Method of Collection:
Volume as mentioned on gel vacutainer (Yellow)
Days for reporting:
|General Considerations :
Homocysteine is a thiol-containing amino acid produced by the intra cellular demethylation of the amino
acid methionine. Homocysteine is metabolised to either methionine (major pathway,involving
remethylation of homocysteine to methionine mainly by the folate and cobalamin - dependent enzyme
methionine synthetase), or to cysteine (by the Vitamin B6 dependent pathway). If any of these pathways is impaired, homocysteine accumulates in the blood, and if severe, in the urine. Epidemioligical research has shown that elevated total homocysteine is an independent risk factor of cardiovascular disease. It was shown that a 5 umol/L increase in total homocysteine is associated with same increased risk of coronary artery disease and cerebrovascular disease as would be caused by 19.5 mg/dL increase in cholesterol.
Some drugs, eg., methotrexate, carbamezapine, phenytoin, nitrous oxide and chronic renal disease may also be associated with elevated levels.
Why is the Test Done?
The homocysteine test may be used a few different ways: ? Homocysteine test helps to determine if a person has a vitamin B12 or folate deficiency. The homocysteine concentration may be elevated before B12 and folate tests are abnormal. It may be recommend in malnourished individuals, the elderly, who often absorb less vitamin B12 from their diet, and individuals with poor nutrition, such as drug or alcohol addicts. ? Homocysteine may be ordered as part of a screen for people at high risk for heart attack or stroke. It may be useful in someone who has a family history of coronary artery disease but no other known risk factors, such as smoking, high blood pressure, or obesity. However, the exact role that homocysteine plays in the progression of cardiovascular disease has not been established. Routine screening, such as that done for total cholesterol, has not been recommended.However many physician order this in routine ? Tests for both a urine and blood homocysteine may be used to help diagnose homocystinuria. If a baby's test is positive, then urine and blood homocysteine tests are often performed to confirm the findings.. Studies from the mid- to late-1990s suggested that people who have elevated homocysteine levels have a much greater risk of heart attack or stroke than those with average levels. Investigating the link between high homocysteine levels andheart disease remains an active area of research. At present, however, the use of homocysteine levels for risk assessment of cardiovascular disease (CVD), peripheral vascular disease, and stroke is uncertain given that several trials investigating folic acid and B vitamin supplementation indicate no benefit or lowering of CVD risk. When test results suggest homocystinuria, liver or skin biopsy samples are sometimes tested to determine whether theenzyme cystathionine beta synthase (CBS) is present. The absence of this enzyme is the most common cause of homocystinuria. Genetic tests may be ordered to test for one or more of the most common gene mutations. If someone has a strong family history of early atherosclerosis or a family member has been diagnosed with homocystinuria, then that person should be tested for the gene mutation that was found in the family member. Homocysteine levels can increase with age, when a person 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.
How to prepare for the Test: