Neutrophil elastase activity in bronchial lavage fluid and the one-year follow-up outcomes in bronchiectasis patients: A multicenter prospective cohort study.

BackgroundBronchiectasis is increasingly recognized as an inflammatory disease in which "disease activity" is not fully captured by radiology or composite severity scores. Although sputum neutrophil elastase (NE) activity is a validated biomarker, the prognostic value of segment-specific NE activity in bronchial lavage fluid (BLF) remains limited.ObjectivesTo evaluate NE activity in BLF collected from affected bronchi and determine its association with one-year bronchiectasis outcomes.DesignMulticenter prospective cohort study.MethodsAdults with stable bronchiectasis undergoing bronchoscopy at two hospitals in Ho Chi Minh City were enrolled between April 2022 and January 2024. BLF was collected from the most affected bronchus (ABLF) and a reference bronchus (NBLF). NE activity was quantified using a fluorogenic assay. Participants were followed for 12 months to assess exacerbations and time to first exacerbation.ResultsOf 168 screened patients, 139 were enrolled and 121 completed follow-up. Post-tuberculosis bronchiectasis was the most common etiology. NE activity was detectable in all BLF samples and was higher in ABLF than NBLF (median 2.0 vs. 0.4 μg/mL). Exacerbations occurred in 42.1% of patients. ABLF NE activity was higher in patients with chronic bacterial infection than in those without (median 3.6 vs. 1.8 μg/mL; p=0.001), and in patients who developed exacerbations compared with those who did not (median 3.0 vs. 1.2 μg/mL; p<0.001). After adjustment for baseline severity indices, higher ABLF NE activity remained associated with increased exacerbation risk. Kaplan-Meier analysis showed shorter exacerbation-free survival with increasing ABLF NE activity, with estimated mean exacerbation-free survival times of 10.5, 8.5, and 6.9 months in the mild, moderate, and high NE groups, respectively (log-rank p=0.001).ConclusionSegment-specific NE activity in BLF is elevated in affected bronchi and is an independent predictor of exacerbations in this TB-endemic Asian bronchiectasis cohort, supporting BLF NE as a clinically meaningful biomarker of disease activity.