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HelpTest ID: CARNS Carnitine, Serum
Reporting Name
Carnitine, SUseful 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 using serum specimens
Specimen Type
SerumNecessary Information
Patient's age is required.
Specimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| 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 |
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.
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
82379
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CARNS | Carnitine, S | 97182-0 |
| 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 is a biochemical screening test 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 1000 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.
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;18;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: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2012. Updated November 3, 2016. Accessed November 27, 2023. Available at www.ncbi.nlm.nih.gov/books/NBK84551/
5. Longo N., Frigeni M., Pasquali M. Carnitine transport and fatty acid oxidation. Biochim. Biophys. Acta. 2016;1863:2422-2435
6. Almannai M, Alfadhel M, El-Hattab AW. Carnitine inborn errors of metabolism. Molecules. 2019;24(18):3251
Report Available
3 to 5 daysMethod Name
Flow Injection Analysis-Tandem Mass Spectrometry (FIA-MS/MS)
Forms
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
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