How Cost–Effective Is the Treatment of Dyslipidemia in Patients With Diabetes but Without Cardiovascular Disease?: A response to Grover et al.

In the January 2001 issue of Diabetes Care, Grover et al. (1) reported on the cost-effectiveness of dyslipidemia treatment in patients with diabetes but without cardiovascular disease. Although the article was interesting and relevant, further review of the assumptions of the study’s Markov model raise several questions.

First, in the cost-effectiveness model, the choice of years of life saved (YOLS) rather than quality-adjusted life years (QALYs) is debatable. Diabetes is known to have a significant effect on morbidity, mortality, and quality of life. In addition, other aspects of diabetes (including cardiovascular disease) are known to influence the quality of life of people with diabetes. Therefore, the use of YOLS as a measure of effectiveness may be simplistic and insufficient as an outcome measure because it usually counts as less than one full QALY (2). What effect would the use of QALYs have had on the study results and conclusions?

Second, the assumptions that lipid levels and the effectiveness of simvastatin therapy were similar to that observed in the Scandinavian Simvastatin Survival Study trial appear problematic in light of current evidence. The assumptions include LDL cholesterol of 188 mg/dl (4.87 mmol/l) and HDL cholesterol of 46 mg/dl (1.18 mmol/l). Expected effects of simvastatin therapy based on a decrease in LDL cholesterol of 35% and an increase in HDL cholesterol of 8% would be 122 mmol/dl (3.15 mmol/l) and 50 mmol/dl (1.29 mmol/l), respectively. However, these targets run contrary to the American Diabetes Association (ADA) practice guidelines for 2001 (3). The goals of lipid therapy include LDL cholesterol of ≤100 mmol/dl (≤2.60 mmol/l) and HDL cholesterol of 45 mg/dl (1.15 mmol/l) and 55 mg/dl (1.40 mmol/l) in men and women, respectively.

Very few patients were likely to meet current standards of lipid treatment based on the assumptions of the study. Therefore, to achieve ADA goals, higher doses of simvastatin or longer duration of lipid treatment may be required. The implication is that the cost calculations are likely to yield higher figures, which may alter the cost-effectiveness ratios. What effect would varying the cost calculations to achieve ADA end points have had on the study results?

These questions and comments should not undermine the importance of the work of Grover et al. Rather, they are important clinical questions that may need consideration in future studies on cost-effectiveness, particularly on primary prevention of cardiovascular disease in people with diabetes.