Acylglycines, Quantitative, Urine

CPT CODE:

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

SPECIMEN REQUIRED:

5 mL from a random urine collection. Send specimen frozen in a plastic, 13-mL urine tube.

TRANSPORT TEMPERATURE:

Frozen\Refrig NO\Ambient NO

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.

CLINICAL 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.

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                           &n