Retrospective evaluation of flow cytometry as a platelet crossmatching procedure

We performed a retrospective analysis of flow cytometry as a platelet crossmatching procedure. Sera from 17 alloimmunized refractory patients were tested against 32 donor platelets, which had been stored as platelet‐rich plasma for up to 36 months. Overall, 14/32 (44%) crossmatches were positive. The mean 1 h posttransfusion corrected count increments (CCIs) were 9,195 and 2,269 for a negative and a positive crossmatch, respectively. The predictive value of a positive crossmatch was 86%, whereas the predictive value of a negative crossmatch was 56%. When samples with low background fluorescence or with high panel‐reactive antibody (PRA) levels were evaluated separately, the accuracy of the crossmatch improved from 69% to 80%. When compared to the platelet adhesion immunofluorescence test (PAIFT) and the standard and antiglobulin‐enhanced lymphocytotoxicity tests for the detection of HLA antibodies, flow cytometry appeared to be more sensitive. We conclude that flow cytometry is a useful technique for platelet crossmatching, particularly for alloimmunized patients for whom HLA compatible platelets may not be readily available. © 1994 Wiley‐Liss, Inc.