Transbronchial lung cryobiopsy in fibrotic hypersensitivity pneumonitis: prognostic differences and intra-lobar variability.

BACKGROUND

Transbronchial lung cryobiopsy (TBLC) is increasingly used to diagnose interstitial lung disease; however, its diagnostic accuracy for fibrotic hypersensitivity pneumonitis (HP) remains uncertain. We aimed to compare disease progression between patients with fibrotic HP diagnosed by TBLC-based multidisciplinary discussion (TBLC-MDD) and those diagnosed by surgical lung biopsy-based MDD (SLB-MDD).

METHODS

This single-center retrospective study included patients diagnosed with fibrotic HP via MDD between January 2005 and June 2023. Histopathological findings-chronic fibrosing interstitial pneumonia, airway-centered fibrosis, and poorly formed nonnecrotizing granulomas-were assessed using the 2020 ATS/JRS/ALAT HP guidelines. For SLB-MDD patients who underwent TBLC prior to SLB, changes in diagnostic confidence were evaluated. To compare overall survival (OS) between the TBLC-MDD and SLB-MDD groups, 1:1 propensity score matching was performed. OS was analyzed using the Kaplan-Meier method and Cox proportional hazards models.

RESULTS

Histopathological features were significantly less prevalent in TBLC than in SLB specimens. In the first lower-lobe specimen, chronic fibrosing interstitial pneumonia was identified in 26% of TBLC compared to 89% of SLB specimens (p < 0.001). Among 31 SLB-MDD patients with prior TBLC, SLB significantly improved diagnostic confidence in 26 patients (84%; p < 0.001). After propensity score matching (96 pairs), TBLC-MDD patients showed significantly better OS than SLB-MDD patients (HR, 0.436; 95% CI, 0.197-0.963; p = 0.035). Within the TBLC-MDD group, concordance for chronic fibrosing interstitial pneumonia between the first and second lower-lobe specimens was poor (κ = 0.092). The presence of chronic fibrosing interstitial pneumonia in the second lower-lobe specimen independently predicted mortality (HR, 3.233; 95% CI, 1.115-9.376; p = 0.031), whereas findings from the first lower-lobe specimen were not statistically significant.

CONCLUSIONS

Patients with fibrotic HP diagnosed by TBLC-MDD exhibited a more favorable prognosis than those diagnosed by SLB-MDD, likely due to insufficient subpleural sampling by TBLC. TBLC should be considered a complementary diagnostic tool to SLB for fibrotic HP, and its interpretative limitations might be carefully addressed during MDD.