Tryptophan

Test Code

959

CPT Codes
82131

Preferred Specimen

2 mL plasma collected in a sodium heparin (green-top) tube

Patient Preparation
Collect plasma specimens after an overnight fast (or at least 4 hours after a meal) if possible.
Non-fasting samples are acceptable for pediatric patients.

Minimum Volume

0.25 mL

Other Acceptable Specimens

Plasma collected in: EDTA (lavender-top) tube or lithium heparin (green-top) tube

Instructions

Date of birth must be provided. Plasma should be separated from cells as soon as possible after collection. Freeze plasma below -20ºC and ship frozen.

Transport Container

Plastic screw-cap vial

Transport Temperature

Frozen

Specimen Stability

Room temperature: Unacceptable
Refrigerated: 7 days
Frozen: 30 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Gross hemolysis

Methodology
Chromatography/Mass Spectrometry

FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Setup Schedule

Set up: Tues, Thurs, Fri; Report available: 6-10 days

Reference Range

≤30 days	17-85 umol/L
31 days-23 months	16-92 umol/L
2-17 years	30-94 umol/L
≥18 years	40-91 umol/L

Clinical Significance

Tryptophanuria is a rare autosomal recessive disease associated with mental retardation, neuropsychiatric dysfunction, and photosensitive skin rash.

Performing Laboratory

Quest Diagnostics Nichols Institute-San Juan Capistrano, CA

33608 Ortega Highway

San Juan Capistrano, CA 92675-2042

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.