Lung function measurement to predict the response to changes in the dose of inhaled corticosteroids among asthmatic patients taking combination therapy

Measurement of lung function at baseline and at review (spirometry, lung volumes). Measurement of lung biomarkers at baseline and at review (exhaled nitric oxide, multiple breath nitrogen washout, forced oscillation device, sputum induction). Dose adjustment of inhaled corticosteroids based on baseline level of asthma control. The frequency of the medication treatment remains the same for each individual patient as it was prior to entry into the study: If patients are not well-controlled at baseline, then the inhaled corticosteroid dose will be doubled over the 8-week period. If patients are well-controlled at baseline, the inhaled corticosteroid dose will be halved in the first 4 weeks and quartered over the subsequent 4 weeks. Patients are reviewed at the end of the 8-week period. If patients remain well-controlled after the initial 8-week period, then patients can stop their inhaled corticosteroid and continue to be monitored over another 8-week period. Patients can return for review if their asthma control worsens at any stage during the study. This is an end-point for the study. In this instance, patients are treated as clinically indicated and will return to the care of their usual treating doctor after the study.