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.
Keywords: Atopic dermatitis; Daily diary; Eczema; Patient-reported outcomes; Pruritus.