Characterisation of the neutrophilic asthma phenotype over time

<b>Background:</b> No specific treatment has been proven effective for asthmatics with non-T2 inflammation, assumed to be neutrophilic, stressing our limited knowledge in this area. Studies looking at triggers and pathophysiological mechanisms leading to neutrophilic inflammation are the first step at improving our understanding of this condition. <b>Aim:</b> To compare the clinical characteristics of asthmatics with persistent (PN), transient (TN) and non-neutrophilic (NN) inflammation over time. <b>Methods:</b> This is a retrospective cross-sectional study of data from adult asthmatics included in databanks from IUCPQ-UL and McMaster University, who underwent two sputum inductions at least one year apart. Patients with PN (neutrophils ≥64.4% on both visits), TN (switch from neutrophils ≥64.4% to &lt;64.4% or from neutrophils &lt;64.4% to ≥64.4%) and NN (neutrophils &lt;64.4% on both visits) were compared for baseline characteristics, asthma severity and lung function decline. <b>Results:</b> Data from 219 patients were analyzed: 22 with PN, 165 with TN, and 32 with NN. Baseline characteristics were similar in the three groups except for age, which was older in PN compared to NN (54.6±15.2 vs 40.4±16.0, respectively, P=0.009). Mean yearly FEV1 decline was increased in patients with TN who switched from neutrophilic to non-neutrophilic inflammation compared to patients with NN (-0.059±0.11 L/year vs 0.006±0.20 L/year, respectively, P=0.01). <b>Conclusions:</b> Switching from neutrophilic to non-neutrophilic inflammation is associated with an increased lung function decline, suggesting sub-optimal therapy.