title: How accurate are diagnoses for rheumatoid arthritis and juvenile idiopathic arthritis in the general practice research database?
abstract: OBJECTIVE
  To identify characteristics that predict a valid rheumatoid arthritis (RA) or juvenile idiopathic arthritis (JIA) diagnosis among RA- and JIA-coded individuals in the General Practice Research Database (GPRD), and to assess limitations of this type of diagnostic validation.
  
  
  METHODS
  Four RA and 2 JIA diagnostic groups were created with differing strengths of evidence of RA/JIA (Group 1 = strongest evidence), based on RA/JIA medical codes. Individuals were sampled from each group and clinical and prescription data were extracted from anonymized hospital/practice correspondence and electronic records. American College of Rheumatology and International League of Associations for Rheumatology diagnostic criteria were used to validate diagnoses. A data-derived diagnostic algorithm that maximized sensitivity and specificity was identified using logistic regression.
  
  
  RESULTS
  Among 223 RA-coded individuals, the diagnostic algorithm classified individuals as having RA if they had an appropriate GPRD disease-modifying antirheumatic drug prescription or 3 other GPRD characteristics: >1 RA code during followup, RA diagnostic Group 1 or 2, and no later alternative diagnostic code. This algorithm had >80% sensitivity and specificity when applied to a test data set. Among 101 JIA-coded individuals, the strongest predictor of a valid diagnosis was a Group 1 diagnostic code (>90% sensitivity and specificity).
  
  
  CONCLUSIONS
  Validity of an RA diagnosis among RA-coded GPRD individuals appears high for patients with specific characteristics. The findings are important for both interpreting results of published GPRD studies and identifying RA/JIA patients for future GPRD-based research. However, several limitations were identified, and further debate is needed on how best to validate chronic disease diagnoses in the GPRD.
authors.affiliation: Department of Epidemiology & Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK. sara.thomas@lshtm.ac.uk
authors.forename: S L
authors.initials: SL
authors.lastname: Thomas
authors.forename: C J
authors.initials: CJ
authors.lastname: Edwards
authors.forename: L
authors.initials: L
authors.lastname: Smeeth
authors.forename: C
authors.initials: C
authors.lastname: Cooper
authors.forename: A J
authors.initials: AJ
authors.lastname: Hall