title: Comparison of long term outcome of patients with rheumatoid arthritis presenting with undifferentiated arthritis or with rheumatoid arthritis: an observational cohort study.
abstract: BACKGROUND
  The outcome of undifferentiated arthritis (UA) ranges from remission to rheumatoid arthritis (RA) fulfilling the American College of Rheumatology (ACR) classification criteria.
  
  
  OBJECTIVE
  To report the outcome of UA after 1 year of follow up and compare the disease course of patients who presented with UA, but evolved into RA within 1 year (UA-RA group), with that of patients who presented with RA fulfilling the ACR criteria (RA-RA group).
  
  
  METHODS
  The diagnosis of 330 patients who presented with UA was recorded at 1 year. The UA-RA and RA-RA groups were then followed up for 3 more years. Outcome measurements were radiographic progression, disease activity, and functional capacity.
  
  
  RESULTS
  From 330 patients who were diagnosed UA, 91 had evolved into RA at 1 year; 62 patients had presented with RA. No significant differences were detected between the UA-RA and RA-RA groups in median Sharp/van der Heijde score at baseline, radiographic progression rates, disease activity, and functional capacity. However, significantly more disease modifying antirheumatic drugs were prescribed in the RA-RA group.
  
  
  CONCLUSIONS
  The disease outcome of patients who present with UA that evolves into RA within 1 year is the same as that of patients who present with RA as measured by radiographic progression, disease activity, and functional capacity.
authors.affiliation: Department of Rheumatology, Leiden University Medical Centre, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van Aken
authors.forename: H
authors.initials: H
authors.lastname: van Dongen
authors.forename: S
authors.initials: S
authors.lastname: le Cessie
authors.forename: C F
authors.initials: CF
authors.lastname: Allaart
authors.forename: F C
authors.initials: FC
authors.lastname: Breedveld
authors.forename: T W J
authors.initials: TW
authors.lastname: Huizinga
mesh_terms: D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001168:Arthritis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000188:drug therapy; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000188:drug therapy; D018450:Disease Progression; D004363:Drug Utilization / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010352:Patient Dropouts; D011379:Prognosis; D011859:Radiography; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
chemical_list: D018501:Antirheumatic Agents