Homocysteine, Plasma

Methodology: 
Enzymatic
Performed: 
Monday - Friday
Use: 
This test is used to screen patients who may be at risk for heart disease and stroke.
 

Limitations

This test is not intended for use in the diagnosis of folate or vitamin B12 deficiency.FUF
Specimen Requirements: 
Important: A fasting specimen is preferred to establish baseline values or monitor treatment.
 

Type: Serum, frozen

Container/Tube: Lavender-top tube (EDTA), green-top tube (heparin), red-top tube or gel-barrier tube
  • Separate plasma or serum from cells immediately to avoid a false elevation of homocysteine. After one hour at room temperature, a 10 percent increase may be seen. Transfer plasma and serum to a plastic transport tube. Homocysteine results increase by approximately 35 and 75 percent for samples not centrifuged and/or not separated from the clot for periods of four and 24 hours, respectively. Serum values are expected to be higher than plasma values. Slightly higher values are observed in nonfasting patients.

Sample Volume: 2 mL

Minimum Volume: 1 mL (Repeat testing is not possible with this specimen volume.)

Storage: Freeze specimens immediately after collection.

Stability (collection to time of analysis/testing): 
  • Ambient: 6 days
  • Refrigerated: 16 days
  • Frozen: 32 months
Rejection Criteria:
  • Plasma specimen
Reference Values: 
0.0 − 15.0 μmol/L
CPT Code (s): 
83090
Notes: 

UFHPL Test #: 28100

UFHPL Epic order code: LAB93

Severe homocysteinemia is typically caused by a rare inborn error of metabolism.1,2 The most common defect that can produce levels >100 μmol/L is homozygous cystathionine-β-synthase (CS) deficiency, which occurs with an incidence of 1 per 300,000 live births. About 1% of the population has heterozygous CS deficiency, a condition that typically results in moderate to intermediate hyperhomocysteinemia. Individuals with CS deficiency are at increased risk for occlusive vascular disease.1,2 Individuals with a thermolabile variant of the enzyme methylene-tetrahydrofolate reductase can have high normal to moderately elevated levels of homocysteine.1,2 Homocysteine can be considered to be an independent risk factor for the development of cardiovascular disease.1-3 Patients with cardiovascular disease, including heart disease, stroke, peripheral vascular disease, and thromboembolic disease generally have higher homocysteine levels than matched controls. The results of a large number of epidemiological studies have been analyzed through a meta-analysis.1 The increased risk, or odds ratio (OR), for coronary artery disease in patients with increased homocysteine levels was estimated to be 1.7. The OR for stroke was estimated to be 2.5 and the OR for peripheral vascular disease was estimated to be 6.8. Several conditions, other than specific genetic defects or cardiovascular disease, have been associated with hyperhomocysteinemia.1 These include vitamin deficiency, advanced age, hypothyroidism, impaired kidney function, and systemic lupus erythematosus. Medications including nicotinic acid, theophylline, methotrexate, and L-dopa have been reported to cause elevated homocysteine levels.

Footnotes

  1. Malinow MR, Bostom AG, Krauss RM. Homocyst(e)ine, diet, and cardiovascular diseases: A statement for healthcare professionals from the nutrition committee, American Heart Association. Circulation. 1999; 99(1):178-182. PubMed 9884399
  2. Clarke R, Stansbie D. Assessment of homocysteine as a cardiovascular risk factor in clinical practice. Ann Clin Biochem. 2001; 38(Pt 6):624-632. PubMed 11732645
  3. Herrmann W. The importance of hyperhomocysteinemia as a risk factor for diseases: An overview. Clin Chem Lab Med. 2001; 39(8):666-674.PubMed 11592431

References

  • Fortin LJ, Genest J Jr. Measurement of homocyst(e)ine in the prediction of arteriosclerosis. Clin Biochem. 1995; 28(2):155-162 (review). PubMed 7628074
  • Kang SS, Wong PW, Malinow MR. Hyperhomocyst(e)inemia as a risk factor for occlusive vascular disease. Annu Rev Nutr. 1992; 12:279-298. PubMed 1503807
  • Malinow MR. Plasma homocyst(e)ine and arterial occlusive diseases: A mini review. Clin Chem. 1995; 41(1):173-176 (review). PubMed 7813076
  • Robinson K, Mayer, E, Jacobsen DW. Homocysteine and coronary artery disease. Cleve Clin J Med. 1994; 61(6):438-450 (review). PubMed 7828335
  • Ueland PM, Refsum H, Stabler SP, et al. Total homocysteine in plasma or serum: Methods and clinical applications. Clin Chem. 1993; 39(9):1764-1779 (review). PubMed 8375046
  • Verhoef P, Stampfer MJ, Buring JE, et al. Homocysteine metabolism and risk of myocardial infarction: Relation with vitamins B6, B12, and folate. Am J Epidemiol. 1996; 143(9):845-859.PubMed 8610698
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