title: The value of rheumatoid factor and anti-citrullinated protein antibodies as predictors of response to infliximab in rheumatoid arthritis: an exploratory study.
abstract: OBJECTIVE
  It remains unclear whether autoantibodies are useful biomarkers to tailor the choice of biological treatment in RA. We investigated the relationship between the presence and levels of different RF and ACPA isotypes and the response to TNF blockade in an exploratory study.
  
  
  METHODS
  A total of 101 active RA patients were prospectively treated with infliximab (3 mg/kg). Changes in disease activity were monitored by the 28-joint DAS (DAS-28). Serum levels of different isotypes [immunoglobulins M, G and A (IgM, IgG and IgA)] of RF and anti-citrullinated peptide antibodies were measured by ELISA.
  
  
  RESULTS
  The mean DAS-28 decreased from 5.9 (1.1) at baseline to 4.0 (1.3) at Week 16 of infliximab treatment (P < 0.001). High baseline levels of different isotypes of RF (all P < 0.008), ACPA IgM (P = 0.008) and ACPA IgG (P = 0.07) were associated with an absolute decrease in DAS-28 after TNF blockade. This relationship persisted after adjusting for DAS-28 at baseline. However, the different isotypes of baseline RF and ACPA levels accounted for only a small proportion of variance in treatment response (RF: R² between 7 and 12% and ACPA: R² between 4 and 7%). The simultaneous presence of all three isotypes of RF or ACPA had no additive value.
  
  
  CONCLUSIONS
  Presence as well as the titres of RF and IgM ACPA at baseline are significantly correlated with better response to infliximab treatment. However, this correlation is not strong enough to allow a reliable prediction in individual patients. Trial Registration. ISRCTN Register, http://www.controlled-trials.com/isrctn/, ISRCTN36847425.
authors: Department of Clinical Immunology and Rheumatology, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands.
authors: Ruth
authors: R
authors: Klaasen
authors: Tineke
authors: T
authors: Cantaert
authors: Carla A
authors: CA
authors: Wijbrandts
authors: Christine
authors: C
authors: Teitsma
authors: Danielle M
authors: DM
authors: Gerlag
authors: Theo A
authors: TA
authors: Out
authors: Monique J
authors: MJ
authors: de Nooijer
authors: Dominique
authors: D
authors: Baeten
authors: Paul P
authors: PP
authors: Tak
mesh_terms: D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D005260:Female; D006304:Health Status; D006801:Humans; D000069285:Infliximab; D007596:Joints / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000097:blood* / Q000276:immunology; D011379:Prognosis; D012217:Rheumatoid Factor / Q000097:blood*; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D001323:Autoantibodies; D015415:Biomarkers; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor; D000069285:Infliximab