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What Is a Homocysteine Test?

Even though it serves an essential function in the body, homocysteine causes damage to blood vessels and cells if there is too much of it circulating in the blood. A high level of homocysteine increases your risk for coronary artery disease, so obtaining a test for homocysteine may be an important part of health screening.

  1. Definition

    • Homocysteine is an amino acid that the body needs to complete an important chemical cycle responsible for building proteins and producing energy. The body needs folate, vitamin B12 and vitamin B6 to metabolize homocysteine. Without sufficient quantities of these nutrients, rather than being metabolized, homocysteine circulates in the blood.

    Test

    • A homocysteine test is a blood test to determine how much homocysteine is in your blood stream. Your doctor will ask you to fast for 12 hours before having your blood drawn. The sample will be sent to a laboratory which will determine the level of homocysteine. A normal level is between 5 and 15 micromoles per liter of blood. If your test indicates a level outside the normal range, it will be classified as moderate (16 to 30), intermediate (31 to 100) or severe (greater than 100 micromoles per liter).

    Risks to Blood Vessels

    • Homocysteine damages the lining of blood vessel walls, causing them to thicken and subsequently narrow. A study published by Kullo, Bielak et al. in the February 2006 issue of the Mayo Clinic Proceedings that associated homocysteine with an increase in the number of calcifications found in the coronary arteries. According to the National Heart, Lung, and Blood Institute homocysteine increases the risk of excessive blood clotting. These factors all contribute to coronary artery disease.

    Risks to Brain

    • The presence of blood clots contributes to the chance of a stroke but there are other ways homocysteine affects the brain. A study published by Sudha, Beiser et al. in the February 2002 issue of the New England of Medicine stated that "an increased plasma homocysteine level is a strong, independent risk factor for the development of dementia and Alzheimer's disease." In the May 2009 issue of the International Journal of Geriatric Psychiatry, Oulhaj, Refsum et al. stated that cognitive abilities in patients with Alzheimer's disease declined more rapidly when their level of homocysteine was high.

    Risks to Kidneys

    • A high level of homocysteine in the blood have been shown to increase the risk of death in people who have received a kidney transplant. It has also been associated with inflammation in the kidneys, a condition that causes permanent damage.

    Significance

    • Depending on your medical history, age and lifestyle factors, some physicians will routinely test for homocysteine in the blood because it is a clear indicator of your risk for heart disease. If you have a history of heart disease, routine screening for elevated homocysteine is advised as a way to measure your overall health. In the majority of people, a high level of homocysteine is the result of the body's inability to metabolize it. Eating a balanced diet with sufficient folate and vitamins B12 and B6 has been shown to reduce homocysteine in the blood.

      In very rare cases a genetic disorder called homocystinuria causes increased homocysteine. This disease can result in serious complications such as mental retardation, impaired vision and life-threatening blood clots.

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