PSYCHOMETRIC EVALUATION OF THE EQ-5D-5L SKIN BOLT-ONS IN MILD-TO-MODERATE PSORIASIS USING POOLED PHASE 3 TRIAL DATA
Author(s)
Maja Kuharic, PhD1, You-Shan Feng, PhD2, Pearl Craig, PharmD3, Fanni Rencz, PhD4.
1Department of Medical Social Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL, USA, 2Institute for Clinical Epidemiology and Applied Biometrics, University of Tübingen, Tübingen, Germany, 3Department of Pharmacy, Systems, Outcomes and Policy, College of Pharmacy, University of Illinois Chicago, Chicago, IL, USA, 4EuroQol Research Foundation, Rotterdam, Netherlands.
1Department of Medical Social Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL, USA, 2Institute for Clinical Epidemiology and Applied Biometrics, University of Tübingen, Tübingen, Germany, 3Department of Pharmacy, Systems, Outcomes and Policy, College of Pharmacy, University of Illinois Chicago, Chicago, IL, USA, 4EuroQol Research Foundation, Rotterdam, Netherlands.
OBJECTIVES: The EQ-5D-5L may underestimate the health-related quality of life (HRQoL) impact of skin conditions due to ceiling effects in core dimensions. This study evaluates the psychometric properties of the Skin Irritation and Self-Confidence bolt-ons from the experimental EQ-5D Bolt-on ToolboxTM.
METHODS: Data were pooled from two phase 3 trials of calcipotriol/betamethasone dipropionate foam, PSO-ABLE (N=464) and PSO-LONG (N=661), yielding 1,125 patients with mild-to-moderate psoriasis. Construct validity was assessed using Spearman correlations with condition-specific patient-reported outcomes (DLQI, Itch VAS, PQoL-12) and clinical measures (mPASI, PGA). Known-groups validity compared Cohen's d for five-dimension (Level Sum Score [LSS-5], UK 5L index) versus seven-dimension (LSS-7, EQ-5D-5L+bolt-ons index) scores across DLQI, PGA, and PASI categories. Responsiveness was evaluated using standardized response means (SRM) from baseline to Week 12 across nine anchor-based responder definitions (PASI75/90/100, PGA success/clear, DLQI reduction≥5, DLQI 0-1). Differential item functioning (DIF) was assessed using IRT-based ordinal logistic regression across sex, age, study, and language (McFadden R²≥0.02).
RESULTS: Pain/Discomfort correlated moderately with Skin Irritation (rs=0.47), confirming that the EQ-5D-5L incompletely captures itch. Skin Irritation correlated strongly with DLQI Item 1 (itchy/sore; rs=0.72) and Itch VAS (rs=0.67); Self-Confidence correlated moderately with DLQI Item 2 (embarrassment; rs=0.47). Both dimensions showed weak correlations with Mobility and Self-Care (rs=0.09-0.13). LSS-7 produced larger known-groups effect sizes than LSS-5, and EQ-5D-5L+bolt-ons outperformed the UK 5L index. For DLQI 0-1 versus 21-30, Cohen’s d increased from 1.86 to 2.87 (LSS) and 1.72 to 2.17 (index). Among PASI75-improved patients, SRM was 0.99 (LSS-7) versus 0.55 (LSS-5), and 0.97 (EQ-5D-5L+bolt-ons) versus 0.47 (UK 5L). Skin Irritation showed no DIF; Self-Confidence exceeded the uniform DIF threshold for sex (R²=0.028) and age <45/≥45 (R²=0.023).
CONCLUSIONS: The two EQ-5D-5L bolt-ons improve known-groups discrimination and responsiveness to clinical change, with EQ-5D-5L+bolt-ons showing greater sensitivity than the UK 5L index.
METHODS: Data were pooled from two phase 3 trials of calcipotriol/betamethasone dipropionate foam, PSO-ABLE (N=464) and PSO-LONG (N=661), yielding 1,125 patients with mild-to-moderate psoriasis. Construct validity was assessed using Spearman correlations with condition-specific patient-reported outcomes (DLQI, Itch VAS, PQoL-12) and clinical measures (mPASI, PGA). Known-groups validity compared Cohen's d for five-dimension (Level Sum Score [LSS-5], UK 5L index) versus seven-dimension (LSS-7, EQ-5D-5L+bolt-ons index) scores across DLQI, PGA, and PASI categories. Responsiveness was evaluated using standardized response means (SRM) from baseline to Week 12 across nine anchor-based responder definitions (PASI75/90/100, PGA success/clear, DLQI reduction≥5, DLQI 0-1). Differential item functioning (DIF) was assessed using IRT-based ordinal logistic regression across sex, age, study, and language (McFadden R²≥0.02).
RESULTS: Pain/Discomfort correlated moderately with Skin Irritation (rs=0.47), confirming that the EQ-5D-5L incompletely captures itch. Skin Irritation correlated strongly with DLQI Item 1 (itchy/sore; rs=0.72) and Itch VAS (rs=0.67); Self-Confidence correlated moderately with DLQI Item 2 (embarrassment; rs=0.47). Both dimensions showed weak correlations with Mobility and Self-Care (rs=0.09-0.13). LSS-7 produced larger known-groups effect sizes than LSS-5, and EQ-5D-5L+bolt-ons outperformed the UK 5L index. For DLQI 0-1 versus 21-30, Cohen’s d increased from 1.86 to 2.87 (LSS) and 1.72 to 2.17 (index). Among PASI75-improved patients, SRM was 0.99 (LSS-7) versus 0.55 (LSS-5), and 0.97 (EQ-5D-5L+bolt-ons) versus 0.47 (UK 5L). Skin Irritation showed no DIF; Self-Confidence exceeded the uniform DIF threshold for sex (R²=0.028) and age <45/≥45 (R²=0.023).
CONCLUSIONS: The two EQ-5D-5L bolt-ons improve known-groups discrimination and responsiveness to clinical change, with EQ-5D-5L+bolt-ons showing greater sensitivity than the UK 5L index.
Conference/Value in Health Info
2026-11, ISPOR Europe 2026, Vienna, Austria
Value in Health, Volume 29, Issue 12S
Code
PCR202
Topic
Patient-Centered Research
Topic Subcategory
Instrument Development, Validation, & Translation
Disease
Sensory System Disorders (Ear, Eye, Dental, Skin), Systemic Disorders/Conditions (Anesthesia, Auto-Immune Disorders (n.e.c.), Hematological Disorders (non-oncologic), Pain)