A Comparison of the Validity and Responsiveness of the EQ-5D-5L and SF-6D for Measuring Health Spillovers: A Study of the Family Impact of Meningitis

The “health spillover” of patient illness on family members is important to capture in economic evaluation. This study compares the construct validity and responsiveness of 2 widely used health-related quality-of-life instruments, the EQ-5D-5L and SF-6D, in capturing health spillover effects for family members with and without an informal care role (carers and noncarers). Construct validity and responsiveness were assessed using data from a 2012 UK survey of the family impact of meningitis-related sequelae. Construct validity was assessed by testing associations between family members’ health status and variables anticipated to be associated with spillover effects (patient health status and informal care). Responsiveness was assessed by testing associations between the longitudinal change in family members’ health status and longitudinal change in patient health and caring hours. Among noncarers, both the EQ-5D-5L and the SF-6D exhibited construct validity with 10 of the 11 associations that were hypothesized being statistically significant on both measures. There was less clear evidence of responsiveness of the measures for noncarers. Among carers, the EQ-5D-5L exhibited greater construct validity, as well as responsiveness, with respect to spillovers from patient health. This was evidenced by the EQ-5D-5L detecting 9 significant associations compared with 4 on the SF-6D. However, the SF-6D exhibited greater construct validity with respect to spillovers generated from informal care provision (5 associations significant compared with 2 on the EQ-5D-5L). Both the EQ-5D-5L and the SF-6D exhibited a degree of validity that could justify their use as measures of health-related quality-of-life spillovers on family members in economic evaluation.