Assessing ICS Responsiveness in Severe Asthma Using BDP/formoterol NEXThaler™ Dose-Counting

Background: 65% of people with severe asthma and FeNO ≥45 ppb are non-adherent to inhaled corticosteroids (ICS). Digital monitoring that records both time-of-use and inhaler technique can identify non-adherence and ICS responsiveness but these devices are not readily available. As the dose counter on the NEXThaler™ only counts down when an inspiratory flow of 35 L/min is achieved, this may present an alternative to identifying ICS responsiveness. Aim: To use BDP/formoterol (200/6 mcg, 2 bd) NEXThaler® (BFN) dose-counting to assess ICS responsiveness in severe asthma. Methods: Severe asthmatics with a FeNO ≥45 ppb were trained to use BFN in place of their usual ICS/LABA. Patients re-attended 28 days later and the dose count was recorded. Day 0 and 28 FeNO, ACQ6 and blood eosinophils were recorded. A log10∆FeNO ≥0.24 defined FeNO suppressors among the study group, confirming ICS responsiveness. Results: All patients(n=25)completed day 28 follow up.12/25 (48%) suppressed their FeNO (median[IQR] pre 104[68-173], post 46[25-54] ppb, p<0.0001). A smaller reduction occurred in FeNO non suppressors (pre 121 [77-198], post 86[64-183] ppb, p=0.015). ACQ6 and blood eosinophil count fell in FeNO suppressors (ACQ mean±SEM pre 2.9[±0.3], post1.9 [±0.3] p=0.0012); Eos median[IQR] pre-0.43[0.32-0.9], post 0.15[0.11-0.33], p=0.016 [n=8]). Of 9 people with baseline ICS/LABA prescription refills of >75%, 6 were FeNO suppressors suggesting prior non-adherence. Conclusion: Nexthaler™ dose counting demonstrates that 50% of people in a severe asthma service with FeNO ≥45 ppb respond to ICS when used regularly. This approach may miss some people with non-intentional non-adherence due to inhaler technique errors.