Association of autoantibody specificity and response to intravenous immunoglobulin G therapy in immune thrombocytopenia: a multicenter cohort study
- Manuscript handled by: F. R. Rosendaal
- Final decision: F. R. Rosendaal, 1 February 2014
Immune thrombocytopenia (ITP) is a common autoimmune bleeding disorder, in which platelet glycoprotein (GP)IIb–IIIa and GPIb–IX are the two most frequently targeted autoantigens. Our previous studies in animal models of ITP demonstrated that intravenous immunoglobulin G (IVIG) could protect against anti-GPIIb–IIIa autoantibody-mediated thrombocytopenia but failed to ameliorate ITP induced by most anti-GPIb–IX autoantibodies.
The objective of this human study was to evaluate the association between the specificity of antiplatelet autoantibodies and response to IVIG treatment.
In this retrospective study, a cohort of 156 previously untreated adults with severe ITP who underwent IVIG therapy (0.4 g kg−1 day−1 for 5 days) was analyzed. The primary outcome was response defined as platelet counts of ≥ 30 × 109 L−1 and a doubling of baseline counts within 7 days of dosing, and an absence of bleeding.
Results and Conclusions
Among the 66 patients with anti-GPIb–IX autoantibodies, only 24 (36.4%) achieved a response, as compared with 72 of 90 patients (80.0%) who were negative for anti-GPIb–IX autoantibodies (relative risk 2.2; 95% confidence interval 1.6–3.1). This study found no difference in response between patients with anti-GPIIb–IIIa autoantibodies (61.7%) and those without anti-GPIIb–IIIa autoantibodies (61.3%). Logistic regressions, including main effects and the interaction between these two autoantibodies, showed no influence of anti-GPIIb–IIIa autoantibodies on the effects of anti-GPIb–IX autoantibodies with regard to their association with IVIG response. Thus, in adults with ITP, the presence of anti-GPIb–IX autoantibodies is a predictive factor for poor response to IVIG treatment. Trial registration: ClinicalTrials.gov NCT01666795.