Indirect detection of anti-platelet antibodies in immune thrombocytopenia

Despite recent advances in the understanding and treatment of immune thrombocytopenia (ITP), its diagnosis remains clinical due to the lack of sensitive laboratory tests. The detection of anti-platelet antibodies (APA) in plasma, although highly specific, is notoriously insensitive. Specialised clinical platelet laboratories routinely perform a screening test of only one dilution for indirect APA testing by flow cytometry. We evaluated the presence of APA using several dilutions of plasma from 61 ITP patients. Herein, we report that serial dilutions can improve the diagnostic value of indirect APA assay for ITP. We show that performing just two dilutions (1:2 and 1:25) would capture over 90% of patients with detectable plasma APA. This method enables indirect testing to become a valuable tool to be incorporated into the management algorithm for ITP.