Validation of the Peak Pruritus‐Numerical Rating Scale in patients with chronic plaque psoriasis: results from a phase 2 study.

Background: Pruritus is a common, bothersome symptom for patients with mild‐to‐moderate plaque psoriasis (PsO), yet no validated scale assesses it in this patient population. We aimed to validate the Peak Pruritus‐Numerical Rating Scale (PP‐NRS) using data from a Phase 2b study investigating the efficacy of brepocitinib in patients with mild‐to‐moderate chronic PsO. Methods: Patients completed the PP‐NRS daily from baseline for the first 2 weeks after the dose administration and subsequently only on visit days. Test–retest reliability (intraclass correlation coefficient [ICC]), construct validity (known group validity and convergent validity), ability to detect change, and meaningful within‐patient change (MWPC) were evaluated using correlation and regression analyses. Results: The PP‐NRS demonstrated acceptable test–retest reliability (ICC: 0.86–0.89). Known‐group evidence demonstrated that PP‐NRS scores could discriminate between different degrees of disease severity. Convergent validity was supported by significant correlation coefficients between the PP‐NRS and Patient Global Assessment (PtGA), Dermatology Life Quality Index, and Psoriasis Symptom Inventory, which generally exceeded 0.50. The ability to detect change was evidenced by an approximately linear relationship between changes in PP‐NRS and Physician Global Assessment or PtGA of psoriasis scores. The value of 2.8 was determined as the MWPC for the PP‐NRS. Conclusions: PP‐NRS is a reliable, practical test for assessing pruritus in mild‐to‐moderate PsO clinical trials. ClinicalTrials.gov identifier NCT03850483. [ABSTRACT FROM AUTHOR]