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Construct and criterion validity of several proposed DAS28-based rheumatoid arthritis flare criteria: an OMERACT cohort validation study
  1. Aatke van der Maas1,
  2. Elisabeth Lie2,
  3. Robin Christensen3,
  4. Ernest Choy4,
  5. Yaël A de Man5,
  6. Piet van Riel6,
  7. Thasia Woodworth7,
  8. Alfons A den Broeder1
  1. 1Department of Rheumatology, Sint Maartenskliniek, Nijmegen, The Netherlands
  2. 2Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway
  3. 3Department of Rheumatology, Musculoskeletal Statistics Unit, The Parker Institute; Copenhagen University Hospital, Frederiksberg, Copenhagen, Denmark
  4. 4Section of Rheumatology, Cardiff University School of Medicine, Cardiff, UK
  5. 5Department of Rheumatology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
  6. 6Department of Rheumatology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
  7. 7Division of Rheumatology, Geffen School of Medicine, UCLA, Los Angeles, and Leading Edge Clinical Research LLC, Stuart, Florida, USA
  1. Correspondence to Aatke van der Maas, Department of Rheumatology, Sint Maartenskliniek, Hengstdal 3, Nijmegen 6522 JV, The Netherlands; a.vandermaas{at}maartenskliniek.nl

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, χ2 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.

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