[Serologic characterization of platelet-associated IgG and its significance for the diagnosis of thrombocytopenias].

Detection of platelet autoantibodies in patients with autoimmune thrombocytopenic purpura (AITP) is a notoriously difficult task. The quantitative measurement of PAIgG is rather unreliable as a diagnostic procedure because it tends to yield false positive results in thrombocytopenic patients. In this study two different techniques allowing discrimination of platelet autoantibodies and unspecific IgG bound to the patients' autologous platelets were compared to the quantitative measurement of PAIgG in thrombocytopenic patients. These two techniques are: 1. investigation in the platelet adhesion immunofluorescence test of eluates prepared from the patients' platelets and 2. detection of platelet autoantibodies on the isolated glycoprotein complexes IIb/IIIa, Ib/IX, and Ia/IIa. Results show that positive results with these two techniques are much more specific for autoimmune thrombocytopenia than elevated amounts of PAIgG measured on whole platelets.