title: Revisiting the role of exhaled nitric oxide in asthma.
abstract: OBJECTIVE
  This review focuses on the most recent studies investigating fractional nitric oxide concentration in exhaled breath (FeNO) as a useful biomarker for identifying specific phenotypes in asthma and as a tool for asthma diagnosis, monitoring and clinical decision-making.
  
  
  RESULTS
  On the basis of the current literature, it has been highlighted that FeNO is a clinically relevant marker in various clinical aspects of asthma: FeNO is a predictor for developing asthma in persistent rhinitis or in infants with respiratory symptoms; FeNO contributes to identification of asthma phenotypes in both children and adults, also in relation to severity; FeNO is useful in monitoring the effectiveness of inhaled corticosteroids (including compliance) and biologic treatments like omalizumab; FeNO, in conjunction with symptom registration and lung function measurements, contributes to asthma diagnosis and optimizes asthma management.
  
  
  CONCLUSIONS
  FeNO provides further information in distinguishing different phenotypes in asthma, allowing a much more appropriate control of the disease, especially in patients with difficult/severe asthma. In the future, it would be interesting to shed light on the hidden biological mechanisms responsible for low or normal FeNO values in symptomatic asthmatic patients.
authors.affiliation: Department of Clinical and Biological Sciences, University of Torino, Torino, Italy.
authors.forename: Fabio L M
authors.initials: FL
authors.lastname: Ricciardolo
mesh_terms: D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests; D045853:Exhalation; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism*; D010641:Phenotype; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D009569:Nitric Oxide