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HelpTest Code LAB1231793 Phenylalanine and Tyrosine, Plasma
Performing Laboratory
Mayo Clinic Laboratories in Rochester
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: Patient should fast overnight (8-12 hour fast); infants should have specimen collected before next feeding (4 hour fast)
Collection Container/Tube:
Preferred: Green top (Sodium heparin)
Acceptable: Green top (Lithium heparin), lavender top (EDTA)
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions:
1. Centrifuge and aliquot plasma into a plastic vial.
2. Send plasma frozen.
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma | Frozen (preferred) | 14 days | |
| Refrigerated | 14 days |
Specimen Minimum Volume
0.1 mL
Day(s) Performed
Monday through Friday
Specimen Retention Time
2 weeksReport Available
2 to 4 daysReference 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
Useful For
Monitoring effectiveness of dietary therapy in patients with hyperphenylalaninemia
CPT Code Information
84030 Phenylalanine
84510 Tyrosine
82542 (if appropriate for government payers)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PKU | Phenylalanine and Tyrosine, P | 101402-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 8380 | Phenylalanine, P | 14875-9 |
| 8627 | Tyrosine, P | 20660-7 |
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 HPA (eg, BH4 deficiency) cannot be excluded by this test alone.
Tyrosinemia, type I: For medical management
Forms
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.