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Selection of end points in economic evaluations of coronary-heart-disease interventions
M F Drummond1, J Heyse, J Cook
1Centre for Health Economics, University of York, UK.
Insights
Different economic evaluation methods for lowering cholesterol and blood pressure exist, impacting cost-effectiveness findings. Quality-adjusted life years (QALYs) and other outcome measures significantly alter cost-effectiveness ratios for interventions.
Area of Science:
- Health Economics
- Clinical Trial Analysis
Background:
- Economic evaluations of interventions for lowering blood pressure or cholesterol utilize diverse outcome measures.
- These measures range from physiologic improvements (e.g., mmHg reduction) to clinical events (e.g., coronary heart disease avoidance) and quality-adjusted life years (QALYs).
Purpose of the Study:
- To illustrate the trade-offs between relevance, accuracy, and precision in economic evaluations.
- To compare various outcome measures in the cost-effectiveness analysis of drug therapy for hypercholesterolemia.
Main Methods:
- Evaluation of drug therapy for hypercholesterolemia in the United Kingdom.
- Calculation of cost-effectiveness ratios using multiple end points: cost per percentage cholesterol reduction, cost per coronary heart disease (CHD) event avoided, cost per CHD-free year gained, cost per life year gained, and cost per quality-adjusted life year (QALY) gained.
Main Results:
- Some outcome measures, like physiologic improvements, cannot be meaningfully discounted, hindering reflection of cost and outcome timing.
- Incorporating quality-of-life adjustments significantly alters cost-effectiveness ratios.
- The discount rate influences the pretreatment cholesterol level at which cost per life year gained equals cost per QALY gained.
Conclusions:
- The choice of outcome measure critically impacts the perceived cost-effectiveness of health interventions.
- Quality-of-life adjustments and discount rates are crucial factors in economic evaluations, particularly for chronic disease management.
- Analytic perspective and data requirements vary significantly based on the chosen end points, influencing the assumptions and relevance of the findings.
Abstract:
Economic evaluations of interventions to lower blood pressure or cholesterol have used different outcome measures, or end points, in the denominator. Some have related the costs of interventions to improvements in physiologic end points such as mm Hg reduction in blood pressure. Some have related costs to avoidance of coronary heart disease (CHD) events or gains in life expectancy. Others have measured improvements in outcome in quality-adjusted life years (QALYs) gained. The different end points imply different analytic perspectives and different data requirements. The more ambitious analyses, though potentially more relevant in certain situations, require more controversial assumptions to be made. This paper illustrates the trade-offs of relevance, accuracy, and precision by reference to an evaluation of drug therapy for hypercholesterolemia undertaken in the United Kingdom. Estimates are given of cost per percentage cholesterol reduction, cost per CHD event avoided, cost per CHD-free year gained, cost per life year gained, and cost per quality-adjusted life year gained. In each case the assumptions required and the potential relevance of the estimate are discussed. The main findings are that: 1) some end points cannot be discounted to present values in a meaningful way and hence the timing of costs and outcomes cannot be reflected in the analysis; 2) the incorporation of quality-of-life adjustments for years on drug therapy and years post-CHD events greatly changes the cost-effectiveness ratios; 3) the rate of discount changes the pretreatment level of cholesterol for which cost per life year gained is equivalent to cost per quality-adjusted life year gained.(ABSTRACT TRUNCATED AT 250 WORDS)