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Test ID CARNS Carnitine, Serum

Reporting Name

Carnitine, S

Useful For

Evaluation of patients with a clinical suspicion of a wide range of conditions including organic acidemias, fatty acid oxidation disorders, and primary carnitine deficiency in serum specimens

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL


Specimen Minimum Volume

0.2 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen (preferred) 60 days
  Refrigerated  21 days
  Ambient  7 days

Reference Values

 

Total Carnitine (TC)

Free Carnitine (FC)

Acylcarnitine (AC)

AC/FC Ratio

Age Group

Range*

Range*

Range*

Range

≤1 day

23-68

12-36

7-37

0.4-1.7

2-7 days

17-41

10-21

3-24

0.2-1.4

8-31 days

19-59

12-46

4-15

0.1-0.7

32 days-12 months

38-68

27-49

7-19

0.2-0.5

13 months-6 years

35-84

24-63

4-28

0.1-0.8

7-10 years

28-83

22-66

3-32

0.1-0.9

11-17 years

34-77

22-65

4-29

0.1-0.9

≥18 years

34-78

25-54

5-30

0.1-0.8

*Values expressed as nmol/mL

Schmidt-Sommerfeld E, Werner E, Penn D: Carnitine plasma concentrations in 353 metabolically healthy children. Eur J Pediatr 1988;147:356-360

Used with permission of European Journal of Pediatrics, Springer-Verlag, New York, Inc., Secaucus, NJ

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

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.

CPT Code Information

82379

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CARNS Carnitine, S In Process

 

Result ID Test Result Name Result LOINC Value
32045 Total 14288-5
32046 Free (FC) 14286-9
32047 Acylcarnitine (AC) 14282-8
32048 AC/FC Ratio 30193-7
32049 Interpretation 59462-2

Clinical Information

Carnitine and its esters are required for normal energy metabolism and serve 4 primary functions:

-Importing long-chain fatty acids into the mitochondria

-Exporting naturally-occurring short-chain acyl-CoA groups from the mitochondria

-Maintaining the ratio of free CoA to esterified CoA

-Removing potentially toxic acyl-CoA groups from the cells and tissues

 

Evaluation of carnitine in serum, plasma, and urine screens patients for suspected primary disorders of the carnitine cycle, or secondary disturbances in carnitine levels as a result of organic acidemias and fatty acid oxidation disorders. In the latter disorders, acyl-CoA groups accumulate and are excreted into the urine and bile as carnitine derivatives, resulting in a secondary carnitine deficiency. More than 100 such primary and secondary disorders have been described. Collectively, their incidence is approximately 1 in 1,000 live births. Primary carnitine deficiency has an incidence of approximately 1 in 21,000 live births based on Minnesota newborn screening data.

 

Other conditions that could cause an abnormal carnitine level include neuromuscular diseases, gastrointestinal disorders, familial cardiomyopathy, renal tubulopathies and chronic renal failure (dialysis), and prolonged treatment with steroids, antibiotics (pivalic acid), anticonvulsants (valproic acid), and total parenteral nutrition.

 

Follow-up testing is required to differentiate primary and secondary carnitine deficiencies and to elucidate the exact cause.

Interpretation

When abnormal results are detected, a detailed interpretation is given, including an overview of the results and of their significance, a correlation to available clinical information, elements of differential diagnosis, recommendations for additional biochemical testing, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Cautions

Increased values may be obtained after carnitine supplementation or meat consumption.

Clinical Reference

1. Magoulas PL, El-Hattab AW: Systemic primary carnitine deficiency: an overview of clinical manifestations, diagnosis, and management. Orphanet J Rare Dis 2012,7:68

2. Longo N, Amat di San Filippo C, Pasquali M: Disorders of carnitine transport and the carnitine cycle. Am J Med Genet C Semin Med Genet 2006;142C(2):77-85

3. Zammit VA, Ramsay RR, Bonomini M, Arduini A: Carnitine, mitochondrial function and therapy. Adv Drug Deliv Rev 2009;61(14):1353-1362

4. El-Hattab AW: Systemic Primary Carnitine Deficiency. In GeneReviews Edited by MP Adam, HH Ardinger, RA Pagon, et al. University of Washington, Seattle; 1993-2019. 2012 Mar 15 (Updated 2016 Nov 3) Accessed 3/22/2019. Available at www.ncbi.nlm.nih.gov/books/NBK84551/

Analytic Time

2 days (not reported on Saturday or Sunday)

Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross OK

Icterus

Mild OK; Gross OK

Other

NA

 

NY State Approved

Yes

Highlights

Carnitine levels are disturbed in primary disorders of the carnitine cycle, or secondary disturbances of carnitine metabolism due to other biochemical disorders.

 

Additional testing is required to distinguish between primary and secondary deficiencies of carnitine.

 

Dietary intake (meat, carnitine supplementation) may cause increased carnitine values.

 

Abnormal results are accompanied by detailed interpretation including recommendations for follow-up testing.

Method Name

Flow Injection Analysis-Tandem Mass Spectrometry (FIA-MS/MS)

Forms

If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.