Antiplatelet antibodies detected by the MAIPA assay in newly diagnosed immune thrombocytopenia are associated with chronic outcome and higher risk of bleeding.

Immune thrombocytopenia (ITP) results in part from the presence of platelet antibodies, which can be demonstrated by the Monoclonal Antibody-Specific Immobilization of Platelet Antigens (MAIPA) assay. The aim of our study was to correlate the presence of antiplatelet autoantibodies and the natural history of ITP. We performed a retrospective, single-center study of 108 adults with newly diagnosed ITP who had indirect MAIPA assay performed at disease onset. Chronic ITP was defined by the presence of thrombocytopenia after 1 year. Bleeding diathesis was evaluated with a bleeding score. At baseline, patients with a positive indirect MAIPA have a greater bleeding score than patients with negative MAIPA assay [median (interquartile) = 8 (6-12) vs 2 (0-6), p = 0.002]. Patients with a positive indirect MAIPA also had a higher rate of chronic ITP (92.9 vs 68.7 %, p = 0.06). In multivariate analysis, a positive indirect MAIPA result and a platelet count at onset ≥10 × 10(9)/L remained independently associated with chronic ITP [adjusted OR (aOR) = 8.01; 95 % confidence interval (CI), 0.98-66.6; p = 0.05 and aOR = 3.09; 95 % CI, 1.18-8.10; p = 0.02, respectively]. Furthermore, when we analyzed together the results of direct (n = 41) and indirect MAIPA, the same results were observed. Thus, indirect MAIPA positivity at disease onset is associated with more severe hemorrhage and predicts a chronic course in adult ITP patients. MAIPA assay could be useful in the management of ITP patients when it is performed at diagnosis.