SELECTION OF END-POINTS IN ECONOMIC EVALUATIONS OF CORONARY-HEART-DISEASE INTERVENTIONS

Economic evaluations of interventions to lower blood pressure or chole sterol have used different outcome measures, or end points, in the den ominator. 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) e vents or gains in life expectancy. Others have measured improvements i n outcome in quality-adjusted life years (QALYs) gained. The different end points imply different analytic perspectives and different data r equirements. The more ambitious analyses, though potentially more rele vant 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 hyper cholesterolemia undertaken in the United Kingdom. Estimates are given of cost per percentage cholesterol reduction, cost per CHD event avoid ed, cost per CHD-free year gained, cost per life year gained, and cost per quality-adjusted life year gained. In each case the assumptions r equired and the potential relevance of the estimate are discussed. The main findings are that: 1) some end points cannot be discounted to pr esent values in a meaningful way and hence the timing of costs and out comes cannot be reflected in the analysis; 2) the incorporation of qua lity-of-life adjustments for years on drug therapy and years post-CHD events greatly changes the cost-effectiveness ratios; 3) the rate of d iscount changes the pretreatment level of cholesterol for which cost p er life year gained is equivalent to cost per quality-adjusted life ye ar gained.