Test ID: AAPD    
Amino Acids, Quantitative, Random, Urine

Evaluating patients with possible inborn errors of metabolism using random urine specimens

May aid in evaluation of endocrine disorders, liver diseases, muscle diseases, neoplastic diseases, neurological disorders, nutritional disturbances, renal failure, and burns

Includes quantitation of the following amino acids: phosphoserine, phosphoethanolamine, taurine, threonine, serine, asparagine, hydroxyproline, glutamic acid, glutamine, aspartic acid, ethanolamine, sarcosine, proline, glycine, alanine, citrulline, alpha-aminoadipic acid, alpha-amino-n-butyric acid, valine, cystine, cystathionine, methionine, isoleucine, leucine, tyrosine, phenylalanine, beta-alanine, beta-aminoisobutyric acid, ornithine, lysine, 1-methylhistidine, histidine, 3-methylhistidine, carnosine, anserine, argininosuccinic acid, allo-isoleucine, homocitrulline, gamma-amino-n-butyric acid, hydroxylysine, tryptophan, and arginine.

Amino acids are the basic structural units that comprise proteins and are found throughout the body. Many inborn errors of amino acid metabolism that affect amino acid transport or metabolism have been identified, such as phenylketonuria and tyrosinemia. Amino acid disorders can manifest at any age, but most become evident in infancy or early childhood. These disorders result in the accumulation or the deficiency of 1 or more amino acids in biological fluids, which leads to the clinical signs and symptoms of the particular amino acid disorder.

The clinical presentation is dependent upon the specific amino acid disorder. In general, affected patients may experience failure to thrive, neurologic symptoms, digestive problems, dermatologic findings, and physical and cognitive delays. If not diagnosed and treated promptly, amino acid disorders can result in mental retardation and possibly death.

In addition, amino acid analysis may have clinical importance in the evaluation of several acquired conditions including endocrine disorders, liver diseases, muscle diseases, neoplastic diseases, neurological disorders, nutritional disturbances, renal failure, and burns. General elevations in urine amino acid levels, called aminoaciduria, can be seen in disorders with amino acid transport defects such as lysinuric protein intolerance and Hartnup disease, as well as in conditions with renal tubular dysfunction including Lowe syndrome and Dent disease.

When no significant abnormalities are detected, a simple descriptive interpretation is provided. 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, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Not all patients with homocystinuria and prolidase deficiency will be detected by this assay. See Additional Testing Requirements and Necessary Information for more information.

1. The Online Metabolic and Molecular Bases of Inherited Disease (OMMBID). Part 8 Amino Acids.Edited by D Valle, AL Beaudet, B Vogelstein, et al. New York, McGraw-Hill. Accessed May 28, 2019. Available at https://ommbid.mhmedical.com/book.aspx?bookid=2709#225069340

2. Camargo SMR, Bockenhauer D, Kleta R: Aminoacidurias: Clinical and molecular aspects. Kidney Int 2008;73:918-925

3. Duran M: Amino acids. In Laboratory Guide to the Methods in Biochemical Genetics. Edited by N Blau, M Duran, KM Gibson. Springer-Verlag, Berlin Heidelberg, 2008, pp 53-89