Application Of Cytometric Bead Array In Detecting Platelet-specific Autoantibodies In Patients With Chronic Idiopathic Thrombocytopenic Purpura

Background: Idiopathic thrombocytopenic purpura is an autoimmune disorder characterized by destructive thrombocytopenia due to the formation of autoantibodies against platelet-associated antigens.Despite its clinical importantance,the diagnosis of ITP is one of exclusion at present.The search for a useful clinical laboratory diagnostic assay for the antiplatelet antibodies has been long and difficult.Measurement of platelet associated IgG(PAIgG) are no longer recommended for the diagnosis of ITP .This is primarily due to the fact that platelets normally contain IgG in their alpha granules in an amount that varies with plasma IgG levels and age of the platelets.Fuethermore,the amount of platelet associated IgG is affected by the presence of circulating immune complexes,platelet activation,and drug dependent antibodies.Measurement of platelet specific autoantibodies have different apporach,such as the platelet-associated IgG characterization assay(PAICA),monoclonal antibody immobilization of platelet antigen technique(MAIP).However,they were limitted by low specificity and/or low sensitivity,complicated operation and needing large amount of blood.Objective: To establish a method for detecting platelet-specific autoantibodies by cytometric bead array(CBA) to diagnosis chronic idiopathic thrombocytopenic purpura (CITP).Methods: 40 cases of CITP patients, 20 patients with non-immune thrombocytopenic(NITP) patients and 20 healthy blood samples were extracted from platelets, incubating platelet lysate with coated microbeads after solubilizing the platelets, and then adding FITC labeled goat anti Human polyclonal IgG antibodies,finally analyzing the microbead with flow cytometry analysis.Results: The individual fluorescence level was calculated as a ratio to the negtive control. The mean ratios were 5.50 (range 0.59-22.89) in the CITP group, the NITP group were 1.15 (range 0.67-3.76), the healthy group were 1.05 (range 0.39-1.59).there was highly significant difference (P <0.05)between the CITP patients and both the NITP patiens and the healthy group. If the upper limit of the healthy groups as a community value, the ratio is greater than 1.59 were considered positive, the cytometric bead array diagnostic sensitivity of 92.5% and specificity of 90%.Conclusion: The application of cytometric bead array for detection of platelet-specific antibodies in the diagnosis of CITP has great clinical significance.