Phenylalanine/Tyrosine, Plasma/Serum (Referred Out) - Saskatoon

Overview

Description

Ordering recommendations

• ​​Phenylalanine, Tyrosine, and the ratio will automatically be done on specimens that are monitoring the diet of known PKU patients

Testing ordering requirements​ ​

Forms required

• Requisitions must have specific test indicated
• Miscellaneous Specimen Requisition Form #101878 or SHR Laboratory Medicine Community Laboratory Requisition Form #101064 or Acute Care Phlebotomy Requisition Form #10162

Alias

• Phenylketonuria(PKU)
• PKU diet monitoring
• Phenylalanine
• Tyrosine
• Phenylalanine/tyrosine ratio

Specimen Information

Specimen types accepted

• Plasma
• Serum 

Specimen collection container

• Preferred Collection Container: Dark Green (Lithium Heparin) 4mL
• Alternative Collection Container: Dark Green (Sodium Heparin) 4mL
• Alternative Collection Container: Light Green (Lithium Heparin Gel) 4.5mL
• Alternative Collection Container: Gold (Gel) 5mL
• Alternative Collection Container: Red (clot activator)4mL
• Alternative Collection Container: Red (No Additive) 6mL
• Alternative Collection Container: Lavender (EDTA)4mL

Required volume

• Optimal Volume: 4.0 mL whole blood
• Minimum/Pediatric Volume: 2.0 mL whole blood

(Submitting the minimum volume makes it impossible to repeat the test or perform confirmatory/reflex testing. In some situations, a minimum volume may require a second collection)

Transport and stability

• Store plasma/serum at 2-8 °C
• Send to referral lab refrigerated.

Rejection criteria

• Specimens received where the proper collection protocols were not followed
• Pathology and Laboratory Medicine Acceptance and Rejection Criteria   

Testing Information

Relevant clinical history

• ​Family history
• Must include diagnosis and/or patient symptoms on the requisition

Clinical interpretation

• Result interpretation should be correlated with clinical and other laboratory findings.

Performance

Days/times performed

Availability​	Shipped daily Monday to Friday
Testing site​	Referred out by St. Paul's Hospital Laboratory to Roy Romanow Provincial Laboratory

 

Maximum laboratory time

​Results reporting

• ​Routine results within 5 days

Other information

​Additional comments

• ​Follow up for newborn screening (PKU)
• Used in diet monitoring of PKU and Tyrosinemia

Last Updated: March 18, 2026