New Search

Laboratory Test Directory

Phenylalanine and Tyrosine

Components

Name Method Department Units
Phenylalanine/Tyrosine Tandem Mass Spectrometry (MS/MS)
Core Lab, Metabolic chemistry mg/dL

Specimen Requirements

Whole blood

Container Type Container Size Specimen Volume
Preferred

Blood filter paper card

N/A
Stability

Room temperature - Indefinite week(s)

Alternate

Green tube (Lithium heparin), No Gel

3 mL 2 mL
Stability

Refrigerated - 4 hour(s)

Alternate

Red tube, (no anticoagulant), No Gel

3 mL 2 mL
Stability

Refrigerated - 4 hour(s)

Specimen Preparation

  • Collect sample after a 3-4 hour fast
  • Collect from infants just prior to feeding
  • Place on ice immediately after collection
  • Transport to the lab immediately after collection

Serum Spun, Plasma Spun

Container Type Container Size Specimen Volume
Preferred

Red tube, (no anticoagulant), No Gel

3 mL 3 mL
Alternate

Green tube (Lithium heparin), No Gel

3 mL 3 mL
Stability

Refrigerated - 4 hour(s)
Frozen - Indefinite week(s)

Specimen Preparation

  • Centrifuge, remove plasma/serum and freeze

Reasons for Rejection

  • Inadequate filling of circles on filter paper card
  • Collected in tube with gel separator
  • Wrong collection tube
  • Patient on TPN therapy
  • Not received at proper temperature
  • Not received within specified time frame

Comments

Used to monitor known PKU and maternal hyperphenylalanemia patients; NOT for diagnostic purposes. A FULL serum amino acid profile (QAAS) is the recommended test for the follow-up to an abnormal newborn screening test. If collecting specimen with a blood spot card, do not allow capillary tube or patient heel to touch the collection card. Completely fill 1-2 circles. Allow card to air dry for 3 hours before sending to laboratory. Cards are available from Laboratory Services (614-722-5477).

CPT Code

  • 84510
  • 84030