Home
HelpTest Code PNYF Phenytoin, Free, Serum
Reporting Name
Phenytoin, Free, SUseful For
Monitoring for appropriate therapeutic concentration of free phenytoin: free phenytoin level is the best indicator of adequate therapy in renal failure
Assessing compliance and toxicity
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum RedSpecimen Required
Container/Tube: Red top
Specimen Volume: 2 mL
Collection Instructions: Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Refrigerated (preferred) | 7 days | |
| Frozen | 14 days | ||
| Ambient | 7 days |
Reference Values
Therapeutic: 1.0-2.0 mcg/mL Critical value: ≥2.5 mcg/mLDay(s) Performed
Monday through SundayTest 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
80186
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PNYF | Phenytoin, Free, S | 3969-3 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| PNYF | Phenytoin, Free, S | 3969-3 |
Clinical Reference
Richens A: Clinical pharmacokinetics of phenytoin. Clin Pharmacokinet 1979;4:153-169
Method Description
Fresh serum subjected to ultra-filtration to generate a protein-free filtrate, which is then analyzed for free phenytoin by the kinetic interaction of microparticles in a solution (KIMS). Phenytoin antibody is covalently coupled to microparticles and the drug derivative is linked to a macromolecule. The kinetic interaction of microparticles in solutions is induced by binding of drug-conjugate to the antibody on the microparticles and is inhibited by the presence of phenytoin in the sample. A competitive reaction takes place between the drug conjugate and phenytoin in the serum sample for binding to the phenytoin antibody on the microparticles. The resulting kinetic interaction of microparticles is indirectly proportional to the amount of drug present in the sample.(Package insert: Roche Phenytoin reagent, Roche Diagnostic Corp, Indianapolis, IN)
Report Available
Same day/1 dayReject Due To
| Gross hemolysis | Reject |
Method Name
Membrane Separation/Kinetic Interaction Microparticles in Solution (KIMS)
Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.