Phenotyping and Endotyping Asthma Based on Biomarkers

Asthma is a chronic inflammatory airways disorder mainly characterized by heterogeneity. A phenotype is defined as a group of patients that present similar clinically observable characteristics, without establishing a direct etiologic relationship with a distinct pathophysiologic mechanism. An endotype, on the other hand, describes a subgroup that shares the same pathophysiologic processes that lead to the development, the progression and the presentation of a disease. A biomarker has been defined as a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacologic responses to a therapeutic intervention. Several inflammatory phenotypes have been identified by the use of biomarkers. Most of them are based on the predominant type of cells in different biological fluids with sputum to be remained the most representative one. Eosinophilia represents the major characteristic of what we called classic atopic asthma. This particular phenotype usually responds well to corticosteroids, except for a small subgroup of severe asthma where even in the presence of eosinophils the ICS seem to have a less responsive role. Neutrophilic phenotype driven by the presence of neutrophils shows inadequate response to corticosteroid treatment, even in mild asthma. The major approach in order to define an endotype is driven by three main parameters. The statistical clustering approach, the use of advanced statistical mathematics to create distinct patient clusters, the specific targeted immune therapies and finally the application of omics' approach. Both phenotypes and endotypes are trying to clarify mechanisms and processes that driven the complexity of asthma. Both concepts could identify approaches which could establish new targeted to specific biomarkers treatment therapies/strategies.