Platelet antibody determination by platelet factor 3 assay (comparison with radiolabelled serotonin release and platelet aggregometry).

Platelet antibody determination by the PF3 test was carried out in 96 thrombocytopenic patients with various disorders, 31 repeatedly transfused patients with or without thrombocytopenia and 24 patients with autoimmune disease (SLE and myasthenia gravis) without thrombocytopenia. The frequency of a positive test was greatest in the patients with ITP (61%), SLE (50%) or a history of numerous blood transfusions (60%). The patients with myasthenia gravis also showed a considerable frequency (20%) of platelet antibodies detectable by the PF3 test. The PF3 test is less sensitive than the serotonin release test in detecting autoantibodies, but it is more sensitive than aggregometry in detecting isoantibodies and drug-related antibodies.