Theophylline analysis at the chest clinic—comparison of a portable versus conventional system

The running cost and clinical application of a new, portable, direct-injection, high-performance, liquid chromatograph for the measurement of theophylline was compared with conventional laboratory-based analysis by studying the two methods in two parallel chest clinics. Thirty-six patients were managed with the portable method and 33 by the conventional system. They were already receiving theophylline preparations for treatment of their asthma or chronic airflow limitation. Over the 12-week period of study, the percentage of patients with levels in the therapeutic range rose from 33% to approximately 87% in both clinics, but this change was achieved in only 6 weeks using the portable system. Patients whose theophylline levels were increased into the therapeutic range had improved symptom scores as measured by visual analogue scales but we were unable to demonstrate any significant change in spirometry. The cost of the portable system compared favourably with laboratory analysis, and had the additional benefit of quicker detection of non-compliance and facility for discussion with the patients at the time of consultation.