Study selection criteria

PopulationAdults (≥18 years) with diagnosis of asthma including pregnant women.Studies that included cohorts with a mean age <18 years of age
Recruited patients were not diagnosed with asthma
Animal models
Unselected specific population (e.g. firefighters, obese or athletes)
InterventionStudies that measured FeNO according to the ATS 2005 criteria [20] for the management of asthma, either with or without other indicators of asthma control. ATS criteria relating to multiple testing were relaxed to allow inclusion of studies that operated electrochemical devices in line with the manufacturer's instructions, which state only one test is required. Studies where monitoring was performed at home were excluded as this was not within the scope of the assessment.Device which is not validated for measuring FeNO
Offline measurements
Studies where FeNO is measured on a more regular basis (i.e. not during a routine annual review)
ComparatorStudies comparing the intervention to any other management strategy that does not utilise FeNO measurements.Includes the use of FeNO measurement as part of the management strategy
OutcomePrimary outcome of interest included incidence of acute exacerbation (any definition of exacerbation severity was acceptable, including “use of oral corticosteroids”), inhaled corticosteroid use, unscheduled contact with healthcare officials, hospitalisations and emergency department visits expressed or calculable as rates per person year or as the number of patients experiencing exacerbations. These outcomes were chosen as they have the greatest impact both clinically and economically.
Other outcomes included clinical complications associated with acute exacerbation, asthma control and symptoms, adverse events, health-related quality of life, mortality and compliance.
Does not report data on FeNO-guided step-up/step-down therapy
Measure of alveolar nitric oxide or nasal nitric oxide
Study typeRandomised controlled trials.Preclinical and biological studies
Editorials and opinion pieces
Studies only published in languages other than English
  • FeNO: fractional exhaled nitric oxide; ATS: American Thoracic Society.