Estimation of Utilities for the Effects of Depression From the SF-12

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Abstract
Utilities for health conditions, including major depressive disorder, have a theoretical relationship to health-related quality of life (HRQOL). Because of the complexity of utility measurement and the existence of large numbers of completed studies with HRQOL data but not utility data, it would be desirable to be able to estimate utilities from measurements of HRQOL. The objective of this study was to estimate utility for remission in major depression by use of information on associated variation in Short Form 12 (SF-12) scores. A mapping function for SF-12 scores (based on a 6-health-state model with patient-weighted preferences) was applied to longitudinal data from a large naturalistic study to estimate changes in utilities. Preference ratings for states were performed in a convenience sample of depressed primary care patients (n = 140). Outcomes were evaluated in patients in the Course of Depression Study (n=295) with a DSM III diagnosis of depression at the onset of the study. From clinical interview data, differences in utilities and global physical and mental health-related quality of life at 1- and 2-year follow-up were compared for patients who did and did not experience remission as determined by the Course of Depression Interview. Remission of depression resulted in health status improvement, as measured by the SF-12, equivalent to a gain of 0.11 quality-adjusted life-years over 2 years. Utilities for changes in health status, associated with a clinical change in depression, can be modeled from the SF-12 scales, which results in utilities within the range of estimates described in the literature.