Investigating inadequate tryptophan intake and monitoring dietary treatment
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Tryptophan
Plasma
1. Patient's age is required.
2. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.
Patient Preparation: Fasting (overnight preferred, 4 hours minimum). Infants should be drawn just before next feeding (2-3 hours without total parenteral nutrition if possible).
Collection Container/Tube:
Preferred: Green top (sodium heparin)
Acceptable: Lavender top (EDTA), plasma gel tube, green top (lithium heparin)
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions:
1. Collect specimen and place on wet ice. Note: Thrombin-activated tubes should not be used for collection.
2. Centrifuge immediately or within 4 hours of collection if the specimen is kept at refrigerated temperature.
3. Being careful to ensure that no buffy coat is transferred, aliquot plasma into a plastic vial and freeze.
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
0.3 mL
Gross hemolysis | OK |
Gross lipemia | OK |
Gross icterus | OK |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Plasma | Frozen | 14 days |
Investigating inadequate tryptophan intake and monitoring dietary treatment
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 are 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 L-carnitine supplementation and strict adherence to an emergency protocol. Dietary protein, particularly lysine and tryptophan, 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.
< or =23 months: 17-75 nmol/mL
2 years-17 years: 23-80 nmol/mL
> or =18 years: 29-77 nmol/mL
If the result is within the respective age-matched reference range,
Abnormal plasma concentrations of tryptophan are not diagnostic for a specific disorder and must be interpreted in the context of a patient's clinical presentation and other laboratory results.
1. Hoffmann GF, Schulze A: Organic acidurias. In: Sarafoglou K, Hoffmann GF, Roth KS, eds. Pediatric Endocrinology and Inborn Errors of Metabolism. McGraw-Hill Medical Division; 2009:108-112
2. Larson A, Goodman S. Glutaric acidemia type 1. In: Adam MP, Everman DB, Mirzaa GM, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2019. Accessed March 08, 2023. Available at www.ncbi.nlm.nih.gov/books/NBK546575/
3. Goodman SI, Frerman FE. Organic acidemias due to defects in lysine oxidation: 2-ketoadipic acidemia and glutaric acidemia. In: Valle DL, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA. eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw Hill; 2019. Accessed March 08, 2023. https://ommbid.mhmedical.com/content.aspx?bookid=2709§ionid=225086303
Quantitative analysis of amino acids (AA) is performed by liquid chromatography tandem mass spectrometry (LC-MS/MS) by labeling amino acids present in plasma, spinal fluid, and urine with aTRAQ Reagent 121. Samples are dried and reconstituted with aTRAQ Reagent 113-labeled Standard Mix. Amino acids are separated and detected by LC-MS/MS. The concentrations of AA are established by comparison of their ion intensity (121-labeled amino acids) to that of their respective internal standards (113-labeled amino acids).(Unpublished Mayo method)
Monday through Friday
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 US Food and Drug Administration.
82131
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
TRYPP | Tryptophan, P | 20659-9 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
82955 | Tryptophan | 20659-9 |
34619 | Interpretation (TRYPP) | 59462-2 |
38056 | Reviewed By | 18771-6 |