Sorted By Test Name - Mayo Medical Laboratories

TRYPU
83823
associated with clinical observations of insomnia, anxiety, and depression. Glutaric acidemia type 1 is an
autosomal recessive disorder of tryptophan and lysine metabolism caused by a deficiency of glutaryl-CoA
dehydrogenase. Early diagnosis and treatment is essential to help prevent encephalopathic crises leading
to brain degeneration. These can be provoked by infections, trauma, fever, and fasting. Treatment consists
of preventing neurodegeneration through strict adherence to an emergency protocol. Dietary protein, in
particular, lysine, is restricted during the vulnerable period of brain development from 0 to 5 years of age.
In addition to other indices of malnutrition, the measurement of plasma concentration of tryptophan is
used as an indicator of appropriate dietary therapy. Determination of tryptophan by conventional amino
acid profiling methods (ninhydrin-based, HPLC) is hampered by coelution with other compounds. This
liquid chromatography-tandem mass spectrometry (LC-MS/MS) method quantifies tryptophan and is
interference free.
Useful For: Investigating inadequate tryptophan intake and monitoring dietary treatment
Interpretation: If the result is within the respective age-matched reference range, no interpretation is
provided. When an abnormal result is reported, an interpretation may be added including a correlation to
available clinical information, elements of differential diagnosis, and recommendations for additional
biochemical testing, if applicable.
Reference Values:
< or =23 months: 17-75 nmol/mL
2 years-17 years: 23-80 nmol/mL
> or =18 years: 29-77 nmol/mL
Clinical References: 1. Bremer HJ, Duran M, Kamerling JP, et al: In Disturbances of amino acid
metabolism: Clinical Chemistry and Diagnosis. Edited by HJ Bremer, M Duran, JP Kamerling, et al.
Baltimore-Munich, Urban and Schwarzenberg, 1981, pp 171-173 2. Hoffmann GF, Schulze A: Organic
acidurias. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF
Hoffmann, KS Roth, New York, McGraw-Hill Medical Division, 2009, pp 108-112
Tryptophan, Urine
Clinical Information: Amino acids are the basic units that make up proteins and are crucial to
virtually all metabolic processes in the body. Tryptophan is an essential amino acid necessary for the
synthesis of serotonin, melatonin, and niacin. Hartnup disease is a rare, usually benign, autosomal
recessive disorder of renal and intestinal neutral amino acid transport. The clinical features associated
with Hartnup disease include an erythematous skin rash on exposed surfaces that is identical to the rash
seen in pellagra (niacin deficiency) and cerebral ataxia. Biochemically, it is characterized by increased
renal excretion of tryptophan and other neutral amino acids. Newborn screening studies reveal that most
affected individuals remain asymptomatic, suggesting that clinical expression of symptoms is dependent
on additional genetic or environmental factors (ie, multifactorial disease). Determination of tryptophan by
conventional amino acid profiling methods (ninhydrin-based, HPLC) is hampered by co-elution with
other compounds. This liquid chromatography-tandem mass spectrometry method quantifies tryptophan
and is interference free.
Useful For: An aid in the screening and monitoring of Hartnup disease
Interpretation: Increased urinary excretion of tryptophan is suggestive of Hartnup disease. If the result
is within the respective age-matched reference range, no interpretation is provided. When an abnormal
result is reported, an interpretation may be added, including a correlation to available clinical information
and recommendations for additional biochemical testing, if applicable.
Reference Values:
< or =35 months: 14-315 nmol/mg creatinine
3-8 years: 10-303 nmol/mg creatinine
9-17 years: 15-229 nmol/mg creatinine
> or =18 years: 18-114 nmol/mg creatinine
Clinical References: 1. Roth KS: Disorders of membrane transport. In Pediatric Endocrinology and
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