Heterogeneity of asthma according to blood inflammatory patterns

Abstract

Rationale: There is increasing interest regarding asthma heterogeneity in relation to inflammatory patterns. Objectives: To assess phenotypic characteristics, in particular clinical presentation of the disease, in 381 well-characterised adults with asthma from the French Epidemiological study on the Genetics and Environment of Asthma (EGEA) according to their blood inflammatory pattern. Methods: Four blood inflammatory patterns were defined according to eosinophil (EOS) and neutrophil (NEU) count cut-off points. Samples with ≥250 EOS/mm3 were classified as EOShi and those with ≥5000 NEU/mm3 as NEUhi. Clinical characteristics include typical asthma and chronic obstructive pulmonary disease (COPD)-like symptoms, as well as composite quantitative scores addressing the activity of the disease. Results: A substantial number of those with asthma (56.2%) had the EOS lo pattern (<250 EOS/mm3). Patients with asthma who had the EOShi pattern had higher immunoglobulin E (IgE), a lower forced expiratory volume in 1 s (FEV1) and presented a more active asthma than those with the EOSlo pattern. Among those with the EOS lo pattern, neutrophil inflammation (NEUhi) was related to a less frequent positive skin prick test response (OR 0.44, 95% CI 0.20 to 0.96). Among those with the EOShi pattern, neutrophil inflammation did not explain current asthma or asthma activity, and was significantly related to nocturnal symptoms (OR 5.21, 95% CI 1.44 to 18.8) independently of age, sex, smoking and inhaled corticosteroid treatment. In non-smokers with asthma, COPD-like symptoms, in particular chronic phlegm, were more frequent in those with neutrophil inflammation, independent of eosinophil inflammation (OR 2.35, 95% CI 1.08 to 5.10). Conclusions: Besides eosinophilia, neutrophil inflammation assessed in the blood is related to specific characteristics of asthma. Considering simultaneously neutrophilic and eosinophilic inflammation may contribute to help to disentangle this complex disease.