Qualitative evidence on EQ-5D-5L skin irritation and self-confidence bolt-ons in Darier's disease and Hailey-Hailey disease

Abstract

Objectives Limited evidence is available about the content validity of the EQ-5D-5L in rare skin fragility disorders. Previous research has demonstrated that the skin irritation and self-confidence additional dimensions (bolt-ons) improve the content validity of the EQ-5D-5L in psoriasis and atopic dermatitis. Our aim was to investigate the content validity of the EQ-5D-5L and the two bolt-ons in Darier’s disease and Hailey-Hailey disease. Methods In 2023, we conducted qualitative, semi-structured interviews with 15 adult patients at a university dermatology clinic. Patients completed the EQ-5D-5L with two bolt-ons using a think-aloud technique. We used probing questions to explore the relevance, comprehensiveness and comprehensibility. Thematic analysis was applied to analyze the transcripts from the interviews. Results Most patients found both the EQ-5D-5L and the two bolt-ons comprehensible and relevant to their disease. All patients preferred the EQ-5D-5L with the two bolt-ons over the EQ-5D-5L alone. Twelve potential missing concepts were identified after the EQ-5D-5L + bolt-ons, but only financial impact and sex life were identified by more than one patient. Only one patient reported a conceptual overlap between the skin irritation bolt-on and the pain/discomfort dimension. Conclusions Our findings suggest that there is no actionable evidence indicating gaps in the content validity of the EQ-5D-5L with two bolt-ons in Darier’s and Hailey-Hailey disease. Future studies are encouraged to conduct quantitative psychometric testing of the bolt-ons in this and other chronic dermatological patient populations.