ABO Antigen Front Type Discrepancies

  1. 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
  2. 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).
    • Neutralization
  3. Resolution to Excess AB Substance yielding weak or negative front types?
    • Wash patient's cells with saline to remove ABH substance then:
    • Repeat testing.
  4. Resolution of Bone Marrow Transplants of group O donor to group A recipient yielding weak or negative front types.
    • Patient Hx
    • Issue Crossmatch compatible
  5. What are the causes for unexpected front type agglutinations (unexpected antigen)?
    • Rouleaux
    • Polyagglutination
    • Whartons jelly
    • Acquired B
    • Cold Auto
    • Contaminating Antibody
    • Chimera
  6. Resolution of Rouleaux yielding unexpected front type agglutination?

    note: Rouleaux does not occur in AHG phase testing!
    First: Look under scope for stacked coins

    • Foward Typing:
    • Use washed cell suspension

    • For Reverse Typing:
    • Saline replacement
  7. 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
    • or
    • Use monoclonal reagent (non human source)
  8. 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
  9. 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.
  10. 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
  11. Resolution of contaminating antibody in reagent yielding unexpected front type agglutination.
    Use monoclonal reagents.
Card Set
ABO Antigen Front Type Discrepancies
ABO Front Type antigen Discrepancy