Does the choice of EQ-5D tariff matter? A comparison of the Swedish EQ-5D-3L index score with UK, US, Germany and Denmark among type 2 diabetes patients

OBJECTIVE: To compare the performance of the recently developed Swedish experience-based time trade-off (TTO) valuation of the EuroQol-5D-3L (EQ-5D-3L) against the hypothetical-based TTO valuations from UK, US, Germany and Denmark. METHODS: Type 2 diabetes patients from the Swedish National Diabetes Register (N = 1 757) responded to EQ-5D-3L questionnaire in 2008. Health utilities were compared using a range of parametric and nonparametric tests. Absolute agreement and consistency were investigated using intra-class correlations coefficients (ICCs) and Bland-Altman plots. Differences in health utilities between known-groups were evaluated. Transition scores for pairs of observed EQ-5D-3L health states were calculated and compared. RESULTS: The Swedish tariff (SWT) resulted in substantially higher health utilities and differences were more profound for more severe health problems. ICC ranged 0.6 to 0.8 and Bland-Altman plots showed wide limits of agreement. While all tariffs discriminate between known-groups, the effect sizes were generally small. The SWT had higher (lower) known-group validity for macrovascular (microvascular) complications. The SWT and UK tariff were associated with the lowest and the highest mean absolute transition scores, respectively, for 2775 observed pairs of the EQ-5D-3L health states. CONCLUSION: There were systematic differences between the SWT and tariffs from other countries meaning that the choice of tariff might have substantial impact on funding decisions. The Swedish experienced-based TTO valuation will give higher priority to life-extending interventions than those which improve quality of life. We suggest that economic evaluations in Sweden include both Swedish experience-based and non-Swedish hypothetical-based valuations through a sensitivity analysis.