Induced sputum supernatant bioactive lipid mediators can identify subtypes of asthma

Induced sputum (IS) allows to measure mediators of asthmatic inflammation in bronchial secretions. The specific role of induced sputum supernatant (ISS) endogenous bioactive lipid mediators in subtypes of asthma is not well understood.

To investigate the interactions between airway inflammation and clinical phenotypes of asthma, we integrated induced sputum supernatant (ISS) eicosanoids and quantitative assessment of infiltrating cells into new subtypes with the means of latent class analysis (LCA).

One hundred and thirty-nine asthmatics with and without aspirin hypersensitivity underwent sputum induction. High-performance liquid chromatography or gas chromatography coupled with mass spectrometry was used to profile eicosanoids. Nineteen variables covering clinical characteristics, IS inflammatory cells and eicosanoids were considered in the LCA.

Four phenotypic asthma classes were distinguished. Class 1 with mild-to-moderate asthma, chronic rhinosinusitis (CRS), high PGA2 in ISS and almost equal distribution of inflammation cell patterns. Class 3 subjects also had mild-to-moderate asthma but without upper airway symptoms. Induced sputum was often paucigranulocytic with low levels of lipid mediators. Classes 2 and 4 represented severe asthma with CRS and impaired lung function despite high doses of steroids. High blood and sputum eosinophilia was in line with high cysteinyl leukotrienes and PGD2 in ISS only in class 2. Class 4 subjects tended to have increased sputum neutrophilia and PGE2 in ISS. Aspirin hypersensitivity was most frequent among class 2 subjects.

The LCA revealed four distinct asthma classes differing in eicosanoid pathways.