Significance of Combined Emphysema in Idiopathic Pulmonary Fibrosis and Serum Surfactant Protein-D as a Prognostic Factor

Background and Objectives: Idiopathic pulmonary fibrosis (IPF) is a chronic disease of unknown aetiology and is often associated with a syndrome called combined pulmonary fibrosis and emphysema (CPFE). This study aimed to identify practical predictors of prognosis in IPF patients associated with CPFE. Subjects and Methods: We retrospectively studied 72 patients with IPF and evaluated the threshold of emphysematous area affecting prognosis on high-resolution computed tomography (HRCT) scans. As predictor candidates, various pulmonary function tests (PFTs) and biomarkers, e.g. surfactant protein (SP)-A and SP-D, were assessed. Results: The survival rate of the CPFE group, defined as having an emphysematous area greater than 25% on HRCT, was significantly worse than that of the non-CPFE group, despite no significant difference in fibrosis scores. An annual percent decline of diffusing capacity of the lung for carbon monoxide (% DLCO) of more than 5% was a significant prognostic factor in the CPFE group. High concentration of serum SP-D was a significant prognostic factor in both the CPFE and non-CPFE groups. However, cut-off levels in the CPFE group were lower than those in the non-CPFE group. Conclusions: We demonstrated worse prognosis in IPF associated with CPFE syndrome compared to the other subset of IPF, and showed that % DLCO and SP-D are useful predictors of poor prognosis.