Homocysteine

Test Code

HOMO

CPT Codes
83090

Preferred Specimen

Green

Minimum Volume

1 mL

Other Acceptable Specimens

Lithium Heparin Plasma (green top tube) or Serum (gold top tube)

Instructions

Specimens must be collected in plasma tubes that are at least half full. Smaller volumes can result in negative biases.

Whole blood samples should be centrifuged within 1 hour after collection or refrigerated for up to 8 hours prior to centrifugation. After blood is drawn, homocysteine is released from erythrocytes and the concentration will increase at a rate of approximately 1 μmol/L per hour at room temperature.

Transport Container

EDTA (purple top), Lithium Heparin (green top), or Serum (gold top) tube.

Transport Temperature

Room Temperature or Refrigeration

Specimen Stability

Room Temperature - 3 days; Refrigerated - 10 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Quantity Not Sufficient, IV contamination

Methodology
Photometric

Setup Schedule

Daily upon receipt

Report Available

Upon completion of analysis

Limitations

Results should be interpreted with caution. Certain drugs and clinical conditions are known to alter homocysteine concentration in vivo. For example, patients who are taking methotrexate, carbamazepine, phenytoin, nitrous oxide, anticonvulsants, or 6â€‘gazuridine triacetate, may have higher levels of homocysteine due to metabolic interference with homocysteine metabolism. Patient samples containing cystathionine (reference interval: 0.065 to 0.301 Î¼mol/L) show positive equimolar interference with this method. For example, a sample containing 10.0 Î¼mol/L homocysteine and 0.3 Î¼mol/L cystathionine will generate a result with this method of approximately 10.3 Î¼mol/L. Elevated cystathionine levels can be observed in patients with certain conditions, such as renal disease, folate deficiency, and cystathionine beta-lyase deficiency. Patient samples containing elevated levels of L-cysteine (normal range: 178 to 196 Î¼mol/L) can show positive interference with the VITROS Chemistry Products HCY 2 assay. For example, a sample containing 6.2 Î¼mol/L homocysteine and an additional 600 Î¼mol/L added L-cysteine could generate a result using this method of approximately 8.6 Î¼mol/L (bias of +2.4 Î¼mol/L).

Reference Range

Female: 4.7 - 12.6 umol/L
Male: 6.6 - 14.8 umol/L

Clinical Significance

Homocysteine is a thiol-containing amino acid intermediate produced by cellular demethylation of methionine. It readily oxidizes to form various disulfides at physiological conditions. Homocysteine is at a metabolic branch point from which it can either be remethylated to form methionine or condensed with serine to form cystathionine through the trans-sulfuration pathway. Deficiencies of enzymes involved in methionine metabolism lead to severe increases of plasma homocysteine. Cross-sectional epidemiological studies have demonstrated that mild increases in total homocysteine may pose a significant, independent risk factor for coronary heart disease.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.