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Interpretive Handbook

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Test 81249:
Acylglycines, Quantitative, Urine

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

 

Acylglycines are glycine conjugates of acyl-CoA species. Acylglycines are normal intermediates of amino acid and fatty acid metabolism; however, in abnormal concentrations are biochemical markers of selected inborn errors of metabolism (IEM). Analysis of acylglycines is a useful screening test in the evaluation of patients with a suspected IEM, though additional studies are necessary to establish a diagnosis. The biochemical diagnosis of these disorders is a complex process achieved by multiple tests and their integrated interpretation.

 

Acylglycines are often ordered in conjunction with organic acids. Analysis of acylglycines is a more sensitive and specific method in particular for the identification of asymptomatic patients or those with mild and/or intermittent biochemical phenotypes which could be missed by organic acid analysis alone. The quantitative analysis of urinary acylglycines is particularly effective for identifying asymptomatic patients affected with disorders including:

-Short chain acyl-CoA dehydrogenase (SCAD) deficiency

-Functional SCAD deficiency (G625A, C611T variants)

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

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

-Electron transfer flavoprotein (ETF) deficiency (glutaric acidemia type 2)

-ETF: ubiquinone oxidoreductase (ETF-QO) deficiency (glutaric acidemia type 2)

-Riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency

-Ethylmalonic encephalopathy

-2-Methylbutyryl-CoA dehydrogenase deficiency

-Isovaleryl-CoA dehydrogenase deficiency

-Glutaryl-CoA dehydrogenase deficiency

Useful For Suggests clinical disorders or settings where the test may be helpful

Biochemical screening of asymptomatic patients affected with 1 of the following inborn errors of metabolism:

-Short chain acyl-CoA dehydrogenase (SCAD) deficiency

-Functional SCAD deficiency (G625A, C611T variants)

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

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

-Electron transfer flavoprotein (ETF) deficiency (glutaric acidemia type 2)

-ETF: ubiquinone oxidoreductase (ETF-QO) deficiency (glutaric acidemia type 2)

-Riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency

-Ethylmalonic encephalopathy

-2-Methylbutyryl-CoA dehydrogenase deficiency

-Isovaleryl-CoA dehydrogenase deficiency

-Glutaryl-CoA dehydrogenase deficiency

Interpretation Provides information to assist in interpretation of the test results

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 Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Due to the limited number of metabolites included in the acylglycine analysis, it is recommended that OAU/80619 Organic Acids Screen, Urine be performed concurrently.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Control Values

Results Expressed as mg/g Creatinine

 

Range

Ethylmalonic Acid

0.5-20.2

2-Methylsuccinic Acid

0.4-13.8

Glutaric Acid

0.6-15.2

Isobutyrylglycine

0.00-11.0

n-Butyrylglycine

0.1-2.1

2-Methylbutyrylglycine

0.3-7.5

Isovalerylglycine

0.3-14.3

n-Hexanoylglycine

0.2-1.9

n-Octanoylglycine

0.1-2.1

3-Phenylpropionylglycine

0.00-1.1

Suberylglycine

0.00-11.0

trans-Cinnamoylglycine

0.2-14.7

Dodecanedioic Acid (12 DCA)

0.00-1.1

Tetradecanedioic Acid (14 DCA)

0.00-1.0

Hexadecanedioic Acid (16 DCA)

0.00-1.0

 

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Rinaldo P: Laboratory diagnosis of inborn errors of metabolism. In Liver Disease in Children. Second edition. Edited by FJ Suchy. Philadelphia, Lippincott, Williams and Wilkins, 2001, pp 171-184

2. Rinaldo P, Hahn SH, Matern D: Inborn errors of amino acid, organic acid, and fatty acid metabolism. In Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Fourth edition. Edited by CA Burtis, ER Ashwood, DE Bruns. WB Saunders Company, 2005, pp 2207-2247

3. Rinaldo P: Organic Acids. In Laboratory Guide to the Methods in Biochemical Genetics. Edited by N Blau, M Duran, KM Gibson. Springer-Verlag Berlin Heidelberg, 2008, pp 137-170