Serology Flashcards
(40 cards)
Name three ways to enhance agglutination by IgG molecules
- Add AHG reagent
- Enzyme - removes proteins and acid from RBC surface therefore reducing net negative charge
- Reducing charge of suspending medium
- PEG
- Albumin
Haemolysis can only be detected as an endpoint when a clotted blood sample (serum) is used. Why is this?
Complement requires calcium.
Calcium is chelated by EDTA and citrate.
Why do RBCs need to be washed before grouping?
Most people secrete free A, B and H antigens into bodily fluids including plasma. If RBCs are not washed first, these free antigens may mop up antisera and weaken the reaction causing a grouping anomaly.
3 characteristics of anti-A1 antibodies
- Naturally occurring, cold reactive
- Produced by group A2 and A2B
- Not clinically significant
What is acquired B?
When a group A person acquires the B antigen ==> bacteria modify the A antigen
What antibody do -D- individuals make?
anti-Rh17
What antibody do Rh-null individuals make?
anti-Rh29
Do anti-S and anti-s cause haemolytic transfusion reactions?
Yes
anti-M and anti-N are usually cold reacting and not clinically significant but may be if reacting at 37 degrees.
What antigens are in the Kell system?
Kell (K)
cellano (k)
Kpa and Kpb
Jsa and Jsb
What blood is transfused in an emergency?
Haemolysin-free, group O negative red cells.
Indications for an elution
DAT positive RBCs:
- AIHA
- Drug-induced haemolysis
- HDFN
- Transfusion reaction investigation
Describe how an elution is performed
Acid elution (other methods = heat, chemicals)
Most important step is washing the RBCs well to ensure you are testing antibodies from the RBC, not antibodies in the plasma.
1. Wash DAT positive RBCs in PBS then in wash solution x4. Keep last wash solution (should NOT contain any antibodies)
2. Add acid
3. Add buffer
4. Get supernatant
5. Test supernatant, native plasma and LWS against antibody panel.
Why is EGA treatment of RBCs done?
Removes IgG without destroying RBC antigens ==> allows typing of DAT positive cells.
Indications for genotyping (4)?
- To confirm serotyping e.g. weak D testing
- Recent transfusion
- Rare phenotypes (non anti-sera available)
- Paternal zygosity testing
When is plasma reduced whole blood given to neonates? WBPR
- Exchange transfusion
- Large volume transfusion
* *haematocrit is 60%
Name a requirement specific for donors whose components are used for neonates.
They must have donated (and therefore had donor screening) in the last 6 months
Indications for the use of irradiated blood products
- Allogeneic and Autologous Bone Marrow/PBSC Transplant recipients
- Congenital Cellular Immunodeficiency Disorders
- Intrauterine and all subsequent transfusion and neonatal exchange transfusions
- Hodgkin’s Disease
- Patients receiving purine analogues with associated immunosuppression e.g. fludarabine, pentostatin, cladribine, clofarabine and bendamustine
- Patients receiving alemtuzumab for malignant or non-malignant disorders and transplantation
- Dedicated [directed] donations (from blood relatives)
- HLA matched single donor platelets
- Granulocyte transfusions
What are neonatal platelets suspended in?
Plasma
PAS is not licensed for use in children <6 months old
Plasma units are single donor apheresis units
Approach to transfusion reaction investigation (7)
- Assess patient and symptoms - important to establish etiology and severity. Fever is a key symptom.
- Clerical check - units, patient, request form
- Visual inspection - units, giving sets, pre and post-transfusion sample
- Serology testing - pre and post-transfusion samples (ABO and Rh group, antibody screen, DAT, IAT crossmatch)
==> may need to do antibody ID, eluate, antigen typing etc - Microbiological testing - gram stain and culture on units, blood cultures on patient
- Patient testing for haemolysis - LDH, haptoglobins, bili, retics, haemoglobinuria
- Send haemovigilance report
4 types of transfusion reactions
- Immunologic (acute vs delayed)
- Infectious (bacterial vs viral)
- Metabolic (citrate, K+, iron overload)
- Mechanical/physical e.g. air embolism, TACO
Approach to antenatal diagnosis of HDFN
- Demonstrate maternal alloantibody that is capable of causing HDFN and work out titre
- Determine risk to fetus - paternal phenotyping and/or zygosity testing OR fetal DNA testing
- Assess whether there is fetal anaemia
- MCA PSV
- Invasive - only done at the time of IUTs
Prevention of HDFN
- Anti-D immunoglobulin
- Prophylactic (constant small volume FMH during pregnancy). 28 and 34 weeks.
- At times of sensitising events - Use of O neg blood in emergencies
- Give Kell negative units to women of child-bearing age/potential
- Screening for alloantibodies at booking and at 28 weeks
- Avoidance of unnecessary transfusion
Requirements of blood for IUTs
ABO and Rh matched, Kell negative, antigen negative Hct 0.8 IAT cross match compatible DAT negative Leukodepleted <5 days old Irradiated then transfused within 24 hours CMV negative
Methods of determining FMH volume
- Kleihauer-Bekte - fix in methanol, acid, stain, count (pos, neg and mix controls)
- Flow - Anti-gamma
- Flow - Anti-D
