Responsiveness of clinical measures to flare of disease activity in juvenile idiopathic arthritis

Objective: To compare the responsiveness of clinical measures in the assessment of disease flare in patients with juvenile idiopathic arthritis (JIA). Methods: The clinical records of all consecutive patients with JIA who were diagnosed between 1995 and 2000 were retrospectively reviewed. In each patient, all visits made during follow-up were analyzed and those meeting the criteria for disease flare were recorded. The definition of flare was based on the therapeutic alterations made by the attending physician. Responsiveness of JIA clinical measures to relevant increase in disease activity (a flare) was evaluated by assessing the score change of each measure from a visit made 6 (±3) months before a flare and the flare visit. Responsiveness statistics included the standardized response mean (SRM) and the effect size (ES). Results: A total of 115 patients, who were followed for 0.5 to 6.2 years (mean 2.8 years), were studied. During follow-up, 51 patients (44%) experienced 1 or more disease flares, with the total number of flares being 75. Strong responsiveness (ES and SRM ≥ 0.8) to increase in disease activity was demonstrated by the physician's and parent's global assessments, the global articular severity score, and the morning stiffness. The active, swollen and painful joint counts, the swelling, pain on motion/tenderness and limited range of motion (LROM) scores, and the erythrocyte sedimentation rate revealed moderate responsiveness (ES and SRM ≥ 0.5). The poorest performances (ES and/or SRM < 0.5) were provided by the parent's assessment of pain, the functional ability tool, the number of joints with LROM, the LROM score, the C-reactive protein, the white blood cell and platelet count, and the hemoglobin level. Conclusion: Our analysis suggests that the swollen or painful joint counts are better suited than the count of joints with LROM for the assessment of disease flare in patients with JIA.