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Test ID: CARN Carnitine, Plasma

Reporting Name

Carnitine, P

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 plasma specimens

Specimen Type

Plasma


Specimen Required


Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: EDTA, lithium heparin

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL


Specimen Minimum Volume

0.2 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma 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
CARN Carnitine, P In Process

 

Result ID Test Result Name Result LOINC Value
32050 Total 14288-5
32051 Free (FC) 14286-9
32052 Acylcarnitine (AC) 14282-8
21032 AC/FC Ratio 30193-7
21549 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

-Buffering 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, tissue, 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. Individually, the incidence of these disorders varies from less than 1 in 10,000 to more than 1 in 1,000,000 live births. 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 which could cause an abnormal carnitine level are 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.

Clinical Reference

1. Magoulas PL, El-Hattab AW: Systemic primary carnitine deficiency: an overview of clinical manifestations, diagnosis, and management. Orphanet Journal of Rare Diseases 2012,7:68 Available at www.ojrd.com/content/7/1/68. Accessed 1/22/15

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

Analytic Time

2 days (not reported on Saturday or Sunday)

Method Name

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

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical