Test Id : HCYSP
Homocysteine, Total, Plasma
Useful For
Suggests clinical disorders or settings where the test may be helpful
An aid for screening patients suspected of having an inherited disorder of methionine metabolism including:
-Cystathionine beta-synthase deficiency (homocystinuria)
-Methylenetetrahydrofolate reductase deficiency 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 deficiency
-Glycine N-methyltransferase deficiency
-Methionine adenosyltransferase I/III deficiency
Screening and monitoring patients suspected of, or confirmed with, an inherited disorder of methionine metabolism using plasma specimens
Evaluating individuals with suspected deficiency of vitamin B12 or folate
Method Name
A short description of the method used to perform the test
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Cystathionine beta-synthase deficiency
Methylenetetrahydrofolate reductase deficiency (MTHFR)
MTHFR deficiency
Methionine synthase deficiency
Cobalamin (Cbl) metabolism
Methyl-Cobalamin deficiency
Adenosyl-cobalamin deficiency
Cbl C2 deficiency
Cbl D2 deficiency
Cbl F3 deficiency
Cbl D-Var1 deficiency
Cbl E deficiency
Cbl G deficiency
Transcobalamin II deficiency
Adenosylhomocysteinase (AHCY) deficiency
Glycine N-methyltransferase (GNMT) deficiency
Methionine adenosyltransferase (MAT) I/III deficiency
Cobalamin F3 deficiency
Cobalamin D-Variant 1 deficiency
Cobalamin E deficiency
Cobalamin G deficiency
Cobalamin C2 deficiency
Cobalamin D2 deficiency
Specimen Type
Describes the specimen type validated for testing
Plasma EDTA
Necessary Information
1. Patient's age and sex are required.
2. Biochemical Genetics Patient Information (T602) is recommended, but not required, for suspected cases of inherited disorders of methionine metabolism.
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Green top (sodium or lithium heparin)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Immediately place specimen on wet ice.
2. Within 4 hours of collection, centrifuge and aliquot plasma into a plastic vial.
3. If blood cannot be placed on wet ice immediately, then within 1 hour of collection, centrifuge and aliquot plasma into a plastic vial.
4. A refrigerated centrifuge is not required if the above time restrictions are met.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Forms
1. Biochemical Genetics Patient Information (T602)
2. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.3 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma EDTA | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 309 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
An aid for screening patients suspected of having an inherited disorder of methionine metabolism including:
-Cystathionine beta-synthase deficiency (homocystinuria)
-Methylenetetrahydrofolate reductase deficiency 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 deficiency
-Glycine N-methyltransferase deficiency
-Methionine adenosyltransferase I/III deficiency
Screening and monitoring patients suspected of, or confirmed with, an inherited disorder of methionine metabolism using plasma specimens
Evaluating individuals with suspected deficiency of vitamin B12 or folate
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Homocysteine is an intermediary in the sulfur-amino acid metabolism pathways, linking the methionine cycle to the folate cycle. Inborn errors of metabolism that lead to homocysteinemia or homocystinuria include cystathionine beta-synthase deficiency (homocystinuria) and various defects of methionine remethylation. Genetic defects in vitamin cofactors (vitamins B6, B12, and folate) and nutritional deficiency of vitamin B12 and folate also lead to abnormal homocysteine accumulation.
Homocysteine concentration is an indicator of acquired folate or cobalamin deficiency and is a contributing factor in the pathogenesis of neural tube defects. Homocysteine was once thought to be an independent predictor of cardiovascular disease (atherosclerosis, heart disease, thromboembolism), as early observational studies prior to the year 2000 linked homocysteine to cardiovascular risk and morbidity and mortality. However, following US Food and Drug Administration mandated folic acid supplementation in 1998, homocysteine concentrations decreased by approximately 10% without a similar change in cardiovascular or ischemic events. Currently, the use of homocysteine for assessment of cardiovascular risk is uncertain and controversial. Based on several meta-analyses, at present, homocysteine may be regarded as a weak risk factor for coronary heart disease, and there is a lack of direct causal relationship between hyperhomocysteinemia and cardiovascular disease. It is most likely an indicator of poor lifestyle and diet.
This test should be used in conjunction with plasma amino acids, quantitative acylcarnitines, methylmalonic acid, and urine organic acids to aid in the biochemical screening for primary and secondary disorders of methionine metabolism.
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
| Age | Total homocysteine (nmol/mL) | |
| Female | Male | |
| 0-11 months | 3.1-8.3 | 3.2-9.7 |
| 12-23 months | 3.2-8.3 | 3.3-9.6 |
| 24-35 months | 3.2-8.2 | 3.3-9.6 |
| 3 years | 3.2-8.2 | 3.3-9.6 |
| 4 years | 3.3-8.2 | 3.4-9.5 |
| 5 years | 3.4-8.1 | 3.5-9.4 |
| 6 years | 3.5-8.1 | 3.6-9.4 |
| 7 years | 3.5-8.1 | 3.7-9.4 |
| 8 years | 3.6-8.2 | 3.8-9.3 |
| 9 years | 3.7-8.2 | 3.9-9.4 |
| 10 years | 3.8-8.3 | 4.1-9.4 |
| 11 years | 3.9-8.4 | 4.3-9.4 |
| 12 years | 3.9-8.6 | 4.4-9.5 |
| 13 years | 4.0-8.7 | 4.6-9.6 |
| 14 years | 4.1-8.8 | 4.8-9.7 |
| 15 years | 4.2-8.9 | 5.0-9.8 |
| 16 years | 4.2-9.1 | 5.2-9.9 |
| 17 years | 4.3-9.2 | 5.4-10.0 |
| 18 years | 4.3-9.3 | 5.6-10.1 |
| 19 years | 4.4-9.5 | 5.7-10.3 |
| 20 years | 4.4-9.6 | 5.9-10.5 |
| 21 years | 4.4-9.8 | 6.0-10.6 |
| 22 years | 4.4-9.9 | 6.1-10.8 |
| 23 years | 4.4-10.1 | 6.2-11.0 |
| 24 years | 4.4-10.3 | 6.2-11.1 |
| 25 years | 4.4-10.4 | 6.3-11.3 |
| 26 years | 4.4-10.6 | 6.3-11.4 |
| 27 years | 4.3-10.8 | 6.4-11.6 |
| 28 years | 4.3-11.0 | 6.4-11.7 |
| 29 years | 4.3-11.2 | 6.4-11.8 |
| 30 years | 4.3-11.4 | 6.4-11.9 |
| 31 years | 4.4-11.6 | 6.4-12.1 |
| 32 years | 4.4-11.8 | 6.4-12.2 |
| 33 years | 4.4-11.9 | 6.4-12.3 |
| 34 years | 4.5-12.1 | 6.4-12.4 |
| 35 years | 4.5-12.2 | 6.4-12.6 |
| 36 years | 4.6-12.4 | 6.4-12.8 |
| 37 years | 4.6-12.5 | 6.4-12.9 |
| 38 years | 4.7-12.7 | 6.4-13.1 |
| 39 years | 4.7-12.8 | 6.4-13.2 |
| 40 years | 4.8-13.0 | 6.5-13.4 |
| 41 years | 4.8-13.2 | 6.5-13.5 |
| 42 years | 4.8-13.4 | 6.5-13.7 |
| 43 years | 4.9-13.5 | 6.6-13.9 |
| 44 years | 4.9-13.7 | 6.6-14.0 |
| 45 years | 4.9-13.9 | 6.6-14.2 |
| 46 years | 4.9-14.0 | 6.7-14.4 |
| 47 years | 4.9-14.2 | 6.7-14.5 |
| 48 years | 5.0-14.3 | 6.8-14.7 |
| 49 years | 5.0-14.4 | 6.8-14.9 |
| 50 years | 5.0-14.5 | 6.8-15.0 |
| 51 years | 5.1-14.6 | 6.8-15.2 |
| 52 years | 5.1-14.7 | 6.9-15.4 |
| 53 years | 5.1-14.8 | 6.9-15.5 |
| 54 years | 5.2-14.9 | 6.9-15.6 |
| 55 years | 5.2-15.0 | 6.9-15.7 |
| 56 years | 5.3-15.0 | 6.9-15.8 |
| 57 years | 5.3-15.1 | 6.9-15.9 |
| 58 years | 5.3-15.2 | 6.9-16.0 |
| 59 years | 5.4-15.2 | 6.9-16.0 |
| 60 years | 5.4-15.3 | 6.9-16.1 |
| 61 years | 5.4-15.4 | 7.0-16.2 |
| 62 years | 5.5-15.4 | 7.0-16.2 |
| 63 years | 5.5-15.5 | 7.0-16.3 |
| 64 years | 5.6-15.5 | 7.1-16.3 |
| 65 years | 5.6-15.6 | 7.1-16.3 |
| 66 years | 5.7-15.6 | 7.1-16.3 |
| 67 years | 5.7-15.7 | 7.2-16.3 |
| 68 years | 5.8-15.7 | 7.2-16.3 |
| 69 years | 5.9-15.7 | 7.2-16.3 |
| 70 years | 6.0-15.8 | 7.3-16.3 |
| 71 years | 6.1-15.8 | 7.3-16.3 |
| 72 years | 6.2-15.8 | 7.3-16.3 |
| 73 years | 6.3-15.9 | 7.3-16.3 |
| 74 years | 6.4-15.9 | 7.3-16.3 |
| 75 years | 6.5-15.9 | 7.3-16.3 |
| 76 years | 6.6-15.9 | 7.3-16.3 |
| 77 years | 6.7-16.0 | 7.4-16.3 |
| 78 years | 6.8-16.0 | 7.4-16.3 |
| 79 years | 6.9-16.0 | 7.5-16.3 |
| 80 years | 7.0-16.0 | 7.5-16.3 |
| 81 years | 7.1-16.0 | 7.7-16.2 |
| 82 years | 7.2-16.0 | 7.8-16.2 |
| 83 years | 7.2-16.0 | 7.9-16.2 |
| 84 years | 7.3-16.0 | 8.0-16.2 |
| 85 years | 7.3-16.0 | 8.2-16.2 |
| >85 years | 7.4-16.0 | 8.3-16.2 |
Interpretation
Provides information to assist in interpretation of the test results
Elevated homocysteine concentrations are considered informative in patients evaluated for suspected nutritional deficiencies (vitamin B12, folate) and inborn errors of metabolism. Measurement of methylmalonic acid (MMA) distinguishes between vitamin B12 (cobalamin) and folate deficiencies, as MMA is only elevated in vitamin B12 deficiency. Treatment response can be evaluated by monitoring plasma homocysteine concentrations over time.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Homocysteine concentration is affected by supplementation of vitamins B12, B6, or folate.
Factors that may influence and increase plasma homocysteine include:
-Age
-Smoking
-Poor diet/cofactor deficiencies
-Chronic kidney disease/renal disease
-Hypothyroidism
Table. Medications that may increase homocysteine concentrations include:
| Medication | Effect |
| Methotrexate | 5-Methyltetrahydrofolate depletion |
| Azuridine | Vitamin B6 antagonist |
| Nitrous oxide | Inactivation of methionine synthase |
| Phenytoin | Interference with folate metabolism |
| Carbamazepine | Interference with folate metabolism |
| Oral contraceptives | Estrogen-induced vitamin B6 deficiency |
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Mudd SH, Levy HL, Kraus JP: Disorders of transsulfuration. In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill, 2019. Accessed December 2, 2024. Available at https://ommbid.mhmedical.com/content.aspx?sectionid=225084718&bookid=2709
2. Chrysant SG, Chrysant GS. The current status of homocysteine as a risk factor for cardiovascular disease: a mini review. Expert Rev Cardiovasc Ther. 2018;16(8):559-565. doi:10.1080/14779072.2018.1497974
3. Refsum H, Smith AD, Ueland PM, et al. Facts and recommendations about total homocysteine determinations: an expert opinion. Clin Chem. 2004;50(1):3-32
4. Turgeon CT, Magera MJ, Cuthbert CD, et al. Determination of total homocysteine, methylmalonic acid, and 2-methylcitric acid in dried blood spots by tandem mass spectrometry. Clin Chem. 2010;56(11):1686-1695
5. Sacharow SJ, Picker JD, Levy HL. Homocystinuria caused by cystathionine beta-synthase deficiency. In: Adam MP, Feldman J, Mirzaa GM, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2004. Updated May 18, 2017. Accessed December 2, 2024. Available at www.ncbi.nlm.nih.gov/books/NBK1524/
Method Description
Describes how the test is performed and provides a method-specific reference
Total homocysteine is measured by stable isotope dilution microflow liquid chromatography tandem mass spectrometry.(Unpublished Mayo method)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
83090
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| HCYSP | Homocysteine, Total, P | 13965-9 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 80379 | Homocysteine, Total, P | 13965-9 |