Hospital volume and outcomes following bronchoscopy in patients with interstitial lung disease: A retrospective observational study using a national inpatient database in Japan.

BACKGROUND: Interstitial lung diseases (ILDs) are a group of diffuse parenchymal lung disorders that cause inflammation and fibrosis in the interstitium of the lungs. Histopathological examination is pivotal to accurately diagnose the type of ILD, and bronchoscopy (BS) is often performed to collect lung tissue. This study aimed to determine the relationship between hospital volume and outcomes following BS in patients with ILD. METHODS: Inpatient data on patients with ILD who underwent BS between July 1, 2010 and March 31, 2021 were extracted from the Japanese Diagnosis Procedure Combination database. The annual hospital volume of BS was categorized into four (very low- [≤15 cases/year], low- [16-29 cases/year], high- [30-54 cases/year], and very high- [≥55 cases/year] volume) groups. The primary outcome was all-cause 14-day mortality after BS. Multiple imputation methods followed by multivariable logistic regression analyses fitted with generalized estimating equations were used to estimate the association between hospital volume and 14-day mortality after BS. RESULTS: A total of 89,454 patients with ILD from 1002 hospitals underwent BS. The all-cause mortality within 14 days after BS was 0.77%. An inverse trend was observed between mortality and hospital volume. Compared with the very low-hospital volume group, the very high-hospital volume group was significantly associated with a lower mortality (adjusted odds ratio = 0.63, 95% confidence interval: 0.48-0.85, p = 0.002). CONCLUSIONS: Hospital volume was inversely associated with all-cause mortality within 14 days after BS for hospitalized patients with ILD.