Prognostic implications of cluster analysis in patients with chronic bronchial infection under nebulized antibiotic therapy: A multicentre retrospective cohort study (INBREATHING STUDY)

<bold>Introduction:</bold> The clinical heterogeneity of patients with chronic bronchial infection (CBI) under nebulized antibiotics (NA) suggests the existence of different phenotypes with prognostic implications. Our objective was to analyse sociodemographic and clinical characteristics prior to the start of NA in these patients and evaluate their influence on prognosis and treatment response. <bold>Material and Methods:</bold> Multicentre, retrospective, observational study of patients with CBI under NA were included between January 2018 and December 2022 in 8 centres in Spain. Patients were classified by Partitioning Around Medoids algorithm on clinical characteristics prior the start of treatment. The response outcomes were exacerbations and eradication. Specific predictors of response for each cluster were assessed using stepwise logistic regression. <bold>Results:</bold> A total of 244 patients were recruited, predominantly male (50.4%) with a median age of 73 [61.0;80.2] years. Two clusters were identified: (1) females with bronchiectasis and fewer comorbidities, and (2) older males with COPD and a higher burden of comorbidities. Cluster 1 demonstrated a superior response to NA, showing a greater reduction in exacerbations [100% vs 66.7%; p<0.001] along with clinical enhancements, including reduced sputum production [87.6% vs 74.2%; p=0.05],diminished purulence [89.9% vs 75.8%; p=0.03] and decreased dyspnoea [72.4% vs 54.8%; p=0.04]. Cluster 1 experienced fewer adverse events [12.7% vs 29.8%; p<0.001]. <bold>Conclusions:</bold> In this pilot study, specific phenotypes were identified and showed differences in responses to treatment with NA.