Phenylalanine/Tyrosine


Phenylalanine/Tyrosine

Laboratory Fee Schedule

Procedure #:  BZZ0003A 

CPT:  83789

Phenylalanine/Tyrosine
 Synonym(s):  Phenylketonuria (PKU) Dietary Monitoring
 Requisition Form G-1B
 Test Description Testing of phenylketonuria (PKU) dietary monitoring specimens to detect elevated concentrations of the amino acids phenylalanine and tyrosine.
 Pre-Approval Needed N/A
 Supplemental Information   Required N/A
 Supplemental Form(s) N/A
 Performed on Specimens from   (sources) Human
 Sample/Specimen Type for Testing Dried whole blood on DSHS approved filter paper card.
 Minimum Volume/Size Required Two completely filled ½ inch dried blood spots
 Storage/Preservation Prior to   Shipping
  •  Allow card to dry thoroughly at room temperature in a horizontal position for at least 3 hours. Do NOT allow specimen to touch any surface.
  • Keep specimen away from heat and direct sunlight.
  • Cover dried specimen with attached flap.
 Transport Medium N/A
 Specimen Labeling
  •  Two patient-specific identifiers required (e.g., patient full name, date of birth)
  • Identifiers on specimen must match submission form exactly
 Shipping and Specimen Handling   Requirements

 Ship all specimens according to Dangerous Good Regulations, IATA, and/or CFR 49. 

 Must include one completed G-1B form per specimen.

 DRIED FILTER PAPER BLOOD SPECIMENS

  • U.S. Postal regulations require Double containment of dried blood filter paper specimens. Ensure specimens are thoroughly dried prior to placing in envelope.
  • 1st containment: Use the attached wrap-around cover with printed universal biohazard symbol. Do not put biohazard labels on outside of envelope.
  • 2nd containment:  Place dried filter paper blood specimen in an envelope that is not hermetically sealed. Do not put specimens in plastic bags
  • Ship as soon as possible; within 24hrs of collection. 
  • Avoid temperatures greater than 100°F. 
 Method Tandem Mass Spectrometry
 Turn-around Time Within 4 working days after receipt of specimen
 Interferences/Limitations Alcohol swab with a topical pain killer such as benzocaine can interfere with the testing, 
 Common Causes for Rejection
  •  Use of expired specimen collection device
  • No date of collection provided
  • Missing/invalid patient demographic information
  • Specimen is too old upon receipt (received more than 21 days following collection)
  • No blood samples received with request form
  • Insufficient blood has been submitted
  • Specimen is contaminated or discolored
  • Serum separation due to improper drying or collection

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 Additional Information Reference Range:
 Phenylalanine values less than 4.0 mg/dL are normal. Tyrosine values less than 3.0 mg/dL are normal.

 Additional information for specimen collection:


Last updated June 10, 2022