Haematology Watch, Vol 3, Issue 2.
LABORATORY HAEMATOLOGY
Discrepancies in blood grouping for ABH system
Mehmood
Definition:
A state of mismatch between forward (cell) and reverse (serum) ABH blood grouping test results.
Types:
1. False:
Due to technical/clerical errors:
i. Mislabelling of blood samples
ii. Failure to add sample in reaction tube
iii. Failure to add reagent in reaction tube
iv. Expired reagent
v. Failure to enter result
vi. Using dirty glass ware
vii. Poor quality control
viii. Uncalibrated centrifuge
ix. Over-/Under-centrifugation
x. Failure to detect proper grade of agglutination
xi. Failure to detach button from tube
xii. Failure to observe haemolysis
xiii. Contaminated reagents
xiv. Warming during centrifugation
xv. Making cell suspension too light or too heavy
xvi. Delaying each step in procedure
xvii. Delay in reading results
2. True:
Due to patient factors.
Presentation:
A. Homogenous reduced/missing agglutination when it is expected
B. Homogenous increased/extra agglutination when it is not expected
C. Mixed-field
agglutination (after O blood group transfusion, Chimerism, Mosaicism, Bone Marrow
transplant,
Exchange transfusion, Foeto-maternal bleeding).
[Note: 1. The weaker reaction is the one to be misleading! Consider stronger reactions as true ones.
2. Therefore, it is very important to detect properly the strength of agglutination]
CLASSIFICATION:
1. Group I Discrepancies:
- This occurs when an expected antibody is missing or weak (in reverse grouping).
- Most common among ABH discrepancies.
- Causes:
New born
Old age
Immunosuppression (Chemotherapy, Stem cell transplant)
Hypogammaglobulinemia (e.g. CLL)
Agammaglobulinemia
2. Group II Discrepancies:
-This occurs when an expected antigen is missing or weak (in forward grouping), or extra antigen is found.
- Causes:
Subgroup of A or B
Weak antigen during leukaemia
Acquired B phenomenon (in group A people)
3. Group III Discrepancies:
- This occurs when extra proteins in plasma cause rouleaux formation or pseudoagglutination.
- Causes:
Elevated globulins (e.g. Multiple myeloma)
Increased fibrinogen
Plasma expanders
Wharton’s jelly
4. Group IV Discrepancies:
- This occurs due to miscellaneous causes.
- Causes:
Alloantibody
Autoantibody
ABO Isoagglutinins
Antibodies other than ABO system
Polyagglutination
Cases to solve:
|
Patient |
Anti-A |
Anti-B |
Anti-A,B |
A1 cells |
B cells |
O cells |
Autocontrol |
|
1 |
4+ |
- |
4+ |
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+ |
- |
After identification of a discrepancy, next step is to resolve them to find out definitely the true blood group. That will be discussed later.