The relationship between health-state utilities and the SF-12 in a general population

It would be a major advance if quality-of-life instruments could be translated into health-state utilities. The aim with this study was to investigate the relationship between the SF-12 and health-state utilities, based on responses to a postal questionnaire sent to a random sample of 8,000 inhabitants, aged 20-84 years, in the general population. The questionnaire included the SF-12, a rating-scale (RS) question, and a time-tradeoff (TTO) question; the response rate was 68%. Age, gender, and the 12 items of the SF-12 were used as explanatory variables in a linear regression analysis of the health-state utilities. The regression models explained about 50% of the variance in the RS answers and about 25% of the variance in the TTO answers. Most of the SF-12 items were related to the health-state utilities in the expected ways, with especially strong results for the RS method. The results suggest that the SF-12 can be converted to health-state utilities, but that further work is needed to reliably estimate the conversion function.