Difficult asthma is a heterogeneous disease of the airways including various types of bronchial
inflammation and various degrees of airway remodeling. Therapeutic response of severe asthmatics
can be predicted by the use of biomarkers of Type2-high or Type2-low inflammation. Based on
sputum cell analysis, four inflammatory phenotypes have been described. As induced sputum is timeconsuming
and expensive technique, surrogate biomarkers are useful in clinical practice.
Eosinophilic phenotype is likely to reflect ongoing adaptive immunity in response to allergen. Several
biomarkers of eosinophilic asthma are easily available in clinical practice (blood eosinophils, serum
IgE, exhaled nitric oxyde, serum periostin). Neutrophilic asthma is thought to reflect innate immune system activation in
response to pollutants or infectious agents while paucigranulocytic asthma is thought to be not inflammatory and characterized
by smooth muscle dysfunction. We currently lack of user-friendly biomarkers of neutrophilic asthma and airway
In this review, we summarize the biomarkers available for the management of difficult asthma.