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Test Code PNTFT Phenytoin, Total and Free, Serum

Reporting Name

Phenytoin, Total and Free, S

Useful For

Monitoring for appropriate therapeutic concentration of both free and total phenytoin: free phenytoin level is the best indicator of adequate therapy in renal failure

Specimen Type

Serum Red


Specimen Required


Collection Container/Tube: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 2 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial within 2 hours of collection.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Refrigerated (preferred) 7 days
  Frozen  14 days
  Ambient  7 days

Reject Due To

Gross hemolysis Reject

Reference Values

Phenytoin, Total

Therapeutic: 10.0-20.0 mcg/mL

Critical value: ≥30.0 mcg/mL

 

Phenytoin, Free

Therapeutic: 1.0-2.0 mcg/mL

Critical value: ≥2.5 mcg/mL

Day(s) Performed

Monday through Sunday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

Phenytoin, total-80185

Phenytoin, free-80186

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PNTFT Phenytoin, Total and Free, S 34540-5

 

Result ID Test Result Name Result LOINC Value
PNYF Phenytoin, Free, S 3969-3
PNYA Phenytoin, Total, S 3968-5

Method Name

PNYF: Membrane Separation/KIMS

PNYA: Kinetic interaction of Microparticles in a Solution (KIMS)

Profile Information

Test ID Reporting Name Available Separately Always Performed
PNYF Phenytoin, Free, S Yes Yes
PNYA Phenytoin, Total, S Yes Yes

Report Available

Same day/1 day

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.