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Unit Code 81249:
Acylglycines, Quantitative, Urine

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Useful For

Biochemical diagnosis of selected inborn errors of metabolism

(see below) by quantitative determination of target urinary metabolites

that are present in amounts below the detection limit of routine organic

acid analysis.

 

Acylglycine analysis is the method of choice, in urine, for the

biochemical evaluation 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

Glycine conjugates (acylglycines) of acyl CoA species, which are

normal intermediates of amino acid and fatty acid metabolism, are

informative biochemical markers of selected inborn errors of

metabolism.

 

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 (GC-MS) 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

                                Control Values

          Results Expressed as ug/mg 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 (12:0)                           0.00-1.1

Tetradecanedioic Acid (14:0)                       0.00-1.0

Hexadecanedioic Acid (16:0)                       0.00-1.0

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 or elsewhere; and a phone number to reach one of the

laboratory directors in case the referring physician has additional

questions.

Cautions

Due to the limited number of metabolites included in the acylglycine

analysis, it is recommended that an #80619 "Organic Acids Screen,

Urine" also be performed concurrently.

Clinical Reference

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

Key