Abstract
Background and PurposeSeveral imaging-based indices were constructed quantitatively using the emphysema index (EI) and fibrosis score (FS) on high-resolution computed tomography (HRCT). We evaluated the ability of these indices to predict mortality compared to physiologic results. Additionally, prognostic predictive factors were compared among subgroups with biopsy-proven fibrotic idiopathic interstitial pneumonia (IIP) (biopsy-proven CPFE) and in a separate cohort with subclinical CPFE.Materials and MethodsThree chest radiologists independently determined FS. EI was automatically quantified. PFTs, smoking history, and composite physiologic index (CPI) were reviewed. Predictors of time to death were determined based on clinico-physiologic factors and CT-based CPFE indices.ResultsThe prevalence of biopsy-proven CPFE was 26% (66/254), with an EI of 9.1±7.1 and a FS of 19.3±14.2. In patients with CPFE, median survival and 5-year survival rates were 6.0 years and 34.8%, respectively, whereas those in fibrotic IIP without emphysema were 10.0 years and 60.9% (p = 0.013). However, the extent of fibrosis did not differ significantly between the two cohorts. In subclinical CPFE, prevalence was 0.04% (93/20,372), EI was 11.3±10.4, and FS was 9.1±7.1. FVC and a fibrosis-weighted CT index were independent predictors of survival in the biopsy-proven CPFE cohort, whereas only the fibrosis-weighted CT index was a significant prognostic factor in the subclinical CPFE cohort.ConclusionsRecognition and stratification using CT quantification can be utilized as a prognostic predictor. Prognostic factors vary according to fibrosis severity and among cohorts of patients with biopsy-proven and subclinical CPFE.
Highlights
In idiopathic pulmonary fibrosis (IPF), there is a dire need for accurate noninvasive measures of disease severity [1]
Prognostic factors vary according to fibrosis severity and among cohorts of patients with biopsy-proven and subclinical Combined Pulmonary Fibrosis and Emphysema (CPFE)
Wiggins et al [8] demonstrated that these atypical physiologic and radiological features can be explained by co-existent IPF and emphysema, and that high-resolution computed tomography (HRCT) is valuable for assessing these patients
Summary
In idiopathic pulmonary fibrosis (IPF), there is a dire need for accurate noninvasive measures of disease severity [1]. The DLco has the strongest correlation with the morphologic extent of disease, both histologically and on high-resolution computed tomography (HRCT). The quantification of disease severity using PFTs is often confounded by the concurrent presence of emphysema, resulting in spurious preservation of lung volumes and devastating depression of gas transfer [6,7]. The overall extent of fibrosis itself seen on HRCT is an important independent predictor of mortality in patients with IPF [9,10]. Several imaging-based indices were constructed quantitatively using the emphysema index (EI) and fibrosis score (FS) on high-resolution computed tomography (HRCT). We evaluated the ability of these indices to predict mortality compared to physiologic results. Prognostic predictive factors were compared among subgroups with biopsy-proven fibrotic idiopathic interstitial pneumonia (IIP) (biopsy-proven CPFE) and in a separate cohort with subclinical CPFE
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