Objective: To develop and validate a self- or parent-administered instrument for measuring functional status in children with juvenile rheumatoid arthritis (JRA).
Methods: We adapted the Stanford Health Assessment Questionnaire (HAQ) for use in children ages 1-19 years, by adding several new questions, such that for each functional area, there was at least 1 question relevant to children of all ages. The face validity of the instrument was evaluated by a group of 20 health professionals and parents of 22 healthy children. The questionnaire was then administered to parents of 72 JRA patients (mean age 9.1 years, onset type systemic in 16, polyarticular in 21, pauciarticular in 35).
Results: The instrument showed excellent internal reliability (Cronbach's alpha = 0.94), with a mean inter-item correlation of 0.6. The convergent validity was demonstrated by strong correlations of the Disability Index (average of scores on all functional areas) with Steinbrocker functional class (Kendall's tau b = 0.77, P < 0.0001), number of involved joints (Kendall's tau b = 0.67, P < 0.0001), and morning stiffness (Kendall's tau b = 0.54, P < 0.0001). Spearman's correlation coefficient between Disability Index scores from questionnaires administered to parents and those from questionnaires administered to older children (> 8 years) was 0.84 (n = 29; P < 0.001), showing that parents can accurately report for their children. The test-retest reliability, studied at a 2-week interval, revealed virtually identical Disability Index scores measured on the 2 occasions (0.96 versus 0.96; P > 0.9 by paired t-test; Spearman's correlation coefficient = 0.8, P < 0.002).
Conclusion: The Childhood HAQ, which takes less than 10 minutes to complete, is a valid, reliable, and sensitive instrument for measuring functional status in children with JRA.