title: Validity and predictive ability of the juvenile arthritis disease activity score based on CRP versus ESR in a Nordic population-based setting.
abstract: OBJECTIVE
  To compare the juvenile arthritis disease activity score (JADAS) based on C reactive protein (CRP) (JADAS-CRP) with JADAS based on erythrocyte sedimentation rate (ESR) (JADAS-ESR) and to validate JADAS in a population-based setting.
  
  
  METHODS
  The CRP and ESR values and the corresponding JADAS scores (JADAS10/27/71) were compared in a longitudinal cohort study of 389 children newly diagnosed with juvenile idiopathic arthritis (JIA) in the Nordic JIA study. The construct validity and the discriminative and predictive ability of JADAS were assessed during a median disease course of 8 years by comparing JADAS with other measures of disease activity and outcome.
  
  
  RESULTS
  At the first study visit the correlation between JADAS27-CRP and JADAS27-ESR was r=0.99 whereas the correlation between CRP and ESR was r=0.57. Children with higher JADAS scores had an increased risk of concomitant pain, physical disability and use of disease-modifying antirheumatic drugs (DMARDs). A higher JADAS score at the first study visit also significantly predicted physical disability, damage and no remission off medication at the final study visit, and also use of DMARDs during the disease course. Sensitivity to change, demonstrated as change in JADAS score compared with the American College of Rheumatology paediatric measures of improvement criteria, mostly showed excellent classification ability.
  
  
  CONCLUSIONS
  The JADAS-CRP and JADAS-ESR correlate closely, show similar test characteristics and are feasible and valid tools for assessing disease activity in JIA.
authors.affiliation: Department of Pediatrics, University Hospital of North Norway, N 9038, Tromsø, Norway. ellen.nordal@unn.no
authors.forename: E B
authors.initials: EB
authors.lastname: Nordal
authors.forename: M
authors.initials: M
authors.lastname: Zak
authors.forename: K
authors.initials: K
authors.lastname: Aalto
authors.forename: L
authors.initials: L
authors.lastname: Berntson
authors.forename: A
authors.initials: A
authors.lastname: Fasth
authors.forename: T
authors.initials: T
authors.lastname: Herlin
authors.forename: P
authors.initials: P
authors.lastname: Lahdenne
authors.forename: S
authors.initials: S
authors.lastname: Nielsen
authors.forename: S
authors.initials: S
authors.lastname: Peltoniemi
authors.forename: B
authors.initials: B
authors.lastname: Straume
authors.forename: M
authors.initials: M
authors.lastname: Rygg
mesh_terms: D000293:Adolescent; D001171:Arthritis, Juvenile / Q000175:diagnosis / Q000503:physiopathology*; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007596:Joints / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011237:Predictive Value of Tests; D012720:Severity of Illness Index
chemical_list: D002097:C-Reactive Protein