Dry-reagent strips used for determination of theophylline in serum

A reagent strip for quantifying theophylline in serum or plasma has been developed for use with the Apoenzyme Reactivation Immunoassay System (ARIS) with the Ames Seralyzer reflectance photometer. The test takes 80 s and involves comparison with a two-point calibration line, which can validly be stored in the instrument for two weeks. Results for theophylline in clinical serum samples correlate well (r greater than 0.98) with results by liquid chromatography, fluoroimmunoassay, and enzyme immunoassay procedures. The within-run CV for four concentrations of controls ranged from 3.5 to 6%; the between-run CVs ranged from 3 to 5%. This assay for use in therapeutic drug monitoring is convenient, rapid, and simple, and thus is appropriate for use in emergency rooms, physician's offices, and small laboratories.