Evaluating score distributions in the revised Dutch version of the Childhood Health Assessment Questionnaire

Two convenience samples of 59 and 31 children with JIA were studied. Box-and-whisker plots and the Kolmogorov-Smirnov (K-S) one-sample test of normality were used, to explore the score distributions.The results of this study confirm a ceiling effect when using the original CHAQ-30 with either score calculation method. The original CHAQ with the added eight more challenging items and the "mean" score calculation method, as well as the revised CHAQ showed less ceiling effect.The original CHAQ-38 with the "mean" score calculation method as well as the revised CHAQ are a possible alternative for future studies. However, there is a need for further prospective studies to improve the CHAQ and to support our findings.The Childhood Health Assessment Questionnaire (CHAQ) is the most widely utilized functional status measure in paediatric rheumatology today. The CHAQ consists of a disability index (30 items; 8 domains), and a discomfort scale (two visual analogue scales) and can be completed by children as well as their parents/guardians. The CHAQ has shown to be a valid, reliable, and sensitive functional status measure in children with Juvenile Idiopathic Arthritis (JIA) [1]. Over the years the use of the CHAQ has also broadened to other childhood rheumatic conditions [2-5].Despite its advantages and wide use, the CHAQ suffers from a ceiling effect [6]. Therefore it is difficult to discriminate distinct levels of function at the mild end of the disability continuum and to assess improvement in health for less impaired patients [6]. Lam et al. (2004) tried to influence this ceiling effect by testing different response options (visual analogue scale (CHAQVAS), categorical (CHAQCat), and choice (CHAQChoice)) and by adding eight more challenging items [6]. Respondents were instructed to compare their capabilities to that of their age peers over the last week. The different response options made it possible to asses not only patient's limitations (original CHAQ), but also the pa