title: Construct and criterion validity of several proposed DAS28-based rheumatoid arthritis flare criteria: an OMERACT cohort validation study.
abstract: BACKGROUND
  To describe rheumatoid arthritis (RA) worsening that leads to change or re-initiation of treatment, several Disease Activity Score 28 (DAS28)-based flare criteria have been described, but none validated.
  
  
  METHODS
  Six previously published DAS28-based flare criteria ((1) increase in DAS28 >1.2, or >0.6 if DAS28 >5.1; (2) increase in DAS28 >1.2, or >0.6 if DAS28 ≥3.2; (3) increase >0.6 or DAS28 >3.2; (4) increase in DAS28 >1.2; (5) DAS28 >3.2; (6) DAS28 >2.6) were tested against five hypotheses concerning criterion and construct validity: (1+2) Sensitivity and specificity >70% compared with patient's/physician's judgment; (3) difference in proportion with disease modifying anti-rheumatic drug/corticosteroid initiation/increase >0.2; (4) mean difference in C-reactive protein (CRP) >10 mg/l; and (5) no statistical difference in Short Form-36 Mental Health subscale change. Three different RA patient databases in which flare might occur were used. Sensitivity/specificity, χ(2) and two-sample student t test analyses were done.
  
  
  RESULTS
  The analyses included 51, 147 and 744 RA patients, from the three databases. Criterion 2 fulfilled most hypotheses: 4 out of 5. Sensitivity and specificity varied between 63%-78% and 84%-92%. Construct validity was demonstrated with 23% more treatment change, higher mean CRP (11.4 mg/l) and depression scale change of -5. Criteria 3, 5 and 6 were more sensitive, criteria 1, 2 and 4 more specific.
  
  
  CONCLUSIONS
  An increase in DAS28 >1.2 or >0.6 if DAS28 ≥3.2 appears most discriminating and valid by our predefined validation criteria. Considering the other criteria, sensitivity and specificity shown here might facilitate use in different settings.
authors.affiliation: Department of Rheumatology, Sint Maartenskliniek, , Nijmegen, The Netherlands.
authors.forename: Aatke
authors.initials: A
authors.lastname: van der Maas
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Lie
authors.forename: Robin
authors.initials: R
authors.lastname: Christensen
authors.forename: Ernest
authors.initials: E
authors.lastname: Choy
authors.forename: Yaël A
authors.initials: YA
authors.lastname: de Man
authors.forename: Piet
authors.initials: P
authors.lastname: van Riel
authors.forename: Thasia
authors.initials: T
authors.lastname: Woodworth
authors.forename: Alfons A
authors.initials: AA
authors.lastname: den Broeder
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis*; D015331:Cohort Studies; D016208:Databases, Factual; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity