6. ABO and Rh Discrepancies Flashcards
Most common ABO discrepancy?
No reverse typing rxns (missing antibodies in reverse group)
May be seen in bone marrow or transplant recipients
Mixed field
What reagent is used to distinguish A1 from A2 red cells?
Dolichos biflorus (=anti-A1)
Strong rxn w/ _____ proves that it is not Bombay phenotype
anti-H
Reasons for A1 reverse reacting positively discrepancy?
Probable A2 subgroup with anti-A1
Anti-H lectin
Ulex europaeus
% of A1 and A2 individuals?
80% A1 or A1B
20% A2 or A2B
Cause of B(A) phenotype
Group B individuals have trace amounts of A antigen
What change causes acquired B phenotype?
Bacterial enzyme alters A sugar to resemble B sugar = cross-rxn
This subgroup has strong agglutination reactions w/ anti-H
Other A subgroups (A3,Ax, Aend, Am, Ay, Ael)
How to resolve a positive Rh control?
Repeat w/ washed patient cells
Perform DAT
Most likely reason for no reverse typing rxns?
Patient - old age
Why does A2 subgroup have less A antigen than A1?
A2 gene’s transferase is less efficient at converting H to A substance
Associated w/ multiple myeloma and Waldenstrom’s macroglobulinemia
Rouleaux
Seen in group A1 individuals with diseases of the lower GI tract, Ca of the
colon or rectum, intestinal obstruction, or gram-neg septicemia
Acquired B phenotype
