Phenylalanine and Tyrosine, Self-Collect, Blood Spot
Use
This test is useful for monitoring the effectiveness of therapy in patients who have hyperphenylalaninemia. Hyperphenylalaninemia is characterized by an increased level of phenylalanine and can be improved with dietary management and, in some cases, additional treatments such as tetrahydrobiopterin supplementation or enzyme replacement therapy. While this test provides critical monitoring for patients receiving therapy, it should not be used as a follow-up to abnormal newborn screenings or for diagnosing the specific cause of hyperphenylalaninemia, like tetrahydrobiopterin deficiency, as it cannot rule out all causes on its own.
Special Instructions
Blood spot samples must be self-collected by the patient using a specified collection kit provided by Mayo Clinic Laboratories. It is important that all necessary patient information, including complete address and home phone number, is provided as PO Box delivery is not accepted. Orders should be placed at least 3 days prior to the desired collection date to ensure timely shipping of collection materials.
Limitations
This test does not provide comprehensive follow-up for abnormal newborn screening results or an in-depth analysis to diagnose specific causes of hyperphenylalaninemia. Conditions such as tetrahydrobiopterin deficiency remain undetectable solely through this test due to its methodological constraints. Additionally, samples showing serum rings, multiple layers, or using unapproved filter papers are subject to rejection.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 79621-9
- 35571-9
- 29573-3
- 18771-6
- 56799-0
- 68997-6
- 46499-0
- 45401-7
- 77983-5
- 42077-8
Result Turnaround Time
3-5 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
2 Blood spots
Minimum Volume
1 Blood spot
Container
Blood Spot Card
Collection Instructions
Order test each time the patient is to collect a dried blood specimen at home and mail the specimen directly to Mayo Clinic Laboratories.
Causes for Rejection
Blood spot specimen that shows serum rings or has multiple layers, insufficient specimen, unapproved filter papers
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 90 days |
| Refrigerated | 90 days |
| Frozen | 90 days |