--- Query Results ---

  
Program:Genetics and Genomics
 
Test Name:Homocysteine - Total, blood (G&G South ACH)
Test Code:THCYS-P, THCYS-S
Performing Site: Alberta Children's Hospital
Performing Dept:Biochemical Genetics
 
Availability:Test is performed on a monthly basis.
TAT:30 days
 
Preferred Tube/Container:Sodium heparin (dark green - NOT PST)
Alternate:Lithium heparin (dark green - NOT PST)
Non-additive (red top - NOT SST)
 
Specimen Requirements:1.  Collect 1 x 4.0 mL sodium heparin tube (or alternate tube type).
2.  Collect following a minimum four-hour fast; or just before next feed for newborns.
3.  Indicate length of fast, or time of last feeding on the requisition (with collection time).
 
Min. Sample Required:0.25 mL plasma
 
Specimen Processing:At ACH only
The primary heparinized tube can be put on ice (ensure not to freeze sample) or refrigerated for routine pick-ups between 8:30 am – 2:30 pm, Monday through Friday.

For all other collections
1. Centrifuge.
2. Transfer plasma or serum to aliquot tube.
3. Write "NaHep", "LiHep" or "Red Top" on the aliquot tube label.
4. Freeze.
 
Specimen Handling:Transport frozen samples on ice. Samples must not thaw during transport.
 
Additional Information:Samples will be rejected if:
  • Primary tube not refrigerated
  • Aliquot tube received thawed
  • Tube type not written on aliquot tube label
  •  
    Requisition/Form:Submit request using Biochemical Genetics Laboratory Requisition.
    Please ensure all required information, including patient's clinical history/indication, is provided on the requisition.
     
    Order Restrictions:This test is considered specialty testing; this test will be cancelled if sufficient clinical justification is not provided.

    Test only available for pediatric patients (less than 16 years of age) and monitoring of known homocystinuria patients; all other types of testing should refer to the Calgary Lab Services Guide to Lab Services entry Homocysteine.
     
    Indications:This test is for the investigation of a primary disorder associated with methionine or cobalamin metabolism based on clinical presentation, or when an initial cystinuria/homocystinuria (a.k.a., nitroprusside) screen was found to be abnormal and there was insufficient sample for reflexive testing.
    This test should not be ordered for the investigation of nutritional vitamin B12 deficiency, nor for assessing carrier status of the common methylene tetrahydrofolate reductase (MTHFR) polymorphisms.
    Method:Total homocysteine is detected following reduction using liquid chromatography, electrospray-ionization tandem mass spectrometry (LS-MS/MS) with a deuterium-labelled internal standard.
    Method Details:Total homocysteine can be elevated in the following enzyme deficiencies:

    Disorders Detectable by Elevated Plasma Total Homocysteine:
  • cystathionine beta-synthase deficiency (classical homocystinuria)
  • methylenetetrahydrofolate reductase deficiency (MTHFR)
  • methionine synthase deficiency
  • Cobalamin (Cbl) C, D, E, F, G, J and X deficiencies
  • transcobalamin II deficiency
  • S-adenosylhomocysteine hydrolase (SAHH) deficiency
  • glycine N-methyltransferase (GNMT) deficiency
  • methionine adenosyltransferase (MAT) I/III deficiency
  • adenosine kinase (ADK) deficiency

    Other causes of Elevated Plasma Total Homocysteine:
  • nutritional vitamin B12 deficiency
  • folate deficiency
  • nutritional B6 deficiency
  •  
    Reference Interval:
    Plasma/Serum Total Homocysteine         (<1 year)2.2 - 13.8µmol/l
    Plasma/Serum Total Homocysteine   (1-11 years)3.1 - 11.1µmol/l
    Plasma/Serum Total Homocysteine (11-16 years)3.8 - 12.3µmol/l
     
    Comments:Contact ACH Biochemical Genetics Laboratory (403-955-7379) for priority turn-around.
     
     
    Last Updated On:Monday, March 26, 2018
    Date of Last Review:Jan 2 2018 12:00AM