A Comparison of UK and Brazilian SF-6D Preference Weights When Applied to a Brazilian Urban Population

Background: The 6-dimensional health state short form (SF-6D) is a health preference measure used in economic evaluations of many treatments. Objectives: To compare the results provided by the SF-6D index, when applied to a representative sample of the Brazilian population, using Brazilian and UK preference weights. Methods: Five thousand individuals were assessed in the 5 regions of Brazil. Preference measures in healthcare were assessed using the SF-6D Brazil, version 2002. To calculate the single utility score, 2 preference weights were used: one established for the Brazilian population (SF-6D Brazil) and the other for the UK population (SF-6D UK). Agreement between the SF-6D Brazil and the SF-6D UK was assessed using the intraclass correlation coefficient, the Wilcoxon signed rank test, confidence intervals (CIs), and the Bland-Altman method. Results: The mean values of the SF-6D Brazil and the SF-6D UK were 0.83 +/- 0.15 and 0.84 +/- 0.15, respectively. The intraclass correlation coefficient was 0.952 (CI 0.9420.960; P<.010). The Wilcoxon signed rank test and CI showed a statistically significant difference between the 2 measures; this difference was, however, very small and considered clinically irrelevant (CI 0.011-0.013; P<.010). Using the Bland-Altman method resulted in a mean difference of 0.012 and the limits of agreement were between -0.077 and 0.101. Conclusions: The present study identified very small quantitative differences between UK- and Brazilian-derived SF-6D scores. Tests of agreement, however, showed that the impact of using different sets of preference weights in the construction of quality-adjusted life-year might be considered irrelevant.