Fractional Exhaled Nitric Oxide for Asthma

Publication Date: November 15, 2021

Key Points

Key Points

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  • Asthma endotypes have replaced the single entity model of asthma. One of the major endotypes is “T2” asthma.
  • Nitric oxide (NO) is produced by airway cells, particularly the airway epithelium, and is a marker of inflammation of the airways: in general, a higher level of exhaled NO (FeNO) is associated with the T2 endotype.
  • T2 high endotype is eosinophilic asthma; T2 low is non-eosinophilic.
  • In the appropriate setting, elevated levels of FeNO reflect airway inflammation and hyperresponsiveness of the airways. This finding may indicate the need to intensify therapy for asthma.
  • This focused CPG addresses a single important question that is complementary to other broad guidelines, and provides Evidence to Decision (EtD) knowledge-based recommendations* regarding whether patients with asthma in whom treatment is contemplated should undergo FeNO testing. This CPG does not provide specific cut-off values for the interpretation of the test.
  • The recommendations are designed for treatment decisions in ambulatory settings for the ongoing management of asthma, and the use of FeNO testing should be placed in the individualized context of asthma treatment (Figure 1).
* See the “For clinicians” section of Table 1.



...patients with asthma in whom treatment...

...FeNO Treatment for Individuals With AsthmaConcep...