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Development and testing of a utility measure for major, unipolar depression (McSad)
K J Bennett1, G W Torrance, M H Boyle
1Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada. kbennett@fhs.mcmaster.ca
Objective:
To develop and test a direct utility measure (McSad) for major, unipolar depression.
Methods:
A depression specific, multi-attribute health state classification system was created; clinical validity was evaluated by experts using specially designed structured exercises; a cross-sectional survey was conducted to obtain directly measured utilities for depression health states.
Setting:
Tertiary care, university medical centre.
Participants:
Three psychiatrists, 3 psychiatric nurses and 3 social workers assessed depression health state clinical validity. Survey participants were referred by psychiatrists and consisted of 105 outpatients, currently in remission with at least one episode of major, unipolar depression in the past two years.
Survey Results:
Respondent self-health state utility (mean and 95% confidence interval (CI)) was 0.79 (0.74-0.83). Utilities for hypothetical, untreated depression health states were: mild depression, 0.59 (0.55-0.62); moderate depression, 0.32 (0.29-0.34); severe depression, 0.04 (0.01-0.07). Fifty-six percent of respondents rated severe depression worse than being dead. Utilities for the hypothetical health states were not correlated with self-health utility. The intra-class correlation coefficient (ICC) was satisfactory for 13 of the 14 health states assessed.
Conclusions:
McSad was feasible and acceptable in patients with a history of major unipolar depression. The utilities for mild, moderate and severe untreated depression show the low health-related quality of life associated with depression. Initial assessments of test-retest reliability and validity yielded satisfactory results but further studies are needed to extend our knowledge of the measurement properties of McSad.