April W Armstrong1, Emily Edson-Heredia2, April N Naegeli2, Russel Burge2,3, Jiat-Ling Poon4, Milena Anatchkova4,5, Luna Sun2, Baojin Zhu2, Kathleen W Wyrwich2. 1. Department of Dermatology, Keck School of Medicine of USC, Los Angeles, CA, USA. 2. Eli Lilly and Company, Indianapolis, IN, USA. 3. Department of Pharmaceutical Sciences, James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA. 4. Evidera, Bethesda, MD, USA. 5. Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, MA, USA.
Abstract
Background: Psoriasis is a chronic inflammatory skin disease.Objective: To establish content validity and assess psychometric properties of the Psoriasis Symptoms Scale (PSS) in patients with moderate-to-severe psoriasis (Ps). Methods: The PSS is an eight-item patient-completed questionnaire assessing symptoms (itch, pain, stinging, burning), signs (redness, scaling, cracking), and discomfort. Content validity was established during interviews of patients (n = 14) with Ps. PSS Symptoms and Signs domain scores were evaluated for reliability, construct validity, and responsiveness using data from a clinical study (NCT02899988) in Ps (n = 205). Results: Patients confirmed content validity; the PSS was understandable and relevant. Cronbach's alphas were 0.84 (Symptoms) and 0.86 (Signs), demonstrating internal consistency reliability. Test-retest reliability was confirmed in patients before receiving study drug (intraclass coefficient: 0.82 [Symptoms]; 0.81 [Signs]). Convergent and discriminant validity were demonstrated at baseline and Week 16 by large (≥0.50) correlations between PSS Symptoms and Signs domain scores and Dermatology Life Quality Index total and symptoms and feelings domain scores, and small (<0.30) correlations with Short Form-36 Mental Component Summary score, respectively. Symptoms and Signs scores responded to clinical changes (p < .001).Conclusions: The PSS Symptoms and Signs domains are valid and reliable assessments of patient-reported symptoms and signs, useful for assessing treatment efficacy.
Background: Psoriasis is a chronic inflammatory skin disease.Objective: To establish content validity and assess psychometric properties of the Psoriasis Symptoms Scale (PSS) in patients with moderate-to-severe psoriasis (Ps). Methods: The PSS is an eight-item patient-completed questionnaire assessing symptoms (itch, pain, stinging, burning), signs (redness, scaling, cracking), and discomfort. Content validity was established during interviews of patients (n = 14) with Ps. PSS Symptoms and Signs domain scores were evaluated for reliability, construct validity, and responsiveness using data from a clinical study (NCT02899988) in Ps (n = 205). Results:Patients confirmed content validity; the PSS was understandable and relevant. Cronbach's alphas were 0.84 (Symptoms) and 0.86 (Signs), demonstrating internal consistency reliability. Test-retest reliability was confirmed in patients before receiving study drug (intraclass coefficient: 0.82 [Symptoms]; 0.81 [Signs]). Convergent and discriminant validity were demonstrated at baseline and Week 16 by large (≥0.50) correlations between PSS Symptoms and Signs domain scores and Dermatology Life Quality Index total and symptoms and feelings domain scores, and small (<0.30) correlations with Short Form-36 Mental Component Summary score, respectively. Symptoms and Signs scores responded to clinical changes (p < .001).Conclusions: The PSS Symptoms and Signs domains are valid and reliable assessments of patient-reported symptoms and signs, useful for assessing treatment efficacy.