FREQUENCY OF HUMAN PLATELET ANTIGENS AMONG BLOOD-DONORS IN NORTHEASTERN THAILAND

Background: Platelet transfusions have been widely used in Thailand, but little is known about the phenotyping of human platelet antigens. Study Design and Methods: Whole blood was collected from 483 blood donors for preparation of platelets. An improved mixed passive hemagglutination assay was used for this study. Results: Frequencies demonstrated were 100 percent for HPA-1a (PIA1), 15.94 percent for HPA-2b (Sib(a)), 60.25 percent for HPA-3a (Bak(a)), 98.76 percent for HPA-4a (Yuk(b)), 1.86 percent for HPA-4b (Yuk(a)), 5.38 percent for HPA-5b (Br-a), and 97.72 percent for Nak(a). Conclusion: HPA-1a was found in 100 percent of Thais, which is the same frequency as in other Asian populations but somewhat different from that in whites (97.9%). Therefore, HPA-1a will not cause neonatal alloimmune thrombocytopenia or posttransfusion purpura in Thais. According to the frequencies of HPA-2b, HPA-3a, HPA-4a, HPA-4b, HPA-5b, and Nak(a) antigens, they may induce neonatal alloimmune thrombocytopenia, posttransfusion purpura, and platelet refractoriness in Thais.