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Test ID PKUSC Phenylalanine and Tyrosine, Self-Collect, Blood Spot

Ordering Guidance

For follow-up of an abnormal newborn screen for potential phenylketonuria, order PKU / Phenylalanine and Tyrosine, Plasma

Necessary Information

1. Patient's age is required.

2. Patient's street address, city, state, ZIP (postal) code, country, and home phone are required (post-office [PO] boxes are not acceptable delivery locations).

Specimen Required

Supplies: Blood Spot Collection-Self Collect (T858)

Container/Tube: Blood Spot Self Collection Card

Specimen Volume: 2 Blood spots

Additional Information:

1. Order test each time the patient is to collect a dried blood specimen at home and mail the specimen directly to Mayo Clinic Laboratories.

2. Order should be placed a minimum of 3 days prior to desired date of collection.

3. Enter patient's address information for each order created, including street address (post office [PO] boxes are not acceptable delivery locations), city, state abbreviation, zip code, country, and home phone number.

4. For each order, the Blood Spot Collection-Self Collect kit will be mailed directly to the patient for self-collection (delivery to a PO box will not occur).

5. For more information on how to collect blood spots, see the following

-Dried Blood Spot Collection Tutorial (video)

-Blood Spot Collection Instructions-Fingerstick

-Blood Spot Collection Instructions-Fingerstick-Spanish

Useful For

Monitoring effectiveness of therapy in patients with hyperphenylalaninemia in a patient-collected specimen


This test is not sufficient for follow-up for abnormal newborn screening results or for establishing a diagnosis of a specific cause of hyperphenylalaninemia.

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Phenylalanine and Tyrosine, SC, BS

Specimen Type

Whole blood

Specimen Minimum Volume

1 Blood spot

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Ambient (preferred) 21 days FILTER PAPER
  Frozen  10 days FILTER PAPER
  Refrigerated  10 days FILTER PAPER

Reference Values


27.0-107.0 nmol/mL



<4 weeks: 40.0-280.0 nmol/mL

≥4 weeks: 25.0-150.0 nmol/mL

Performing 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. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
PKUSC Phenylalanine and Tyrosine, SC, BS 79621-9


Result ID Test Result Name Result LOINC Value
610515 Tyrosine, BS 35571-9
610516 Phenylalanine, BS 29573-3
610514 Reviewed By 18771-6
BG735 Patient Street Address (No PO Box) 56799-0
BG736 Patient City 68997-6
BG737 Patient State 46499-0
BG738 Patient Zip Code 45401-7
BG742 Patient Country 77983-5
BG739 Patient Home Phone 42077-8

Day(s) Performed

Monday through Friday

Report Available

3 to 5 days