Flow cytometry antibody screening using pooled red cells

For red cell alloantibody screening, the column agglutination technique (CAT) is used extensively, and flow cytometry (FC) screening has recently been demonstrated to be accurate, rapid, and cost effective. We attempted to determine whether the high sensitivity of FC allows pooling of screening red cells, which is generally not an acceptable technique in CAT.

For FC screening, a commercial two-cell screening panel was utilized for the preparation of individual cells (CSi), as well as pooled cells diluted 1 in 2 (CSp), and 1 in 3 (CS1/3). Another panel was pooled from 120 randomly selected group O donors (RSp).

Comparing the endpoint titrations of serial dilutions, CS1/3 was found to be one dilution, on the average, less sensitive than CSi. In 33 CAT-positive patient samples, the sensitivities of CSi and CSp did not differ significantly without polyethylene glycol (PEG) (30/33, 26/33, respectively, P = 0.125), although they did differ significantly with PEG (32/33, 25/33, respectively, P = 0.016). The percentages of reactive cells among the total cells from RSp were roughly proportional to the relevant antigen frequencies of the local donors.

A trend toward reduced sensitivity was observed using pooled red cells, even via FC. Pooled cells from randomly selected group O donors may be employed as another method by which the characteristics of known antibodies might be assessed.