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Test Code PKUBS Phenylalanine and Tyrosine, Blood Spot

Specimen Required

Supplies: Card-Blood Spot Collection (Filter Paper) (T493)

Preferred: Blood Spot Collection Card (T493)

Acceptable: Whatman Protein Saver 903 Paper, Ahlstrom 226 filter paper

Specimen Volume: 2 Blood spots

Collection Instructions:

1. Let blood dry on filter paper at room temperature in a horizontal position for 3 or more hours.

2. At least 2 spots should be complete, ie, unpunched.

3. Do not expose specimen to heat or direct sunlight.

4. Do not stack wet specimens.

5. Keep specimen dry.

Additional Information:

1. Dried blood spots collected with EDTA, sodium heparin, lithium heparin, or ACD containing devices are acceptable.

2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777) in Special Instructions.

3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800) in Special Instructions.

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, BS

Specimen Type

Whole blood

Specimen Minimum Volume

Blood Spots: 1

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Ambient (preferred) 21 days
  Frozen  10 days
  Refrigerated  10 days

Reject Due To








Blood spot specimen that shows serum rings or has multiple layers


Reference Values


29-95 nmol/mL


29-149 nmol/mL

Day(s) and Time(s) Performed

Monday through Friday; 1 p.m.

Analytic Time

3 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

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 U.S. Food and Drug Administration.

CPT Code Information



LOINC Code Information

Test ID Test Order Name Order LOINC Value
PKUBS Phenylalanine and Tyrosine, BS In Process


Result ID Test Result Name Result LOINC Value
92405 Phenylalanine, BS In Process
92406 Tyrosine, BS In Process
92407 Reviewed By 18771-6