Antiplatelet antibody determination using platelet factor 3 assay in thrombocytopenic patients.

Platelet factor 3 assay was used to detect antiplatelet antibodies in thrombocytopenic patients with platelet count less than 100,000/cu.mm. A total of 121 specimens was tested. The results gave a positive rate of 83% (61/74) for idiopathic (immune) thrombocytopenic purpura (ITP), 67% for systemic lupus erythematosus (SLE) and 54% (15/28) for others with & 13% (2/16) without history of blood components therapy. The sera from SLE without thrombocytopenic were also checked for the antibody, and a 14% positive rate was obtained. Patients with ITP with complete remission and normal platelet count were 40% positive. Antiplatelet antibody determination by platelet factor 3 assay is a sensitive and reproducible method. It can be performed in most laboratories and requires no specific equipment.