Validation and Interpretation of Short Form 12 and Comparison with Dermatology Life Quality Index in Atopic Dermatitis in Adults

Abstract

Quality-of-life assessments are not standardized in atopic dermatitis (AD). We sought to determine the validity of the Short Form (SF)-12, a generic quality-of-life assessment, in AD and compare its measurement properties with the Dermatology Life Quality Index (DLQI). A cross-sectional, population-based study of 3,495 adults was performed, including 602 adults who met the modified United Kingdom Working Party Criteria for AD. The SF-12 mental component score and the SF-Six Dimension (SF-6D) had a strong correlation with each other and moderate inverse correlations with the Patient-Oriented Eczema Measure, the Patient-Oriented Scoring Atopic Dermatitis, the Patient-Oriented Scoring Atopic Dermatitis-itch, the Patient-Oriented Scoring Atopic Dermatitis-sleep, and the Numerical Rating Scale of pain (Pearson correlations, P < 0.0001 for all). The SF-12 mental component score and the SF-6D showed good discriminant validity as judged by the analysis of variance and receiver operating curves. The SF-12 physical component score had weak correlations with AD severity assessments and poor discriminant validity. The DLQI had better convergent and discriminant validity than the SF-12. The SF-12 and the DLQI showed good internal consistency (Cronbach alpha, 0.89 and 0.94, respectively). Differential item functioning was found for items in the SF-12 and the DLQI. Floor effects were observed for the DLQI but not for the SF-12 mental component score, the SF-12 physical component score, and the SF-6D. Severity thresholds were selected. In conclusion, the SF-12 mental component score and the SF-6D showed good validity in AD but inferior construct validity compared with the DLQI.