Homocysteine




Test Mnemonic

HOMCYS

CPT Codes

  • 83090 - QTY (1)

LOINC ®

13965-9

Performing Laboratory

n/a


Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
1 mLPlasmaLithium heparin PST (Lt. Green)Place specimen on ice after draw.RefrigeratedCentrifuge and separate plasma/serum from cells less than one hour after collection. If collected in a non-gel separator tube, centrifuge and transfer plasma/serum to a CCL tube and refrigerate.

Alternate Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
1 mLSerumSST (Gold)Place specimen on ice after draw.RefrigeratedCentrifuge and separate plasma/serum from cells less than one hour after collection. If collected in a non-gel separator tube, centrifuge and transfer plasma/serum to a CCL tube and refrigerate.

Minimum Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
0.5 mL     

Stability

Environmental Condition Description
AmbientAfter separation from cells: 4 days
RefrigeratedAfter separation from cells: 4 weeks
FrozenAfter separation from cells: 10 months

Days Performed

Sun - Sat

Turnaround Time

8 hours

Methodology

Name Description
Enzymatic 

Reference Range

Homocysteine
Sex Age From Age To Type Range Range Unit
 18 Years99 YearsNormal<15.1umol/L

Special Info

Homocysteine is not available for Add-On test orders.

Clinical Info

The assay can assist in the diagnosis of patients suspected of having hyperhomocysteinemia or homocystinuria. Elevated tHcy levels are caused by four major factors, including: 1. genetic deficiencies in enzymes involved in Hcy metabolism such as cystathionine beta-synthase (CBS), methionine synthase (MS), and methylenetetrahydrofolate reductase (MTHFR); 2. nutritional deficiency in B vitamins such as B6, B12 and folate; 3. renal failure for effective amino acid clearance; and 4. drug interactions, such as with nitric oxide, methotrexate and phenytoin that interfere with Hcy metabolism. Excess Hcy is related to a higher risk of coronary heart disease, stroke, and peripheral vascular disease (fatty deposits in peripheral arteries). Specimens from patients who are on drug therapy involving S-adenosylmethionine may show falsely elevated levels of homocysteine. Patients who are taking methotrexate, carbamazepine, phenytoin, nitrous oxide, anticonvulsants, or 6-azauridine triacetate may have elevated levels of homocysteine due to their effect on the pathway.