Cleveland HeartLab P, Test

CPT Code: 80185
Order Code: C2354
ABN Requirement: No
Synonyms: Dilantin; Diphenylhydantoin
Specimen: Serum
Volume:  1.0 mL
Minimum Volume:  0.5 mL
Container: Gel-barrier tube (SST, Tiger Top)


  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 10 times immediately after draw. DO NOT SHAKE.
  3. Allow blood to clot 30 minutes.
  4. Centrifuge at 1300 rcf for 10 minutes.

Special Instructions:  Collect sample immediately prior to next dose. Record the time of the last dose of phenytoin on the requisition.

Transport:   Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions provided with the Cleveland HeartLab, Inc. shipping box.


Ambient (15-25°C): 48 hours
Refrigerated (2-8°C): 7 days
Frozen (-20°C): 30 days
Deep Frozen (-70°C): 30 days

Causes for Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits

Methodology: Fluorescence Polarization Immunoassay (FPIA)

Turn Around Time: 4 days

Reference Range:

Age ug/mL
All Ages 10.0-20.0

Urgent Values:

Age ug/mL
All Ages >40.0

Intended Use: A phenytoin test is performed to monitor the concentration of the drug in the blood.

Limitations: Falsely elevated results may occur if sample is not drawn at the specified time associated with the administration of this drug.

Additional Information: Small increases in drug dose can lead to large increases in blood concentrations due to the way in which the drug is metabolized within the body.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.