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Test ID HCYSP Homocysteine, Total, Plasma

Useful For

An aid for screening patients suspected of having an inherited disorder of methionine metabolism including:

-Cystathionine beta-synthase deficiency (homocystinuria)

-Methylenetetrahydrofolate reductase deficiency (MTHFR) and its thermolabile variants:

-Methionine synthase deficiency

-Cobalamin (Cbl) metabolism:

-Combined methyl-Cbl and adenosyl-Cbl deficiencies: Cbl C2, Cbl D2, and Cbl F3 deficiencies

-Methyl-Cbl specific deficiencies: Cbl D-Var1, Cbl E, and Cbl G deficiencies

-Transcobalamin II deficiency:

-Adenosylhomocysteinase (AHCY) deficiency

-Glycine N-methyltransferase (GNMT) deficiency

-Methionine adenosyltransferase (MAT) I/III deficiency

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Stable Isotope Dilution Analysis

Reporting Name

Homocysteine, Total, P

Specimen Type

Plasma EDTA

Specimen Required

Patient Preparation: Fasting (12 hours preferred but not required)


Preferred: Lavender top (EDTA)

Acceptable: Plasma Preparation Tube (PPT), citrate, sodium fluoride, heparin

Specimen Volume: 0.4 mL

Collection Instructions:

1. Immediately place specimen on wet ice.

2. Spin down and separate plasma from cells within 4 hours of draw. A refrigerated centrifuge is not required if 4-hour time restraint is met.

3. Alternatively, if blood is not immediately placed on ice, plasma must be removed from cells within 1 hour of draw. A refrigerated centrifuge is not required if 1-hour time restraint is met.

Specimen Minimum Volume

0.15 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma EDTA Refrigerated (preferred)

Reference Values

Adults: ≤13 mcmol/L

Reference values apply to fasting specimens only.

Day(s) and Time(s) Performed

Monday through Saturday; 8 a.m.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
HCYSP Homocysteine, Total, P 13965-9


Result ID Test Result Name Result LOINC Value
80379 Homocysteine, Total, P 13965-9

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

NY State Approved