Assessing whether child and parent reports of the KINDL questionnaire measure the same constructs of quality of life in children with attention-deficit hyperactivity disorder

BACKGROUND: Discrepancy between child self-report and parent proxy-report has long been documented in the health-related quality of life (HRQoL) measurement of children with chronic health conditions. This study aims to assess whether child and parent reports of the Kinder Lebensqualität fragebogen (KINDL) questionnaire measure the same construct of HRQoL in children with attention-deficit hyperactivity disorders (ADHD). METHODS: Participants were 122 Iranian children with ADHD and 127 of their parents, who completed the child and parent reports of the KINDL, respectively. Internal consistency of the child and parent reports were assessed by Cronbach's alpha. The intra-class correlation (ICC) coefficient and factor analysis were applied to assess whether the child self-report and the parent proxy-report measured the same construct of HRQoL. Additionally, convergent and discriminant validity were assessed using the Spearman correlation. RESULTS: The results of factor analysis revealed that the child self-report and parent proxy-report measure two different aspects of HRQoL. Moreover, both versions of the KINDL instrument showed excellent convergent and discriminant validity. The internal consistency was close to or greater than 0.7 for all domains of both child and parent reports. CONCLUSIONS: Although the child self-report and the parent proxy-report of the Persian version of the KINDL have good psychometric properties, they are not interchangeable. This finding indicates that Iranian children with ADHD and their parents evaluate children's HRQoL from their own viewpoints.