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Test Code LAB0291054 Phenylalanine and Tyrosine, Plasma

Additional Codes

Mayo Test ID
PKU

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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, P

Specimen Type

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.


Specimen Minimum Volume

0.1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Frozen (preferred) 14 days
  Refrigerated  14 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

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

Interpretation

The quantitative results of phenylalanine and tyrosine with age-dependent reference values are reported without added interpretation. When applicable, reports of abnormal results may contain an interpretation based on available clinical interpretation.

 

A phenylalanine:tyrosine ratio higher than 3 is considered abnormal.

Day(s) Performed

Monday through Friday

Report Available

2 to 4 days

Specimen Retention Time

2 weeks

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