FLOW CYTOMETRIC DETECTION OF PLATELET-REACTIVE ANTIBODIES AND APPLICATION IN PLATELET CROSS-MATCHING

Background: Alloimmunization against HLA or platelet antigens can caus e refractoriness to platelet transfusions in multiply transfused patie nts. Crossmatching of platelet concentrates is effective in overcoming this problem. Study Design and Methods: A Row cytometric assay was us ed for simultaneous detection of lymphocyte-reactive and platelet-reac tive antibodies in a single sample using fluorescein isothiocyanate-la beled anti-IgG. This assay was compared with the monoclonal antibody-s pecific immobilization of platelet antigens (MAIPA) assay in selected sera containing HLA and platelet antibodies. In a further study, this assay was compared with lymphocytotoxicity test results from thrombocy topenic patients, for whom platelet concentrates were ordered. The res ults of both assays were then correlated with the 1-hour corrected cou nt increment, with a corrected count increment greater than 7500 consi dered as an adequate transfusion response. Results: The results of the MAIPA and flow cytometric assay in detecting platelet-reactive antibo dies correlated well (p<0.0001, r = 0.84). The sensitivity and specifi city of the flow cytometric assay in detecting platelet-reactive antib odies were 94.7 and 96.3 percent, when the MAIPA assay was taken as a reference. in unselected sera from patients, the sensitivity and speci ficity of the flow cytometric assays were, respectively, 72.7 and 91.7 percent in detecting lymphocyte-reactive antibodies and 70.6 and 77.7 percent in detecting platelet-reactive antibodies, when the lymphocyt otoxicity test was used as a reference. With regard to an adequate tra nsfusion response, the sensitivities and efficiencies were 20.0 and 82 .1 percent, 33.3 and 84.3 percent, and 70.0 and 88.6 percent for the l ymphocytotoxicity test and the lymphocyte-reactive and platelet-reacti ve flow cytometric assays, respectively. Conclusion: Flow cytometric c rossmatching appears to be an effective method of detecting platelet-r eactive antibodies that may affect the success of platelet transfusion s. This procedure is well-suited for routine conditions and can be per formed within 2 hours.