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Test Code C5OHU C5-OH Acylcarnitine, Quantitative, Urine

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

C5-OH Acylcarnitine, QN, U

Specimen Type

Urine


Necessary Information


Include patient's age, family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.

Specimen Required


Patient Preparation: If clinically feasible, discontinue L-carnitine supplementation at least 72 hours before specimen collection.

Supplies: Urine Tubes, 10 mL (T068)

Collection Container/Tube: Clean, plastic urine collection container

Submission Container/Tube: Plastic, 10-mL urine tube (T068)

Specimen Volume: 5 mL

Collection Instructions:

1. Collect a random urine specimen.

2. Freeze specimen immediately.


Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen (preferred) 7 days
  Refrigerated  24 hours

Specimen Minimum Volume

1 mL

Day(s) and Time(s) Performed

Monday, Wednesday, Friday

Specimen Retention Time

2 months

Analytic Time

2 days (not reported on Sunday)

Reference Values

<2.93 millimoles/mole creatinine

Useful For

Evaluation of patients with an abnormal newborn screen showing elevations of 3-hydroxyisovaleryl-/2-methyl-3-hydroxybutyryl-carnitine (C5-OH)

Method Name

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

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

82017

LOINC Code Information

Test ID Test Order Name Order LOINC Value
C5OHU C5-OH Acylcarnitine, QN, U In Process

 

Result ID Test Result Name Result LOINC Value
88830 C5-OH Acylcarnitine, QN, U 50091-8
28125 C5-OH Interpretation 59462-2
34469 Reviewed By No LOINC Needed

Clinical Information

The differential diagnosis of an isolated elevation of 3-hydroxyisovaleryl-/2-methyl-3-hydroxy acylcarnitine (C5-OH) in plasma or (newborn screening) blood spots includes the following disorders:

-3-Methylcrotonyl-CoA carboxylase deficiency (common name: 3-methylcrotonylglycinuria), either infantile or maternal

-3-Hydroxy 3-methylglutaryl-(HMG)-CoA lyase deficiency

-Beta-ketothiolase deficiency

-2-Methyl 3-hydroxybutyryl-CoA dehydrogenase deficiency

-3-methylglutaconic aciduria type I

-Biotinidase deficiency

-Holocarboxylase deficiency

 

Confirmatory and diagnostic testing are necessary to differentiate these clinical entities. This test can be useful in differentiating patients with 3-methylcrotonylglycinuria and with 3-methylglutaconic aciduria as they typically excrete larger amounts of C5-OH in urine compared to patients with the other diagnoses.

 

The American College of Medical Genetics (ACMG) newborn screening work group published diagnostic algorithms for the follow-up of infants who had positive newborn screening results. For more information, see http://www.acmg.net.

Interpretation

Preliminary data showed that an elevated excretion in urine and concentration in plasma of 3-hydroxyisovaleryl-/2-methyl-3-hydroxy acylcarnitine (C5-OH) can be the only biochemical abnormalities in patients with 3-methylcrotonylglycinuria.

 

Contact Mayo Medical Laboratories for assistance in test interpretation and additional testing options.

Cautions

The results of urine acylcarnitines are typically not informative when the patient is receiving L-carnitine supplements.

Clinical Reference

Wolfe LA, Finegold DN, Vockley J, et al: Potential misdiagnosis of 3-methylcrotonyl-coenzyme A carboxylase deficiency associated with absent or trace urinary 3-methylcrotonylglycine. Pediatrics 2007 Nov;120(5):e1335-1340

Method Description

Acylcarnitines, including 3-hydroxy isovalerylcarnitine, are determined in urine by flow injection analysis tandem mass spectrometry using acetyl-d(3)-carnitine, propionyl-d(3)-carnitine, butyryl-d(3)-carnitine, octanoyl-d(3)-carnitine, dodecanoyl-d(3)-carnitine, and palmitoyl-d(3)-carnitine as internal standards. A total of 20 mcL of the diluted urine is extracted with an acidified acetonitrile solution containing the internal standards. The supernatant is evaporated and the residue treated with n-butanolic HCl yielding the acylcarnitines for analysis as their n-butyl esters.(Tortorelli S, Hahn SH, Cowan TM, et al: The urinary excretion of glutarylcarnitine is an informative tool in the biochemical diagnosis of glutaric acidemia type I. Mol Genet Metab 2005;84:137-143)

Genetics Test Information

Evaluation of patients with an abnormal newborn screen showing elevations of C5-OH. The results are not informative when patient is receiving L-carnitine supplements.

Forms

New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.