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HelpTest Code Phenytoin Phenytoin, Total, Plasma
Performing Laboratory
NRL-Chemistry
Methodology
Fluorescence Polarization Immunoassay (FPIA)
Specimen Requirements
Specimen Type: Plasma
Container/Tube: Light-green top (lithium heparin)
Acceptable: Gold or Red
Specimen Volume: 1 mL
Additional: Usual sampling time varies dependent upon desired measurement of peak or trough values. Due to the observed cross-reactivity of this assay to fosphenytoin, it is recommended that samples for serum phenytoin measurements be collected at least 2 hours after an intravenous dose of fosphenytoin and at least 4 hours after an intramuscular dose.
Reference Values
Therapeutic concentration: 10-20 mg/L
Toxic concentration (automatic call-back): ≥30 mg/L
Reported as absent if below the limit of detection. Lower limit of
detection is 0.0 mg/L.
Day(s) Test Set Up
Monday through Sunday
Specimen Transport Temperature
Refrigerate
Test Classification and CPT Coding
80185