Clinical impact of pre-determined guideline selection for the diagnosis of fibrotic hypersensitivity pneumonitis.

Introduction and objectives: International guidelines for the diagnosis of Hypersensitivity Pneumonitis (HP) have improved the diagnostic standardization of this heterogeneous interstitial lung disease. Our goal was to determine how the final multidisciplinary discussion confidence level for suspected fibrotic HP (fHP) can be impacted by the application of different guidelines validated in this context.

Materials and methods: Retrospective study including patients submitted to transbronchial lung cryobiopsy (TBLC) with a final multidisciplinary meeting diagnosis of fHP. Both guidelines were applied to all patients in a stepwise fashion and directly compared according to the level of confidence in a fHP diagnosis.

Results: A total of 170 patients were diagnosed with fHP after TBLC and subsequent multidisciplinary discussion. Overall, there was a statistically significant change in proportion towards higher confidence diagnostic levels using the CHEST guideline (p < 0.0001). Changes were significant at three different levels: ATS/JRS/ALAT's "fHP not excluded" subgroup significantly upscaled to CHEST's "provisional low-confidence" subgroup (76.2 % increase; p < 0.001) and the proportion of patients in ATS/JRS/ALAT's "low confidence" subgroup significantly upscaled to both CHEST's "provisional high-confidence" (67.4 % increase; p < 0.001) and "definitive fHP" (50 % increase; p < 0.001) subgroups. The alternative application of the CHEST guideline in multidisciplinary discussion would have resulted in 73 less TBLC (42.9 % decrease versus the ATS/JRS/ALAT-oriented decision).

Conclusions: This study suggests a significant increase in definite fHP diagnosis when applying the CHEST versus the ATS/JRS/ALAT guideline, resulting in almost a 43 % decrease in referrals to TBLC when compared with the latter due to a combination of less strict radiological criteria and a more prominent role of BAL.