ZPNYL – “Phenylalanine” replaced by PHETY – “Phenylalanine and Tyrosine”

Collect the specimen after an overnight fast (or at least 4 hours after a meal), if possible. Non-fasting samples are acceptable for pediatric patients.
Note: If non-PKU types of hyperphenylalanemia are suspected, additional testing for tetraahydrobiopterin pathway enzyme defects should be performed.

Green sodium heparin

Centrifuge, separate plasma from cells within 2 hours of collection and send 0.4 mL plasma in a screw capped plastic vial.

Plasma: Lavender EDTA or Green lithium heparin
Serum: Red top

0.2 mL

Frozen

Serum separator tube (SST)

Room temperature: Unacceptable
Refrigerated: 7 days
Frozen: 28 days