|Plasma Separator Tube 4.5 mL
Call laboratory for additional acceptable specimen collection containers.
3 mL whole blood from light green top tube or TWO
Daily. Sample must be in the lab by 1200; results available by 1600.
24 hours (upon receipt in laboratory)
Average percent free is 9.6% with a range of 7.0-14.6% (N=91).
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.
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.
Homogeneous Enzyme Immunoassay