Systematic Review and Empirical Comparison of Contemporaneous EQ-5D and SF-6D Group Mean Scores

Background. Group mean estimates and their underlying distributions are the focus of assessment for cost and outcome variables in economic evaluation. Research focusing on the comparability of alternative preference-based measures of health-related quality of life has typically focused on analysis of individual-level data within specific clinical specialties or community-based samples. Purpose. To explore the relationship between group mean scores for the EQ-5D and SF-6D across the utility scoring range. Methods. Studies were identified via a systematic search of 13 online electronic databases, a review of reference lists of included papers, and hand searches of key journals. Studies were included if they reported contemporaneous mean EQ-5D and SF-6D health state scores. All (sub)group comparisons of group mean EQ-5D and SF-6D scores identifiable from text, tables, or figures were extracted from identified studies. A total of 921 group mean comparisons were extracted from 56 studies. The nature of the relationship between the paired scores was examined using ranked scatter graphs and analysis of agreement. Results. Systematic differences in group mean estimates were observed at both ends of the utility scale. At the lower (upper) end of the scale, the SF-6D (EQ-5D) provides higher mean utility estimates. Conclusions. These findings show that group mean EQ-5D and SF-6D scores are not directly comparable. This raises serious concerns about the cross-study comparability of economic evaluations that differ in the choice of preference-based measures, although the review focuses on 2 of the available instruments only. Further work is needed to address the practical implications of noninterchangeable utility estimates for cost-per-QALY estimates and decision making.