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Test Code C5OHU C5-OH Acylcarnitine, Quantitative, Random, Urine

Reporting Name

C5-OH Acylcarnitine, QN, U

Useful For

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

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Urine


Ordering Guidance


This second-tier test is used specifically to evaluate a newborn screening elevation of 3-hydroxyisovaleryl-/2-methyl-3-hydroxy acylcarnitine and must not be ordered with either C4U / C4 Acylcarnitine, Quantitative, Random, Urine or C5DCU / C5-DC Acylcarnitine, Quantitative, Random, Urine.

 

For general screening for metabolic disorders, see OAU / Organic Acids Screen, Random, Urine; ACRN / Acylcarnitines, Quantitative, Plasma; and AAQP / Amino Acids, Quantitative, Plasma.



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

Specimen Volume: 5 mL

Collection Instructions:

1. Collect a random urine specimen.

2. Freeze specimen immediately.


Specimen Minimum Volume

1 mL

Specimen Stability Information

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

Reference Values

<2.93 millimoles/mole creatinine

Day(s) Performed

Monday, Wednesday, 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

82017

LOINC Code Information

Test ID Test Order Name Order LOINC Value
C5OHU C5-OH Acylcarnitine, QN, U 50091-8

 

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 18771-6

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-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 used to differentiate 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 and Genomics Newborn Screening Work Group published diagnostic algorithms for the follow-up of infants who had positive newborn screening results. For more information, see the Practice Resources: ACT Sheets and Algorithms at 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 can be the only biochemical abnormalities in patients with 3-methylcrotonylglycinuria.

Cautions

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

Report Available

2 to 5 days

Reject 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)