title: Anticitrullinated protein antibodies and rheumatoid factor fluctuate in early inflammatory arthritis and do not predict clinical outcomes.
abstract: OBJECTIVE
  In inflammatory arthritis, rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPA) are believed to be associated with more severe clinical outcomes. Our objective was to determine whether ACPA and RF remain stable in early inflammatory arthritis and whether their trajectories over time or baseline levels predicted clinical outcomes.
  
  
  METHODS
  The study population consisted of patients enrolled in the Canadian Early Arthritis Cohort Study with baseline and at least 12-month followup values of RF and ACPA. Primary outcomes were Disease Activity Score (DAS) remission and the presence of erosions at 12 and 24 months. Other objectives included swollen joint count, Health Assessment Questionnaire score, and DAS.
  
  
  RESULTS
  At baseline, 225/342 (66%) patients were ACPA-positive and 334/520 (64%) were RF-positive. At 24 months, 15/181 (8%) ACPA-positive patients became negative. A larger number of patients changed from ACPA-negative to positive: 13/123 (11%). For RF, fluctuations were more common: 67/240 (28%) reverted from positive to negative and 21/136 (18%) converted from negative to positive. RF and ACPA fluctuations did not predict disease outcomes. Patients who remained ACPA-positive throughout followup were more likely to have erosive disease (OR 3.86, 95% CI 1.68, 8.92).
  
  
  CONCLUSIONS
  RF and ACPA have the potential to revert and convert during the early course of disease. Fluctuations in RF and ACPA were not associated with clinical outcomes.
authors: Department of Medicine, Division of Rheumatology, St. Joseph's Health Care London, University of Western Ontario, London, Ontario, Canada. lbarra2@uwo.ca
authors: Lillian
authors: L
authors: Barra
authors: Vivian
authors: V
authors: Bykerk
authors: Janet E
authors: JE
authors: Pope
authors: Boulos P
authors: BP
authors: Haraoui
authors: Carol A
authors: CA
authors: Hitchon
authors: J Carter
authors: JC
authors: Thorne
authors: Edward C
authors: EC
authors: Keystone
authors: Gilles
authors: G
authors: Boire
mesh_terms: D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000188:drug therapy*; D015415:Biomarkers / Q000097:blood; D002170:Canada; D015331:Cohort Studies; D004185:Disability Evaluation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012217:Rheumatoid Factor / Q000097:blood*; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D000888:Antibodies, Anti-Idiotypic; D018501:Antirheumatic Agents; D015415:Biomarkers; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor
keywords: ANTICITRULLINATED PROTEIN ANTIBODIES; EROSIONS; REMISSION; RHEUMATOID ARTHRITIS; RHEUMATOID FACTOR