Mapping the SF-12 to the EuroQol EQ-5D index in a national US sample

Background. Preference scores for the Medical Outcomes Study (MOS) SF-12 would enable its use in cost-effectiveness analyses. Previous mapping studies of MOS instruments to preference-based instruments have not examined performance in national samples. Participants. 15,000 adults in the 2000 Medical Expenditure Panel Survey annual survey including the SF-12 and EQ-5D Index. Methods. Regression of the EQ-5D Index scores onto the physical and mental component summary scores of the SF-12, testing 2nd-4th degree polynomial and spline models, including and excluding sociodemographics. Results. A 2nd degree polynomial model explained 63% of the variance in EQ-5D scores, with robust internal and external validation. More complex models explained minimally additional variance. Compared with EQ-5D valuations, prediction models overestimated the lowest health states (6% of the population). Conclusions. The mapped SF-12 yields usable preference-scaled scores, with some caution for the lowest health states.