Psychometric validation and responder definition of the sleep disturbance numerical rating scale in moderate-to-severe atopic dermatitis*

Abstract

Background: Sleep disturbance (SD) is an important part of the burden of atopic dermatitis (AD), but patient-reported outcomes that are easy to understand and interpret in the target population have been lacking. A daily, single-item, self-reported SD 11-point numerical rating scale (NRS) was recently developed to assess SD for patients with moderate-to-severe AD, but its psychometric properties have not yet been described. Objectives: To assess the psychometric properties of the SD NRS in patients with moderate-to-severe AD. Methods: The psychometric properties of the SD NRS were assessed using data from a phase IIb clinical trial in 218 adults with moderate-to-severe AD. Results: Test–retest reliability of the SD NRS was substantial to almost perfect (interclass correlation 0·66–1·00) in participants who had stable SD or stable pruritus scores over 1 week. Baseline correlations were moderate to large (r > 0·30) between SD NRS and pruritus or sleep loss scores, but were small (r = −0·11 to 0·17) between SD NRS and EQ-5D-3L index and visual analogue scores, Hospital Anxiety and Depression Scale, Scoring Atopic Dermatitis, and Investigator’s Global Assessment. The SD NRS could discriminate groups of participants in the expected direction according to different quality-of-life scores but not according to different clinician-reported disease severity scores. SD NRS scores significantly decreased as sleep loss, itch and quality-of-life scores improved. Analysis of meaningful change suggested a 2–5-point improvement as the initial range of responder definition in the SD NRS score. Conclusions: The SD NRS is a reliable, valid and responsive measure of SD in adults with moderate-to-severe AD.