Characteristics, treatment, and lung function outcomes of pulmonary exacerbations in cystic fibrosis: insights from the BEAT-CF cohort.

BACKGROUND Pulmonary exacerbations pose a significant clinical burden on people with cystic fibrosis (pwCF). Whether management of exacerbations should change in the context of modulator therapy is unclear. We describe the characteristics, treatment and lung function outcomes of pulmonary exacerbations requiring intravenous antibiotic therapy (PERITs) in a contemporary Australian cohort of pwCF, in an era of rapidly broadening access to modulator therapy. METHODS PwCF receiving care at 11 Australian specialist centres were prospectively enrolled between 14 October 2020 and 9 October 2024. Spirometry data and treatments received during a PERIT were collected systematically. RESULTS A total of 982 pwCF were enrolled, with 593 PERITs recorded in 323 individuals. The median age at PERIT start was 12 years (IQR:7-17) and the mean baseline ppFEV1 across PERITs was 80% (sd:21%). Approximately 62% (n=366) of PERITs occurred in people receiving modulator therapy. Intravenous tobramycin (63%) and piperacillin-tazobactam (43%) were the most frequently used antibiotics. Among participants with spirometry at baseline and at Day7 (n=296) or Day60 (n=383), 41% (n=120) and 44% (n=169) were below their baseline at Day7 and Day60 after commencing treatment, respectively; 8% were >10% below their baseline ppFEV1 at both timepoints. Recovery patterns were consistent regardless of baseline lung function, Pseudomonas aeruginosa colonisation, or modulator use. CONCLUSION The pattern and magnitude of lung function impairment during PERITs is similar among those receiving and not receiving modulator therapy. This underscores the continued need for evidence to help clinicians balance treatment burden against the risk of irreversible loss of lung function.