542 - Validation of the skin pain numerical rating scale of the Pruritus and Symptoms Assessment for Atopic Dermatitis for adults and adolescents with moderate-to-severe atopic dermatitis
Authors: Silverberg Jonathan I , Ständer Sonja , Kim Brian S , Bewley Anthony , Misery Laurent , Vestergaard Christian , Gooderham Melinda J , Bushmakin Andrew G , Cappelleri Joseph C , Güler Erman , Alderfer Justine , Watkins Melissa , Selfridge Andrew , Myers Daniela E 
Published: February 2024

Background

Skin pain is a common and burdensome symptom of atopic dermatitis (AD), and its severity increases with disease progression. The Pruritus and Symptoms Assessment for Atopic Dermatitis (PSAAD) is a validated 11-item patient-reported instrument developed in accordance with regulatory agency guidance for assessment of the daily symptoms of patients with AD, including skin pain.

Objective

To establish content validity and evaluate the psychometric properties of the skin pain numerical rating scale (NRS) item of the PSAAD.

Methods

The skin pain NRS is a single-item measure from the PSAAD and is used to assess skin pain severity over the past 24 hours with the question “How painful was your skin over the past 24 hours?” on a 10-point scale from 0 (not painful) to 10 (extremely painful). A qualitative validation analysis consisting of concept elicitation (CE) interviews; electronic completion of the PSAAD measure, including the skin pain NRS; and cognitive debriefing (CD) interviews was conducted for adults and adolescents with mild-to-severe AD. Evaluation of psychometric properties of the skin pain NRS—including test-retest reliability, estimation of meaningful within-patient change (MWPC), known-group validity, ability to detect change, construct validity, quality of completion, and ceiling and floor effects—was conducted based on a post hoc qualitative and quantitative analysis of pooled data, with skin pain NRS as part of the PSAAD in the abrocitinib monotherapy phase 3 trials JADE MONO-1 (NCT03349060) and JADE MONO-2 (NCT03575871). Data from patients (≥12 years of age) with moderate-to-severe AD were pooled across all treatment arms.

Results

Among 30 CE interviews (adolescents [12-17 years], n=15; adults [≥18 years], n=15) conducted over 2 rounds of testing, 20 of 30 (67%) patients reported skin pain. During CD interviews (n=30), 100% of patients interpreted the skin pain NRS item as intended, and 73% reported it as relevant. The psychometric validation analysis included 736 patients (JADE MONO-1, N=347; JADE MONO-2, N=389). The test-retest reliability of the skin pain NRS was evidenced by large intraclass correlation coefficients (ICC; 0.76 and 0.72 in JADE MONO-1 and MONO-2, respectively) for a single daily skin pain score, which increased to 0.93 and 0.91 for a measurement averaging at least 4 scores per week. Convergent validity was demonstrated by correlations between skin pain and other clinician- and patient-­reported AD measures (median correlation &gt;0.4 starting at week 4). The skin pain NRS distinguished between “clear” and “severe” disease severity groups, assessed using the Patient Global Assessment (PtGA) and Investigator’s Global Assessment (IGA) as continuous and categorical anchors (P&lt;0.0001); differences were also significant among other disease severity groups using the PtGA and IGA as continuous anchors (P&lt;0.0001). Based on the PtGA and IGA anchor analysis, the estimated MWPC was 1.9 and ranged from 2.7 to 3.9 points using the empirical cumulative distribution function analysis. Ability to detect change was demonstrated by linear relationships between disease severity measures and skin pain scores (correlation of ≥0.5 between the skin pain NRS and the PtGA). More than 90% of patients provided at least 4 daily skin pain scores each week. No floor or ceiling effects were observed.

Conclusions

The qualitative and quantitative data from initial PSAAD development and psychometric evaluation of the skin pain NRS from the PSAAD support its content validity, reliability, construct validity, and ability to detect change. These findings corroborate the 4-point improvement in skin pain as the adequate and meaningful cut-off to define a skin pain responder in JADE MONO-1 and MONO-2.