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Test ID: TRYPP Tryptophan, Plasma

Reporting Name

Tryptophan, P

Useful For

Investigating inadequate tryptophan intake and monitoring dietary treatment

Specimen Type

Plasma


Necessary Information


1. Patient's age is required.

2. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.



Specimen Required


Patient Preparation:

Fasting (overnight preferred, 4 hours minimum). Infants should be drawn just before next feeding (2-3 hours without total parenteral nutrition [TPN] if possible).

Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: EDTA

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge within 4 hours if specimen is stored at refrigerated temperature and aliquot plasma. Send plasma frozen.


Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma Frozen 14 days

Reference Values

≤23 months: 17-75 nmol/mL

2 years-17 years: 23-80 nmol/mL

≥18 years: 29-77 nmol/mL

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82131

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TRYPP Tryptophan, P 20659-9

 

Result ID Test Result Name Result LOINC Value
82955 Tryptophan 20659-9
34619 Interpretation (TRYPP) 59462-2
38056 Reviewed By No LOINC Needed

Clinical Information

Amino acids are the basic structural units that comprise proteins and are found throughout the body. Many inborn errors of amino acid metabolism have been identified, including glutaric acidemia type 1, which affect other metabolic activities. Amino acid disorders can manifest at any time in a person's life, 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.

 

Tryptophan is an essential amino acid necessary for the synthesis of serotonin, melatonin, and niacin. Low plasma concentrations of tryptophan have been 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.

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.

Clinical Reference

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

Analytic Time

3 days (not reported on Saturday or Sunday)

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical