Healthy blood donors with selective absence of immunoglobulin A: prevention of anaphylactic transfusion reactions caused by antibodies to IgA.

Gel diffusion analysis of sera from 73,569 healthy volunteer blood donors revealed apparent lack of IgA in 113 (1:650) samples, all with normal levels of IgG and IgM. Of these, 30 sera had low levels of IgA, while the remaining 83 had no IgA detectable by a more sensitive hemagglutination inhibition assay. The frequency of absent IgA (algA) was 1:886.