Low incidence of specific anti-platelet antibodies detected by the MAIPA assay in the serum of thrombocytopenic MDS patients and lack of correlation between platelet autoantibodies, platelet lifespan and response to danazol therapy.

We prospectively studied the mechanism of thrombocytopenia in 30 patients with myelodysplastic syndrome (MDS), who had a platelet count <or= 70 x 10(9)/l, and marrows blasts <or= 10% by analysis of platelet lifespan, platelet-bound IgG antibodies by platelet radioactive antiglobulin test (PRAT), and circulating and platelet-bound autoantibodies specifically directed against platelet glycoproteins by indirect and direct MAIPA test. PRAT analysis was positive in 21/30 patients (70%), but antiplatelet antibodies were found in only eight by the MAIPA test. Platelet lifespan was shortened in five cases, only one of whom had a positive MAIPA test. Patients were treated by danazol (600 mg/d), and 9/26 evaluable patients (35%) responded, including three of the five patients with shortened platelet lifespan. No correlation between platelet lifespan, results of PRAT and MAIPA tests, and response to danazol was found. In conclusion, specific antiplatelet autoantibodies, reduced platelet lifespan, and efficacy of androgen therapy on platelets were seen in 20%, 17% and 35% of MDS with thrombocytopenia, respectively, but no correlation between these findings was found in this study.