Real-world Elexacaftor/Tezacaftor/Ivacaftor(ETI) changes prospective sputum collection and microbiological reporting in a single centre pilot CF cohort.

Microbiological analysis of patients-with-cystic-fibrosis (PWCF) is aided by spontaneous sputum expectoration at clinic visits. Clinical trial and anecdotal real-world experience suggest this is changing post ETI. In our centre all PWCF transitioning to ETI have quarterly prospective data collected over 12 months for real-world analysis of their response, including, 2 sputum samples at each visit (Fig.1A). We reviewed sputum collection for the first 69 patients. 66 PWCF had 12-month prospective data. 77% (n=51) were able to produce a sample for culture at assessment prior to commencement of ETI. 62% (n=41) could give a second sample suitable for research analysis at that time. 18% (n=9/51) of patients who gave pre-ETI samples were unable to provide any samples over the subsequent 12 months. 8% (n=5) could provide samples for analysis at all 5 visits. At 12 months there was a 43% relative reduction in sputum available for culture and 80% relative reduction for research analysis. Microbiological changes are seen (Fig.1B) with 31% of samples demonstrating no growth. Our data demonstrates a reduction in available sputum for real-world clinical and research analysis. Changes in microbiology at 12 months may reflect sampling issues and/or ETI related effects. Moving forward alternative sampling methods may prove critical to the prospective analysis of the CF airway.