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HelpTest Code PKU Phenylalanine and Tyrosine, Plasma
Necessary 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.
Useful For
Monitoring effectiveness of dietary therapy in patients with hyperphenylalaninemia
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Phenylalanine and Tyrosine, PSpecimen Type
PlasmaSpecimen 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
Report Available
2 to 4 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.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 |
Forms
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.