Detection of various platelet-associated immunoglobulins by flow cytometry in idiopathic thrombocytopenic purpura

Background: In 1975, Dixson reported that anti-platelet IgG on platelets from patients with idiopathic thrombocytopenic purpura (ITP) is greater than in normal people, by determining anti-platelet antibodies directly on the platelet surface with a quantitative complement lysis-inhibition-assay. Since then, platelet-associated IgG (PAIgG) has been thought of as evidence of ITP. Although platelets from ITP patients show significantly higher PAIgG values than from normal control individuals, PAIgG is not specific for autoantibody because it increases in other than immune ITP patients. Methods: We analyzed positive platelet percentage with various platelet-associated immunoglobulins: IgG, IgM, IgA, and total immunoglobulins, in the blood from 17 normal donors and 23 ITP patients. Results: The specificity for ITP disease was better in flow cytometry than in ELISA, because, other than ITP, only aplastic anemia was positive in flow cytometry; however, various disorders (aplastic anemia, chronic lymphocytic leukemia, acute myeloid leukemia, and myelodysplastic syndrome) showed positive in ELISA. Flow cytometry methods had the same sensitivity for ITP disease as ELISA. However, it is supposed that there was no nonimmune ITP in this study because the PAIgG negative patients (n = 1) showed positive results in flow cytometry. Conclusion: Flow cytometry method was effective for ITP screening, especially for specificity. (c) 2005 International Society for Analytical Cytology.