A blood sample taken by needle from a vein in the arm
You may be instructed to fast for 10 to 12 hours prior to this test
This test measures the level of homocysteine in the blood. Homocysteine is a sulphur-containing amino acid that is normally present in very small amounts in all cells of the body. Homocysteine is a product of methionine metabolism, and methionine is one of the eleven “essential” amino acids (an essential amino acids must be derived from the diet since the body cannot make them). In healthy cells, homocysteine is quickly converted to other products.
Folic acid (folate) is one of the "B" vitamins that is needed to metabolise homocysteine. Vitamin B12, another B vitamin, helps keep folate in its active form, allowing it to keep homocysteine levels low. People who are deficient in these vitamins may have increased levels of homocysteine.
How is it used?
Homocysteine is sometimes used to help in the investigation of people who might be at high risk for heart attack or stroke. For example, it may be useful in patients who have a family history of coronary heart disease (CHD) but no other known risk factors.
Occasionally, a doctor may also request a homocysteine test in the investigation of suspected vitamin B12 or folate deficiency.
When is it requested?
What does the test result mean?
At present, a direct correlation between homocysteine levels and heart attacks has not been established, but there does seem to be strong evidence of a relationship between homocysteine levels and heart attack/stroke survival rates.
While earlier studies suggested that people who have elevated homocysteine levels have a much greater risk of heart attack or stroke than those with average levels, at present, the use of homocysteine levels for risk assessment of cardiovascular disease (CVD), is uncertain given that several trials investigating folic acid and B vitamin supplementation indicate no benefit or lowering of CVD risk.
Is there anything else I should know?
Homocysteine levels can increase with age, when a patient smokes, and with the use of drugs such as carbamazepine, methotrexate, and phenytoin. Homocysteine levels are lower in women than in men. Women’s concentrations increase after menopause, possibly due to decreased estrogen production.
Homocystinuria is a rare inherited metabolic disorder characterised by an increased blood and urine concentration of homocysteine. Classical homocystinuria is due to a deficiency in cystathionine beta synthase (CBS). Affected individuals appear normal at birth but develop serious complications in childhood. Diagnosis and treatment started sufficiently early in life can effectively prevent or reduce the severity of these complications.
What are some good sources of folic acid and vitamins B6 and B12?
Green leafy vegetables and cereal grains are the main source of folic acid. Fruits and vegetables have significant amounts of vitamin B6, and vitamin B12 can be found in red meats, poultry, fish, and other seafoods. People with high homocysteine levels also may benefit from taking multivitamins to supplement this amount.
Is there a difference in risk between men and women?
Could any drugs I may be taking have an effect on my homocysteine level?