Mannitol challenge for assessment of airway responsiveness, airway inflammation and inflammatory phenotype in asthma

Background: Assessment of airway inflammation in asthma is becoming increasingly important, as the inflammatory phenotype underpins the treatment response. Objective: This study aimed to evaluate mannitol as a tool for assessing airway responsiveness and airway inflammation in asthma, compared with hypertonic saline. Methods: Fifty-five subjects with stable asthma completed a hypertonic (4.5%) saline challenge and a mannitol challenge at two separate visits, performed 48–72 h apart, in random order. Results: Induced sputum was obtained from 49 (89%) subjects during the saline challenge and 42 (76%) subjects during the mannitol challenge (P>0.05). There was a significant correlation between the greatest percentage fall in forced expiratory volume in 1 s (FEV₁)(r=0.6, P