CT findings associated with survival in chronic hypersensitivity pneumonitis

Objectives: To identify CT findings in chronic hypersensitivity pneumonitis (cHP) associated with survival. Material and methods: Two thoracic radiologists assessed CT scans for specific imaging findings and patterns in 132 subjects with cHP. Survival analyses were performed. Results: The majority of subjects had an inconsistent with usual interstitial pneumonitis pattern on CT (55.3%,73/132). Hypersensitivity pneumonitis (HP) diagnosis on CT was less common in those with fibrosis (66.1%, 74/112) than those without fibrosis (85%,17/20). Smoking was associated with a lower prevalence of HP on CT (p=0.04). CT features of pulmonary fibrosis, especially traction bronchiectasis (HR 8.34, 95% CI 1.98–35.21) and increased pulmonary artery (PA)/aorta ratio (HR 2.49, 95% CI 1.27–4.89) were associated with worse survival, while ground-glass opacity (HR 0.31, 95% CI 0.12–0.79) was associated with improved survival. Survival association with imaging was less pronounced after adjustment for gender, age and physiology score. Conclusions: A substantial proportion of cHP cases have a non-HP-like appearance. Ground-glass opacity, pulmonary fibrosis features and elevated PA/aorta ratio on CT likely reflect varying degrees of disease severity in cHP and may inform future clinical prediction models. Key Points: • A substantial proportion of subjects with chronic HP have a UIP-like pattern. • A UIP pattern in HP may be potentiated by smoking. • A diagnosis of HP should not be excluded based solely on CT appearance. • CT fibrosis and increased PA/aorta ratio signal worse survival.