Validity and responsiveness of the EQ-5D and the KIDSCREEN-10 in children with ADHD

The aim of our study is to compare the validity of a generic preference-based Quality of Life (QoL) instrument for adults to that of a generic child-specific QoL instrument in children and adolescents with attention deficit hyperactivity disorder (ADHD). EQ-5D and KIDSCREEN-10 data were collected using a questionnaire survey performed among parents with a child or adolescent diagnosed with ADHD. The measurements were compared to assess (dis)similarities of the instruments' constructs and responsiveness to different health states. Principal component analysis (PCA) with varimax rotation was used to identify factors underlying the constructs of both instruments. Instruments' index scores of respondents with different treatment and comorbidity profiles were compared using Student's t tests. Cohen's effect sizes were calculated for an indirect comparison of the instruments' responsiveness and discriminating ability. Separate analyses were performed in children aged 8-12 and 13-18 years. A strong relation was found between the EQ-5D and KIDSCREEN-10 index scores. However correlations between EQ-5D and KIDSCREEN-10 items were moderate or low. The PCA identified five separate factors of quality of life. A physical and a mental factor included a combination of three EQ-5D dimensions and six KIDSCREEN-10 items; the remaining EQ-5D and KIDSCREEN-10 items constituted complementary factors without any overlap between the separate instruments. Scores of both instruments differed significantly according to respondents' response to treatment and comorbidity profile. Cohen's effect sizes indicated comparable results of the instruments' responsiveness and discriminative ability. The results highlight that the instruments measure different constructs of QoL in children with ADHD. Despite this, the analyses showed comparable responsiveness and discriminative ability of the instruments. These results suggest that for economic evaluations, the EQ-5D is an appropriate and valid instrument for measuring QoL in children.