title: Predictive value of antibodies to cyclic citrullinated peptide in patients with very early inflammatory arthritis.
abstract: OBJECTIVE
  To study the prognostic value of antibodies to cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF), alone and in combination, in patients with very early synovitis.
  
  
  METHODS
  A cross-sectional study was performed in patients with established inflammatory and noninflammatory disease to validate the assay in our unit and confirm previously reported sensitivities and specificities of anti-CCP antibodies. Subsequently, patients with synovitis of 3 months' duration were followed for 72 weeks and the ability of anti-CCP antibodies and RF to predict the development of rheumatoid arthritis (RA) and persistent inflammatory arthritis was assessed.
  
  
  RESULTS
  One hundred twenty-four patients were assessed in the initial cross-sectional study. Anti-CCP antibodies and RF were detected by ELISA in only 4% of patients with non-RA inflammatory disease and in no patient with noninflammatory disease. Ninety-six patients with very early synovitis were assessed longitudinally. In these patients with early arthritis, the combination of anti-CCP antibodies and RF had a specificity, positive predictive value (PPV), sensitivity, and negative predictive value (NPV) for a diagnosis of RA of 100%, 100%, 58%, and 88%, respectively. The specificity, PPV, sensitivity, and NPV of this antibody combination for the development of persistent disease-fulfilling classification criteria for RA were 97%, 86%, 63%, and 91%, respectively.
  
  
  CONCLUSIONS
  In patients with synovitis of 3 months' duration, a combination of anti-CCP antibodies and RF has a high specificity and PPV for the development of persistent RA. This autoantibody combination can be used to identify patients with disease destined to develop RA who may be appropriate for very early intervention.
authors.affiliation: MRC Centre for Immune Regulation, Division of Immunity and Infection, The University of Birmingham, Birmingham, UK. k.raza@bham.ac.uk
authors.forename: Karim
authors.initials: K
authors.lastname: Raza
authors.forename: Mike
authors.initials: M
authors.lastname: Breese
authors.forename: Peter
authors.initials: P
authors.lastname: Nightingale
authors.forename: Kanta
authors.initials: K
authors.lastname: Kumar
authors.forename: Tanya
authors.initials: T
authors.lastname: Potter
authors.forename: David M
authors.initials: DM
authors.lastname: Carruthers
authors.forename: Deva
authors.initials: D
authors.lastname: Situnayake
authors.forename: Caroline
authors.initials: C
authors.lastname: Gordon
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Buckley
authors.forename: Mike
authors.initials: M
authors.lastname: Salmon
authors.forename: George D
authors.initials: GD
authors.lastname: Kitas
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology*; D001323:Autoantibodies; D003430:Cross-Sectional Studies; D042241:Early Diagnosis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D011237:Predictive Value of Tests; D011379:Prognosis; D012217:Rheumatoid Factor / Q000276:immunology; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor