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A COMPARISON OF STANDARD GAMBLE, TIME TRADE-OFF, AND ADJUSTED TIME TRADE-OFF SCORES

Published online by Cambridge University Press:  04 May 2001

Andrew J. Martin ,
P. P. Glasziou ,
R. J. Simes  and
T. Lumley
Andrew J. Martin
Affiliation:
NHRMC Clinical Trials Centre, University of Sydney
P. P. Glasziou
Affiliation:
University of Queensland
R. J. Simes
Affiliation:
NHRMC Clinical Trials Centre, University of Sydney
T. Lumley
Affiliation:
NHRMC Clinical Trials Centre, University of Sydney
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Abstract

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Objective: To adjust patients' time trade-off (TTO) scores using information on their utility functions for survival time to derive a measure of health state utility equivalent to the standard gamble (SG).

Methods: A sample of 199 cardiovascular patients were asked three TTO and SG questions (to assess their own health state), and three certainty equivalent questions (to assess their utility function for survival time) in an interview.

Results: Patients' utility functions for time were increasingly concave, but being unable to model this successfully, a constant function with an averaged level of concavity was used. The raw TTO scores were significantly higher than SG scores, while the adjusted TTO scores were equivalent to the SG.

Conclusions: Raw time trade-off scores will give biased estimates of health state utility when patients' utility functions for time are not linear, but these can be adjusted to yield true utilities. The constant proportional risk-posture assumption of the conventional QALY model, on which previous attempts to adjust time trade-offs have been based, was not supported by the data.

Keywords

Quality of lifeQuality-adjusted life-yearsDecision support techniquesHeart diseases
Type
Research Article
Information
International Journal of Technology Assessment in Health Care , Volume 16 , Issue 1 , January 2000 , pp. 137 - 147
Copyright
© 2000 Cambridge University Press