Test ID: ACYLG
Acylglycines, Quantitative, Urine

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

The following algorithms are available in Special Instructions:

-Newborn Screening Follow-up for Elevations of C8, C6, and C10 Acylcarnitines (also applies to any plasma C8, C6, and C10 acylcarnitine elevations)

-Newborn Screening Follow-up for Isolated C4 Acylcarnitine Elevations (also applies to any plasma C4 acylcarnitine elevation)

-Newborn Screening Follow-up for Isolated C5 Acylcarnitine Elevations (also applies to any plasma C5 acylcarnitine elevation)

• Newborn Screening Follow-up for Isolated C4 Acylcarnitine Elevations (also applies to any plasma C4 acylcarnitine elevations)
• Newborn Screening Follow-up for Elevations of C8, C6, and C10 Acylcarnitine (also applies to any plasma C8, C6, and C10 acylcarnitine elevations)
• Newborn Screening Follow-up for Isolated C5 Acylcarnitines Elevations (also applies to any plasma C5 acylcarnitine elevation)

Gas Chromatography-Mass Spectrometry (GC-MS) Stable Isotope Dilution Analysis

Container/Tube: Plastic, 10-mL urine tube (Supply T068)

Specimen Volume: 10 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.

Additional Information:

1. Patient's age is required.

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

Forms: If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) with the specimen.

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

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.

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.

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

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, then extracted with ethyl acetate. 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.(Rinaldo P, O'Shea JJ, Welch RD, Tanaka K: Stable isotope dilution analysis of n-hexanoylglycine, 3-phenylpropionylglycine and suberlglycine in human urine using chemical ionization gas chromatography-mass spectrometry selected ion monitoring. Biomed Environ Mass Spectrom 1989;18:471-477)

Monday, Wednesday, Friday; 8 a.m.

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