PHENYLALANINE AND TYROSINE

Test Code

LAB480

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 hrs after a meal) if possible. Non-fasting samples are acceptable for pediatric patients.

Minimum Volume

0.2 mL

Other Acceptable Specimens

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

Instructions

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

Transport Container

Transport tube

Transport Temperature

Frozen

Specimen Stability

Room temperature: Unacceptable
Refrigerated: 7 days
Frozen: 28 days

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 FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Setup Schedule

Tues, thurs

Report Available

7-12 days

Limitations

If non-PKU types of hyperphenylalanemia are suspected, additional testing for tetraahydrobiopterin pathway enzyme defects should be performed.

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.