title: Prevalence and progression of combined pulmonary fibrosis and emphysema in asymptomatic smokers: A case-control study.
abstract: OBJECTIVE
  We aimed to estimate the prevalence of combined pulmonary fibrosis and emphysema (CPFE) and describe the follow-up CT results of CPFE in asymptomatic smokers.
  
  
  METHODS
  This study was retrospective, and approved by an institutional review board. CT images of 2,016 current or previous male smokers who underwent low-dose chest CT at our healthcare centre were reviewed. Quantitative CT analysis was used to assess the extent of emphysema, and two radiologists visually analyzed the extent of fibrosis. Changes in fibrosis (no change, improvement, or progression) were evaluated on follow-up CT imaging (n = 42). Kaplan-Meier survival analysis, multivariate logistic regression and its ROC curve were used for survival and progression analysis.
  
  
  RESULTS
  The prevalence of CPFE among asymptomatic male smokers was 3.1 % (63/2,016). The median follow-up period was 50.4 months, and 72.7 % (16/22) of continued smoker had progressing fibrosis on follow-up CT. CPFE progressed more rapidly in continuous smokers than in former smokers (p = 0.002). The 3.5-year follow-up period after initial CPFE diagnosis maximized the sum of sensitivity and specificity of CPFE progression prediction in continuous smokers.
  
  
  CONCLUSIONS
  The prevalence of CPFE turned out not to be inconsiderable in asymptomatic male smokers, but serial CT follow-up would be helpful in recognizing disease progression.
  
  
  CONCLUSIONS
  • The prevalence of CPFE in asymptomatic smokers is 3.1 % (63/2,016). • Progression of CPFE is associated with smoking status. • 3.5 years of follow-up period would be needed to identify CPFE progression.
authors: Department of Radiology, Institute of Medical Science, Research Institute of Clinical Medicine, Chonbuk National University Medical School and Hospital, 634-18 Keumam-Dong, Jeonju, Jeonbuk, 561-712, South Korea, para2727@gmail.com.
authors: Kum Ju
authors: KJ
authors: Chae
authors: Gong Yong
authors: GY
authors: Jin
authors: Young Min
authors: YM
authors: Han
authors: Yong Seek
authors: YS
authors: Kim
authors: Su Bin
authors: SB
authors: Chon
authors: Young Sun
authors: YS
authors: Lee
authors: Keun Sang
authors: KS
authors: Kwon
authors: Hye Mi
authors: HM
authors: Choi
authors: David
authors: D
authors: Lynch
mesh_terms: D016022:Case-Control Studies; D015897:Comorbidity; D018450:Disease Progression; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011656:Pulmonary Emphysema / Q000150:complications / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D011658:Pulmonary Fibrosis / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D012372:ROC Curve; D012189:Retrospective Studies; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*; D014057:Tomography, X-Ray Computed / Q000379:methods