title: Association of autoantibody specificity and response to intravenous immunoglobulin G therapy in immune thrombocytopenia: a multicenter cohort study.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  The objective of this human study was to evaluate the association between the specificity of antiplatelet autoantibodies and response to IVIG treatment.
  
  
  METHODS
  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 × 10(9)  L(-1) and a doubling of baseline counts within 7 days of dosing, and an absence of bleeding.
  
  
  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.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT01666795.
authors: Qilu Hospital, Shandong University, Jinan, China.
authors: J
authors: J
authors: Peng
authors: S-H
authors: SH
authors: Ma
authors: J
authors: J
authors: Liu
authors: Y
authors: Y
authors: Hou
authors: X-M
authors: XM
authors: Liu
authors: T
authors: T
authors: Niu
authors: R-R
authors: RR
authors: Xu
authors: C-S
authors: CS
authors: Guo
authors: X-M
authors: XM
authors: Wang
authors: Y-F
authors: YF
authors: Cheng
authors: H
authors: H
authors: Ni
authors: M
authors: M
authors: Hou
mesh_terms: D000328:Adult; D000918:Antibody Specificity; D001323:Autoantibodies / Q000737:chemistry*; D001792:Blood Platelets / Q000276:immunology; D001835:Body Weight; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000627:therapeutic use*; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000276:immunology; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000097:blood / Q000276:immunology* / Q000628:therapy*; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G; D016756:Immunoglobulins, Intravenous; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019038:Platelet Glycoprotein GPIb-IX Complex; C032193:glycoprotein receptor GPIb-IX
keywords: Platelet Glycoprotein GPIb-IX Complex; antibody specificity; autoimmune thrombocytopenia; intravenous immunoglobulins; therapy