Estimating meaningful change thresholds for Skin Pain‐Numeric Rating Scale, Sleep‐Numeric Rating Scale and Dermatology Life Quality Index in patients with prurigo nodularis

Abstract Background Prurigo nodularis (PN) is characterized by intensely itchy nodules/lesions and skin pain, which can have a substantial impact on health‐related quality of life (HRQoL). Treatment benefits on such symptoms and impacts are best assessed in trials using patient‐reported outcome (PROs) instruments such as Skin Pain Numerical Rating Scale (NRS), Sleep‐NRS and Dermatology Life Quality Index (DLQI). However, no guidance exists for interpreting meaningful changes in scores using these PROs in patients with PN. Objectives The main objective was to derive within‐patient (responder definition) and between‐group improvement thresholds for interpreting Skin Pain‐NRS, Sleep‐NRS and DLQI total scores in patients with PN. The measurement properties of the three PROs were also evaluated. Methods Intention‐to‐treat (ITT), blinded and pooled data were used from the Phase 3 PRIME (NCT04183335) and PRIME2 (NCT04202679) studies evaluating the efficacy of dupilumab in adult patients with PN. Anchor‐ and distribution‐based methods were applied to derive responder definition and between‐group thresholds for Skin Pain‐NRS, Sleep‐NRS and DLQI. Data were additionally used to examine the instrument measurement properties, including reliability, validity and responsiveness. Results A total of 311 patients (mean age 49.5 years, 65.3% female) were included in the pooled ITT population. The within‐patient improvement threshold for Skin Pain‐NRS was estimated as 4.0 points, 2.0 points for Sleep‐NRS and 9.0 points for DLQI total score. A 1.5‐point improvement in Skin Pain‐NRS scores, 1.0‐point in Sleep‐NRS and 4.0‐point in DLQI indicated a between‐group meaningful change. Adequate to good psychometric properties were demonstrated for all three instruments. Conclusions The results of this study can aid interpretation of Skin Pain‐NRS, Sleep‐NRS and DLQI scores in patients with PN in both clinical trials and clinical practice to better understand and treat PN‐related skin pain and the impact of PN on sleep quality and HRQoL.