Measurement of functional status in juvenile chronic arthritis: evaluation of a Swedish version of the Childhood Health Assessment Questionnaire.

Few well-validated self-and/or parent-administered instruments are available for measuring functional status in children with rheumatic diseases. Parts of the Stanford Health Assessment Questionnaire (HAQ) have been adapted for use in children in the so-called Child HAQ. The aim of this study was to investigate the validity of this instrument in a Swedish setting. The Child HAQ was administered to 186 patients and 211 patients participating in a population-based follow-up study of juvenile chronic arthritis (JCA) in southwestern Sweden. The EULAR criteria were used for inclusion. Children who were 9 years of age or older self-reported. Reliability, evaluated by test-retest, inter-observer correlations and internal reliability, was excellent. Convergent validity was demonstrated by strong correlations of the disability index, pain, and morning stiffness with disease activity and the Steinbrocker functional classes. Discriminant validity was evidenced by the capacity of the instrument to evaluate patients as being active or in remission. Thus, the Child HAQ showed excellent measurement performance in a Swedish setting when using parents or children more than 9 years old as responders.