title: Validity of a three-variable Juvenile Arthritis Disease Activity Score in children with new-onset juvenile idiopathic arthritis.
abstract: OBJECTIVE
  To investigate the validity and feasibility of the Juvenile Arthritis Disease Activity Score (JADAS) in the routine clinical setting for all juvenile idiopathic arthritis (JIA) disease categories and explore whether exclusion of the erythrocyte sedimentation rate (ESR) from JADAS (the 'JADAS3') influences correlation with single markers of disease activity.
  
  
  METHODS
  JADAS-71, JADAS-27 and JADAS-10 were determined at baseline for an inception cohort of children with JIA in the Childhood Arthritis Prospective Study. JADAS3-71, JADAS3-27 and JADAS3-10 were determined using an identical formula but with exclusion of ESR. Correlation of JADAS with JADAS3 and single measures of disease activity/severity were determined by category.
  
  
  RESULTS
  Of 956 eligible children, sufficient data were available to calculate JADAS-71, JADAS-27 and JADAS-10 at baseline in 352 (37%) and JADAS3 in 551 (58%). The median (IQR) JADAS-71, JADAS-27 and JADAS-10 for all 352 children was 11 (5.9-18), 10.4 (5.7-17) and 11 (5.9-17.3), respectively. Median JADAS and JADAS3 varied significantly with the category (Kruskal-Wallis p=0.0001), with the highest values in children with polyarticular disease patterns. Correlation of JADAS and JADAS3 across all categories was excellent. Correlation of JADAS71 with single markers of disease activity/severity was good to moderate, with some variation across the categories. With the exception of ESR, correlation of JADAS3-71 was similar to correlation of JADAS-71 with the same indices.
  
  
  CONCLUSIONS
  This study is the first to apply JADAS to all categories of JIA in a routine clinical setting in the UK, adding further information about the feasibility and construct validity of JADAS. For the majority of categories, clinical applicability would be improved by exclusion of the ESR.
authors.affiliation: Arthritis Research UK Epidemiology Unit, University of Manchester, , Manchester, UK.
authors.forename: Flora
authors.initials: F
authors.lastname: McErlane
authors.forename: Michael W
authors.initials: MW
authors.lastname: Beresford
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Baildam
authors.forename: S E Alice
authors.initials: SE
authors.lastname: Chieng
authors.forename: Joyce E
authors.initials: JE
authors.lastname: Davidson
authors.forename: Helen E
authors.initials: HE
authors.lastname: Foster
authors.forename: Janet
authors.initials: J
authors.lastname: Gardner-Medwin
authors.forename: Mark
authors.initials: M
authors.lastname: Lunt
authors.forename: Lucy R
authors.initials: LR
authors.lastname: Wedderburn
authors.forename: Wendy
authors.initials: W
authors.lastname: Thomson
authors.forename: Kimme L
authors.initials: KL
authors.lastname: Hyrich
mesh_terms: D001171:Arthritis, Juvenile / Q000097:blood / Q000175:diagnosis*; D001799:Blood Sedimentation; D002648:Child; D002675:Child, Preschool; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D010147:Pain Measurement; D015203:Reproducibility of Results; D012720:Severity of Illness Index