Reliability, validity, and the ability to detect change of the Psoriasis Symptom Scale (PSS) in patients with plaque psoriasis
Introduction: The primary objective of the study was to evaluate the measurement properties of the patient-reported four-item Psoriasis Symptom Scale (PSS). Methods: Analysis of phase-III data on the efficacy of risankizumab to assess psychometric characteristics of the PSS in patients with moderate...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Taylor & Francis Group
2020-07-01
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| Series: | Journal of Dermatological Treatment |
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1080/09546634.2019.1709612 |
| Summary: | Introduction: The primary objective of the study was to evaluate the measurement properties of the patient-reported four-item Psoriasis Symptom Scale (PSS). Methods: Analysis of phase-III data on the efficacy of risankizumab to assess psychometric characteristics of the PSS in patients with moderate-to-severe psoriasis. Results: PSS items had a good range of symptom severity coverage. The PSS had good test–retest reliability (ICCs >0.90). Convergent and discriminant validity was indicated by moderate-to-strong correlations between the PSS and Dermatology Life Quality Index (DLQI), PSS pain item and EQ-5D pain/discomfort item at week 12 (0.63), and moderate negative correlation with EQ-Visual Analog Scale score at week 12 (−0.37). Known groups validity demonstrated as mean PSS total scores varied by Psoriasis Area and Severity Index (PASI) and Static Physician’s Global Assessment (sPGA) defined groups (p < .0001). PSS total scores were responsive to changes in PASI score (p < .0001) and sPGA (p < .0001). PSS minimal, clinical, and meaningful change is estimated to be 1 to 2 points; a preliminary responder definition is a total change score of 3 to 4 points. Conclusions: The PSS is a short, valid unidimensional measure of psoriasis symptom severity, well suited for use in clinical trials. |
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| ISSN: | 0954-6634 1471-1753 |