Platelet antibody screening in patients with leukemia and aplastic anemia

Twenty-three patients with leukemia and ten patients with aplastic anemia who needed long-term platelet transfusion were regularly screened for platelet associated antibodies by a combination of platelet suspension immunofluorescence test (PSIFT) and lymphocytotoxicity test (LCT). Subsequently 13 of the patients (56.5%) with leukemia and 7 of the patients with aplastic anemia (70%) became alloimmunized. The overall incidence was 60.6% (20/33). The concordance of PSIFT and LCT was 100%, suggesting that all the platelet associated antibodies were of HLA specificity. The identified antibodies were anti-A2, A11, A24, B5, B40, B46, B57, B60 and B62. Most of them were antibodies against the high frequency HLA antigens in the Chinese population. There was no dose-response relationship in the development of alloimmunization. The interval between the initiation of platelet transfusion and the development of antibody varied from 10 to 192 days. The immunization is of all or none response. In our study group, about 40% of the patients who did not develop alloantibody within six months will never do so. We concluded that platelet transfusion should not be withheld for fear of alloimmunization and that HLA matched or lymphocytotoxic compatible platelet-donors may be helpful to alloimmunized patients.