Mapping the SF-12 to preference-based instruments - Convergent validity in a low-income, minority population

BACKGROUND. The profile-based SF-12 has a low respondent burden and is used widely in clinical settings to monitor health and evaluate programs. Deriving preference scores for the SF-12 health profile would permit its use in cost-effectiveness analyses. Previous mapping studies of SF family instruments to preference-based instruments have not examined convergent validity or performance in low-income, minority populations. OBJECTIVES. To map the SF-12 to the EuroQol (EQ-5D Index) and the Health Utilities Index Mark 3 (HU13) in a low-income, predominantly minority sample. RESEARCH DESIGN. We used a cross-sectional survey data. SUBJECTS. We studied a convenience sample of 240 low-income, predominantly Latino and black patients attending a community health center in New York. MEASURES. We used separate regressions of the EQ-5D Index and HU13 onto the physical (PCS-12) and mental (MCS-12) components of the SF-12 scores as measures. RESULTS. For the EQ-513 Index regression, the adjusted variance explained was 58% (bootstrap validation 95% confidence interval [CI], 46-66). For the HU13 regression, the adjusted variance explained was 51% (bootstrap 95% CI, 39-59). The correlation coefficient between the 2 predicted measures was 0.96. The correlation of the predicted HU13 with the EQ-5D Index (0.73) and the predicted EQ-513 Index with the HU13 (0.70) exceeded that between the 2 original preference-based measures themselves (0.69). CONCLUSIONS. These pilot results suggest that the SF-12 could be successfully mapped to both the EQ-5D Index and HU13, yielding preference-based scores that demonstrate convergent validity in a low-income, minority sample.