Presence of Air Trapping and Mosaic Attenuation on Chest Computed Tomography Predicts Survival in Chronic Hypersensitivity Pneumonitis

Rationale: Significant heterogeneity of computed tomography (CT) presentation exists within chronic hypersensitivity pneumonitis (HP). There are limited data aimed at delineating the prognostic value of specific CT features, distribution, and patterns in chronic HP. Objectives: To examine whether the presence of CT mosaic attenuation (MA) and air trapping (AT), and the distribution or patterns of fibrosis impact survival in subjects with chronic HP. Methods: We retrospectively identified 110 consecutively enrolled, well-characterized, biopsy-proven adult subjects with chronic HP between 1982 and 2015 from the National Jewish Health interstitial lung disease research database. The first available CT scan of diagnostic quality from each subject was formally evaluated for specific CT findings associated with chronic HP and for overall CT pattern. A Cox proportional hazards model was used to identify independent predictors in time-to-death analysis, and bootstrap analysis was performed for internal model validation. Results: Fibrotic HP(65%; 72/110) was most often peripheral in the axial plane and lower lung preponderant. The distribution of lung disease in those without fibrosis was most often axially and zonally diffuse. There was no association between survival and CT distribution or CT pattern in the whole cohort or within the fibrotic subset of subjects. After multivariate adjustment, AT/MA was independently associated with survival in the whole cohort (HR = 0.26; 95% confidence interval = 0.07-0.97). Results were similar after restricting the analyses to fibrotic HP cases. Conclusions: Among subjects with chronic HP, the presence of CT AT/MA may identify subjects with better prognosis.