Amino Acid Profile, Quantitative, Urine

CPT: 82139
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Test Details

Use

Diagnosis and monitoring of inherited aminoacidurias, organic acidurias, and urea cycle defects. May be used as a follow-up confirmatory test to some abnormal newborn screen results. In most, but not all, cases where an amino acid is elevated in blood, it will also be elevated in urine. Some disorders, primarily those involving defective renal transport, will only manifest elevated amino acids in urine. In general, urinary amino acid levels are more variable than plasma levels. For this reason, screening for aminoacidopathies in urine alone is discouraged unless a disorder is suspected that predominantly manifests abnormalities in urine (eg, cystinuria, renal Fanconi syndrome).

Limitations

False-negative results can occur, especially when a patient is affected with a mild or intermittent variant of a disorder or when a clinical condition or dietary treatment causes secondary changes to the profile. Results of amino acid profiling should be interpreted in the context of clinical presentation as well as other laboratory tests.

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the US Food and Drug Administration (FDA).

Methodology

Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference Interval

See Urine Amino Acid Reference Intervals in the Test Resources pages online.

Specimen Requirements

Specimen

Urine, frozen

Volume

5 mL

Minimum Volume

2 mL

Container

Plastic urine container without preservative

Storage Instructions

Freeze.

Stability Requirements

Temperature

Period

Room temperature

Unstable

Refrigerated

Unstable

Frozen

14 days

Causes for Rejection

Room temperature or thawed specimens

Clinical Information

References

Bremer HJ, Duran M, Kamerling JP, et al. Disturbances of Amino Acid Metabolism: Clinical Chemistry and Diagnosis. Baltimore, Md: Urban and Schwarzenberg; 1981.

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The LOINC® codes are copyright © 1994-2018, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf