Flow cytometric analysis of anti-platelet antibodies in idiopathic thrombocytopenic purpura.

Anti-platelet antibody measurement may be important in defining the pathogenesis of thrombocytopenic states. In this paper we compared three anti-human immunoglobulin reagents by using them to detect anti-platelet antibodies on the platelet surface and in the serum of 14 patients with chronic idiopathic thrombocytopenic purpura (ITP) and 22 thrombocytopenic disorders. Samples were analyzed by both flow cytometry and a fluorescence microscope. In ITP patients, the direct test was positive in 50% of the cases, while the indirect technique proved to be positive in a slightly higher number of those tested (56%). Furthermore, the number of positive cases was similar for the three reagents used in this study, although the mean percentage of positive platelets was higher for the kappa/lambda monoclonal reagent. These data further support the sensitivity and reproducibility of flow cytometry analysis, which was capable of detecting antiplatelet antibodies in all patients with transfused Cooley's disease (regarded as positive control), as well as in a significant number of patients with ITP or related diseases. On the basis of the data presented here, definitive proof regarding the presence of anti-platelet antibodies in patients with thrombocytopenia still has to be found, and further studies are needed in order to ascertain the autoimmune nature of these disorders.