Phenylalanine and Tyrosine
Use
Phenylalanine and Tyrosine testing is 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.
Special Instructions
Not provided.
Limitations
If non‑PKU types of hyperphenylalanemia are suspected, additional testing for tetrahydrobiopterin pathway enzyme defects should be performed.
Methodology
Mass Spectrometry
Biomarkers
Phenylalanine
AnalyteTyrosine
Analyte
Result Turnaround Time
4-9 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
0.4 mL preferred; 0.2 mL minimum
Minimum Volume
0.2 mL
Container
sodium heparin (green‑top) tube
Collection Instructions
Separate plasma from cells as soon as possible and freeze below −20 °C.
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.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Unacceptable |
| Refrigerated | 7 days |
| Frozen | 28 days |
Other tests from different labs that may be relevant