High-resolution CT findings of parenchymal fibrosis correlate with prognosis in hypersensitivity pneumonitis

Background: Histopathologic evidence of fibrosis on surgical lung biopsy has been associated with reduced survival in patients with hypersensitivity pneumonitis (HP). Changes of pulmonary fibrosis detected on CT may also correlate with prognosis in patients with HP. Methods: We identified 69 consecutive patients with HP diagnosed between January 1997 and December 2002 at Mayo Clinic, Rochester, MN. Patients were stratified into fibrotic and nonfibrotic groups based on the CT findings. Fibrosis was defined by the presence of irregular linear opacities, traction bronchiectasis, or honeycombing. Measurements and main results: Of 69 patients, 26 were classified as fibrotic and 43 as nonfibrotic. Patients in the fibrotic group were older, had longer symptom duration, were more likely to have crackles on auscultation, more likely to be exposed to avian antigen, and had greater restrictive lung impairment (p < 0.05 for all comparisons). There were 11 deaths in the fibrotic group and 1 death in the nonfibrotic group (p < 0.0001). In the regression analysis, CT evidence of fibrosis, more severe pulmonary function abnormalities, and the presence of crackles on auscultation were predictive of reduced survival (p < 0.05 for all). The presence as well as the extent of fibrosis on CT was associated with increased mortality. The age-adjusted hazard ratio for mortality in patients with fibrosis was 4.6 (95% confidence interval, 2.0 to 20.1; p < 0.0001). Conclusion: CT findings of parenchymal fibrosis are associated with reduced survival in patients with HP and may serve as a useful prognostic indicator.