[Establishment of Flow Cytometric Immunobead Array Assay for Quantitation of Platelet-Specific Antibodies and Its Application].

Objective: To establish a flow cytometric immunobead array assay (FCIA) to quantify platelet antibodies and to explore its application in the diagnosis and treatment of ITP.

Methods: The guantitative standard curve was established by binding the human IgG of known concentration on antibody-coated microbeads; at the same time, the platelet-specific antigen and antibody complex was captured and levels of platelet antibodies were detected using the microbeads coated by 5 kinds of antibodies against platelets suca as GPIX (SZ1), GPⅠb (SZ2), GpⅢa (SZ21), GPⅡb (SZ22) and p-selection (SZ51). The fluorescence signal detected by flow cytometry were transformed into the conentration of platelet antibodies in samples through the quantitative standard curve, thereby establishing the method for quantititive detection of platelet-specific antibodies in plasm samples (FCIA), moreover the property, efficiency and clinical application of establishod FCIA method were evaluated.

Results: The FCIA could detect 5 kinds of antibodies against GPIX, GPⅠb, GpⅢa, GPⅡb and β-selection within a broad range of 33.29-1280 ng/ml, 45.17-1280 ng/ml, 42.07-1280 ng/ml, 46.40-1280 ng/ml, 42.48-1280 ng/ml and 42.48-1280 ng/ml respectively, and their recovery rates were 115.23%, 112.58%, 117.47%, 107.64% and 112.67% respectively. The intra-assay coefficient of variation (CV) for anti- GPIX, -GPⅠb, -GpⅢa, -GPⅡb and p-selection antibodies was 3.54%, 3.63%, 4.66%, 6.43% and 6.67% respectively, and the inter-assay CV for above mentioned antibodies were 10.89%, 7.57%, 10.34%, 6.95% and 10.72% respectively. The detection showed that the levels of 5 kinds of platelet-specific antibodies in ITP group all were higher than those in non-ITP and healthy control groups (P＜0.01). The sensitivity, specificity and accuracy of quantitatively detecting 5 kinds of antibodies for diagnosis of ITP by FCIA were 68.29%, 84.98% and 78.95% respectively, while the sensitivity, specificity and accuracy of detecting 5 kinds of antibodies by modified indirect MAIPA were 41.46%, 90.41% and 72.81% respectively.

Conclusion: The established quantitative FCIA for detection of antibodies provides a powerful tool for diaghosis and evaluation of therapeutic efficacy and prognosis of ITP patients.