The Childhood Health Assessment Questionnaire (CHAQ) is widely used to measure functional impairment in juvenile idiopathic arthritis (JIA). However, the original version (CHAQ30) has reduced overall validity in terms of an increasing ceiling effect and decreasing discriminative ability because of considerable improvements in functional ability of children with JIA. The aim of this study was to validate a revised CHAQ including eight new physically demanding questions (CHAQ38) with two categorical response and scoring models (CAT1 and CAT2) in Danish children with JIA and healthy controls of a comparable age and gender. The CHAQ versions with both response models were validated in relation to distribution of data, evaluation of the ceiling effect, sensitivity, and discriminative ability.
Four different version of the CHAQ were completed by 68 patients and 118 controls aged 10-16 years. Demographic data in both groups and disease-specific data among patients were obtained. Statistical analysis of all CHAQ versions was performed to evaluate score distribution and to test the ability to distinguish between patients and controls.
The use of the CHAQ38 broadened the range of scores and reduced the number of scores at zero. The ceiling effect, which was high in all versions, was best reduced using the CAT2 response model. Adding the new questions increased the sensitivity to discriminate between physically well-functioning JIA patients and healthy controls in either of the CAT models used. Overall, the CHAQ38 and to some extent the CAT2 had the best outcomes.
The discriminative validity increased with the CHAQ38, though still not optimally.