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Order Code 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:

-How to Collect Dried Blood Spot Samples via fingerstick.

-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.

Genetics Test Information

This test is intended for monitoring effectiveness of therapy for patients with hyperphenylalaninemia.

 

This test does not provide sufficient follow-up for abnormal newborn screening results because other causes of hyperphenylalaninemia (eg, tetrahydrobiopterin deficiency) cannot be excluded by this test alone.

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) 90 days FILTER PAPER
  Frozen  90 days FILTER PAPER
  Refrigerated  90 days FILTER PAPER

Reject Due To

Blood spot specimen that shows serum rings or has multiple layers Reject
Insufficient specimen Reject
Unapproved filter papers Reject

Reference Values

PHENYLALANINE:

27-107 nmol/mL

 

TYROSINE

<4 weeks: 40-280 nmol/mL

≥4 weeks: 25-150 nmol/mL

Method Description

A 3-mm disk is punched out of the dried blood spot onto a 96-well plate. The amino acids are extracted by the addition of acetonitrile and known concentrations of isotopically labeled amino acids as internal standards. The extract is moved to another 96-well plate, dried under a stream of nitrogen, and derivatized by the addition of n-butanol hydrochloric acid. Analytes are measured by liquid chromatography tandem mass spectrometry. The concentrations of the phenylalanine and tyrosine are established by computerized comparison of ion intensities of these analytes to that of the respective internal standards.(Unpublished Mayo method)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

0382U

Day(s) Performed

Monday through Friday