Validation of the childhood health assessment questionnaire iu the juvenile idiopathic myopathies

Objective. To examine the validity of the Childhood Health Assessment Quest ionnaire (CHAQ) in patients with juvenile idiopathic inflammatory myopathy (IIM). Methods. One hundred fifteen patients were enrolled in a multicenter collab orative study, during which subjects were assessed twice, 7-9 months apart. Physical function was measured using the CHAQ. Internal reliability was as sessed using adjusted item-total correlations and item endorsement rates. C onstruct validity was assessed by comparing predicted and actual correlatio ns of the CHAQ with other measures of physical function and disease activit y. Responsiveness was assessed by calculating effect size (ES) and standard ized response mean (SRM) in a group of a priori defined "improvers." Results. Item-total correlations were high (r(s) range = 0.35-0.81), sugges ting all items were related to overall physical function. Manual muscle tes ting and the Childhood Myositis Assessment Scale correlated moderate to str ongly with the CHAQ (r(s) = -0.64 and -0.75. both p < 0.001). Moderate corr elations were also seen with the physician global assessment of disease act ivity (r(s) = 0.58, p < 0.001). parent global assessment of overall health (r(s) = -0.65, p < 0.001). Steinbrocker function class (r(s) = 0.69, p < 0. 001), and global skin activity (r(s) = 0.40, p < 0.001), while global disea se damage and skin damage had low correlations (r(s) = 0.13 and 0.07, p <gr eater than or equal to> 0.17). Responsiveness of the CHAQ was high. with ES = 1.05 and SRM = 1.20. Conclusion. In this large cohort of patients with juvenile IIM, the CHAQ ex hibited internal reliability, construct validity and strong responsiveness. We conclude that the CHAQ is a valid measure of physical function in juven ile IIm, appropriate for use in therapeutic trials, and potentially in the clinical carl of these patients.