title: Toward a data-driven evaluation of the 2010 American College of Rheumatology/European League Against Rheumatism criteria for rheumatoid arthritis: is it sensible to look at levels of rheumatoid factor?
abstract: OBJECTIVE
  Recently, new classification criteria for rheumatoid arthritis (RA) have been devised by methodology that used first a quantitative approach (data from databases), then a qualitative approach (consensus; based on paper patients), and finally a common sense-based approach (evaluation of the former phases). Now the individual items that make up these criteria are being evaluated. This study was undertaken to analyze the item "autoantibodies," in particular rheumatoid factor (RF) level.
  
  
  METHODS
  Three separate cohorts comprising a total of 972 patients with undifferentiated arthritis were studied for RA development (according to the 1987 American College of Rheumatology criteria) and arthritis persistence. The positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios (LRs) were compared between different levels of RF and the presence of anti-citrullinated protein antibody (ACPA). A similar comparison was made in 686 RA patients for the rate of joint destruction and achievement of sustained disease-modifying antirheumatic drug-free remission during 7 years of followup. The variation in RF levels obtained by different measurement methods in the same RF-positive sera was explored.
  
  
  RESULTS
  Compared to high RF levels, presence of ACPA had a better balance between positive LR and negative LR and between PPV and NPV for RA development. The additive value of ACPA assessment after testing for RF level was higher than vice versa. The association between high RF level and RA severity was not as strong as that between ACPA antibodies and RA severity. The RF level obtained by different methods in the same patients' sera varied considerably.
  
  
  CONCLUSIONS
  Our findings indicate that determination of RF level is subject to large variation; high RF level has limited additive prognostic value compared to ACPA positivity. Thus, omitting RF level and using RF presence, ACPA presence, and ACPA level may improve the 2010 criteria for RA.
authors.affiliation: Leiden University Medical Center, Leiden, The Netherlands. M.P.M.van_der_Linden@lumc.nl
authors.forename: M P M
authors.initials: MP
authors.lastname: van der Linden
authors.forename: M R
authors.initials: MR
authors.lastname: Batstra
authors.forename: L E
authors.initials: LE
authors.lastname: Bakker-Jonges
authors.forename: J
authors.initials: J
authors.lastname: Detert
authors.forename: H
authors.initials: H
authors.lastname: Bastian
authors.forename: H U
authors.initials: HU
authors.lastname: Scherer
authors.forename: R E M
authors.initials: RE
authors.lastname: Toes
authors.forename: G-R
authors.initials: GR
authors.lastname: Burmester
authors.forename: M D
authors.initials: MD
authors.lastname: Mjaavatten
authors.forename: T K
authors.initials: TK
authors.lastname: Kvien
authors.forename: T W J
authors.initials: TW
authors.lastname: Huizinga
authors.forename: A H M
authors.initials: AH
authors.lastname: van der Helm-van Mil
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000175:diagnosis*; D015415:Biomarkers / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011237:Predictive Value of Tests; D012217:Rheumatoid Factor / Q000097:blood*; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012955:Societies, Medical
chemical_list: D015415:Biomarkers; D012217:Rheumatoid Factor