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Test ID: ACYLG
Acylglycines, Quantitative, Urine

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

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

Glycine conjugates (acylglycines) of acyl CoA species, which are normal intermediates of amino acid and fatty acid metabolism, 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 that cannot be achieved by a single test and requires the performance of multiple analyses and their integrated interpretation. While a major acylglycine accumulation may be detected by organic acid analysis (#80619 Organic Acids Screen, Urine), especially when the specimen is collected during an acute illness, asymptomatic patients may demonstrate mild and intermittent biochemical phenotypes that are likely to be missed by standard urine organic acid analysis. The quantitative analysis of urinary acylglycines by stable isotope dilution gas chromatography/mass spectrometry is a more sensitive and specific method and is particularly effective for identifying asymptomatic patients affected with 1 of the disorders listed below.

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

 

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 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 #80619 Organic Acids Screen, Urine also be performed concurrently.

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

1. Rinaldo P, O'Shea JJ, Coates PM, et al: Medium-chain Acyl-CoA dehydrogenase deficiency. Diagnosis by stable-isotope dilution measurment of urinary n-hexanoylglycine and 3-phenylpropionyl-glycine. N Engl J Med 1988;319:1308-1313

2. Rinaldo P, Welch RD, Previs SF, et al: Ethylmalonic/adipic aciduria: effect of oral medium-chain triglycerides, carnitine, and glycine on urinary excretion of organic acids, acylcarnitines, and acylglycines. Pediatr Res 1991;30:216-221

3. Gibson KM, Terry G, Burlingame TG, et al: 2-Methylbutyryl-coenzyme A dehydrogenase deficiency: a new inborn error of L-isoleucine metabolism. Pediatr Res 2000;47:830-833

4. Rinaldo P: Laboratory diagnosis of inborn errors of metabolism. In Liver Disease in Children. 2nd edition. Edited by FJ Suchy. Philadelphia, Lippincott, Williams & Wilkins, 2001, pp 171-184

5. Corydon MJ, Vockley G, Rinaldo P, et al: Role of common variant alleles in the molecular basis of short-chain acyl-CoA dehydrogenase deficiency. Pediatr Res 2001;49:18-23

6. 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. 4th edition. Edited by CA Burtis, ER Ashwood, DE Bruns. WB Saunders, 2005, pp 2207-2247

7. 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