Enzyme labeled immunosorbant assay (ELISA) for detection of platelet antibodies

Although it is widely accepted that patients with immune thrombocytopenia produce platelet antibodies, the demonstration of such antibodies has been difficult and time consuming. A simple and quick enzyme linked immunoassay for platelet antibodies is presented. The platelet associated IgG is coupled with alkaline phosphatase labeled anti-IgG. The resultant complex is determined spectrophotometrically using p-nitrophenyl phosphate as substrate. With this technique, excess of IgG on platelets was detected in 24 out of 33 patients (72 percent) with immune thrombocytopenic purpura and four out of four thrombocytopenic patients with systemic lupus erythematosus. The results of this assay correlate quantitatively with Dixon er al3 complement lysis inhibition assay (r = 0.82).