OBJECTIVES: The EQ-5D-5L is a widely used generic preference-based measure of health-related quality of life. Additional dimensions (bolt-ons) may improve the instrument’s content validity and responsiveness in certain patient populations. This study aimed to assess the content validity of the EQ-5D-5L and skin irritation, self-confidence, social relationships and sleep bolt-ons, for people with chronic skin conditions: atopic dermatitis (AD) and chronic urticaria (CU).

METHODS: Thirty adults with AD (n=15) or CU (n=15) in the United Kingdom, with varying AD/CU severity, participated in semi-structured interviews. During the interviews participants described the symptoms and impacts of their condition, then completed the EQ-5D-5L and the four bolt-ons using ‘think-aloud’ and retrospective probing. Interviews were recorded, transcribed, then analysed using content and thematic analysis.

RESULTS: Participants were 23-62 years old (mean AD 36.1, CU 39.6) and mostly female (AD 73%, CU 80%). Itch was the most reported symptom (AD 100%, CU 93%). Impacted self-confidence (AD: 100%, CU: 47%), sleep (AD: 53%; CU: 53%), and social relationships (AD: 27%; CU: 60%) were frequently spontaneously reported. For all participants, skin irritation and self-confidence bolt-ons improved the EQ-5D-5L’s comprehensiveness. The skin irritation bolt-on was the most relevant or important dimension for 60% of AD and 73% of CU participants. Some dimensions were considered to be linked by some participants, including skin irritation and pain/discomfort (AD n=10, CU n=6), and self-confidence and anxiety/depression (AD n=11, CU n=5). Impacted social relationships was most frequently ranked least relevant or important among the bolt-ons.

CONCLUSIONS: In this study, skin irritation and self-confidence bolt-ons showed good evidence of content validity for people with AD and CU. Whilst there is also preliminary support for the sleep bolt-on in these populations, the value of a social relationships bolt-on was less clear. Quantitative psychometric research is recommended to further support the use of EQ-5D-5L bolt-ons in CU and AD.