Phenylalanine/Tyrosine, Dried Blood Spot (Referred Out) - Saskatoon
Discipline
Biochemistry
Overview
Description
Ordering Recommendations
- Used in diet monitoring with an established diagnosis of phenylketonuria (PKU).
- EDTA specimen is acceptable for diet monitoring but not for other new-born screening tests due to known interference.
- 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
Alias
- Phenylketonuria(PKU)
- PKU diet monitoring
- Phenylalanine
- Tyrosine
- Phenylalanine/tyrosine ratio
Specimen Information
Specimen types accepted
- Whole Blood
Specimen collection container
- Preferred collection container: Dark Green (Lithium Heparin) 4.0mL
- Alternative collection container: Dark Green (Sodium Heparin) 4.0mL
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Alternative collection container: Lavender (EDTA) 4.0mL (acceptable for diet monitoring only)
Required volume
- Optimal volume: 4.0mL
- Minimum/Pediatric volume: 1.0mL 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.) - Capillary volume: 1.0mL whole blood
Transport and stability
- Whole blood must be received within 24 hours of collection
- Store whole blood at room temperature
- Neonatal Screen Card should be spotted with whole blood within 24 hours of collection
- Once spotted, Neonatal Screen Card should be allowed to dry for 3-4 hours & shipped to referral laboratory at ambient temperature.
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
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Maximum laboratory time
Results reporting
- Routine results within 5 days
Other information
Additional comments
- The Neonatal Screen card will be spotted when whole blood is received in the lab
Last Updated: October 7, 2024