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Phenylalanine & Tyrosine (PHNTYR)
MessageCollect after overnight fast (or at least 4 hours after a meal) if possible. Non-fasting samples are acceptable for pediatric patients.
Test Code
LAB2347
Quest Code
26336
Alias/See Also
PHNTYR
CPT Codes
84030, 84510
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. Freeze immediately after separating from cells at below -20 C. Do not thaw. Patient age is required for correct reference range.
Transport Container
Transport tube
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: 7 days
Frozen: 30 days
Refrigerated: 7 days
Frozen: 30 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.
Reference Range
Phenylalanine
Tyrosine
| ≤30 days | 30-79 umol/L |
| 31 days-23 months | 31-92 umol/L |
| 2-17 years | 38-86 umol/L |
| ≥18 years | 40-74 umol/L |
Tyrosine
| ≤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 |
Performing Laboratory
| Quest Diagnostics Nichols Institute-San Juan Capistrano, CA |
| 33608 Ortega Highway |
| San Juan Capistrano, CA 92675-2042 |
