Asthma Endotypes

The protocol defines type 2 high asthma using asthma diagnosis plus FeNO, blood eosinophil, or tissue eosinophilia criteria. Likely type 2 low asthma is defined using low FeNO, low blood eosinophils, and no available airway eosinophilia. Type 2 high asthma may be identified clinically by elevated eosinophils or fractional exhaled nitric oxide. The likely type 2 low group may include some participants with lower-level type 2 inflammation. Asthma is treated in the article as a heterogeneous disease with type 2 high and type 2 low inflammatory endotypes. Type 2 low asthma has low or absent type 2 biomarkers and may involve neutrophilic immune responses.