Alberta Precision Laboratories

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Organization:

Alberta Precision Laboratories

Message Alert:

PLEASE NOTE: This Test Directory is in an interim state and due to changes pertaining to the DynaLIFE transition, performing site for routing has not been updated. Please refer to Laboratory Information System for appropriate routing.

Test Name/Synonym:

Homocysteine, Total, Blood (Metabolic Disorders) (Synonym: Homocystine, Reduced, Homocysteine BGL)

Clinical Indications:

This test is not recommended for the investigation of nutritional vitamin B12 deficiency, as total homocysteine is not a sensitive marker for this purpose, nor for assessing carrier status of the common methylene tetrahydrofolate reductase (MTHFR) polymorphisms.

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.

Total homocysteine can be elevated in the following enzyme deficiencies:

Disorders Detectable by Elevated Plasma Total Homocysteine:

cystathionine beta-synthase deficiency (classical homocystinuria)
cystathionase
methylenetetrahydrofolate reductase deficiency (MTHFR)
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
liver disease

Ordering Alert:

This test is considered specialty testing; this test will be cancelled if sufficient clinical justification is not provided.

This test is only performed for patients suspected of having an inherited metabolic disorder and for monitoring of known patients previously diagnosed with a primary disorder of methionine or cobalamin metabolism.

Minimum 4 hour fast recommended or as specified by physician.

For all other types of testing Homocysteine, Total, Blood (select applicable zone page) must be ordered.

LABID (Connect Care):

LAB12302093

Test Code:

CALGARY ZONE	BGLBL; IN BGL TEST NAME FIELD ENTER HOMOCYST, TOTAL (METABOLIC)
SOUTH ZONE	HOMORO
OTHER ZONES	NOT SPECIFIED

Specimen Type:

Blood

Primary Container:

Green top – Sodium heparin (no gel)

Alternate Containers:

Green top – Lithium heparin (no gel)
Lavender top - EDTA
Red top – Non-additive (no gel)

Minimum Collection Volume:

0.25 mL plasma or serum

Specimen Collection Requirements:

Collect one Sodium heparin (or alternate) tube.
Indicate length of fast on the requisition.

Test Resources:

Submit request using the applicable requisition or Connect Care online order entry:

Biochemical Genetics Laboratory Requisition

Please ensure all required information, including patient's clinical history/indication, is provided on the requisition.

Stability and Storage:

Frozen: plasma or serum aliquot

Processing:

For ALL collection locations except for Alberta Children’s Hospital (ACH):
1. Centrifuge; If red top tube is collected, allow to fully clot prior to centrifugation.
2. Transfer plasma or serum to aliquot tube.
3. Write "NaHep", "LiHep", "EDTA" or "Red Top" on the aliquot tube label.
4. Freeze aliquot tube.

If collected at ACH outpatient Lab:

The primary tube can be put on ice (ensure not to freeze sample) or refrigerated for routine pick-ups between 08:30 to 14:30, Monday through Friday (excluding holidays).
If specimen is collected after 14:30, process sample as described above.

Transportation:

Transport frozen specimens on dry ice.
Samples must not thaw during transport.

Method:

Liquid chromatography tandem mass spectrometry (LC-MS/MS).

Method and Interpretation of Results:

Total homocysteine is detected following reduction using liquid chromatography, electrospray-ionization tandem mass spectrometry (LC-MS/MS) with a deuterium-labelled internal standard.

Routine Turn Around Time:

14 days

Testing Schedule:

Monthly

Reference Interval:

Plasma/Serum Total Homocysteine Normal Reference Interval by Age

Age	Normal Range	Units
Less than 1 year	2.2 - 13.8	µmol/L
1 to 11 years	3.1 - 11.1	µmol/L
11 to 16 years	3.8 - 12.3	µmol/L
Greater than 16 years	4.9 - 13.7	µmol/L

Testing Area:

Biochemical Genetics

Performing Site:

Alberta Children’s Hospital

Additional Test Information:

For priority turn-around contact Biochemical Genetics South Laboratory.

Contact Comments:

Biochemical Genetics 403-955-7379

Last Updated On:

Monday, September 26, 2022

Date of Last Review:

Aug 1 2022 12:00AM