Dry-reagent strips for measuring phenytoin in serum

Area of Science:

• Clinical Chemistry
• Immunoassay Technology

Background:

• Phenytoin is a critical anticonvulsant medication requiring therapeutic drug monitoring.
• Existing methods for phenytoin measurement can be time-consuming or require specialized laboratory equipment.

Purpose of the Study:

• To develop and evaluate a novel reagent strip for rapid phenytoin determination.
• To assess the performance of the new assay using the Apoenzyme Reactivation Immunoassay System (ARIS) on the Seralyzer reflectance photometer.

Main Methods:

• A new reagent strip assay utilizing ARIS chemistry was developed for phenytoin measurement.
• The assay was performed on the Seralyzer reflectance photometer with a 90-second test time.
• Assay performance was evaluated using quality controls and clinical serum samples, comparing results with liquid chromatography and fluorescent immunoassay.

Main Results:

• The assay demonstrated excellent precision, with within-run coefficients of variation (CVs) ranging from 2.7% to 5.6% and between-run CVs from 2.3% to 6.3%.
• Phenytoin measurements showed high correlation (r > 0.99) with established methods like liquid chromatography and substrate-labeled fluorescent immunoassay.
• The calibration curve remained valid for two weeks when stored in the instrument.

Conclusions:

• The new reagent strip assay provides a fast, accurate, and reliable method for quantifying phenytoin in serum or plasma.
• Its speed and ease of use make it ideal for point-of-care settings, including emergency rooms and physician's offices.
• This assay facilitates timely therapeutic drug monitoring for improved patient management.