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Mapping the SF-12 to preference-based instruments: convergent validity in a low-income, minority population
Peter Franks1, Erica I Lubetkin, Marthe R Gold
1Department of Family and Community Medicine, Center for Health Services Research in Primary Care, University of California, Davis, Sacramento, California 95817, USA. pfranks@ucdavis.edu
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 (HUI3) 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 HUI3 onto the physical (PCS-12) and mental (MCS-12) components of the SF-12 scores as measures.
Results:
For the EQ-5D Index regression, the adjusted variance explained was 58% (bootstrap validation 95% confidence interval [CI], 46-66). For the HUI3 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 HUI3 with the EQ-5D Index (0.73) and the predicted EQ-5D Index with the HUI3 (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 HUI3, yielding preference-based scores that demonstrate convergent validity in a low-income, minority sample.