Evaluation of responsiveness and estimation of smallest detectable change and minimal important change scores for the Childhood Atopic Dermatitis Impact Scale

Abstract

Background: The Childhood Atopic Dermatitis Impact Scale (CADIS) is an instrument to measure quality of life in young children affected by atopic dermatitis, and their parents.

Objectives: To evaluate the responsiveness (sensitivity to change), smallest detectable change (SDC) and minimal important change (MIC) of the CADIS.

Methods: Parents and primary caregivers of 300 young children completed the CADIS and a global rating of their child's skin condition at baseline and a 4-week follow-up. Kruskal-Wallis tests, Wilcoxon tests and effect sizes were used to assess responsiveness. The SDC can be seen as a change beyond measurement error. Anchor-based and distribution-based methods, and an integration of both methods were used to estimate the MIC.

Results: In total, 270 families provided data at baseline and 228 at follow-up. The CADIS total change score and most of the domain scores had moderate-to-strong correlations with the skin change score. Patients were grouped according to the skin change score, which served as an anchor. Children whose parents noted an improvement of the skin showed lower CADIS scores at follow-up (P < 0·001). For the SDC we obtained score changes of 1·34 points on the total score and < 1·0 points on each domain score. All detected MIC values passed the SDC cut-off.

Conclusions: The CADIS is sensitive to change towards improvement of quality of life. A change > 12% on the total score or each domain score very likely represents a clinically important change. What's already known about this topic? Atopic dermatitis reduces the quality of life of affected children and their parents. The Childhood Atopic Dermatitis Impact Scale (CADIS) has been evaluated and translated into two further languages. What does this study add? Further validation of the responsiveness of the CADIS, and whether it is sensitive to change in patients whose condition had changed. Calculation of the smallest detectable change. What are the clinical implications of this work? Estimation of the minimal important change in CADIS provides benchmarks for clinical practice.