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Test ID TRYPU Tryptophan, Random, Urine

Useful For

Aiding in the screening and monitoring of Hartnup disease


Determination of tryptophan by conventional amino acid profiling methods (ninhydrin based, HPLC) is hampered by coelution with other compounds. This test utilizes liquid chromatography-tandem mass spectrometry to quantify tryptophan and is interference free.

Method Name

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

Reporting Name

Tryptophan, U

Specimen Type


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

Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube

Specimen Volume: 2 mL

Collection Instructions: Collect a random urine specimen.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Frozen (preferred) 70 days
  Refrigerated  14 days

Reference Values

≤35 months: 14-315 nmol/mg creatinine

3-8 years: 10-303 nmol/mg creatinine

9-17 years: 15-229 nmol/mg creatinine

≥18 years: 18-114 nmol/mg creatinine

Day(s) Performed

Monday through Friday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
TRYPU Tryptophan, U 28608-8


Result ID Test Result Name Result LOINC Value
83823 Tryptophan, U 28608-8
34618 Interpretation (TRYPU) 59462-2
113131 Reviewed By 18771-6

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 US Food and Drug Administration.

Report Available

3 to 5 days

NY State Approved