Adaptation of Total Phenytoin Reagent Pack for Measuring Free Phenytoin Levels With the Abbott AxSYM Immunoassay Analyzer

Abstract

One hundred and four serum samples submitted to our laboratory for total phenytoin levels were also assayed for free phenytoin levels using the Abbott TDx and AxSYM immunochemistry analyzers (Abbott Laboratories; Abbott Park, IL, U.S.A.). Free phenytoin levels were assessed using ultrafiltrates obtained with the Centrifree Microfiltration system (Amicon, Inc.; Beverly, MA, U.S.A.). There was an acceptable correlation of free phenytoin levels between the two instruments (r = 0.994; mean value of free fraction was TDx = 1.7 microg/mL and AxSYM = 1.6 microg/mL). The mean free phenytoin values correlated well with previously reported values in the literature. Acceptable recovery (88.8%-101.5%) and precision (CV = 2.3%-11.0%) were also obtained. The results of this study indicated that free phenytoin levels can be obtained with acceptable accuracy and precision using the total phenytoin reagents.

Linker-Mediated Modulation of the Chemiluminescent Signal from N10-(3-Sulfopropyl)-N-sulfonylacridinium-9-carboxamide Tracers

“…To assess the magnitude of these effects, haptens for the high-concentration analytes phenobarbital (28) and phenytoin (29)(30)(31)(32) were conjugated to N 10 -(3-sulfopropyl)-N-sulfonyl-acridinium-9-carboxamides via representative linking groups from the previous model study (26). The effect of the linker on the observed signal using a short read time was evaluated in a microtiter plate chemiluminescent immunoassay format using the complementary sheep polyclonal antibodies specific for the respective tracers.…”