Chronic hypersensitivity pneumonitis: identification of key prognostic determinants using automated CT analysis

Background: Chronic hypersensitivity pneumonitis (CHP) has a variable disease course. Computer analysis of CT features was used to identify a subset of CHP patients with an outcome similar to patients with idiopathic pulmonary fibrosis (IPF). Methods: Consecutive patients with a multi-disciplinary team diagnosis of CHP (n = 116) had pulmonary function tests (FEV1, FVC, DLco, Kco, and a composite physiologic index [CPI]) and CT variables predictive of mortality evaluated by analysing visual and computer-based (CALIPER) parenchymal features: total interstitial lung disease (ILD) extent, honeycombing, reticular pattern, ground glass opacities, pulmonary vessel volume (PVV), emphysema, and traction bronchiectasis. Mean survival was compared between both CHP and IPF patients (n = 185). Results: In CHP, visual/CALIPER measures of reticular pattern, honeycombing, visual traction bronchiectasis, and CALIPER ILD extent were predictive of mortality (p < 0.05) on univariate analysis. PVV was strongly predictive of mortality on univariate (p < 0.0001) and multivariate analysis independent of age, gender and disease severity (represented by the CPI [p < 0.01]). CHP patients with a PVV threshold > 6.5% of the lung had a mean survival (35.3 +/- 6.1 months; n = 20/116 [17%]) and rate of disease progression that closely matched IPF patients (38.4 +/- 2.2 months; n = 185). Conclusions: Pulmonary vessel volume can identify CHP patients at risk of aggressive disease and a poor IPF-like prognosis.