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.