Objective. To develop a scoring system for juvenile idiopathic arthritis (JIA) in which joints are weighted to reflect their relative importance to children's function and to examine whether weighting increases the correlation of joint counts with subjective and laboratory outcome measures. Methods. A weighted joint score was devised by a panel of experienced paediatric rheumatologists, who assigned a weight from 1 (not very important) to 10 (essential for key functional activities) to each

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... t based on its functional importance to children's physical and daily activities. The associations of simple and weighted counts of swollen, tender, limited and active joints with the physician's global assessment of overall disease activity, the parent's global assessment of the child's overall well-being and intensity of pain, the Childhood Health Assessment Questionnaire (C-HAQ), the Child Health Questionnaire (CHQ) and the erythrocyte sedimentation rate were compared using Spearman's correlation analysis in 60 unselected patients seen in the clinic and in 61 consecutive patients with disease duration¸5 yr. Results. Weighted counts of swollen and active joints yielded greater correlation with the physician's global assessment than did simple counts. The correlation of weighted counts of swollen, painful and active joints with the parent's assessment of overall well-being and intensity of pain was superior to that provided by simple counts. Weighting increased most of the correlations between joint counts and the C-HAQ score and the physical component of the CHQ. Conclusion. Weighting improves the information provided by joint counts on the severity of arthritis and its impact on patients' well-being.