Evaluation of a noninstrumented disposable method for quantifying serum theophylline concentrations.

Study Objective: To compare the performance of a new point-of-care theophylline assay (AccuMeter) with that of a standard laboratory assay (TDx), and another point-of-care method (AccuLevel).

Design: Prospective evaluation of consecutive patients receiving theophylline.

Setting: University-based, ambulatory, allergy-pulmonary clinic.

Patients: Forty subjects receiving maintenance theophylline therapy for asthma.

Interventions: Theophylline concentrations obtained from AccuMeter, TDx, and AccuLevel were compared.

Measurements And Main Results: The error, or difference, between TDx and AccuMeter results in 40 subjects on maintenance theophylline described accuracy. Mean error, an estimate of bias, was 1.1 (95% CI 0.72-1.5), 0.67 (0.34-1.0), and 0.98 (0.79-1.2) microg/ml for AccuMeter capillary, serum, and heparinized blood samples. Square 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) microg/ml for AccuMeter capillary, serum, and heparinized samples. Difference between AccuMeter and AccuLevel ME, an estimate of relative bias, was 0.59 (0.04-1.1) microg/ml. The difference in mean squared errors, an estimate of relative precision, was 0.86 (-0.54-2.3) microg/ml.

Conclusions: AccuMeter demonstrated good precision and minimal bias compared with TDx and AccuLevel . Method of sample collection had no effect on its accuracy.