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Test Code HCY Homocysteine 

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Lavendar + Ice

Specimen Stability

Storage Temperature

Stability

Room temperature

4 days*

Refrigerated

4 weeks

Frozen

10 weeks

 

*Must be separated from cells

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

Collect specimen per standard collection procedure and send to laboratory immediately. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Samples should be centrifuged within 2 hours of collection.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Aliquot sample into plastic transport tube containing a minimum of 0.2 mL of specimen.
  • Samples must be sent refrigerated at 2-8oC.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours.

Reference Values

 

Test

Age

Sex

Reference Range

HCY

All

All

3.7 - 13.9 umol/L

Note: Reference range based on in-house studies, recommendations from Tietz Textbook of Clinical Chemistry, and Roche product literature.  

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: 1 hour

Routine Turnaround Time: 4 hours

Testing Schedule: 24/7

Clinical Indications

Homocysteine (Hcy) is a thiol-containing amino acid produced by the intracellular demethylation of methionine. Total homocysteine (tHcy) represents the sum of all forms of Hcy including forms of oxidized, protein-bound and free. 

Elevated tHcy levels are caused by four major factors including: 

  1. gnetic deficiencies in enzymes involved in Hcy metabolism such as cystathionine beta-synthase (CBS), methionine synthase (MS), andmethylenetetrahydrofolate reductase (MTHFR)
  2. nutritional deficiency in B vitamines such as B6, B12, and folate
  3. renal failure for effective amino acid clearance
  4. drug interactions, such as with nitric oxide, methotrexate and phenytoin that interfere with Hcy metabolism.

Methodology

Immunoturbidimetric Assay (Roche Diagnostics)

CPT Codes

83090

LOINC Codes

N/A

Synonyms/Keyword Search

Hcy

Homocysteine

Last Review Date

5/30/25

Critical Values

Analyte

Unit

Low

High

Age

N/A

N/A

N/A

N/A

N/A

Volume

Preferred Volume: 0.5 mL

Minimum Volume: 0.2 mL

Test Components

Homocysteine
 

Additional Information

Homocysteine Enzymatic Assay is based on a novel enzyme cycling assay principle that assesses the cosubstrate conversion product instead of assessing co-substrate or Hcy conversion products of Hcy.