?
ABH, I/I, Jka, Jkb, Lea, Leb, P1, Rh, U, Dia, Dib.
What does the mnemonic “Lewis is a peeing rotton kid.” stand for?
Blood group antigens that are enhanced by enzyme treatment. Lewis = Lewis. is = I. a = ABO. peeing = P. rotton = Rh. kid = Kidd. But also U, Dia, Dib.
What does the mnemonic “LIPMAN” stand for?
The IgM antibodies seen in the blood bank. L = Lewis. I = I/i. P = P1. M = M. A = ABO. N = N.
Two basic techniques for separating autologous from transfused RBCs are differential agglutination and density separation using centrifugation. How are these techniques performed?
In the first technique, antibodies are used to agglutinate only one population of cells, based on known antigenic differences between recipient and donor. Unagglutinated cells are physically removed from the agglutinates and are sequentially reacted with more antisera until no more agglutinates are formed. In the second technique, washed packed RBCs are centrifuged in multiple sealed microhematocrit tubes. Transfused cells are older, smaller, and denser than newly formed autologous cells (reticulocytes) and will spin toward the bottom of the tube. After centrifugation, the top 5 mm of each tube is cut away, and the cells are harvested from these small segments. These sections will contain the larger and lighter autologous cells. This method will be effective only if the patient is producing normal or high numbers of reticulocytes.
What are the 2 basic techniques used in the blood bank for separating autologous from transfused RBCs?
Differential agglutination and density separation using centrifugation.
What technique can be used in the blood bank to harvest autologous red cells (excluding transfused donor red cells) in patients with sickle cell disease? Because sickle cell patients are regularly transfused, this technique is useful for facilities that provide antigen-matched red cells for their sickle cell patients.
Hypotonic cell lysis. The method is based on the resistance of Hg S red cells to hypotonic saline. The patient sample is repeatedly washed with 0.3% hypotonic saline to lyse normal donor red cells until gross hemolysis is no longer present. The cells are then washed and resuspended in 0.9% saline for antigen typing.
Individuals with warm reactive autoantibodies account for approximately __%–__% of cases of AIHA.
Individuals with warm reactive autoantibodies account for approximately 70%–80% of cases of AIHA.
Autoantibodies in WAIHA are usually Ig__ and (mono/poly)clonal in nature, showing optimal in vitro reactivity at __° C. The DAT will be positive in approximately __% of cases.
Autoantibodies in WAIHA are usually IgG and polyclonal in nature, showing optimal in vitro reactivity at 37° C. The DAT will be positive in approximately 80% of cases.
In WAIHA, the DAT will be positive in approximately 80% of cases. What can be done if the DAT is negative?
In those instances where the DAT is negative, the use of more sensitive techniques, such as radioisotope or enzyme-labeled DAT, can demonstrate low levels of IgG or, less frequently, IgM and IgA on red cells.
In WAIHA, what IgG subtype(s) is involved? Is hemolysis intravascular or extravascular?
In WAIHA, causative antibodies are predominantly IgG1 and/or IgG3. Despite the ability of these subclasses to activate complement, immune destruction of the patient’s autologous cells occurs largely through the spleen and liver via extravascular pathways.
Are the autoantibodies in WAIHA narrowly reactive or broadly reactive?
In general, warm autoantibodies display a broad specificity, reacting with all normal RBCs. Relatively few individuals with WAIHA will show a single simple specificity.
In WAIHA, what serologic testing can be done beyond the DAT?
Transfusion is usually avoided for as long as possible in patients with WAIHA. If transfusion is necessary, it is important to characterize the autoantibody and exclude the presence of RBC alloantibodies. Typical investigation strategies should always include adsorption of the serum (Because a strong, broadly reactive serum autoantibody can mask the presence of significant alloantibodies, adsorption studies should be performed in these patients), followed by antibody detection and identification on the adsorbed serum. Subsequent testing can also be performed on eluted antibody, although it seldom yields further useful information unless the serum is nonreactive.
Brief overview of cold autoantibodies/CAIHA.
Cold autoantibodies may be detected in the serum of many normal individuals if tested under the right conditions. However, most of these antibodies are benign cold agglutinins that show optimal reactivity at 4° C and little or no reactivity at 37° C. Cold agglutinins are often a nuisance that can interfere with ABO/Rh typing, antibody detection, and crossmatching when polyspecific AHG is used. Although usually ignored as clinically insignificant, cold agglutinins may become pathologic by virtue of expanded thermal amplitude and a significant increase in titer, frequently in association with certain disease states. DAT, serum titration, and characterization of thermal amplitude are the most important serologic tests in evaluating a possible diagnosis of CAIHA.
Cold agglutinins are often merely a nuisance that can interfere with ABO/Rh typing, antibody detection, and crossmatching when polyspecific AHG is used. When can cold agglutinins become pathologic?
Although usually ignored as clinically insignificant, cold agglutinins may become pathologic by virtue of expanded thermal amplitude and a significant increase in titer, frequently in association with certain disease states.
What are the 3 most important serologic tests used in evaluation of a possible diagnosis of CAIHA?
DAT, serum titration, and characterization of thermal amplitude are the most important serologic tests in evaluating a possible diagnosis of CAIHA.
What are the clinical significances of the following cold red cell autoagglutinins: I, i, Pr, P, H, IH?
I: Acute CAD associated with Mycoplasma pneumoniae with antibody titers >1000 at 4° C. i: Acute CAD associated with mononucleosis. Pr: Rare cause of CAD. P: PCH associated with certain viral infections in children. H: Benign except as alloantibody in Bombay phenotype. IH: Benign.
Typically, of what Ig classes are the following cold red cell autoagglutinins: I, i, Pr, P, H, IH?
I: IgM. i: IgM. Pr: Reported cases of IgM, IgG, IgA. P: IgG (Autoanti-P is the only pathologic cold autoantibody known to be routinely of the IgG class to IAT). H: IgM. IH: IgM.
Cold agglutinin disease (CAD) accounts for about __% of total cases of AIHA.
Cold agglutinin disease (CAD) accounts for about 20% of total cases of AIHA. As with WAIHA, CAD may be idiopathic or secondary following infection or malignancy.
In contrast to the anti-I cold agglutinins found in normal sera (usually less than 1 : 64 when tested at 4° C), anti-I in CAD is often of very high titer, with ranges of 1 : ___ to 1 : ___.
In contrast to the anti-I cold agglutinins found in normal sera (usually less than 1 : 64 when tested at 4° C), anti-I in CAD is often of very high titer, with ranges of 1 : 10,000 to 1 : 1,000,000. The antibody also has expanded thermal amplitude, reacting with RBCs at temperatures in the range of 30°–34° C in vitro, especially in tests with albumin-suspended RBCs. The DAT is typically positive with polyspecific and anti-C3 reagents.
What are the physiologic processes that occur in cold agglutinin disease?
In vivo hemolysis is the result of binding of antibody to a patient’s RBCs in the peripheral vessels of the extremities, which are cooler (32° C and lower). As the cells recirculate to the body core and warm to 37° C, complement is activated and cells are destroyed. Hemolysis of cells may occur intravascularly but occurs more commonly via extravascular (C3b) pathways by macrophages in the reticuloendothelial system. Hemolysis may be chronic or episodic, depending on the thermal range of the antibody, and may be triggered by exposure to cold temperatures.
What is the most common causative antibody in paroxysmal cold hemoglobinuria?
Autoanti-P, also known as the Donath-Landsteiner (DL) antibody, is the most common causative antibody in PCH. It is an IgG, biphasic autohemolysin capable of binding to RBCs at cold temperatures and causing intravascular hemolysis of those cells at body temperature.
When performing the Donath-Landsteiner test to detect the biphasic hemolysin characteristic of paroxysmal cold hemoglobinuria, why is a fresh blood sample needed, and why should it not be drawn into an EDTA tube?
The DL test requires that a fresh blood sample be used to ensure that an adequate supply of complement is available, because complement is relatively unstable and deteriorates during storage. The sample should be drawn and immediately stored at 37° C until clot formation. It is also important not to draw the blood into an anticoagulant such as EDTA because chelation of calcium ions will prevent complement activation and thus in vitro hemolysis.
What is a “mixed” AIHA?
A “mixed” AIHA occurs in s serum will react in all phases of testing (at room temperature and at 37° C) in the IAT. The cold-reactive antibody is typically anti-I or anti-i, and the warm-reactive antibody is typically a 37° C reactive IgG autoantibody. To adsorb autoantibody in a mixed AIHA, the sample is sequentially adsorbed at 37° C to adsorb warm-reactive autoantibody, followed by incubation in an ice bath for 30 minutes to adsorb cold-reactive antibody. Clinically, mixed AIHA usually is similar to WAIHA, although some patients may have symptoms of both WAIHA and CAD.
Historically, drug-induced hemolytic anemia has been subclassified based on its serologic characteristics into what four types?
Drug-independent antibodies. Drug-dependent antibodies are subclassified into two types: Drug-dependent reactivity with drug-coated cells and Drug-dependent reactivity with uncoated cells. Nonimmunologic protein adsorption. There are also combination mechanisms.
Historically, drug-induced hemolytic anemia has been subclassified based on its serologic characteristics into four types: Drug-independent antibodies. Drug-dependent antibodies (further subclassified into two types): Drug-dependent reactivity with drug-coated cells and Drug-dependent reactivity with uncoated cells. Nonimmunologic protein adsorption. How do they work?
Drug-independent antibodies do not require the addition of drug into the test system for detection, even though the drug is responsible for inducing hemolytic anemia. Drug-dependent antibodies, on the other hand, require the presence of the drug for serologic reactivity. Drug-dependent antibodies can be subclassified into two types, depending on whether antibody reactivity requires drug-coated red cells or simply the presence of drug in serum. Nonimmunologic protein adsorption proposes that a change in the red cell membrane causes immune globulins and other plasma proteins to be adsorbed nonspecifically to the red cell membrane. There are also combination mechanisms.
For the following clinical syndrome(s), give the causative agent(s) (list most common first): Chagas disease and African sleeping sickness.
Chagas disease: Trypanosoma cruzi. African sleeping sickness: Trypanosoma brucei.
Plasmapheresis vs. plasma exchange?
In plasmapheresis, plasma is removed and replaced with a mixture of normal saline and 5% albumin. In plasma exchange, plasma is removed and replaced with allogeneic plasma.
What can be used for treatment of coagulation factor XIII deficiency?
FFP and cryoprecipitate are good sources of FXIII, providing 1 and 3 unit/mL of FXIII respectively; however, these carry the risk of transmission of bloodbourne viruses. Pasteurized FXIII concentrates are safer and have a higher titer of FXIII (~240 U/vial), so are preferred. Also, recombinant FXIII-A is available and can be used in congenital FXIII-A subunit deficiency. The recombinant FXIII-A subunit associates in plasma with the endogenous FXIII-B subunit to form a stable FXIII heterotetramer.
For allogeneic blood donation, what are requirements for temperature, pulse, blood pressure, and Hgb/Hct?
Temperature shall not exceed 37.5 C (99.5 F). Pulse should be regular and 50-100 beats/min. A HR or equal to 12.5 g/dL and 38% as determined from a sample of blood taken at the time of donation.
In whole blood donation, AABB Standards allows a maximum collection of __ mL of blood per kg of the donor’s weight for each donation (including samples).
In whole blood donation, AABB Standards allows a maximum collection of 10.5 mL of blood per kg of the donor’s weight for each donation (including samples).
In the US, what are typical volumes of blood collected in routine whole blood collection?
Either 450 mL +/- 10% (405-495 mL) or 500 mL +/- 10% (450-550 mL). A low volume unit is 300-405 mL.
What is the volume in a “low volume unit” of donated whole blood?
Can low volume units be used for transfusion?
RBCs are made available for transfusion when 300-404 mL of whole blood is collected into an anticoagulant volume calculated for 450 +/- 45 mL, or when 333-449 mL of whole blood is collected into an anticoagulant volume calculated for 500 +/- 50 mL. However, other components such as platelets, FFP, and cryo should not be prepared from low volume units.
IgG and IgM. Which reacts best vs. protein-rich Ags, and which reacts best vs. carbohydrate Ags?
IgG reacts best vs. protein-rich Ags. IgM reacts best vs. carbohydrate Ags.
Potentiating agents in transfusion medicine include LISS, 22% albumin, and PEG. Which one tends to enhance expression of cold antibodies and autoantibodies? Which tends to enhance expression of warm antibodies and autoantibodies?
LISS tends to enhance expression of cold antibodies and autoantibodies. PEG tends to enhance expression of warm antibodies and autoantibodies.
Potentiating agents in transfusion medicine include LISS, 22% albumin, and PEG. For the 37 C phase of tube testing what are the incubation times when using each of the above potentiators, and when using no potentiator (saline)?
LISS: 10-15 min. Albumin: 15-30 min. PEG: 15 min (but do not read the PEG reaction at 37 C due to false positive reactions). Saline: 30-60 min.
Which blood group antigen systems most commonly show dosage effect?
Rh, Kidd, Duffy, MNS.
List the Wiener and Fisher-Race Rh blood group terminology haplotypes.
R1=DCe. R2=DcE. R0=Dce. Rz=DCE. r’=dCe. r’‘=dcE. r=dce. r^y=dCE.
What are the rules for converting Wiener and Fisher-Race Rh blood group terminologies?
R=D, r=d. 1 or ‘=C. 2 or ‘‘=E. 0 or blank=ce. Any letter=CE.
What are the “big four” in reference to Wiener and Fisher-Race Rh blood group terminologies?
Out of the 8 possible combinations, only 4 are important because ~97% of people will have R1, R2, R0, or r. The frequencies of those 4 differ between whites, blacks, and Asians, though.
What are the Rh blood group frequencies in whites, blacks, and Asians in Wiener terminology?
Whites: R1 > r > R2 > R0. Blacks: R0 > r > R1 > R2. Asians: R1 > R2 > r > R0.
Whites: R1 > r > R2 > R0. Blacks: R0 > r > R1 > R2. How can you remember this?
R0 is most common in blacks and least common in whites. r is always second in frequency. R1 always comes before R2. The frequencies for Asians is R1 > R2 > r > R0.
For the Kell antigens: K (AKA K1) / k (AKA K2), Js^a / Js^b, and Kp^a / Kp^b, which of each pair are more common?
Low frequency: K (AKA K1), Js^a, Kp^a. High frequency: k (AKA K2), Js^b, Kp^b.
Kell null phenotype and McLeod phenotype. Which has absent Kell antigens and which has decreased Kell antigens? Which has decreased Kx and which has increased Kx? Which doesn’t develop anti-Ku with exposure, and which does?
Kell null phenotype has absence of all Kell antigens, increased Kx, and significant anti-Ku with exposure. McLeod phenotype has markedly decreased Kell antigens, absent Kx, and no anti-Ku.
What is CD103? What normal and abnormal hematologic entities does it stain?
AKA human mucosal lymphocyte antigen 1, integrin alpha E beta 7, ITGAE. Stains normal and tumor intraepithelial T lymphocytes. Will stain hairy cell leukemia, enteropathy-associated T cell lymphoma, and some splenic marginal zone lymphomas.
Blood donor reactions: both vasovagal reactions and hypotensive shock have hypotension. What vital sign can be used to distinguish the 2?
Vasovagal reaction has bradycardia, while hypotensive shock has tachycardia.
Normovolemic/isovolemic hemodilution. Intraoperative blood salvage. Postoperative blood salvage. What is the shelf life for each product?
Normovolemic/isovolemic hemodilution: 8 hrs at room temp, 24 hrs in refrigerator. Intraoperative blood salvage: 4 hrs at room temp, 24 hrs in refrigerator. Postoperative blood salvage: 6 hrs at room temp.
The RBCs in patients with congenital dyserythropoietic anemia type II (HEMPAS) have a very high density of what antigen on them?
The i antigen. The other subtypes of CDA (types I, III, and IV) have normal levels of i antigen.
Polyagglutination is nonspecific agglutination of red cells in the presence of human serum, not related to blood group specificity. It can be acquired or inherited. What is the pathogenesis of the acquired form?
Polyagglutination happens most often as a consequence of infections, when bacterial enzymes strip off parts of antigens normally present of the surface of the RBC. This action exposes antigens that are normally hidden, called “cryptantigens” (examples include T, Th, Tk, and Tx antigens). Most people have IgM antibodies that react against these cryptantigens, making them incompatible with most other people’s serum (most people that have polyagglutination lack the anti-cryptantigen antibody themselves). By definition, polyagglutination resulting from bacteria is transient, and effective treatment of the infection eliminates the polyagglutination.
Low ionic strength solution vs. polyethylene glycol. Which is better at detecting warm autoantibodies? Cold autoantibodies? Which has higher sensitivity?
PEG is better at detecting warm autoantibodies. LISS is better at detecting cold autoantibodies. PEG is more sensitive than LISS for autoantibody detecting, but has a higher false-positive rate (1.3% vs. 0.1%).
The CAP makes recommendations for the minimum requirements for the retention of laboratory records and materials. They meet or exceed the regulatory requirements specified in the Clinical Laboratory Improvement Amendments of 1988 (CLIA 88). For blood bank, how long must the following be kept: donor and recipient records; patient records; records of employee signatures, initials, and identification codes; quality control records; records of indefinitely deferred donors, permanently deferred donors, or donors placed under surveillance for the recipient’s protection (e.g., those donors that are hepatitis B core positive once, donors implicated in a hepatitis positive recipient); specimens from blood donors units and recipients?
Donor and recipient records - 10 yrs. Patient records - 10 yrs. Records of employee signatures, initials, and identification codes - 10 yrs. Quality control records - 5 yrs. Records of indefinitely deferred donors, permanently deferred donors, or donors placed under surveillance for the recipient’s protection (e.g., those donors that are hepatitis B core positive once, donors implicated in a hepatitis positive recipient) - indefinitely. Specimens from blood donors units and recipients - 7 days post-transfusion.
__% of the white population is homozygous for HPA-1b antigen and are therefore at risk for PTP if alloimmunized against HPA-1a (i.e. previous transfusion or pregnancy). It is estimated that __% are capable of forming anti-HPA-1a.
3% of the white population is homozygous for HPA-1b antigen and are therefore at risk for PTP if alloimmunized against HPA-1a (i.e. previous transfusion or pregnancy). It is estimated that _30% are capable of forming anti-HPA-1a.
What distinguishes TA-GVHD from GVHD after stem cell transplantation?
TA-GVHD has pancytopenia due to immune destruction of host marrow cells. Most die within 1-3 wks of symptoms due to bone marrow failure (severe hemorrhage, infection).
What drug is associated with TA-GVHD?
Fludarabine (Fludara), which is a synthetic purine antimetabolite used to treat lymphoid malignancies. It has been shown to cause lymphocytopenia with sustained reduction of CD4+ T lymphocytes. Fludarabine treatment has been associated with susceptibility to TA GvHD. Similarly, a related nucleoside analogue chemotherapeutic agent, cladribine (Litak, Movectro), has also been associated with severe lymphocytopenia and TA-GvHD. The immunosuppressive effect of these two drugs has been noted for extended periods long after cessation of treatment. It is therefore recommended that prior treatment with fludarabine and 2-CDA, whether for a malignant or non-malignant disease, should be considered an indication for irradiation of blood components, even if the treatment was in the distant past.
One apheresis unit of platelets should increase peripheral platelet count by how much?
25,000 to 50,000.
What is the risk of bacterial sepsis for apheresis platelets vs. pooled random donor platelets?
Apheresis platelets: 1 in 75,000. Pooled random donor platelets: 1 in 33,000.
What is the risk of mild allergic reaction and anaphylactic reaction for RBCs and platelets?
Mild allergic reaction, RBCs - 1 in 144. Mild allergic reaction, platelets - 1 in 33. Anaphylactic reaction, RBCs - 1 in 25,000. Anaphylactic reaction, platelets - 1 in 2000.
Out of the Rh group of blood antigens, D is most antigenic, followed by __ and __.
Out of the Rh group of blood antigens, D is most antigenic, followed by c and E.
In contrast to a blood collection center, weak D testing is not routinely performed in Rh-typing in a hospital blood bank. What situation is the exception?
Rh negative mother with her newborn testing anti-D negative by the immediate spin D testing. Do the weak D testing (incubation period at 37 C for 15-30 min, and includes antiglobulin reagent) to make sure the baby isn’t actually a weak D instead of a true D negative.
How much is a single standard dose of RhIG, and how much is a minidose?
Standard dose: 300 ug IM (1500 IU IV). Minidose: 50 ug IM (250 IU IV).
What is the % risk of the following people developing anti-D if exposed: pregnant patient not given RhIG, pregnant patient given RhIG, immunocompromised or trauma patient, healthy patient?
Pregnant patient not given RhIG: 16%. Pregnant patient given RhIG: 0.1%. Immunocompromised or trauma patient: 25-30%. Healthy patient: 85%.
The rosette test is performed post-delivery with an Rh neg mother and an Rh pos fetus. How is the test performed?
Maternal sample (potentially containing fetal RBCs) is incubated with anti-D, then washed to remove unbound anti-D. Indicator RBCs (ficin-treated R2R2 cells) are added, which form agglutinates (rosettes) around fetal D-pos cells if they are present.
The rosette test is performed post-delivery with an Rh neg mother and an Rh pos fetus. How is the test interpreted?
If ficin-treated R2R2 indicator cells are used, up to 1 rosette in 3 microscopic fields is negative. If untreated indicator cells and an enhancing medium is used, up to 6 rosettes per 5 microscopic fields is negative.
The rosette test is performed post-delivery with an Rh neg mother and an Rh pos fetus. What is done if the test is negative or positive?
If the rosette test is negative, one standard dose of RhIG is given. If the rosette test is positive, the Kleihauer-Betke test (or flow cytometry) is performed to determine the volume of fetal cells and the dose of RhIG needed.
IM is the standard method of delivery for RhIG. Up to __ doses can be given at one time at one injection site.
IM is the standard method of delivery for RhIG. Up to 6 doses can be given at one time at one injection site. If greater than 6 required, then can vary injection site and times of injections as long as total needed is given within 72 hours, or can give via IV dosing.
How can RhIG be used for ITP?
Pts with ITP have platelet destruction in the spleen. RhIG can be used in ITP if pt has intact spleen and is Rh positive. The RhIG attaches to pt’s RBCs, then RBCs are detected by Fc receptors of RES in spleen; These are competing for the same sites as the pt’s platelets, resulting in relative sparing of the platelets. There is a resultant drop in hemoglobin of about 1.7 g/dL.
What is the G antigen?
It is an antigen present on any RBC that carries either D or C antigen. The G antigen is a common amino acid present on the surface of both D and C antigens. The phenotypes with G antigen are D+C+, D-C+, or D+C-. The phenotype without G antigen is D-C-. 15% of the US white population is G negative, while less than 1% of other populations are G negative.
The G antigen is an antigen present on any RBC that carries either D or C antigen. Should pregnant patients with anti-G receive RhIG prophylaxis?
Patients with anti-G do not have anti-D and should receive RhIG prophylaxis if pregnant to prevent immunization to D when indicated.
The G antigen is an antigen present on any RBC that carries either D or C antigen. In routine blood banking, how does an anti-G appear on the Ab panel?
Antibodies to G appear to be anti-D plus anti-C in routine testing. They cannot be separated in routine blood banking, and can be detected only by genotyping.
The G antigen is an antigen present on any RBC that carries either D or C antigen. In what 2 situations can the presence of an anti-G antibody cause clinical confusion?
It can give the appearance of an Rh-negative person having anti-D after being transfused with D-C+ blood. It can give the appearance of an Rh-negative mother developing anti-D after delivering a D-C+ child.
What are compound antigens in transfusion medicine?
Antigens can be formed by the presence of two other antigens present at the same time or in a specific genetic combination. These antigens are known as “compound antigens.” Four recognized compound antigens are ce or f (RH6), Ce (RH7), cE (Rh27), and CE (RH22).
What is the f antigen?
The f antigen is a compound antigen that is present when a person inherits an allele of the RHCE gene that codes for both the c and e antigens (specifically, the RHce allele of the RhCE gene), and absent if the person does not inherit that allele. This means that the Rh haplotypes R0 and r are f-positive, since both haplotypes include the RHce allele. This means that the Rh haplotypes R0 and r are f-positive.
Most f-negative people are Rh (positive/negative).
Most f-negative people are Rh positive.
Extracorporeal photopheresis, AKA extracorporeal photochemotherapy, AKA extracorporeal photoimmunotherapy. It is a leukopheresis-based therapeutic procedure. What is the one FDA indication for it?
Treatment of advanced cutaneous T cell lymphoma. But the procedure has been shown to have efficacy in the treatment of numerous other disorders, including GVHD, solid organ transplant rejection, scleroderma, lichen planus, atopic dermatitis, SLE, type 1 DM, and others.
What are the most common indicator cells used in a solid-phase platelet crossmatch?
The most common platelet crossmatch platform utilizes AHG-coated RBCs as the endpoint which ranges from a single button of cells (negative reaction) to a uniform lawn of cells (4+). To perform a platelet crossmatch, patient serum is added to donor platelets to assess compatibility.
Do febrile non-hemolytic transfusion reactions tend to occur at the beginning or end of a transfusion? Are they more common with platelet transfusion or RBC transfusion?
FNHTRs tend to occur towards the end of a transfusion. They are more common with platelet transfusions than RBC transfusions.
The DAT can detect as few as ___ autoantibodies bound to the RBC membrane.
The DAT can detect as few as 150 autoantibodies bound to the RBC membrane.
Up to __% of patients with autoimmune hemolytic anemia have underlying alloantibodies to red cell antigens.
Up to 33% of patients with autoimmune hemolytic anemia have underlying alloantibodies to red cell antigens.
__% of patients with autoimmune hemolytic anemia have warm autoantibodies, __% have cold autoantibodies, and __% have mixed AIHA.
70-80% of patients with autoimmune hemolytic anemia have warm autoantibodies, 15-20% have cold autoantibodies, and 10% have mixed AIHA.
What is the average unit size of whole blood-derived plasma and apheresis collected plasma?
Whole blood-derived plasma unit: 200-250 mL. Apheresis collected plasma unit: 300-600 mL.
Plasma products can be stored at __ C for 1 year and at __ C for 7 years.
Plasma products can be stored at -18 C for 1 year and at -65 C for 7 years.
Frozen plasma products must be thawed at __ to __ C prior to transfusion (takes __ min in a water bath and __ min in a microwave).
Frozen plasma products must be thawed at __ to __ C prior to transfusion (takes __ min in a water bath and __ min in a microwave).
What is the only FDA approved use for cryoprecipitate reduced plasma?
For transfusion or plasma exchange in patients with TTP refractory to FFP. CRP is not deficient in ADAMTS13, the vWF-cleaving protease that is deficient in TTP.
What infectious disease risk is not a cause for deferral for frequent plasmapheresis?
By AABB standards, what is the required minimum number of granulocytes for 75% of units tested?
Unless prepared for neonates, they must contain a minimum of 1 x 10^10 granulocytes in 75% of units tested. Using modalities to improve yield (stimulate donor with G-CSF and/or with steroids; use hydroxyethyl starch to improve sedimentation and collection during apheresis), the combination should increase yield to greater than 1 x 10^11.
What is the required minimum number of platelets in a unit of apheresis platelets and a unit of whole blood derived platelets?
Apheresis platelets: platelet count greater than 3 x 10^11 in greater than 90% of units. Whole blood derived platelets: platelet count greater than 5.5 x 10^10 in greater than 75% of units.