Test Code

CPT Codes

Preferred Specimen
0.4 mL plasma collected in a sodium heparin (green-top) tube

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

Minimum Volume
0.2 mL

Other Acceptable Specimens
Plasma collected in: lithium heparin (green-top) tube, or EDTA (lavender-top) tube • Serum collected in a red-top tube (no gel)

Separate plasma from cells as soon as possible and freeze below -20° C

Transport Temperature

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

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

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; Report available: 4-9 days

Reference Range
≤30 days 33-160 umol/L
31 days-23 months 24-125 umol/L
2-17 years 31-108 umol/L
≥18 years 38-96 umol/L

Clinical Significance
Use: Phenylalanine and Tyrosine are used in the monitoring of patients with phenylketonuria (PKU) who are on special diets. Tyrosine analysis can also be used for monitoring of patients with tyrosinemia.

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.