4. Observations
We found 51 cases (0.04%) of ABO discrepancies out of
104,010 donors. Frequency wise cause of ABO discrepancy
found at our centre after excluding technical errors
were – weak/low avidity anti B antibodies (58.8%), weak
A or subgroup of A antigen (19.6%), alloantibodies (9.8%),
not resolved (5.8%), weak B or subgroup of B antigen
(3.9%) and Bombay blood group (1.9%) (Table 1). To best
of our knowledge, this is the first study proving the data
on frequency wise occurrence of ABO discrepancies.
Ten cases of weak subgroups of A were observed
(including three with blood group A (subgroup/weak a
antigen) B). One of these is discussed. Forward grouping
showed O blood group, whereas, reverse grouping showed
A blood group (Table 2). A repeat test after incubation at
4 C could not resolve the discrepancy. On reverse grouping
with A1 Cell, A2 Cell, B Cell and O cell at RT & 4 C, reaction
with A1 Cell and no reaction with A2 Cell in both
phases indicated the presence of Anti-A1 in the donor plasma
(Table 3). There was agglutination with AB-antisera in
polyclonal card but not in monoclonal card, indicating
presence of A or B antigen on red cells (Fig. 1). There was
no reaction with Anti A1 (human) and Anti A1 (lectin)
and agglutination with Anti-H (lectin) indicating that there
was no A1 antigen on the red cells. Following cold adsorption
and heat elution studies, strong reaction of eluate
on frequency wise occurrence of ABO discrepancies