Determination of an appropriate size of unrelated donor pool to be registered for HLA-matched platelet transfusion.

HLA-matched platelet transfusions from related or unrelated donors are effective in correcting bleeding tendencies of alloimmunized thrombocytopenic patients. To supply HLA-matched platelets, registration of unrelated HLA-typed donors and selection of compatible donors are necessary and practical considering HLA polymorphism. In this study, the frequencies of each possible HLA phenotype and of corresponding possible compatible donors were calculated with a computer from the table of frequencies of HLA-A and -B haplotypes. Appropriate sizes of such donor pools were theoretically evaluated in Japanese as well as in European Caucasoid and in North American Caucasoid populations. To enable more than 80 percent of patients to get more than five completely compatible donors, only 5000 donor candidates would be necessary for the Japanese population, whereas 18,000 and 25,000, respectively, would be required for European Caucasoid and North American Caucasoid populations.