# Clinical implications of traction bronchiectasis in IPF and fibrotic RA-ILD – a retrospective single-center cohort study

## TL;DR

Traction bronchiectasis in IPF and RA-ILD is linked to fibrosis severity and higher mortality, but not to typical bronchiectasis symptoms.

## Contribution

This study identifies traction bronchiectasis as a marker of fibrotic remodeling rather than a distinct syndrome in ILD.

## Key findings

- Higher bronchiectasis scores correlated with fibrosis extent and lower baseline lung function.
- Increased bronchiectasis scores were independently associated with higher mortality in IPF and RA-ILD patients.
- Pathogen detection was common but not linked to bronchiectasis severity or clinical outcomes.

## Abstract

Bronchiectasis is a common feature in idiopathic pulmonary fibrosis (IPF) and rheumatoid arthritis-associated interstitial lung disease (RA-ILD). While these so-called traction bronchiectasis are often considered a secondary phenomenon in fibrosing ILD, their prognostic significance and relationship to respiratory pathogen detection and outcomes remain unclear.

We conducted a retrospective, single-center cohort study in IPF or fibrosing RA-ILD patients with available high-resolution computed tomography (HRCT) and lower-respiratory tract microbial samples between 2014 and 2024. Bronchiectasis was assessed using the bronchiectasis subscore of the Brody score; fibrosis was quantified by deep-learning–based automated HRCT analysis. Primary outcome was 5-year transplant-free survival; secondary outcomes included isolation of pathogens per CDC criteria, PFT trajectories, bronchiectasis-associated symptoms, and hospitalization. Statistical methods included Cox regression, linear mixed-effects modeling and correlation analysis.

267 IPF and 56 RA-ILD patients were included. Median modified Brody score was 11.5 (IQR 7–16; max possible range 0–72). Higher Brody scores strongly correlated with fibrotic extent (R = 0.6, P < 0.001). Higher scores had significantly lower baseline FVC and DLCO (P < 0.001), but no differences in PFT trajectories over time. In multivariable Cox regression, higher bronchiectasis scores were independently associated with mortality (HR 1.03 per point [95%CI 1.01–1.06], P = 0.003); fibrosis extent showed similar results (HR 1.02, CI 1.00–1.03, P = 0.017). Pathogens were found at a median of 3 months after baseline in 50.9% (IPF) and 46.4% (RA-ILD), without association with survival, symptoms or Brody scores. Staphylococcus aureus was most common (28.9%); Pseudomonas aeruginosa was rare (1.9%).

In both IPF and RA-ILD, higher bronchiectasis scores were associated with fibrosis extent and mortality, but not classical clinical bronchiectasis features. This supports traction bronchiectasis as a marker of fibrotic remodeling rather than a distinct syndrome.

Not applicable.

The online version contains supplementary material available at 10.1186/s12931-026-03497-6.