Study objectives: To assess the practicality and precision of a simple desktop theophylline assay (Biotrack 516TM) in comparison to a standard laboratory assay system (Abbott TDxTM).
Design: A prospective blinded paired sample study.
Setting: The respiratory ward and outpatient clinics, the pulmonary function and biochemistry laboratories of a university teaching hospital.
Patients: Sixty patients with asthma or COPD attending the respiratory service.
Measurements and results: Paired specimens for theophylline assay were collected simultaneously for analysis. There was a highly significant (p<0.001) correlation between the two assay systems for both the total range studied (1.2-39.1 µg/mL; r=0.98), and the clinically important range of 5-15 µg/mL (r=0.95). The limits of agreement for the data by the Bland and Altman method indicated a ±2 µg/mL limit for the 5-15 µg/mL range and a ±2.7 µg/mL limit for the total range studied.
Conclusions: The Biotrack 516 is an easy-to-use system, which provides rapid and reasonably precise measurements of serum theophylline levels. The device should be of particular value in smaller centers without an on-site laboratory assay system.