Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

CARN
8802
Interpretation: An interpretative report will be provided.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Bonnefont JP, Djouadi F, Prip-Buus C, et al: Carnitine
palmitoyltransferases 1 and 2: biochemical, molecular and medical aspects. Mol Aspects Med 2004
Oct-Dec;25(5-6):495-520 2. Siguake E, Rakheja D, Kitson K, Bennet M: Carnitine palmitoyltransferase
II deficiency: a clinical, biochemical, and molecular review. Lab Invest 2003 Nov;83(11):1543-1554
Carnitine, Plasma
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 plasma, tissue, and urine is a screening test for patients suspected of having
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 1:1,000,000 live births.
Collectively, their incidence is approximately 1:1,000 live births. Primary carnitine deficiency has an
incidence of approximately 1:21,000 live births based on Minnesota newborn screening data. Other
conditions which could be indicated by 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.
Useful For: Evaluation of patients with a clinical suspicion of a wide range of conditions that include
inborn errors of metabolism, especially organic acidemias, fatty acid oxidation disorders, and primary
carnitine deficiency
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.
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
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