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Test ID AGU20 Acylglycines, Quantitative, Random, Urine


Additional Testing Requirements


Diagnostic specificity of inborn errors of metabolism via urine acylglycine testing is available only for selected inborn errors of metabolism; it is recommended that urine organic acids (OAU / Organic Acids Screen, Random, Urine) be ordered and assessed simultaneously due to the limited number of metabolites included in this urine acylglycine test.



Necessary Information


1. Patient's age and sex are required.

2. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information



Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube

Specimen Volume: 10 mL

Pediatric: If insufficient collection volume, submit as much specimen as possible in a single container; the laboratory will determine if volume is sufficient for testing.

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.


Useful For

Diagnosis and monitoring for patients affected with one of the following inborn errors of metabolism:

 

Fatty Acid Oxidation Disorders:

-Glutaric acidemia type II

-Medium-chain 3-ketoacyl-coenzyme A (CoA) thiolase (MCKAT) deficiency

-Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency

-Short chain acyl-CoA dehydrogenase (SCAD) deficiency

 

Organic Acidurias:

-2-Methyl-3-hydroxybutyryl-CoA dehydrogenase (2M3HBD) deficiency

-2-Methylbutyryl-CoA dehydrogenase deficiency

-3-Methylcrotonyl-CoA carboxylase deficiency

-3-Methylglutaconyl-CoA-hydratase deficiency

-Aminoacylase 1 deficiency

-Beta-ketothiolase deficiency

-Ethylmalonic encephalopathy

-Glutaryl-CoA dehydrogenase deficiency

-Isobutyryl-CoA dehydrogenase deficiency

-Isovaleryl-CoA dehydrogenase deficiency

-Multiple carboxylase deficiency

-Propionic acidemia

Highlights

This test provides a quantitative report of abnormal levels of acylglycines in urine, identified via gas chromatography mass spectrometry.

Method Name

Gas Chromatography Mass Spectrometry (GC-MS)

Reporting Name

Acylglycines, QN, U

Specimen Type

Urine

Specimen Minimum Volume

4 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Frozen (preferred) 416 days
  Refrigerated  9 days

Reject Due To

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

Clinical Information

Acylglycines are glycine conjugates of acyl-coenzyme A species, which occur as normal intermediates of amino acid and fatty acid metabolism. In abnormal concentrations, acylglycines are biochemical markers of selected inborn errors of metabolism. Analysis of acylglycines is useful for the diagnosis and monitoring for specific fatty acid oxidation disorders and organic acidurias; however, it is recommended to use this testing in conjunction with urine organic acids and plasma acylcarnitines testing in order to establish a diagnosis.

 

In particular, acylglycine analysis is more sensitive and specific for the identification of asymptomatic patients and those who may experience mild or intermittent biochemical phenotypes that could be missed by organic acid analysis alone.

Reference Values

n-Acetylglycine:≤3.50 mg/g Creatinine

n-Propionylglycine:≤2.25 mg/g Creatinine

Isobutyrylglycine:≤3.00 mg/g Creatinine

Ethylmalonic acid:≤25.00 mg/g Creatinine

n-Butyrylglycine:≤2.50 mg/g Creatinine

2-Methylsuccinic acid:≤9.00 mg/g Creatinine

2-Methylbutyrylglycine:≤2.00 mg/g Creatinine

Isovalerylglycine:≤8.00 mg/g Creatinine

Glutaric acid:≤8.00 mg/g Creatinine

3-Methylcrotonylglycine:≤2.25 mg/g Creatinine

n-Tiglylglycine:≤9.00 mg/g Creatinine

3-Methylglutaconic acid:≤25.00 mg/g Creatinine

n-Hexanoylglycine:≤2.00 mg/g Creatinine

n-Octanoylglycine:≤2.00 mg/g Creatinine

3-Phenylpropionylglycine:≤2.00 mg/g Creatinine

trans-Cinnamoylglycine:≤5.50 mg/g Creatinine

Suberylglycine:≤5.00 mg/g Creatinine

Dodecanedioic acid:≤0.50 mg/g Creatinine

Tetradecanedioic acid:≤0.50 mg/g Creatinine

Hexadecanedioic acid:≤0.50 mg/g Creatinine

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 in vitro confirmatory studies (enzyme assay, molecular analysis); name and phone number of key contacts who may provide these studies at Mayo Clinic or elsewhere; and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Cautions

No significant cautionary statements

Clinical Reference

1. Rinaldo P, Hahn SH, Matern D. Inborn errors of amino acid, organic acid, and fatty acid metabolism. In: Burtis CA, Ashwood ER, Bruns DE eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th ed. WB Saunders Company; 2005:2207-2247

2. Roe CR, Ding J. Mitochondrial fatty acid oxidation disorders. In: Valle D, Antonarakis S, Ballabio A, Beaudet A, Mitchell GA. eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed March 21, 2024. http://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=225087274

3. Kolker S, Cazorla AG, Valayannopoulos V, et al. The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 1: the initial presentation. J Inherit Metab Dis. 2015;38(6):1041-1057. doi:10.1007/s10545-015-9839-3

4. Tuncel AT, Boy N, Morath MA, Horster F, Mutze U, Kolker S. Organic acidurias in adults: late complications and management. J Inherit Metab Dis. 2018;41(5):765-776. doi:10.1007/s10545-017-0135-2

5. Pasquali M, Longo N. Newborn screening and inborn errors of metabolism. In: Rifai N, Chiu, RWK, Young I, Burnham CD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:chap 60

Method Description

Urine volumes equivalent to 0.25 to 0.50 mg of creatinine are spiked with the mixture of labeled internal standards, allowed to equilibrate, acidified, and then extracted. After evaporation, the dry residue is derivatized to butyl esters. Specimens are analyzed by capillary gas chromatography mass spectrometry selected ion monitoring using ammonia chemical ionization and a stable isotope dilution method.(Unpublished Mayo method)

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

82542

NY State Approved

Yes

Day(s) Performed

Monday, Thursday

Report Available

3 to 6 days

Testing Algorithm

For more information see Newborn Screen Follow-up for Elevated C5-OH.