Test ID PKU Phenylalanine and Tyrosine, Plasma
Useful For
Monitoring effectiveness of dietary therapy in patients with hyperphenylalaninemia
Genetics Test Information
Defects in phenylalanine hydroxylase (PAH) cause the majority of cases of hyperphenylalaninemia (HPA); however, approximately 2% of infants with HPA have impaired synthesis or recycling of tetrahydrobiopterin (BH4).
Phenylketonuria: Evaluation of patients with hyperphenylalaninemia or monitoring effectiveness of dietary therapy. This test is not sufficient follow-up for abnormal newborn screening results, because other causes of hyperphenylalaninemia (eg, BH4 deficiency) cannot be excluded by this test alone.
Tyrosinemia, type I: For medical management.
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Phenylalanine and Tyrosine, PSpecimen Type
PlasmaNecessary Information
1. Patient's age is required.
2. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.
Specimen Required
Patient Preparation: Fasting (4 hours or more for infants)
Collection Container/Tube:
Preferred: Green top (sodium heparin)
Acceptable: Lavender top (EDTA)
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Specimen Minimum Volume
0.1 mL
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Plasma | Frozen (preferred) | 14 days | |
Refrigerated | 14 days |
Reference Values
PHENYLALANINE
Premature: 98-213 nmol/mL
0-31 days: 38-137 nmol/mL
1-24 months: 31-75 nmol/mL
2-18 years: 26-91 nmol/mL
≥19 years: 35-85 nmol/mL
Conversion Formulas:
Result in mg/dL x 60.5=result in nmol/mL
Result in nmol/mL x 0.0165=result in mg/dL
TYROSINE
Premature: 147-420 nmol/mL
0-31 days: 55-147 nmol/mL
1-24 months: 22-108 nmol/mL
2-18 years: 24-115 nmol/mL
≥19 years: 34-112 nmol/mL
Conversion Formulas:
Result in mg/dL x 55.2=result in nmol/mL
Result in nmol/mL x 0.0181=result in mg/dL
Day(s) Performed
Monday through Friday
Performing Laboratory

CPT Code Information
84030-Phenylalanine
84510-Tyrosine
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
PKU | Phenylalanine and Tyrosine, P | In Process |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
8380 | Phenylalanine, P | 14875-9 |
8627 | Tyrosine, P | 20660-7 |
Test Classification
This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.Report Available
2 to 4 daysNY State Approved
YesForms
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.