Measurement properties of three assessments of burden used in atopic dermatitis in adults.

Abstract

Standardized quality-of-life (QoL) assessments can provide important and clinically relevant information. There is currently a lack of standardization in QoL assessments used in atopic dermatitis (AD). To determine the content validity, construct validity, internal consistency, differential reporting, responsiveness, floor or ceiling effects and feasibility of the Dermatology Life Quality Index (DLQI), Itchy Quality of Life (ItchyQoL) and 5-dimensions (5-D) itch scales for assessing burden of AD in adults and to compare their performance. Self-administered questionnaires and skin examination were performed in 340 adults with AD in a dermatology practice setting. DLQI, ItchyQoL and 5-D all had good content validity. DLQI, mean ItchyQoL and 5-D itch all had strong correlations with frequency of AD symptoms (Patient-Oriented Eczema Measure) and intensity of itch (numerical rating scale for itch), and moderate correlations with AD severity (Eczema Area and Severity Index and Scoring Atopic Dermatitis) (Spearman correlations, P < 0·001 for all). DLQI and 5-D itch showed good internal consistency (Cronbach's alpha = 0·89 and 0·84), although ItchyQoL appeared to have several redundant items (alpha = 0·96). Uniform and nonuniform differential item functioning by age, sex and/or race/ethnicity was found for multiple items in DLQI, ItchyQoL and 5-D itch. DLQI, ItchyQoL and 5-D itch scores all demonstrated responsiveness, although ItchyQoL demonstrated the greatest responsiveness. There were no floor or ceiling effects for total scores. The median times for completion of DLQI, ItchyQoL and 5-D itch were 2 min. The DLQI, ItchyQoL and 5-D itch scales all showed good content and construct validity, and responsiveness in the assessment of AD in adults, and were feasible for use in clinical trials and practice.