Background: The original SF-6D valuation study collected 3503 standard gambled responses from 611 UK respondents to predict quality-adjusted life year (QALY) values.
Methods: Using 19,980 paired comparison responses from 666 US respondents and a stacked probit model, the 25 coefficients of the original SF-6D multiattribute utility (MAU) regression were estimated, such that each coefficient represents a QALY decrement. The US QALY predictions were compared with UK predictions using 8428 SF-6D states in the US Medicare Health Outcomes Survey (MHOS), 1998 to 2003.
Results: Twenty-two of the 25 decrements in the SF-6D MAU regression are statistically significant. The remaining decrements are insignificant based on US and UK results. The US and UK QALY predictions for the MHOS SF-6D states are remarkably similar given differences in experimental design, format, and sampling (Lin's coefficient of agreement, 0.941; absolute mean difference, 0.043). Limitations. The underlying theoretical framework for the
Study design: and econometric analysis builds from the episodic random utility model and the concept of QALYs and inherits their limitations.
Conclusions: This study enhances the potential for US comparative effectiveness research by translating SF-6D states into US QALYs as well as improves upon discrete choice experiment design and econometric methods for health valuation.
Keywords: decision analysis; econometric methods; mathematical models; preferences and quality of life; statistical methods.