| Ordering Code | 5454 |
|---|---|
| Test Name | Phenytoin/Free Phenytoin |
| Alias | Free Dilantin Free Phenytoin |
| Preferred Specimen | Plasma |
| Preferred Container | Lithium Heparin PST (Green) |
| Other Specimen/Container | Serum in Plain (Red), Serum in SST (Gold) |
| Optimum Volume | 2 mL |
| Handling Instructions | Send aliquot if transport time >24 hours. |
| Transport Requirements | Oahu: Ambient Airline: Ambient |
| Specimen Stability | Ambient: 4 Days Refrigerated: 4 Days Frozen Serum: 1-2 Months capped at -20 C Frozen serum samples should be thawed only once. Test cannot be added to >24 hours, unaliquoted specimens Do not freeze Lithium Heparin Plasma. |
| Rejection Criteria | Grossly hemolyzed, Insufficient quantity, Specimen older than stability limits, Uncentrifuged gel separator tube specimens >2 hours old, Unaliquoted gel separator tube specimens >24 hours old, Frozen Lithium Heparin plasma |
| Avail. Stat | YES |
| Analytic Time | 1 Day |
| Methodology | Kinetic Interaction of Microparticles in Solution (KIMS) / Fluorescence Polarization Immunoassay (FPIA) |
Reference range(s)
The reference ranges listed below are valid on this date of December 12, 2025.
| Component | Age | Male Norm | Male Critical Low | Male Critical High | Female Norm | Female Critical High | Female Critical Low | Units | Add'l info |
|---|---|---|---|---|---|---|---|---|---|
| Dilantin | ALL | 10.0-20.0 | >= 30.0 | 10.0-20.0 | >= 30.0 | ug/mL | |||
| Free Phenytoin | ALL | 1.0-2.0 | >= 3.0 | 1.0-2.0 | >= 3.0 | ug/mL |
