Significant numbers of apheresis-derived group O platelet units have "high-titer" anti-A/A,B: implications for transfusion policy.

Transfusion of group O single-donor apheresis PLTs (SDP) to group A recipients has resulted in intravascular hemolysis and mortality. Owing to low availability of type-specific SDPs, transfusion services sometimes issue ABO-mismatched PLTs. After observing two cases of acute hemolysis following infusion of O SDPs to group A patients, where both recipient eluates revealed anti-A specificity, a prospective study to determine the prevalence of "high-titer" anti-A/A,B in group O SDPs was commenced. One hundred group O SDP samples were tested. Titers of at least 64 and/or 256 from either buffered (generally reflective of IgM antibodies) or anti-IgG gel cards, respectively, were considered critically high. Twenty-eight and 39 percent of samples revealed critically high anti-A/A,B IgM and IgG titers, respectively. IgM titers were at 1:64 (18%), 128 (6%), and 256 (4%), whereas IgG titers were at 1:256 (28%), 512 (7%), 1024 (2%), and 2048 (2%). The prevalence of critical anti-A/A,B titers in group O SDPs is relatively high. Thus, the risk of minor side ABO mismatch and potential intravascular hemolysis during group O SDP transfusion to group A recipients may be significant. Based on these data, a policy was instituted to test anti-A/A,B titers in O SDPs prior to "out-of-group" transfusion.