Chronic hypersensitivity pneumonitis: high resolution computed tomography patterns and pulmonary function indices as prognostic determinants.

OBJECTIVES: To investigate high resolution computed tomography (HRCT) and pulmonary function indices (PFTs) for determining prognosis in patients with chronic fibrotic hypersensitivity pneumonitis (CHP).
METHODS: Case records, PFTs (FEV(1), FVC and DLco) and HRCTs of ninety-two patients with chronic hypersensitivity pneumonitis were evaluated. HRCT studies were scored by two observers for total disease extent, ground-glass opacification, fine and coarse reticulation, microcystic and macrocystic honeycombing, centrilobular emphysema and consolidation. Traction bronchiectasis within each pattern was graded. Using Cox proportional hazards regression models the prognostic strength of individual HRCT patterns and pulmonary function test variables were determined.
RESULTS: There were forty two deaths during the study period. Increasing severity of traction bronchiectasis was the strongest predictor of mortality (HR 1.10, P < 0.001, 95%CI 1.04-1.16). Increasing global interstitial disease extent (HR 1.02, P = 0.02, 95%CI 1.00-1.03), microcystic honeycombing (HR 1.09, P = 0.019, 95%CI 1.01-1.17) and macrocystic honeycombing (HR 1.06, P < 0.01, 95%CI 1.01-1.10) were also independent predictors of mortality. In contrast, no individual PFT variable was predictive of mortality once HRCT patterns were accounted for.
CONCLUSION: HRCT patterns, in particular, severity of traction bronchiectasis and extent of honeycombing are superior to pulmonary function tests for predicting mortality in patients with CHP. KEY POINTS: • HRCT is increasingly used to assess chronic fibrotic hypersensitivity pneumonitis. • HRCT patterns are superior to pulmonary function tests for predicting mortality. • Extensive traction bronchiectasis strongly predicts poor survival in chronic hypersensitivity pneumonitis.