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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

Method Name

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

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

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Reference Values

<2.93 millimoles/mole creatinine

Day(s) Performed

Monday, Wednesday, Friday

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.

Specimen Retention Time

1 month

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.

Genetics Test Information

Elevated 3-hydroxyisovaleryl-/2-methyl-3-hydroxy acylcarnitine (C5-OH) in plasma or newborn screening blood spots is due to one of several biochemical genetic diagnoses: 3-methylcrotonylglycinuria, 3-hydroxy 3-methylglutaryl-CoA lyase deficiency, beta-ketothiolase deficiency, 2-methyl 3-hydroxybutyryl-CoA dehydrogenase deficiency, 3-methylglutaconic aciduria, biotinidase deficiency or holocarboxylase deficiency.

 

Urine C5OH is 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.

Report Available

2 to 5 days