Purpose of the Blood test:
Homocysteine is measured in the blood in order to determine if there is an increased risk of a heart attack or stroke or to determine if you are folate-deficient or B12-deficient. Finally it is measured to help diagnose a rare inherited disorder called homocystinurina.
It is prescribed when the patient has had a heart attack or stroke, or as part of a cardiac risk assessment. Also when a doctor suspects a vitamin B12 or folate deficiency or suspects that an infant or young person may have homocystinuria.
Evaluation of risk factors associated with atherosclerosis, coronary heart disease, and arterial/venous thromboembolism
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Aids in the evaluation of B6, B12, Folic Acid, and Riboflavin deficiency
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As an aid in diagnosis of arterial thrombosis and venous thrombosis
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As an aid in diagnosis of neural tube defect (related to folate deficiency)
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As an aid in diagnosis of pregnancy complications such as preeclampsia and recurrent miscarriages
Description
Homocysteine (HCY) is a sulfur-containing amino acid produced during catabolism of methionine, an essential amino acid. There are two major pathways for synthesis of HCY in our body: remethylation and transsulfuration pathway. The remethylation pathway is catalyzed by the enzyme methylenetetrahydrofolate reductase (MTHFR) and methionine synthase, a process requiring vitamin B12, Folic Acid, and riboflavin. In transsulfuration pathway, HCY is converted to cysteine and glutathione, a process requiring vitamin B6 and riboflavin. Folic acid and vitamin B12 function as cofactors and substrates in both pathways. If one or more of the HCY metabolic pathways are inhibited due to enzymatic defects or Vitamin D deficiencies, HCY accumulates, causing an increased HCY level in plasma. Deficiencies in one or more of theseVitamins can lead to acquired hyperhomocysteinemia. Homocystinuria is a rare autosomal recessive disorder caused by mutation and decreased activity of cystathionine synthase. Clinical and epidemiologic studies have demonstrated that hyperhomocysteinemia is an independent risk factor forAtherosclerosis and coronary heart disease and for arterial and venous thromboembolism.
Homocysteine is present in plasma in three forms: free or unbound HCY (1 to 2%), homocysteine-cysteine or homocysteine dimers (10 to 20%), or protein bound (> 80%). Total plasma homocysteine, free and bound, is commonly referred to as either homocysteine or homocyst(e)ine. There are some assays that can measure free or unbound homocysteine but most assays measure total homocysteine level.
Reference range values
0 - 13 mcmol/L
Abnormal findings
High levels of homocysteine in blood are indicative of cardiac risk, vitamin B12 or folate deficiency, or homocystinuria.
Homocysteine levels can increase with age, when a patient smokes, and with the use of drugs such as carbamazepine, methotrexate, and phenytoin.