ABO Antigen Front Type Discrepancies
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What are the causes for weak or missing antigens of ABO front type?
- ABO Subgroup
- Excess AB Substance - Seen with GI Carcinoma
- Bone Marrow Transplant
- Leukemia, Hodgkins
Resolution for ABO Subgroups yielding weak or missing front types?
- Increase incubation time
- Decrease temperature
- Test with anti-A,B
- Adsorption Elution (if you can adsorb antibody on to red cell, then antibody must be there).
Resolution to Excess AB Substance yielding weak or negative front types?
- Wash patient's cells with saline to remove ABH substance then:
- Repeat testing.
Resolution of Bone Marrow Transplants of group O donor to group A recipient yielding weak or negative front types.
- Patient Hx
- Issue Crossmatch compatible
What are the causes for unexpected front type agglutinations (unexpected antigen)?
- Whartons jelly
- Acquired B
- Cold Auto
- Contaminating Antibody
Resolution of Rouleaux yielding unexpected front type agglutination?
note: Rouleaux does not occur in AHG phase testing!
Look under scope for stacked coins
- Foward Typing:
- Use washed cell suspension
- For Reverse Typing:
- Saline replacement
Resolution of Pollyagglutination yielding unexpected front type agglutination.
Usually those with anti-I.
This is caused by an antigen that is NOT normally exposed on the red cell membrane: bacterial enzymes, mutation of hematopoietic tissue, or inherited conditions.
- Test cells with cord sera = Neg Result
- Test cells with adult sera = Pos Result
- Use monoclonal reagent (non human source)
Resolution of Acquired B yielding an unexpected front type agglutination.
Found in those with A1 phenotype who have a hx of colon cancer or septicemia.
- Negative Autocontrol:
- a. Patient's own anti-B does not react with their cells.
- Test pt's cells with human anti-B serum that has been acidified (pH 6.0) = neg reaction
- Test with monoclonal anti-B that manufacturer states will not react with acquired B.
- Secretor Studies
Resolution of Cold Auto yielding an unexpected front type.
- Wash Red Cells with 37C saline to dissociate agglutination.
- Treat pt cells with sulfhydryl reagent (DTT) to break up the IgM molecules.
Resolution of Chimera yielding unexpected front type agglutination?
Seen in twins, 2 sperm fertilize one egg, transplants, transfusions, or fetal maternal bleed.
- Look for MIXED FIELD!
- Patient Hx
Resolution of contaminating antibody in reagent yielding unexpected front type agglutination.
Use monoclonal reagents.
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