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Open Access 01-02-2021 | Atopic Dermatitis | Original Research
Development and Content Validation of Pruritus and Symptoms Assessment for Atopic Dermatitis (PSAAD) in Adolescents and Adults with Moderate-to-Severe AD
Published in: Dermatology and Therapy | Issue 1/2021
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Introduction
Most patient-reported outcome (PRO) instruments that measure atopic dermatitis (AD) symptoms do not have sufficient documented evidence of content validity to satisfy regulatory agency guidance for inclusion in product-labelling claims in the USA or Europe. The objective of this study was to develop a PRO instrument in accordance with regulatory agency guidance to assess daily AD symptoms during the course of therapy and to establish its content validity and psychometric properties.
Methods
The Pruritus and Symptoms Assessment for Atopic Dermatitis (PSAAD) daily diary was developed based on qualitative interviews with US adolescents and adults with mild-to-severe AD. Content validity, test–retest reliability, internal consistency reliability, clinically important difference, clinically important responder, convergent validity, and known-group validity were evaluated using correlational and regression methods from phase 2b data from US adults with moderate-to-severe AD who were treated with abrocitinib.
Results
Patient interviews conducted with US adolescents and adults with mild-to-severe AD identified 11 relevant symptoms (itch, dryness, redness, flaking, discolouration, pain, bleeding, cracking, bumps, swelling, and weeping/oozing) for inclusion in the PSAAD instrument. All PSAAD psychometric parameters were acceptable based on phase 2b data from US adults with moderate-to-severe AD. Convergent validity and known-group validity were confirmed by significant correlations between PSAAD and six other PRO measures (r = 0.24–0.91, all p ≤ 0.01) and Dermatology Life Quality Index category (p ≤ 0.0001), respectively.
Conclusions
Evidence supports the PSAAD instrument validity, reliability, responsiveness and definitions of clinically important changes/differences for adults with moderate-to-severe AD.