Inflammatory subtypes in asthma: Assessment and identification using induced sputum

Induced sputum eosinophil proportion is a good discriminator for eosinophilic asthma, providing a reproducible definition of a homogenous group. The remaining non-eosinophilic subjects are heterogeneous and can be further classified based on the presence of neutrophils. These inflammatory subtypes have important implications for the investigation and characterization of airway inflammation in asthma.