Phenytoin, Free

Label Mnemonic:	FDPH
Epic code:	LAB32
Order form:	Laboratory Requisition
Supply order:	Supply Order Form
Billing:	Billing Policies
CPT code:	80186

Specimen(s):

Plasma

Collection Medium:

Plasma Separator Tube 4.5 mL

Alternate Collection Media:

Call laboratory for additional acceptable specimen collection containers.

Minimum:

3 mL whole blood from light green top tube or TWO Microtainer^® devices.

Testing Schedule:

Daily. Sample must be in the lab by 1200; results available by 1600.

Turn Around Time:

24 hours (upon receipt in laboratory)

Reference Range:

1.0-1.9 μg/mL
Average percent free is 9.6% with a range of 7.0-14.6% (N=91).

Comments:

Note: Phenytoin plasma specimens should not be drawn for 2 hours following completion of an I.V. fosphenytoin infusion or 4 hours following an I.M. fosphenytoin dose (See Fosphenytoin). To accurately determine the percentage of free phenytoin, a total phenytoin should be ordered on the same sample.

Please print, complete and submit the Advance Beneficiary Notice (ABN) along with the Laboratory Requisition before shipping the specimen.

Test Limitations:

Criterion: recovery plus or minus 0.6 μg/mL of initial value 
at concentrations less than 6 μg/mL or plus or minus 10% of 
initial value at concentrations greater than 6 μg/mL.

Methodology:

Homogeneous Enzyme Immunoassay

Sample Processing:

Centrifuge at a speed and time necessary to get barrier separation of plasma/serum and cells within 1 hour of collection. Send specimen in original tube. Do Not transfer to another tube.
Each sample must be labeled with at least TWO full patient identifiers (First/Last Name & DOB are sufficient for non-UIHC affiliated clients) to avoid sample rejection/delays.

Sample Storage:

Refrigerate. DO NOT FREEZE.
All sample storage requirements are intended for delivery to UIHC within 24 hours of collection for testing. If samples won't arrive in this time period, please call the UIHC Core Lab for alternative storage/shipping instructions (319-356-3527).

Transport Instructions:

Place labeled specimen into zip-lock type biohazard bag; seal bag.
Place completed requisition into outside pocket of bag.
Place coolant packs on top of specimen in Styrofoam container to maintain refrigerated temperature.