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HelpTest Code LAB7529 Carnitine, Random, Urine
Additional Codes
CARNU
Useful For
Evaluation of patients with a clinical suspicion of a wide range of conditions including organic acidemias and fatty acid oxidation disorders
Monitoring carnitine treatment
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
UrineSpecimen Required
Supplies: Urine Tubes, 10 mL (T068)
Container/Tube: Plastic, 10-mL urine tube
Specimen Volume: 1.5 mL
Collection Instructions:
1. Collect a random urine specimen.
2. No preservative.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Frozen (preferred) | 365 days | |
| Refrigerated | 72 hours |
On-campus collections: Tube to 99 or deliver to University Extension Hospital Room EH318
Send Frozen.
Off-campus collections: Random urine collection. Specimen to be stored/transported at Frozen temp.
Reference Values
FREE CARNITINE:
77-214 nmol/mg of creatinine
TOTAL CARNITINE:
180-412 nmol/mg of creatinine
RATIO:
Acylcarnitine to free carnitine: 0.7-3.4
Day(s) Performed
Tuesday
CPT Code Information
82379
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CARNU | Carnitine, U | 100428-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 27121 | Total | 17866-5 |
| 27122 | Free (FC) | 17867-3 |
| 15789 | AC/FC Ratio | 43576-8 |
| 21550 | Interpretation | 59462-2 |
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.
Method Description
Free and total carnitines are measured by tandem mass spectrometry (MS/MS) stable isotope dilution analysis. Hydrolysis enables measurement of total carnitine, and esterified carnitine (acylcarnitine) is calculated as the difference between the total and free carnitine. Quantification is enabled using deuterium-labeled carnitine (d3-carnitine) added as internal standard. A selected reaction monitoring experiment is performed by MS/MS. The first mass spectrometer detects carnitine and d3-carnitine precursors and transmits them to a collision cell within the mass spectrometer where they are fragmented. Specific fragments derived from the carnitine and internal standard are monitored in the second mass spectrometer.(Stevens RD, Hillman SL, Worthy S, Sanders D, Millington DS. Assay for free and total carnitine in human plasma using tandem mass spectrometry. Clin Chem. 2000;46(5):727-729; Miller MJ, Cusmano-Ozog K, Oglesbee D, Young S. ACMG Laboratory Quality Assurance Committee. Laboratory analysis of acylcarnitines, 2020 update: a technical standard of the American College of Medical Genetics and Genomics [ACMG]. Genet Med. 2021;23[2]:249-258)
Report Available
3 to 9 daysSpecimen Retention Time
1 monthReject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Method 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.