Test Code

CPT Codes

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

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

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

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

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 days17-85 umol/L
31 days-23 months16-92 umol/L
2-17 years30-94 umol/L
≥18 years40-91 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.