title: Undifferentiated arthritis characteristics and outcomes when applying the 2010 and 1987 criteria for rheumatoid arthritis.
abstract: OBJECTIVE
  Undifferentiated arthritis (UA) is a diagnosis 'per exclusionem'. Therefore this patient population may change since the development of the ACR/EULAR 2010-criteria for RA. This study evaluated characteristics and outcomes of UA in its new shape. Second, it was evaluated whether the 2010-criteria and the Leiden prediction rule were congruent in categorizing UA-patients.
  
  
  METHODS
  2,472 early arthritis patients were studied. RA was classified according to either the 1987 or the 2010-criteria. UA was defined as not fulfilling existing classification criteria. UA-patients were compared for baseline characteristics and outcomes. In 1987-UA-patients both the 2010-criteria and the Leiden prediction rule were applied and categorization compared.
  
  
  RESULTS
  2010-UA-patients (n=776) had milder baseline characteristics than 1987-UA-patients (n=1,166). During follow-up, still 24% of the 2010-UA-patients fulfilled the 1987 RA-criteria compared to 32% of the 1987-UA-patients. The 2010-UA-patients started less frequent DMARD-therapy and reached more frequent sustained DMARD-free remission. 30% of 2010-criteria-positive patients were predicted to have a low risk on RA; these patients achieved more frequent DMARD-free sustained remission than other 2010-criteria-positive patients.
  
  
  CONCLUSIONS
  UA in the era of the 2010-criteria is less prevalent and milder at presentation and in outcome. This implies that UA-patients with unfavorable characteristics are now more often classified as RA.
authors.affiliation: Department of Rheumatology, Leiden University Medical Center, The Netherlands. a.krabben@lumc.nl
authors.forename: A
authors.initials: A
authors.lastname: Krabben
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; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001168:Arthritis / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology; D003937:Diagnosis, Differential; D018450:Disease Progression; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011379:Prognosis
chemical_list: D018501:Antirheumatic Agents