Relative Efficacy Of Steroid Therapy In Immune Thrombocytopenia Mediated By Anti-platelet GPIIbIIIa Versus GPIbα Antibodies

Background: ITP is a common autoimmune disease characterized by autoantibody-induced platelet destruction and resulting in bleeding disorders. The major targeted platelet autoantigens are GPⅡbⅢa and GPIb complexes. We previously demonstrated that anti-GPIbα-mediated-ITP is less responsive to IVIG treatment. We tested here if steroid therapy has equal efficacy in patients with ITP mediated by these two different antibodies.Methods A total of 176 ITP patients (122 females and 54 males) were recruited for the present study and were treated with steroids. Patients were first treated with Dexamethasone, then changed to oral administration of Prednisone. Patients'blood samples were collected before therapy. Specific antibodies were measured with MAIPA. At the same time, compare the influence in checking out of the antoantigens in different anticoagulants.Results From the 176 ITP patients studied, 24.4% (43/176) had antibodies against GPⅡbⅢa, 19.3% (34/176) had antibodies against GPIbα, 30.7% (54/176) had antibodies against both GPⅡbⅢa and GPIbα(double positive), and 25.6% (45/176) had no detectable antibody to either of these two antigens (double negative)。After patients were subjected to the described steroid therapy, we found that a majority of patients with antibodies against GPⅡbⅢa (31/43 = 72.1%) were sensitive to the treatment (Table 2). Their response rate was 2-3 times higher than the response rate from patients with antibodies against GPIbα(9/34 = 26.5%) (χ~2 = 15.832, P <0.01) or those patients double positive for both GPIb? and GPⅡbⅢa antibodies (16/54 = 29.6%) (χ~2 = 17.282, P <0.01). No significant difference in steroid responsiveness was observed between patients with anti-GPIbαantibodies and those with double positive antibodies (χ~2 = 0.102, P >0.05). Furthermore, no significant difference was observed between patients with anti-GPⅡbⅢa antibodies and those with no detectible antibodies (36/45 = 80%) (χ~2 = 0.757, P >0.05), although patients double negative for antibodies had a weak trend towards being more sensitive to steroid therapy. From the 80 ITP patients , 43had antibodies against GPⅡbⅢa in EDTA anticoagulant,while 52 had antibodies against GPⅡbⅢa in heparin anticoagulant. No significant differences between them(χ~2=3.05,P>0.05),and there is the similar results with the GPIb? antibodies(χ~2=2.08,P>0.05).Conclusions Detection of anti-GPIbαantibodies may be an important marker to identify patients who have a high probability of being refractory to steroid therapy. The influence in checking out of the antoantigens in different anticoagulants deed to expend the samples.