<p>BSI and FACED scores.</p>

Associations between BSI and mortality were assessed using Kaplan–Meier survival analysis and Cox proportional hazards models adjusted for COPD, smoking status, and sex. Secondary analyses evaluated associations between BSI and lung function decline (FEV₁ and KCO) and health-related quality of life (SGRQ). A total of 198 patients were included (mean age 54.3 ± 9.7 years; 53.5% male), the majority with the ZZ genotype (97.5%) and coexisting COPD (87.4%).

Median BSI score was 5 (range 0–14). Mortality differed significantly across BSI severity groups (p < 0.001): estimated 1-year mortality was 1.1%, 7.4%, and 20.0% for mild, moderate, and severe disease respectively, while 4-year mortality was 5.7%, 23.7%, and 31.8%. In Cox regression analysis adjusted for COPD, smoking, and sex, BSI remained significantly associated with mortality (hazard ratio 1.13 per point increase; 95% CI 1.05–1.23; p = 0.002).

BSI score was also associated with greater decline in gas transfer (KCO) (β = −0.22% per point per year; p < 0.001), but showed no significant association with FEV₁ decline or SGRQ score. The Bronchiectasis Severity Index is associated with mortality risk in patients with AATD-associated bronchiectasis, supporting its use as a prognostic tool in this population. These findings provide evidence that a severity score derived from all-cause bronchiectasis cohorts can be applied to AATD, although prospective validation in larger multicentre datasets is warranted.</p></div>