EVALUATION OF A NONINSTRUMENTED DISPOSABLE METHOD FOR QUANTIFYING SERUM THEOPHYLLINE CONCENTRATIONS

Study Objective. To compare the performance of a new point-of-care the ophylline assay (AccuMeter) with that of a standard laboratory assay ( TDx), and another point-of-care method (AccuLevel). Design. Prospectiv e evaluation of consecutive patients receiving theophylline.Setting. U niversity-based, ambulatory, allergy-pulmonary clinic. Patients. Forty subjects receiving maintenance theophylline therapy for asthma. Inter ventions. Theophylline concentrations obtained from AccuMeter, TDx, an d AccuLevel were compared. Measurements and Main Results. The error, o r difference, between TDx and AccuMeter results in 40 subjects on main tenance theophylline described accuracy. Mean error, an estimate of bi as, was 1.1 (95% CI 0.72-1.5), 0.67 (0.34-1.0), and 0.98 (0.79-1.2) mu g/ml for AccuMeter capillary, serum, and heparinized blood samples. S quare root of the mean squared error, an estimate of precision, was 1. 6 (1.2-2.0), 1.22 (0.90-1.5), and 1.14 (0.96-1.3) mu g/ml for AccuMete r capillary, serum, and heparinized samples. Difference between AccuMe ter and AccuLevel ME, an estimate of relative bias, was 0.59 (0.04-1.1 ) mu g/ml. The difference in mean squared errors, an estimate of relat ive precision, was 0.86 (-0.54-2.3) mu g/ml. Conclusions. AccuMeter de monstrated good precision and minimal bias compared with TDx and AccuL evel. Method of sample collection had no effect on its accuracy.