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HelpTest ID PKU Phenylalanine and Tyrosine, Plasma
Useful For
Monitoring effectiveness of dietary therapy in patients with hyperphenylalaninemia
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen 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: 8 hours, required; Infants should have specimen collected before next feeding
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.
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| 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
CPT Code Information
84030 Phenylalanine
84510 Tyrosine
82542 (if appropriate for government payers)
Report Available
2 to 4 daysReject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Forms
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.