Asthma Inflammatory Phenotypes: How Can We Distinguish Them?

Background And Objectives: induced sputum is used to assess different inflammatory phenotypes in asthma, but is not used routinely. We aimed to determine the proportion of inflammatory asthma phenotypes based on induced sputum, to find biomarkers that can discriminate between phenotypes, and to evaluate biomarkers in patients with and without biological therapy in different inflammatory asthma phenotypes.

Materials And Methods: this cross-sectional study investigated clinical characteristics, asthma control tests, skin prick test, impulse oscillometry (IOS), spirometry, induced sputum, biomarkers (IgE, eosinophils, fractional exhaled nitric oxide (FeNO), serum periostin, IL-5, IL-6, IL-8, IL-17A, IL-33) in 80 asthmatics. A total of 17/80 patients were treated with biologics (10 with omalizumab, 7 with benralizumab).

Results: a total of 31% of patients had eosinophilic asthma (EA), 30% had mixed granulocytic asthma (MGA), 24% had paucigranulocytic asthma (PGA), and 15% had neutrophilic asthma (NA). The difference was found in blood eosinophils ( = 0.002), the highest observed in EA. The cut-off ≥ 240/μL eosinophils, with 64% sensitivity and 72.7% specificity, identified EA (AUC = 0.743, = 0.001). A higher IL-8 level was associated with NA ( = 0.025). In 63 non-biologic asthma group, eosinophils were higher in EA than in NA, MGA, and PGA ( = 0.012, = 0.028, and = 0.049, respectively). A higher IL-17A was associated with EA without biologics ( = 0.004). A significantly higher IL-5 was found in EA treated with biologics, in comparison with EA without biologics ( = 0.043). The number of leucocytes and neutrophils was higher in MGA without biologics ( = 0.049, = 0.019), while IL-5, IL-6, and IL-8 levels were higher in MGA treated with biologics ( = 0.012, = 0.032, = 0.038, respectively).

Conclusions: EA and MGA were the most prevalent asthma phenotypes. Blood eosinophils can identify EA, both in patients with and without biologics. Apart from the clinical profile, a broad spectrum of biomarkers for assessing inflammatory phenotypes is necessary for an adequate therapy approach to patients with asthma.