Evaluating quality-adjusted life years: Estimation of the Health Utility Index (HUI2) from the SF-36

Quality-adjusted life years (QALYs) are well recognized as a valid measure for outcomes in cost-effectiveness analyses. A summary health utility score is necessary to evaluate QALYs. The objective of this study was to predict a summary utility score (represented by the Health Utility Index [HUI2]) from scores on the SF-36. Methods. A structural equation framework was applied to longitudinal data collected from 1992 to 1995 on a sample of patients insured by Southern California Kaiser Permanente (N = 6921). An ordinary least squares (OLS) method was used to estimate the HUI2. Results. The OLS model on cross-sectional data predicted 50.5% of the observed variance in HUI2 scores. Parameter estimates of all SF-36 components showed statistical significance at the P < 0.05 level. Conclusions. Results of this study provide a quantitative link between two important measures of health status. The present model can be used to estimate health utility summary scores in studies that have collected SF-36 data.