CLINICAL-APPLICATION OF THE BIOTRACK-516 SYSTEM FOR DETERMINATION OF THEOPHYLLINE BY A TURBIDIMETRIC LATEX AGGLUTINATION INHIBITION REACTION

Several automated analytical systems for therapeutic drug monitoring ( TDM) have been developed. In the present study, theophylline concentra tion in plasma was measured by the Biotrack 516 system for theophyllin e, a newly developed automated system based on the turbidimetric latex agglutination inhibition reaction, using whole blood samples obtained from 35 asthmatic patients receiving chronic theophylline therapy. Th e data were compared with those obtained by high-performance liquid ch romatography (HPLC) and fluorescence polarization immunoassay (FPIA). Within-day and between-day precisions for the Biotrack system using bl ood samples obtained from nine patients ranged from 4.1 to 5.8% and fr om 2.0 to 6.2%, respectively. Comparison of this system with HPLC and FPIA methods indicated good correlation coefficients of >0.960, while the respective slope and intercept did not differ from unity and zero. No cross-reactivity of this system with the main metabolites of theop hylline and caffeine was observed, thus indicating that the antibodies possess specificity for theophylline. These findings suggest that the Biotrack-516 system is a method that enjoys both accuracy and precisi on to the same degree as established methods and hence will prove usef ul in the routine monitoring of plasma theophylline concentrations.