Determination of Plasma Theophylline Concentration by Immuno-precipitation Inhibition Technique (i-PiT System)

Plasma theophylline concentration was determined by immuno-precipitation inhibition technique (i-PiT system). Immuno-reaction is dependent on incubation time and temperature, and therefore it is necessary to optimize the reaction. Within-day and between-day variances (C. V.) of analysis on 3 levels were less than 10%. The results of dilution test and recovery test were good. Forty-two plasma specimens of patients receiving theophylline therapy were studied by i-PiT system and high-pressure liquid chromatography (HPLC). The correlation coefficient was 0.988 and the regression line gave y= 0.978 x+0.918 (y: i-PiT, x: HPLC).