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

Abstract

Background

In 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.

Methods

After 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.

Results

Forty-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.

Conclusion

Change in adherence over 1 week following the use of EIM reminders independently predicted change in FENO. This relationship was not maintained at 3 months.

Keywords:

• Asthma
• electronic inhaler monitor
• biomarker
• eosinophil
• FENO suppression
• inhaled corticosteroid

Disclosure statement

The authors have no conflict of interests to disclose.

Additional information

Funding

The study was funded by the Changi General Hospital (CGH) Research Grant (Ref: CHF2016.05-P).