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Methodology: Immunoturbidimetric Assay
Edit Date: 7/14/2009
Performed: Daily
Released: Same day as tested
CPT Code: 80185
Specimen Collection Details
Collection: One 5 mL red top tube preferred. Also acceptable: One 4 mL green top tube (heparin) or one 4 mL lavender top tube (EDTA). Serum separator tube (SST) or gel barrier tubes may decrease phenytoin level from 16-22% in 24 hours and are not recommended.
Handling: Must be centrifuged within 2 hours, the serum or plasma separated from cells and poured into a plastic vial for transport. Refrigerate. Freeze if specimen cannot be assayed within 48 hours. Allow no more than one freeze/thaw cycle. Note date and time of last dose.
Stability: 48 hours refrigerated.
Standard Volume: 0.5 mL serum or plasma.
Minimum Volume: 150 µL serum or plasma.
Transport: Refrigerated, or frozen on dry ice.
Comments: Refer to the drug manufacturer’s package insert or the Physicians’ Desk Reference for proper dosage and for phenytoin measurement sampling times.
Rejection Criteria: Specimen frozen and thawed more than once; refrigerated specimen received in laboratory more than 48 hours after collection.

Reference Range:
10-20 µg/mL

PeaceHealth Laboratories