Carnitine, Free and Total
Label Mnemonic: CARNFT
Epic Lab Code: LAB2795
Downtime Form: A-1a Miscellaneous Request
Commercial Mail-out Laboratory
5231 RCP
Collection Medium:
Green top tube 4 mL (Na Heparin)
Preferred Minimum: 0.5 mL heparinized plasma
Absolute Minimum: 0.2 mL heparinized plasma
Rejection Criteria:
Serum or plasma from a gel tube.
Delivery Instructions:
Submit specimen to laboratory as soon as possible after collection.
Turn Around Time:
3-5 working days upon receipt at reference laboratory
Reference Range:
  Total Free Carnitine Carnitine Acylcarnitine AC/FC (TC) (FC) (AC) Ratio ----------------------------------------------------------------------- Age Group Range* Range* Range* Range < or = 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 > or = 18 years 34-78 25-54 5-30 0.1-0.8 *Values expressed as nmol/mL
Interpretive Data:
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.
Always include Date of Birth on the request form.

Determination of urine carnitine concentration concurrently with plasma concentration is recommended.

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
-Buffering the ratio of free CoA to esterified CoA
-Removing potentially toxic acyl-CoA groups from the cells and tissues

Evaluation of carnitine in plasma, tissue, and urine identifies patients with primary disorders of the carnitine cycle, as well as 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 <1:10,000 to >1:1,000,000 live births. Collectively, their incidence is approximately 1:1,000 live births.

Other conditions that are associated with an abnormal carnitine status 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.

Clinical Reference
1. Chalmers RA, Roe CR, Stacey TE, et al: Urinary excretion of l- carnitine and acylcarnitines by patients with disorders of organic acid metabolism: evidence for secondary insufficiency of l-carnitine. Ped Res 1984;18:1325-1328
2. Scaglia F, Wang YH, Singh RH, et al: Defective urinary carnitine transport in heterozygotes for primary carnitine deficiency. Genet Med 1998;1:34-39
3. Scaglia F, Longo N: Primary and secondary alterations of neonatal carnitine metabolism. Semin Perinatol 1999;23:152-161
4. 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
5. Zammit VA, Ramsay RR, Bonomini M, Arduini A: Carnitine, mitochondrial function and therapy. Adv Drug Deliv Rev 2009;61(14):1353-62
Test Limitations:
Biochemical test results depend in part on the clinical and dietary status at the time of specimen collection. A normal or non-diagnostic test result does not rule out the possibility of an underlying metabolic disorder, including that for which the test was requested.
Flow Injection Analysis-Tandem Mass Spectrometry (FIA-MS/MS)
CPT Code:
See Additional Information:
Specimens Requiring Immediate Delivery