There is interest in using transbronchial cryobiopsies (CBs) for the diagnosis of fibrotic (chronic) hypersensitivity pneumonitis (FHP), but with little information in the literature about what features are diagnostic in CBs.
To determine, using in silico investigation, whether features supporting a diagnosis of FHP in video-assisted thoracoscopic (VATS) biopsies can be identified in CBs.
In silico circular "cryobiopsies," 5.25 mm in diameter (21.6 mm2), were created on the slides of 15 VATS biopsy cases that had been assigned a 60% or greater confident diagnosis of FHP at a specially devised multidisciplinary discussion. Using stratified random sampling, up to 8 "cryobiopsies" per case were analyzed for the presence of giant cells/granulomas or peribronchiolar metaplasia affecting 50% or more of the bronchioles, features that had statistically supported a diagnosis of FHP on the VATS biopsies in the multidisciplinary discussion exercise.
Giant cells/granulomas were detected with very low sensitivities in the "cryobiopsies." Using peribronchiolar metaplasia in 50% or more of bronchioles alone, the sensitivity/specificity for a diagnosis of FHP of 2 "cryobiopsies" compared to the corresponding VATS biopsy was 0.57/0.63; for 4 "cryobiopsies," 0.86/0.75; and for 8 "cryobiopsies," 0.83/0.71. Adding giant cells/granulomas slightly improved these numbers to 0.63/0.71 for 2 "cryobiopsies"; 1.00/0.86 for 4; and 1.00/0.80 for 8.
In the setting of a multidisciplinary discussion where FHP is part of the differential diagnostic choices, 4 actual CBs with an area of roughly 20 mm2 each should have good sensitivity and reasonable specificity for diagnosing FHP using these specific morphologic criteria.