Monitoring inhaled corticosteroid efficacy in persons with asthma in pulmonary function laboratories.

INTERVENTION: In patients with asthma commencing inhaled corticosteroid (ICS) therapy, we will evaluate if monitoring by inhaled mannitol bronchial provocation challenge testing will provide a greater and more sustained control of asthma over 18 weeks compared with monitoring by spirometry alone. We will use the inhaled mannitol bronchial provocation test to monitor bronchial hyperresponsiveness (BHR) in the intervention group. Results of the test would be reviewed by the patients and their treating physicians to allow assessment of the current control of their asthma. The intervention group will have the mannitol challenge at baseline, 6, 12 and 18 weeks. The control group will be seen at the same time points, but will receive the results of spirometry only. The challenge involves inhaling a series of doses of mannitol powder using a small inhaler device, until a total of 635mg has been inhaled or the participant has had a fall in FEV1 of 15% or more from the baseline spirometry for the visit. A lower dose of mannitol required to induce a fall in spirometry indicates more severe bronchial hyperresponsiveness. The participants will be followed for 18 weeks from baseline. CONDITION: Asthma PRIMARY OUTCOME: Asthma Control Questionnaire (ACQ) score The proportion of individuals with improved ACQ score (defined as a difference from baseline of greater than 0.5) SECONDARY OUTCOME: Airway reactance (Xrs) and airway resistance (Rrs) in kPa/l/sec using impulse oscillometry ; Airway reactivity using the dose response ratio (RDR) which is calculated using the percentage fall on the final dose of mannitol divided by the cumulative dose of mannitol in mg. Using the mannitol challenge bronchial provocation test. Airway sensitivity to mannitol using the PD15; the provoking dose to cause a 15% fall in forced expiratory volume in one second (FEV1). Using the mannitol challenge bronchial provocation test. ; Asthma quality of life questionnaire (AQLQ) score ; Exhaled nitric oxide (FeNO) in parts per billion using the Hypair nitric oxide analyser FEV1 (as percent predicted) measured using spirometry ; INCLUSION CRITERIA: ‐Males and females age 18‐75 years ‐Pre‐bronchodilator FEV1 greater than or equal to 70% of predicted and greater than 1L ‐A positive response to mannitol challenge (PD15 of less than 635mg) ‐Prescribed ICS treatment after initial challenge ‐Non‐smokers; ex‐smokers with less than 10 pack years and no cigarettes within the last 12 months ACQ score greater than 0.75