[Study on the relationship of platelet specific-autoantibodies with therapeutic outcomes by dexamethasone in immune thrombocytopenia purpura].

Objective: To investigate the different outcomes by dexamethasone in adults immune thrombocytopenia purpura (ITP) with different types of platelet specific-autoantibodies.

Methods: A total of 185 ITP were enrolled, 61 males and 124 females, with a median age of 42 (18-83) years, including 117 newly diagnosed, 35 persistent, and 33 chronic cases. All the patients received the dexamethasone at an initial dose of 40 mg per day for 4 days and a low dose of 5-10 mg for 3-4 weeks. The platelet specific-autoantibodies were identified by the modified monoclonal antibody-specific immobilization of platelet antigen (MAIPA) assay.

Results: Among the IgG positive patients, the response rates in anti-GPIIb/IIIa antibody, anti-GPIbα antibody, both antibody positive, and both antibody negative were 87.5%, 50.0%, 68.0%, and 72.3% (χ²=11.489, P<0.05), respectively. Among the IgM positive patients, the response rates in the four groups were 82.1%, 71.4%, 61.9%, and 68.9% (χ²=2.719, P=0.437), respectively. Among the GPIbα antibody positive patients, the response rates in IgG alone, IgM alone, both positive, and both negative were 52.4%, 59.1%, 76.1%, and 77.9% (χ²=10.811, P<0.05), respectively. Among the GPIIb/IIIa antibody positive patients, the response rates in the four groups were 73.3%, 71.0%, 78.6%, and 66.3% (χ²=1.374, P=0.719), respectively.

Conclusion: ITP patients with GPIbα-IgG antibody have worse response to dexamethasone treatment.