Evaluation of the Disease Activity Score in Twenty‐Eight Joints–Based Flare Definitions in Rheumatoid Arthritis: Data From a Three‐Year Clinical Trial

OBJECTIVE To assess the flare rate using published criteria (Disease Activity Score in 28 joints [DAS28-2] increase between visits of >1.2 or >0.6 if current DAS28 ≥3.2) in patients receiving constant treatment, and to compare published flare criteria to criteria used by study investigators after biologic treatment discontinuation in the ACT-RAY study. METHODS Patients with rheumatoid arthritis (n = 553) were randomized to add tocilizumab to ongoing methotrexate, or switch to tocilizumab plus placebo. If DAS28 ≤3.2 occurred at week 24, treatment remained constant until week 52; here we assessed the DAS28-2 flare rate. Between weeks 52 and 104, patients in sustained remission (DAS28 <2.6 at 2 consecutive visits 12 weeks apart) discontinued tocilizumab and were assessed every 4 weeks. Per protocol, flare was defined as a worsening of disease activity that required treatment beyond the permitted therapy based on investigator opinions (investigator flare) and was compared with the DAS28-2 definition. RESULTS After tocilizumab discontinuation, DAS28-2 was sensitive (88-100%), but not specific (57-65%), for detecting investigator flare. Under constant treatment, DAS28-2 criteria were met in 136 cases per 100 patient-years despite stable disease activity. Sustained flares were infrequent. Other DAS28-based criteria led to similar conclusions. CONCLUSION DAS28-based flare occurred more often than investigator-defined flares after biologic agent discontinuation. More stringent criteria may be more appropriate for clinical practice.