SF-6Dv2 Valuation Study in South Korea: Uncovering Level Inconsistencies and Next Steps for Research

OBJECTIVES: This study aimed to derive value sets for SF-6Dv2 health states in the South Korean general population.

METHODS: A web-based discrete choice experiment including duration (DCE_TTO) was conducted, following international protocols. The survey included 304 choice sets with 4 duration levels, blocked into 38 groups. A total of 3,800 respondents aged 18 or older were recruited using quota sampling for gender, age, and region. Conditional logit regression models were used to analyze choice results.

RESULTS: The survey was conducted from March 27 to April 23, 2024. While demographic distributions largely reflected the general population, there was an overrepresentation of higher education levels (80% college or above). The average response time was 23.4 minutes. Pain, social functioning, mental health, and survival duration showed expected trends, with pain emerging as the most important dimension. However, physical functioning and vitality exhibited disordering between levels 1 and 2. Notably, role limitation presented a unique challenge, demonstrating unexpected patterns across multiple levels, indicating a need for further investigation into how levels in this dimension were interpreted by respondents.

CONCLUSIONS: This study revealed disordering issues in several dimensions of the SF-6Dv2. Potential factors contributing to these issues include ambiguities arising from double-negative phrasing, respondents' reluctance to trade survival time for minor functional decrements, and, particularly for role limitation, an apparent misinterpretation of level directionality. The findings highlight the need for further investigation into respondents' interpretation of function levels and potential improvements in survey design for future studies.