Annual changes in pulmonary function are independent prognostic factors for the patients with chronic hypersensitivity pneumonia

Background : Chronic hypersensitivity pneumonia (CHP) is characterized by varying degrees of inflammation and progressing fibrosis of the lung caused by persistent exposure to a variety of inhaled antigens. The prognosis of patients with CHP who show fibrosing change in their lung tissue have been reported to be as poor as that of the patients with idiopathic pulmonary fibrosis (IPF). Annual changes in forced vital capacity (FVC) and diffusion capacity for carbon monoxide (DL CO ) have been reported to predict the outcome of patients with IPF. Aim : We conducted this study to clarify whether annual changes in FVC and/or DL CO can predict the prognosis of the patients with CHP. Methods : We retrospectively recruited 45 patients with CHP. Spirometry and DL CO measurements were made by one specialized technician, and annual declines in both FVC and DL CO were calculated as the slope of the regression line. Results : Median overall survival time of 45 patients with CHP was 1891±203.5 days. The mean annual declines in FVC and DL CO were 165.4±46.1 ml/year and 0.92±0.41 ml/year, respectively. The Cox proportional-hazards regression analyses revealed that more than 10% of annual decline in FVC and more than 15% of annual decline in DL CO were significant predictors of poor overall survival ( P =0.001 and P =0.001, respectively). Furthermore, multivariate analyses revealed that annual changes in both FVC and DL CO are independent prognostic factor for the patients with CHP even after adjusted by other covariates. Conclusion : In the present study, we demonstrated that the annual changes in pulmonary function could independently predict the prognosis of the patients with CHP.