Interval change in fractional exhaled nitric oxide (FENO) reflects short-term change in adherence following electronic inhaler reminders.

BackgroundIn asthma, suppression of fractional exhaled nitric oxide (FENO) is a marker of adherence in the short-term. The usefulness of FENO to indicate change in adherence in the longer term is unknown.The aims of this study were to determine the relationship between changes in adherence and corresponding changes in FENO over short (1 week) and long-term (3 month) periods.MethodsAfter establishing initial ICS adherence using electronic inhaler monitor (EIM) devices, reminders were switched on for 1 week ('short-term') to optimize adherence. Reminders were then switched off and patients followed up after 3 months ('long-term'). FENO was measured at the start and end of each period. Using linear regression, we analyzed change in FENO in relation to change in adherence.ResultsForty-two patients contributed complete data for analysis. In the short-term, change in adherence was independently associated with change in FENO (β=-0.36, p = 0.036) even after adjusting for initial adherence and ICS dose. The higher the initial FENO, the greater the decline in FENO with improved adherence. This relationship between change in adherence and change in FENO was not observed in the long-term.ConclusionChange in adherence over 1 week following the use of EIM reminders independently predicted change in FENO. This relationship was not maintained at 3 months.