Sign in →

Test Code HOMO.MY Homocysteine, Total, Plasma

Additional Codes

Mayo Test Code: HCYSP

Reporting Name

Homocysteine, Total, P

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 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

 

Evaluating individuals with suspected deficiency of vitamin B12 or folate

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

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


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. Centrifuge and aliquot plasma into plastic vial within 4 hours of collection.

3. If blood cannot be placed on wet ice immediately, centrifuge and aliquot plasma into plastic vial within 1 hour of collection.

4. A refrigerated centrifuge is not required if the above time restrictions are met.


Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma EDTA Refrigerated (preferred) 28 days
  Frozen  309 days
  Ambient  28 days

Reference Values

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

Day(s) Performed

Monday through Friday

Test Classification

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

83090

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

Clinical Information

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 U.S. 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.

Interpretation

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

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

Report Available

3 to 5 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)