Homocysteine - plasma

Last updated: Monday, 22, March, 2004

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Item Process
Specimen

5 mL blood in EDTA or lithium heparin tube, collected after a 12 hour fast, or after an oral methionine load (100 mg/ Kg body weight).

Method

HPLC, immunoassay.

Reference Interval

5-15 µmol/L.

If there is established vascular disease it is desirable that the fasting concentration is <10 µmol/L.

Application

Diagnosis of homocystinuria and monitoring treatment.

Detection of mild hyperhomocysteinaemia as a risk factor for early onset cerebral and coronary atherosclerosis.

Interpretation

Mild hyperhomocysteinaemia is an established risk factor for atherosclerosis and vascular disease.

In classic homocystinuria, half the vascular complications are of venous origin. It has been established recently that high plasma homocysteine levels per se are a risk factor for deep vein thrombosis in the general population. The association was stronger among women than among men, increased with age, and remained significant after excluding other established factors for thrombosis.

In another case control study hyperhomocysteinaemia was found to be a risk factor for thrombosis in people younger than 40 years of age. The difference in the blood levels of homocysteine between controls and patients was particularly evident after a methionine load.

Elevated homocysteine levels may result from low levels of folic acid, vitamin B6, or vitamin B12, some drugs and renal impairment, as well as a number of inhertited defects.

It remains unclear whether hyperhomocysteinaemia of different causes entails the same risk of thrombosis. It is also unknown whether vitamin supplementation, which can lower blood levels of homocysteine, will affect the natural history of venous thromboembolism.

The role of Thermolabile Methylene Tetrahydrofolate Reductase (MTHFR) caused by the 677C-->T mutation in thrombophilia is controversial.

Reference

Den Heijer M et al. N Engl J Med 1996; 334: 759-762.

Falcon CR et al. Arterioscler Thromb 1994; 14: 1080-1083.

Kluijtmans LA et al. Blood 1998; 91: 2015-2018.

Hackam DG and Anand SS. JAMA 2003; 290(7): 932-940.