Comparative survival analysis between idiopathic pulmonary fibrosis and chronic hypersensitivity pneumonitis

Chronic hypersensitivity pneumonitis (CHP) is an interstitial lung disease with limited treatment response and bad prognosis. Sometimes it is indistinguishable from idiopathic pulmonary fibrosis (IPF) becoming one of the main differential diagnosis. The aim of our study is to compare survival and functional decline between these two entities.

Survival and functional decline more than 10% in FVC were compared using Kaplan Meier (KM) method between patients with CHP and IPF. Cox proportional hazard analysis was used to identify independent predictors of survival and functional decline.

146 patients were included, 54 with CHP and 92 with IPF. KM rate for 2 years survival was 0.71 (CI 95% 0,6-0,8) for CHP group and 0,83 (CI 95% 0,66 - 0,92) for IPF (p=0,027). Nevertheless this difference disappeared using Cox proportional hazard analysis, the adjusted HR for survival among CHP patients was 0,53 (CI 95% 0,25-1,15) (p=0,11). There was no difference in functional evolution between the two groups. KM rate for a decline more than or equal to 10% was 0,64 for CHP (CI 95% 0,43-0,79) and 0,78 for IPF (IC 95% 0,6-0,88) (p=0,22). This observation did not change after using Cox proportional hazard analysis.

Our study shows that both IPF and CHP are fibrosing interstitial diseases with a similar evolution and survival. It might be possible that therapeutic approach in patients with CHP should change in the light of these observations.