To develop preliminary criteria for defining disease flare in patients with polyarticular-course juvenile rheumatoid arthritis (JRA).
Data from a randomized clinical trial of etanercept in JRA (51 patients) and the 6 core response variables (CRV) for JRA were used to derive flare definitions. The criterion standard of flare was treatment with placebo. Candidate flare definitions were assessed by receiver-operator characteristic (ROC) curve properties and other statistics for diagnostic tests.
Of the possible flare definitions tested with acceptable statistical properties, the one that seemed to be the most useful was worsening in any 2/6 CRV by > or = 40% without improvement in more than 1 of the remaining CRV by > or = 30%. Two other superior flare definitions were (1) worsening in 3/6 CRV by > or = 30% and (2) any worsening of the Childhood Health Assessment Questionnaire, worsening of erythrocyte sedimentation rate by > or = 30% and worsening of the active joint count by > or = 10%.
CRV are useful for defining flare in JRA. Worsening in any 2/6 CRV by > or = 40% without concomitant improvement of more than one of the remaining CRV by > or = 30% appears to be the most suitable preliminary flare definition. Because the proposed flare criteria were derived from a small number of patients, it is essential to perform more definitive testing of this and several alternative flare definitions in larger patient populations.