Challenges to time trade-off utility assessment methods: when should you consider alternative approaches?

Abstract

In recent years, the time trade-off (TTO) method, most commonly with a 10-year time horizon, has been the most frequently used approach for direct health state utility assessment, likely due to National Institute for Health and Care Excellence (NICE) preference for comparability with the EQ-5D, which has a utility scoring algorithm derived via this method. Although comparability to previous utility studies is important, there are situations when the TTO method may not be appropriate. The purpose of the current review is to highlight challenges to the TTO method. Five challenges to the TTO method are discussed: mild health states, small differences among health states, temporary health states, pediatric health states, and assessment of samples with particular characteristics. Some of these challenges are associated with the 10-year time horizon, while other situations may raise issues for TTO methods regardless of the time horizon. Alternative approaches for valuing health states are suggested.

Keywords::

• patient preference
• QALY
• standard gamble
• time horizon
• time trade-off
• TTO
• utility

Acknowledgements

The authors would like to thank Mary K Devine for proofreading and literature review as well as Amara Tiebout for production assistance.

Financial & competing interests disclosure

Funding for this study was provided by Eli Lilly and Co. K Boye, J Johnston and L Bowman are employees of Lilly, but their input into the conceptualization and interpretation of this study represented their own opinions, rather than those of the company. L Matza and J Jordan are employees of Evidera, a company that received funding from Lilly for this research. D Feeny received funding from Lilly for time spent contributing to this research. Further, it should be noted that D Feeny has a pecuniary interest in Health Utilities Incorporated, which distributes copyrighted Health Utilities Index materials.

No writing assistance was utilized in the production of this manuscript.

Key issues

• In recent years, the time trade-off (TTO) method with a 10-year time horizon has been the most frequently used approach for direct health state utility assessment.

• It is likely that researchers have favored the 10-year TTO because the UK NICE Guide to the Methods of Technology Appraisal has stated a preference for comparability with the EQ-5D, which has a utility scoring algorithm derived via 10-year TTO valuations.

• Although comparability to previous utility elicitation studies is important, there are situations when TTO methods, particularly with the 10-year time horizon, may not be appropriate.

• Because the TTO method is so commonly used, it is important to carefully consider its strengths, limitations and appropriate use.

• The purpose of the current review is to highlight five challenges to the TTO method: mild health states, small differences among health states, temporary health states, pediatric health states and assessment of samples with particular characteristics.

• Some of these challenges are associated with the 10-year time horizon, while other situations may raise issues for TTO methods regardless of the time horizon.

• Alternative approaches for valuing health states are suggested, including variations of the TTO (e.g., varying the time horizon), other direct utility assessment methods (e.g., standard gamble methods with or without chaining), measures developed specifically for children, mapping condition-specific health-related quality of life questionnaires to generic preference-based measures, and condition-specific preference-based measures derived from condition-specific questionnaires using item response theory and Rasch analysis.

• Pilot studies are often helpful in identifying an appropriate utility assessment approach.

• Although it is important to consider comparability with previous studies and published utility values, the selection of a utility assessment method should also be based on the relevance and validity of the methodology for the health states being valued, the target population and the specifications of the cost–utility model in which utility scores will be used.