IntroductionThe fraction of NO in exhaled air (FeNO) is a marker of inflammation in asthma. The aim of the present study was to assess, in a real-world setting, whether only high (⩾50ppb) FeNO levels predict improvement in asthma control when being treated with inhaled corticosteroids (ICS), as suggested by current guidelines on the clinical use of FeNO. MethodsFeNO and asthma control were assessed in a retrospective observational study in 153 non-smoking, steroid-naïve, adult subjects with asthma with a mean age of 40years both before and after 6weeks (median follow-up time) of treatment with 500μg beclomethasone (median). ResultsHaving at the initial visit intermediate FeNO (⩾25 and <50ppb) and high FeNO (⩾50ppb), compared to normal FeNO (<25ppb), were associated with a larger proportion of subjects achieving an improvement of Asthma Control Questionnaire (ACQ) score with ⩾1 (78% and 67% vs 43%, p<0.05) or both ⩾1 improvement and asthma control at follow-up (31% and 37% vs 4%, p<0.05). These associations were consistent in multiple logistic regression models after adjustments for confounders. ConclusionsIt is not only high but also intermediate FeNO levels that are associated with a significant improvement in asthma control after starting ICS treatment. This challenges current clinical guidelines stating that only high FeNO levels predict response to ICS treatment.
Read full abstract