A rapid desktop theophylline assay. Evaluation of use in clinical management.

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 micrograms/mL; r = 0.98), and the clinically important range of 5-15 micrograms/mL (r = 0.95). The limits of agreement for the data by the Bland and Altman method indicated a +/-2 micrograms/mL limit for the 5-15 micrograms/mL range and a +/-2.7 micrograms/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.