Phenylalanine/Tyrosine

Laboratory Fee Schedule
Procedure #:  BZZ0003A 
CPT:  83789

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: