Phenylalanine

Test Code
37356

CPT Codes
84030<br /> ** This test is not available for New York patient testing. For New York patient testing, use test code 19730**

Preferred Specimen
0.4 mL plasma collected in 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)

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

Transport Temperature
Frozen

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

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

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 a.m.; Report available: 4-9 days

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

Reference Range
0-30 Days  30-79 µmol/L
31 Days-23 Months  31-92 µmol/L
2-17 Years 38-86 µmol/L
≥18 Years 40-74 µmol/L
To convert µmol/L to mg/dL, multiply the result in µmol/L by 0.0165.

Clinical Significance
Abnormalities in phenylalanine metabolism are autosomal recessive disorders that occur in 1 in 10,000 births. The most common form is phenylketonuria. Heterozygotes can have transient cognitive impairment with large phenylalanine loads.

Performing Laboratory
Quest Diagnostics Nichols Inst San Juan Capistrano
33608 Ortega Highway
San Juan Capistrano, CA 92690-6130



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.