[Skip to Content]

Homocysteine (HCYS)

Send to a FriendPrint Page

EPIC Test Name

HOMOCYSTEINE, SERUM

EPIC Code

LAB93

Specimen Requirements

plasma
Minimum Volume:0.5 mL
Collection:Collect specimens using standard laboratory procedures.
Transport:Should be kept on ice and arrive in the lab within 1 hour
Stability:Seperated blood :
Room Temperature: 4 days at 15-25 degrees C
Refrigerated: 4 weeks at 2-8 degrees C
Frozen: 10 months at -20 degrees C
Container:LT GRN-on Ice
Processing/Storage:Put on ice, immediately after collection.
Centrifuge within 1 hour and separate from cells.
Rejection Causes:Hemolysis, lipemic,
Insufficient Sample Volume
Notes:Put on ice, immediately after collection.
Centrifuge within 1 hour and separate from cells.

Methods

Homogeneous Enzymatic

Turnaround Time

SpecimenTurnaround TimeFrequency
plasmaRoutine: 4 hours24/7

Reference Ranges

Homogeneous Enzymatic
All RangeUnit
<15 µmol/Lµmol/L

Clinical Indications

Homocysteine (Hcy) is biosynthesized intracellularly via demethylation of methionine, a thiol-containing amino acid. Total homocysteine (tHcy) is a sum of all forms of Hcy including forms of oxidized, protein-bound and free.
Elevated tHcy levels can be caused by any of the four major factors, including:
• Genetic deficiencies in enzymes involved in Hcy metabolism such as cystathionine beta-synthase (CBS), methionine synthase (MS), and methylenetetrahydrofolate reductase (MTHFR).
• Nutritional deficiency in B vitamins such as B6, B12, and folate.
• Renal failure for effective amino acid clearance.
• Drug interactions, such as with nitric oxide, methotrexate and phenytoin that interfere with Hcy metabolism.
Elevated Hcy level is related to a higher risk of coronary heart disease, stroke, and peripheral vascular disease (fatty deposits in peripheral arteries). Increased Hcy concentrations in the blood stream may cause injuries to arterial vessels due to its irritant nature, and result in inflammation and plaque formation, which may eventually cause blockage of blood flow to the heart. Homocysteine levels may be reduced with treatment, but that does not necessarily reduce the occurrence of cardiovascular disease (CVD) events such as stroke and heart attack. Because findings from studies that evaluated the association between the increase in Homocysteine levels and CVD have been inconsistent, the American Heart Association has not yet called hyperhomocysteinemia (elevated Hcy in the blood) a major risk factor for CVD. Elevated Hcy concentration is an indicator of acquired folate or cobalamin deficiency and is a contributing factor in the pathogenesis of neural tube defects.

Additional Information

Patients under treatment with the following drugs (effect) may have false high levels of Hcy due to metabolic interference with Hcy metabolism: methotrexate (5-Methyltetrahydrofolate depletion), carbamazepine and phenytoin (interfering folate metabolism), nitrous oxide (interfering methionine synthase), or 6-azuridine triacetate (Vitamin B6 antagonist), certain contraceptives (estrogen induced vitamin B6 deficiency).

Performed

Lab
Chemistry - Downtown

Interpretative Information

Elevated homocysteine concentrations are consistent to patients with suspected nutritional deficiencies (vitamin B12, folate) and inborn errors of metabolism. Measurement of methylmalonic acid (MMA) distinguishes vitamin B12 (cobalamin) from folate deficiencies. MMA is elevated in vitamin B12 deficiency but not folate deficiency.

CPT

83090

LOINC

13965-9

References

1. Chrysant SG, Chrysant GS: The current status of homocysteine as a risk factor for cardiovascular disease: a mini review. Expert Rev Cardiovas Ther. 2018;16:559-65. doi: 10.1080/14779072.2018.1497974
2. Refsum H, Smith AD, Ueland PM, et al: Facts and recommendations about total homocysteine determinations: an expert opinion. Clin Chem. 2004;50:3-32.
3. Turgeon CT, Magera MJ, Cuthbert CD, et al: Determination of total homocysteine, methylmalonic acid, and 2-methylcitric acid in dried blood spots by tandem mass spectrometry. Clin Chem. 2010;56:1686-95.
4. Deficiencies of folate and vitamin B6 exert distinct effects on homocysteine, serine, and methionine kinetics Geraldine J. Cuskelly, Peter W. Stacpoole, Jerry Williamson, Thomas G. Baumgartner, and Jesse F. Gregory, III. American Journal of Physiology-Endocrinology and Metabolism 2001;281:6, E1182-E1190.

Contact Information

Chemistry - Downtown: (315)464-4460
Top