Label Mnemonic: HOMCY
Epic code: LAB93
Downtime form: A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery
6240 RCP
Collection Medium:
Plasma Separator Tube 4.5 mL
Alternate Collection Media:
Call laboratory for additional acceptable specimen collection containers.
Adults - 3 mL whole blood in a light green top tube
Pediatrics - ONE Microtainer®
Delivery Instructions:
Mix well and place on wet ice. Keep on ice and deliver to laboratory immediately.
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around Time:
1 hour (upon receipt in laboratory)
Reference Range:
< 10 μmol/L

Patients with end stage renal disease may have elevated levels of 
cystathionine which may cause a significant positive interference in 
the homocysteine assay.
Test Limitations:
Homocysteine plasma levels are dependent on B-Vitamin status. The AHA target for those with cardiovascular or other risks is < 10 micromol/L. (Circulation 1999;99:178-182.)

Cystathionine is measured with homocysteine, but in the general population the cystathionine level (0.065 to 0.03 umol/l) has a negligible effect. In very rare, end stage renal disease patients with severe metabolic disturbances, cystathionine levels may rise dramatically and cause greater than 20% interference. Refer to the SPECIFICITY section of the package insert for cross-reactivity data of this drug. Drugs, such as methotrexate, carbamazepine, phenytoin, nitrous oxide, or 6-azauridine triacetate may affect plasma concentration of homocysteine. The mechanism of action affects different parts of the metabolic pathway of homocysteine. Serum concentrations can be up to 10% higher than EDTA plasma concentrations.

Hemolysis: No significant interference up to an H index of 500 (approximate hemoglobin concentration: 500 mg/dL).

Lipemia: No significant interference up to an L index of 500 (approximate triglycerides concentration: 1000 mg/dL). Note there is poor correlation between turbidity and triglyceride concentration.

Icterus: No significant interference up to an I index of 20 (approximate conjugated and unconjugated bilirubin concentration: 20 mg/dL).
CPT Code:
See Additional Information:
Specimens Requiring Immediate Delivery