Frequency and characterization of platelet-specific antibodies in patientswho received multiple platelet transfusions

Background and purpose: Multiple platelet transfusions may induce alloimmun ization. Platelet alloimmunization involves human leukocyte antigen (HLA) a ntibodies and platelet-specific antibodies, which recognize platelet glycop roteins. No data are available about the frequency and characteristics of p latelet-specific antibodies in patients who have received multiple platelet transfusions in Taiwan. Methods: From June through December 1998, blood samples from 103 patients w ho had received multiple platelet transfusions were submitted to our labora tory for examination of platelet antibodies. The samples were first screene d for HLA antibodies or platelet-specific antibodies using a solid phase me thod. Positive sera were further tested using an enzyme-linked immunosorben t assay (ELISA) to identify the specificities of the alloantibodies. Results: Forty of the 103 patients who had received multiple platelet trans fusions were positive for platelet-reactive antibodies. Further study using ELISA showed that 22 patients had both HLA and platelet-specific antibodie s, 12 patients had HLA antibodies alone, and five patients produced platele t-specific antibodies in the absence of HLA antibodies. Most platelet-speci fic antibodies were found among patients who had HLA. antibodies: 81% of pl atelet-specific antibodies were found in HLA-immunized patients. The most f requently involved platelet glycoprotein antigens were Ia/IIa and IIb/IIIa. Conclusions: HLA antibodies were the most frequently found platelet-reactiv e antibodies in Taiwanese patients who had received multiple transfusions, although platelet-specific antibodies were also common. The frequency of pl atelet-specific antibodies was not as low as previously reported.