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Invariance and inconsistency in utility ratings
Dena M Bravata1, Lorene M Nelson, Alan M Garber
1Center for Primary Care and Outcomes Research, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305-6019, USA. dbravata@stanford.edu
Summary
Invariance and order inconsistencies in health state utility ratings are common, affecting nearly half of participants. These inconsistencies can lead to different utility values, highlighting the need to report such patterns in assessments.
Area of Science:
- Gerontology
- Health Economics
- Psychometrics
Background:
- Assessing patient preferences for health states is crucial for cost-effectiveness analyses.
- Dependence in activities of daily living (ADLs) significantly impacts health state utilities.
- Understanding factors influencing utility assessments is vital for reliable healthcare decision-making.
Purpose of the Study:
- To evaluate the frequency and characteristics of invariance and order inconsistency in utility ratings for composite activities of daily living (ADL) dependencies.
- To identify demographic and cognitive factors associated with these response patterns.
- To determine if inconsistent utility ratings affect the valuation of specific health states.
Main Methods:
- 400 participants aged 65+ provided standard-gamble utilities for single and combined ADL dependencies.
- Invariance was defined as assigning a utility of 1.0 to all health states.
- Order inconsistency was defined as valuing a combined ADL dependency higher than any of its subsets.
Main Results:
- 44% of participants exhibited at least one order inconsistency.
- Invariance was linked to lower Mini-Mental Status Examination scores, less education, non-White/Caucasian ethnicity, and shorter task completion times.
- Inconsistent participants had lower mean utilities for continence dependence compared to consistent, non-invariant participants.
Conclusions:
- Invariance and order inconsistencies are frequent in utility assessments of complex health states.
- These response patterns are associated with specific demographic and cognitive characteristics.
- Differences in utilities between consistent and inconsistent responders suggest that reporting these patterns is important for accurate health state valuation.