Qualitative testing of the EQ-HWB-9 with a ‘blank’ EQ-HWB VAS and EQ-5D-5L with skin bolt-ons in a rare genetic skin disease population

All procedures performed in studies involving human participants were by the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The research was approved by the Semmelweis University Regional and Institutional Committee of Science and Research Ethics (No. 220-1/2022, SE RKEB).

Abstract

Purpose Epidermal differentiation disorders (EDDs) are rare genetic skin disorders that significantly impact patients’ health and wellbeing. This study assessed the content validity of two experimental EuroQol instruments (EQ-5D-5Lbolt-ons and EQ-HWB-9) and explored potential endpoint options for a visual analogue scale (VAS) for EQ-HWB-9 in this population. Methods Semi-structured interviews were conducted with 20 adult patients with EDDs at a university dermatology clinic (2024–2025). Participants completed the EQ-5D-5L with skin irritation and self-confidence bolt-ons and EQ-HWB-9 using a think-aloud protocol. Probing questions explored item relevance, missing concepts, and comprehensibility. An EQ-HWB VAS with endpoints blanked out was also presented for feedback. Results Participants found both instruments generally comprehensive, understandable, and relevant for EDD. The EQ5D-5L with bolt-ons was considered suitable for measuring health- and disease-related aspects (e.g., skin irritation bolt-on was the most relevant item for all but one patients), while the EQ-HWB-9 was seen as relevant to measure broader life impacts. Three participants suggested combining the EQ-HWB-9 loneliness item with others, and three participants recommended splitting the sadness/depression item. One participant noted missing social/romantic relationship items in both instruments. Overall, 32 different concepts were proposed as EQ-HWB VAS endpoint labels, including both health-related and broader wellbeing concepts, such as overall feeling, mood, quality of life, and harmony. Conclusion Both the EQ-5D-5L with bolt-ons and EQ-HWB-9 demonstrated acceptable content validity in this genetic disease population. Our findings provide useful input for finalizing these experimental instruments and offer the first exploratory qualitative results about potential endpoints for an EQ-HWB VAS.