Diagnostic yield of flexible bronchoscopy and bronchoalveolar lavage in children with chronic cough.

<bold>Introduction:</bold> Chronic cough is defined as a daily cough lasting more than 4 weeks. Flexible bronchoscopy (FB) with bronchoalveolar lavage (BAL) allows for detailed airway assessment, BAL fluid analysis and microbiological studies. It is recommended in the current diagnostic pathway for unexplained chronic cough. <bold>Objectives:</bold> This study aimed to describe clinical features, FB and BAL findings in children with chronic cough. <bold>Methods:</bold> Retrospective review of children who underwent FB and BAL for chronic cough or a history of more than 3 episodes of chronic wet cough in a single centre in South Africa between 2015 to 2021. <bold>Results:</bold> 77 patients (mean age 5.1) were included. 21 (27%) patients had more than 3 episodes of chronic cough in 12 months. Clinical features included wet cough (83%), wheeze (61%), atopy (16%) and chronic inhaled corticosteroid use (60%). 20 (26%) patients had lower airway anatomical abnormalities. 57% and 16% had an increased neutrophil and eosinophil % in BAL fluid (BALf) respectively. In 45% at least one bacteria was isolated and 37% had at least one positive viral PCR. The most common bacteria were <italic>H. influenzae</italic> (26%), <italic>S. pneumoniae</italic> (10%) and <italic>M. catarrhalis</italic> (8%). Mycobacterial cultures were negative. The BALf neutrophil % was correlated with a positive bacterial culture (p=0.002). Eosinophilic inflammation in BALf was associated with blood eosinophilia (p=0.044). <bold>Conclusion:</bold> Flexible bronchoscopy identified an anatomical airway abnormality in a quarter of all patients. A BALf neutrophil percentage >5% is strongly correlated with bacterial infection. These findings support the current guidelines for the role of flexible bronchoscopy and BAL in chronic cough.