The effect of emphysema in patients with idiopathic pulmonary fibrosis; evaluation using quantitative CT analysis

BACKGROUND: Many patients with idiopathic pulmonary fibrosis (IPF) have smoking history and emphysematous lesions. However, there are no reports using quantitative computed tomography (CT) analysis of both emphysema and fibrosis in IPF patients. We have recently reported the method to quantify honeycombing area (HA) using CT. We hypothesized that the extent of fibrosis and emphysema might predict the survival in IPF. In this study, we measured both HA and emphysematous area in IPF patients with smoking history. METHODS: Chest CTs of 61 IPF patients were retrospectively evaluated. We first measured HA and then calculated the emphysematous area as subtracted Low Attenuation Area (sLAA). The percentage of HA and sLAA to total lung area were also calculated (%HA and %sLAA, respectively). RESULTS: The mean %HA and %sLAA were 4.5% and 21.5%, respectively. The optimal cut-off values for survival of %HA and %sLAA were set at 5% and 10% by receiver operating characteristic curve. Patient with %HA more than 5% had significantly lower survival rate (Median survival time (MST): 1.8 vs 5.9 years; log-rank: p=0.0037). Patient with %sLAA more than 10% had significantly higher survival rate (MST: 4.3 vs 1.8 years; log-rank: p=0.0001). Combined %HA with %sLAA (%HA≥5% and %sLAA CONCLUSION: %HA and %sLAA may predict the survival of IPF patients with smoking history.