Detection Of Platelet-Associated Immunoglobulins By Flow Cytometry For The Diagnosis Of Immune Thrombocytopenia: A Prospective Study And Critical Review

Background and Objectives. Flow cytometry (FC) to Identify platelet-associated (PA) Immunoglobulin (Ig) is a potentially useful diagnostic test for idio-pathic thrombocytopenic purpura (ITP). However, the restricted application of PAIg measurement to thrombocytopenic populations primarily comprised of ITP patients will artificially enhance the test's diagnostic specificity. For this reason, we performed a prospective study in which the results of sensitive technique for detecting PAIg, as is FC, are correlated to the cause of the thrombocytopeniaDesign and Methods. A total of 118 patients with let counts <100x10(9)/L and 30 normal donors with a platelet count >200x10(9)/L were studied for PAIg; employing a flow cytometer, Forty-two children and 20 adults were diagnosed as having immune thrombocytopenia and 27 children and 29 Its had non-immune thrombocytopenia of different etiologies.Results. Raised levels of PAIg were found in 56/62 patients with immune thrombocytopenia and in 34/56 patients with non-immune thrombocytopenia. Diagnostic values of PAIg for the detection of uno thrombocytopenia were: sensitivity 90.3% specificity 39.3%, An enzyme-linked immunoabsorbant assay (ELISA) for the detection of autoantibodies to platelet glycoprotein (GP) complexes used in adults, 9 with immune-related thrombocytopenia and 16 with non-immune thrombocytopenia, in order to determine the true non-specific nature of the positive PAIg test, By ELISA, 8/9 patients with immune thrombocytopenia and 7/16 with non-immune thrombocytopenic disorders showed autoantibodies to platelet GP complexes.Interpretation and Conclusions: PAIg detection by constitutes a sensitive but non-specific assay thus making it unnecessary and inappropriate for establishing the diagnosis of ITP. (C) 2000, Ferrata Storti Foundation.