HPA-genotyping and antiplatelet antibodies in female blood donors.

Cases of passive alloimmune thrombocytopenia have been reported due to transfusions of blood products with antiplatelet antibodies. The aim of our study was to search for antiplatelet antibodies in HPA-homozygous blood donor women once pregnant and also to perform, in case of positivity, a retrospective analysis of platelet counts of the recipients of their blood products. HPA-1, -2, -3 and -5 genotyping were performed on 500 platelet donors (42% women). Circulating antiplatelet antibodies were screened for by MAIPA assay in 122 women who experienced at least one pregnancy and who were homozygous for either HPA-1a, -1b, -3a, -3b, -5a or -5b. None of the women homozygous for HPA-1 or -3 had circulating antiplatelet antibodies. In contrast, two of the 98 women homozygous for HPA-5a and one of the two women homozygous for HPA-5b had circulating antibodies. A retrospective analysis of the medical charts of the 37 recipients of 55 blood components from these three women showed no case of passive alloimmune thrombocytopenia. Our study indicates the presence of platelet-specific antibodies in 2.5% of HPA-homozygous female platelet donors who were previously pregnant. Although none of the recipients developed passive alloimmune thrombocytopenia, this aspect of blood transfusion safety should be addressed by a large prospective trial.