ABO-RH and DONOR SCREENING.pdf-brainscape

Question 1

What are the key characteristics of the ABO blood group system?

Answer 1

Discovered by Karl Landsteiner in 1901. Differences in human blood are due to the presence or absence of certain antigens and antibodies. Individual blood group depends on inherited genes. ABO and RH are the most important blood groups.

Question 2

Where are the genes located that determine ABO blood type?

Answer 2

Two codominant genes are located at the ABO locus. The precursor H gene is located at the Hh locus. Genes at three separate loci: ABO, Hh, and Se.

Question 3

What are the roles of the H and Se genes in ABO antigen production?

Answer 3

H gene is responsible for the production of H-antigen, a precursor structure on which A and B antigens are made. Se gene forms ABO antigen in secretion.

Question 4

What glycosyltransferases, immunodominant sugars, and antigens are associated with H, A, and B genes?

Answer 4

H: L-fucosyltransferase, Immunodominant Sugar: L-fucose, Antigen: H. A: N-acetylgalactosaminyltransferase, Immunodominant Sugar: N-acetyl-D-galactosamine, Antigen: A. B: D-galactosyltransferase, Immunodominant Sugar: D-galactose, Antigen: B.

Question 5

What are the key differences between monoclonal and polyclonal antibodies?

Answer 5

Monoclonal: Tissue culture derived, gives more specific reactions, very sensitive for weaker reactions. Polyclonal: Human source.

Question 6

What are the characteristics and components of Anti-A and Anti-B reagents?

Answer 6

Anti-A reagent: Monoclonal antibody (IgM), highly specific, blue dye (bromophenol blue, thymol blue, Patent blue). Anti-B reagent: Lectin (Dolichos biflorus), monoclonal antibody (IgM), highly specific, yellow dye (acriflavine, tartrazine yellow), lectin (Griffonia Simplicifolia).

Question 7

What is the difference between forward and reverse typing?

Answer 7

Forward typing: Process of antigen detection in an individual’s RBC. Reverse typing: Detects present antibodies anti-a and anti-b in their serum.

Question 8

What are the expected reactions for blood types A, B, AB, and O in forward and reverse typing?

Answer 8

A: Anti-A (+), Anti-B (0), Known A (0), Known B (+). B: Anti-A (0), Anti-B (+), Known A (+), Known B (0). AB: Anti-A (+), Anti-B (+), Known A (0), Known B (0). O: Anti-A (0), Anti-B (0), Known A (+), Known B (+).

Question 9

What are common technical errors that can lead to ABO discrepancies?

Answer 9

Incorrect labeling, failure to add reagents, mix-up in samples, contaminated reagents, uncalibrated centrifuge. Results must be recorded as soon as they are obtained.

Question 10

How are ABO discrepancies resolved?

Answer 10

Review technical factors, obtain patient history (age, diagnosis, transfusion history, medications, pregnancy). Repeat testing with saline suspension of RBCs. Draw a new sample if necessary.

Question 11

What are the four main groups of ABO discrepancies?

Answer 11

Group 1: Weakly reacting/missing antibodies. Group 2: Weakly reacting/missing antigens. Group 3: Protein/plasma abnormalities. Group 4: Miscellaneous problems.

Question 12

What causes weakly reacting/missing antibodies (Group 1 discrepancies)?

Answer 12

Missing or weak isoagglutinins due to decreased antibody production. Commonly seen in newborns, elderly, patients with CLL, immunodeficiency diseases, or hypogammaglobulinemia.

Question 13

How are weakly reacting/missing antibodies (Group 1 discrepancies) resolved?

Answer 13

Check patient’s medical history. Allow 15-30 minutes for serum to react with reagent cells at room temperature. Incubate serum-cell mixtures at 4°C for 15-30 minutes. Utilize auto control and O cell control.

Question 14

What causes weakly reacting/missing antigens (Group 2 discrepancies)?

Answer 14

Subgroups of A or B, leukemias, Hodgkin’s disease, acquired B phenomenon, presence of excessive BGSS molecules, antibodies to low-prevalence antigens in reagent anti-A or anti-B.

Question 15

How are weakly reacting/missing antigens (Group 2 discrepancies) resolved?

Answer 15

Allow test mixture to sit at room temperature for up to 30 minutes. Incubate at 4°C for 15-30 minutes. Use Group O and autologous cells as controls. Retest RBCs. Washing the patient cells free of the BGSS substances with saline.

Question 16

What causes protein or plasma abnormalities (Group 3 discrepancies)?

Answer 16

Elevated levels of globulin or fibrinogen, plasma expanders, Wharton’s Jelly.

Question 17

How are protein or plasma abnormalities (Group 3 discrepancies) resolved?

Answer 17

Microscopic examination, washing with saline, run antibody screen.

Question 18

What are some miscellaneous problems that can cause ABO discrepancies (Group 4)?

Answer 18

Cold-reactive autoantibodies, patient has circulating RBCs of more than one ABO group, unexpected ABO isoagglutinins, unexpected non-ABO alloantibodies.

Question 19

How are miscellaneous ABO discrepancies (Group 4) resolved?

Answer 19

Incubate at 37°C, wash with saline 3x, retype. Pre-warm serum and reagent at 37°C for 10-15 minutes. Treat with 0.01M DTT. Perform cold auto adsorption. Use Anti-A1 lectin. Test serum with A1, A2 and O cells. Run autologous control. Perform AB panel.

Question 20

What are the key characteristics of the Rh blood group system?

Answer 20

D is the most immunogenic. Antibodies are mostly immune type.

Question 21

What are the advantages and disadvantages of different types of Rh antisera?

Answer 21

Saline-based: Limited availability, increased incubation. High protein: Potentiators may cause false positive reactions, detects weak D. Low protein: Decreased false positive, readily available. Monoclonal blends: More specific encounters, not human derived.

Question 22

What are the mechanisms behind weakened expression of the D antigen?

Answer 22

Genetic cause: Inheritance of genes that code for D antigens are complete but few in number. Position effect: Steric arrangement of C antigen interferes with D antigen expression. Partial D or D mosaic: D antigen is weakened or missing. Del: Extremely low number of D antigen sights.

Question 23

How is Weak D testing performed?

Answer 23

All negative tubes should be incubated at 37 deg C for 15 minutes. Add AHG to enhance any weak reactions, centrifuged, read. If weak D test and patient control are negative, add Coombs check cells. If agglutination does not occur, the AHG has been inactivated, and the test is invalid. Repeat test on well washed cell suspension

Question 24

What can cause false negative reactions in Rh typing?

Answer 24

Immunoglobulin-coated cells, saline suspended cells, unwashed cells, resuspension too vigorous, centrifugation too short, RPM too low.

Question 25

What can cause false positive reactions in Rh typing?

Answer 25

Cell suspension too heavy, cold agglutinins, test incubated too long or drying, rouleaux, fibrin interference, bacterial contamination of reagent, centrifugation too long, RPM too high.

Question 26

How are false negative reactions in Rh typing corrected?

Answer 26

Use saline-active typing reagent. Resuspend all tube test gently. Repeat test using longer centrifugation time. Repeat using higher RPM.

Question 27

How are false positive reactions in Rh typing corrected?

Answer 27

Adjust suspension, retype. Wash with warm saline, retype. Follow manufacturer’s instructions. Use saline washed cells, retype. Open new vial of reagent, retype. Repeat the test using shorter centrifugation time. Repeat test using lower RPM.

Question 28

What is the purpose of donor screening?

Answer 28

Ensures safety of both blood donor and recipient. Includes medical history questionnaire, physical examination, and serologic testing.

Question 29

What are the steps in the donor screening process?

Answer 29

Donor registration, medical history questionnaire, counselling, physical examination, informed consent, donation (autologous, directed, apheresis), post-donation care.

Question 30

What information is included in donor registration?

Answer 30

Full name, date and time of donation, permanent address, contact number, gender, birthday, age, consent to donate, additional information.

Question 31

What are the age requirements for allogeneic and autologous blood donation?

Answer 31

Allogeneic donation: Minimum age >16 years (16-17 requires parental consent, 60-65 requires doctor’s clearance). Autologous donation: No age restriction.

Question 32

What additional information may be collected during donor registration?

Answer 32

Civil status, nationality, religion, education, occupation, email address, ID number, name of patient (directed donation), race (matching specific phenotypes), CMV status.

Question 33

What elements are essential for informed consent in blood donation?

Answer 33

Autonomy of the donor, informed on procedure and risks, educated on transfusion transmissible infections, voluntary donation, consented to screening.

Question 34

What are the key characteristics of the Donor History Questionnaire (DHQ)?

Answer 34

Self-administered questionnaire (yes/no questions), reviewed by trained personnel in a secluded area, standardized.

Question 35

What is blood donor deferral?

Answer 35

Temporary or permanent exclusion from donating blood due to health or behavioral factors.

Question 36

What are the different types of blood donor deferral?

Answer 36

Permanent: Donor is never qualified to give blood. Indefinite: Donor is not permitted to provide blood for an unanticipated period. Temporary: Donor is prohibited from giving blood for a brief amount of time.

Question 37

Give examples of conditions leading to permanent blood donor deferral.

Answer 37

Hepatitis C infection, CJD infection.

Question 38

Give examples of conditions leading to indefinite blood donor deferral.

Answer 38

People receiving insulin (bovine), people having M2M sexual contact (1977), receiving blood from United Kingdom.

Question 39

Give examples of conditions leading to temporary blood donor deferral.

Answer 39

12 months: blood transfusion, Yellow Fever vaccination, sexual contact with M2M or Hepatitis. 3 years: diagnosed for Malaria. 48 hours: Aspirin intake.

Question 40

How is the anticoagulant adjusted for underweight donors?

Answer 40

Each blood bag contains 63 mL anticoagulant for 450 mL of blood. Volume to collect = (donor’s weight in kg/50) x 450 mL. Volume of Anticoagulant = (Volume to collect/450) x 63 mL. Volume of Anticoagulant to be removed = 63mL - Volume of Anticoagulant.

Question 41

What are the key components of the physical examination during donor screening?

Answer 41

General appearance (jaundice, anxiety, drug/alcohol influence), weight (minimum 110 lbs or 50 kgs), temperature (≤37.5°C), pulse (60-100 bpm), blood pressure (<180 mmHg systolic, <100 mmHg diastolic).

Question 42

What are some medications that cause deferral?

Answer 42

Feldene (2 days), Plavix and Ticlid (14 days), Proscar, Avodart, Propecia (1 month), Accutane (6 months), Hep B Immune Globulin (12 months), Experimental Medication or unlicensed (experimental) vaccine (1 year, unless stated otherwise), Soriatane (3 years), Growth hormone from human pituitary glands (Permanent deferral), Tegison (Permanent deferral), Insulin from cows (bovine or beef, insulin) (Indefinite deferral).

Question 43

What is pre-transfusion testing?

Answer 43

Use of serologic principles and tests to ensure the compatibility and safety of blood units during transfusion. Involves proper specimen collection, compatibility tests, and special clinical situations.