Amino Acid Profile, Quantitative, Urine

Overview:

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).

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).

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