Haematology Watch, Vol.4 , Issue 1.
LABORATORY HAEMATOLOGYResolving discrepancies in blood grouping for ABH system
Mehmood
Discrepancies in blood grouping for ABH system are important challenges in transfusion medicine. Inability to detect such discrepancies can be fatal for the patients.
Before declaring a discrepancy as a true discrepancy, some steps should be taken to exclude pseudo (or apparent) discrepancy to avoid unnecessary workup for a non-existing problem:
1. Repeat the blood grouping procedure.
2. Review clerical work.
3. Check validity of check cells.
4. Verify the strength of grouping reaction.
If repeated grouping reveals same results, there is no clerical error, check cells are valid, and strength of reaction is correctly noted, then it can be said that there is some true ABH discrepancy, which should be recorded, and should be resolved.
The tools for resolving ABH discrepancies include:
1. History suggestive of low levels of expected antibodies or antigens.
2. Warming the sample: for removing agglutination due to cold antibodies, and to give adequate time and temperature for weakly present antibodies..
3. Testing the plasma with A1 cells: for detection of anti-A1 antibody.
4. Saline washing for rouleaux: rouleaux will disappear, agglutination will not.
5. Using anti-A1 lectins
6. Using Oh cells
7. Using potent anti-H
8. Using anti-H lectins
9. Using Absorption & Elution technique
10. Using Saliva studies.
11. Using own anti-B antibody: acquired B antigen will not react with own anti-B antibody
12. Using Antibody panel: to find type of warm-reacting antibody
13. Using DTT (Dithiothreitol): to differentiate IgM from IgG as DTT will lyse IgM only.
14. Using Cold panel: to find type of cold-reacting antibody
Point to ponder:
i. Find the weakest reaction as it is this which is causing trouble. Strong reaction is the true reflection of the test sample ABH status.
ii. Find out missing antibodies or antigens for which a strong reaction is there in reciprocal test slot.
iii. Find out extra reactions.
Resolution of true ABH discrepancies:
|
Patient |
Anti-A |
Anti-B |
Anti-A,B |
A1 cells |
B cells |
O cells |
Autocontrol |
|
1 |
3+ |
- |
3+ |
1+ |
4+ |
- |
- |
|
2 |
3+ |
4+ |
4+ |
1+ |
- |
- |
- |
|
3 |
- |
- |
- |
4+ |
4+ |
4+ |
- |
|
4 |
4+ |
2+ |
4+ |
- |
4+ |
- |
- |
|
5 |
- |
4+ |
4+ |
4+ |
1+ |
1+ |
1+ |
|
6 |
- |
- |
- |
- |
- |
- |
- |
|
7 |
4+ |
4+ |
4+ |
2+ |
2+ |
2+ |
2+ |
|
8 |
4+ |
- |
4+ |
- |
4+ |
3+ |
- |
|
9 |
- |
- |
2+ |
2+ |
4+ |
- |
- |
|
10 |
4+ |
4+ |
4+ |
2+ |
- |
2+ |
- |
Patient 1:
Forward reaction with Anti-A and Anti-AB coupled with reverse reaction with B cells is expected; This patient’s plasma reacts with A1 cells, showing that it has anti-A1 antibody. As the cells of this patients react with Anti-A and anti-AB, this patient has A2 group with anti-A1 antibody.
Next step:
Use anti-A1 Lectin; there will be no reaction.
Patient 2:
Forward reaction with Anti-A, Anti-B, and Anti-AB coupled with reverse reaction with A cells is unexpected; This patient’s plasma reacts weakly with A1 cells, showing that it has anti-A1 antibody. As the cells of this patients react with Anti-A, Anti-B, and anti-AB, this patient has A2B group with anti-A1 antibody.
Next step:
Use Anti-A1 Lectin to react with test cells; there will be no reaction. Or use A2 cells in reverse grouping to yield no reaction as A2B people have no anti-A2 antibody.
Patient 3:
Forward reaction shows that there is no antigen to react with Anti-A or Anti-B. Antibodies in serum against A1 cells and B cells are expected, but not against O cells. This means that that in this patient there is no H substance and thus has developed antibody against O cells having maximum unused H substance. Thus the patient's group is Oh Bombay, with anti-H (warm reacting IgM)
Next step:
Use Anti-H Lectin; there will be no reaction.
Patient 4:
Forward reaction with anti-A and Anti-AB, while reverse reaction with B cells show that this patient has A antgen and anti-B antibody. Forward reaction with anti-B is weak showing a blood group A with acquired B antigen,
Next step:
Take history of bowel obstruction, carcinoma of bowel, Infection by E. coli (it deacetylates Group A antigen)
Test patient cells with own anti-B. Acidified anti-B doesn't agglutinate acquired B antigen.
Patient 5:
B with cold auto-antibody.
Next step:
Use pre-warmed technique; weak reactions will abolish.
Perform elution technique and re-group.
Wash, Using DTT
will help in identification of IgM, then use cold panel.
Patient 6:
Blood group O without anti-A and anti-B.
Next step:
History (new
born, elderly, immunosuppressed).
Incubate at 25 C for 30 minutes to allow any antibody to react more strongly.
Patient 7:
Rouleaux, Cold autoantibody.
Perform elution technique and re-group.
Use DTT to lyse
IgM and thus to abolish the reaction with autocontrol .
Patient 8:
A1 with potent anti-H (cold reacting).
Next step:
Check history of transfusion of O blood group.
Use Anti-A1 and Oh cells.
Patient 9:
Subgroup of A, probably Ax with Anti-A1.
Next step:
Adsorption with anti-A/Elution, saliva studies.
Use anti-A1 Lectin; there will be no reaction.
Patient 10:
Group
Next step:
Antibody panel.