title: FeNO as a predictor of asthma control improvement after starting inhaled steroid treatment.
abstract: BACKGROUND
  The 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 (⩾50 ppb) 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.
  
  
  METHODS
  FeNO 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 40 years both before and after 6 weeks (median follow-up time) of treatment with 500 μg beclomethasone (median).
  
  
  RESULTS
  Having at the initial visit intermediate FeNO (⩾25 and <50 ppb) and high FeNO (⩾50 ppb), compared to normal FeNO (<25 ppb), 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.
  
  
  CONCLUSIONS
  It 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.
authors.affiliation: Department of Medical Sciences: Clinical Physiology, Uppsala University, Uppsala, Sweden. Electronic address: Andrei.Malinovschi@medsci.uu.se.
authors.forename: Andrei
authors.initials: A
authors.lastname: Malinovschi
authors.affiliation: Chest Department, Erasme University Hospital and Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Alain
authors.initials: A
authors.lastname: Van Muylem
authors.affiliation: Chest Department, Erasme University Hospital and Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Sebastien
authors.initials: S
authors.lastname: Michiels
authors.affiliation: Chest Department, Erasme University Hospital and Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Alain
authors.initials: A
authors.lastname: Michils
mesh_terms: D000280:Administration, Inhalation; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage / Q000627:therapeutic use*; D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy*; D015415:Biomarkers / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000008:administration & dosage / Q000032:analysis*; D012372:ROC Curve; D012189:Retrospective Studies
chemical_list: D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D009569:Nitric Oxide
keywords: ACQ; Asthma control; Exhaled nitric oxide; Longitudinal study; Lung function; Real-life study