ARUP's Laboratory Test Directory

0090090: Phenytoin

Test Mnemonic: DIL
Methodology: Enzyme Immunoassay

Performed: Sun-Sat

Reported: Within 24 hours

Specimen Required:  
Collect: One 5 mL plain red.

Transport: 1 mL serum at 2-8°C. (Min: 0.2 mL)  Submit specimen in an ARUP Standard Transport Tube.

Pediatric Collection/Transport: 0.2 mL serum at 2-8°C.

Remarks: Allow specimen to clot completely at room temperature.  Separate serum from cells ASAP. Avoid use of separator tubes and gels.

Unacceptable Conditions: Specimens collected in separator tubes, sodium fluoride, potassium oxalate, EDTA tubes.  Hemolyzed specimens.

Stability: After separation from cells: Ambient: 8 hours; Refrigerated: 4 days; Frozen: 1 month

Reference Interval:
0-2 months: 6.0-14.0 µg/mL
  Toxic: 14.1 µg/mL  or greater 
3 months and older: 10.0-20.0 µg/mL
  Toxic: 30.1 µg/mL or greater 

Interpretive Data:
Falsely elevated phenytoin levels may occur in critically ill, uremic patients receiving fosphenytoin. 



CPT Code(s):
80185