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Clinical Decisionmaking

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Lowering elevated homocystine levels could result in substantial clinical benefits at a reasonable cost

Elevated total plasma levels of the amino acid homocystine (tHcy) of 11 µmol/L or greater are a potential risk factor for atherosclerosis and coronary heart disease (CHD). In fact, among the U.S. population, elevated tHcy levels may account for up to 10 percent of CHD deaths in men and 6 percent in women. Elevated tHcy levels are most often caused by mild nutritional deficiencies and can be lowered with folic acid in doses as low as 400 μg, which is the Food and Drug Administration's recommended daily allowance.

Brahmajee K. Nallamothu, M.D., M.P.H., and other researchers from the University of Michigan recommend screening 40-year-old men and 50-year-old women with a single tHcy assay, followed by use of folic acid and vitamin B12 supplements for those with elevated tHcy levels. Their study, which was supported by the Agency for Healthcare Research and Quality (National Research Service Award training grant T32 HS00053), found this approach to be more cost effective than universal supplementation.

The researchers constructed a decision model to estimate the clinical benefits and economic costs of two homocystine-lowering strategies: treat all—no screening, daily supplementation with 400 µg folic acid and 500 µg vitamin B12; or screen and then treat with daily supplements only those with elevated tHcy levels. The model was based on simulated groups of 40-year-old men and 50-year-old women in the general population and assumed that lowering elevated tHcy levels would reduce excess CHD risk by 40 percent.

Although the treat-all strategy was slightly more effective overall, the screen and treat strategy resulted in much lower costs per life-year saved ($13,600 in men and $27,500 in women) when compared with no intervention. These costs are comparable to traditional CHD prevention strategies. Incremental cost-effectiveness ratios for the treat-all strategy compared with the screen and treat strategy were more than $500,000 per life-year saved in both groups. Cost-effectiveness ratios for the screen and treat strategy remained less than $50,000 per life-year saved, even when the effect of homocystine lowering was assumed to reduce the risk of CHD-related death by only 11 percent in men and 23 percent in women.

More details are in "Potential clinical and economic effects of homocystine lowering," by Dr. Nallamothu, A. Mark Fendrick, M.D., Melvyn Rubenfire, M.D., and others, in the December 11, 2000 Archives of Internal Medicine 160, pp. 3406-3412.

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