Exhaled nitric oxide to predict corticosteroid responsiveness and reduce asthma exacerbation rates

Until recently, no point-of-care tool was available for assessing the underlying airway inflammation associated with asthma. Fractional exhaled nitric oxide (FeNO) emerged in the last decade as an important biomarker for asthma assessment and management. Evidence also indicates that FeNO is most accurately classified as a marker of T-helper cell type 2 (Th2)-mediated airway inflammation with a high positive and negative predictive value for identifying corticosteroid-responsive airway inflammation. This manuscript evaluates the evidence for FeNO as a predictor of Th2-mediated corticosteroid-responsive airway inflammation and presents the results of a meta-analysis of three adult studies comparing asthma exacerbation rates with FeNO-based versus clinically-based asthma management algorithms, one of which was not included in a 2012 Cochrane meta-analysis. The primary purpose of the updated meta-analysis was to evaluate asthma exacerbation rates. The results demonstrate that the rate of exacerbations was significantly reduced in favor of FeNO-based asthma management (mean treatment difference = -0.27; 95% CI [-0.42, -0.12] as was the relative rate of asthma exacerbations (relative rate = 0.57; 95% CI [0.41, 0.80]). In summary, FeNO has value for identifying patients with airway inflammation who will and will not respond to corticosteroids. Importantly, the use of FeNO in conjunction with clinical parameters is associated with significantly lower asthma exacerbation rates compared with asthma managed using clinical parameters alone. Together these data indicate that FeNO testing has an important role in the assessment and management of adult asthma. Further studies will continue to define the exact role of FeNO testing in adult asthma.