Evaluating the role of ATS/ERS/JRS/ALAT high resolution CT-Thorax UIP imaging categories in selecting candidates for transbronchial lung cryobiopsy for undifferentiated ILD, a retrospective study

<bold>Aims and objectives:</bold> To assess if High-Resolution CT-Thorax (HRCT) imaging can predict utility of transbronchial lung cryobiopsy (TBLC) in impacting diagnosis of interstitial lung disease (ILD) that lacks a confident diagnosis despite prior investigations. <bold>Methods:</bold> Retrospective study of 75 patients who underwent TBLC for undifferentiated diffuse ILD at a university hospital between 2018 and 2023. HRCT imaging was reviewed on each patient and categorised as per their ATS/ERS/JRS/ALAT UIP imaging pattern. Chart history and examination, PFTs, ILD blood panel, HRCT, previous BAL results and MDT discussion were assessed to determine the pre-cryobiopsy diagnostic consensus. These were compared against post-cryobiopsy MDT discussion to confirm if TBLC altered the diagnosis and management of the patients. <bold>Results:</bold> The diagnosis was changed in 44% (33/75) cases at post-TBLC MDT. Significantly, TBLC altered the pre-TBLC diagnosis in 68.4% (13/19) of the indeterminate UIP HRCT category, 41.9% (13/31) in the alternative diagnosis, 30% (6/20) in probable UIP and 20% (1/5) in definite UIP categories. TBLC led to a confirmed post-MDT diagnosis in 81.3% of cases overall, which is in keeping with standard cryobiopsy outcomes. <bold>Conclusions:</bold> TBLC is a really effective diagnostic tool in those with indeterminate UIP and alternative diagnosis HRCT patterns. When UIP/IPF is felt likely (definite/probable UIP) on pre-TBLC HRCT, TBLC is less useful.