Tuesday, April 03, 2007

Metabolite, homocysteine, and relevance

In the Metabolite case, the claim at issue was (schematically) a method of measuring a deficiency of X in warm-blooded animals by assaying a body fluid for an elevated level of Y and correlating an elevated level of Y with a deficiency in X. X can be cobalmin or folate and Y is homocysteine.

At the time of the Metabolite case, there was not much discussion of the underlying relevance of the method to health problems. Pubpat had a press release on March 29, 2005:

The issue stems from a case that involves a patent granted by the U.S. Patent Office on diagnosing B12 or folic acid deficiency, which can cause serious human illnesses such as cancer and vascular disease, simply by knowing if a patient has an elevated homocysteine level.

Some pertinent papers are as follows:

Homocysteine and Risk of Cardiovascular Disease Among Postmenopausal Women, JAMA. 1999;281:1817-1821. Conclusion: Among healthy postmenopausal US women, elevated levels of homocysteine moderately increased the risk of future cardiovascular disease. Whether lowering the homocysteine level reduces risk of cardiovascular events requires testing in randomized controlled trials.

Do low doses of folic acid result in maximum lowering of homocysteine? American Journal of Clinical Nutrition, Vol. 82, No. 4, 717-718, October 2005. Summary: it can be expected that a near-maximum homocysteine-lowering effect would be achieved with the dose of folic acid most commonly included in multivitamins (0.4 mg/d). Because of lower baseline homocysteine values due to consumption of folic acid–fortified food, the magnitude of the homocysteine response to supplemental folic acid would be expected to be considerably less in North American countries than in countries without food fortification.





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