title: Interstitial lung abnormalities in a CT lung cancer screening population: prevalence and progression rate.
abstract: OBJECTIVE
  To determine the prevalence of interstitial lung abnormalities (ILAs) at initial computed tomography (CT) examination and the rate of progression of ILAs on 2-year follow-up CT images in a National Lung Screening Trial population studied at a single site.
  
  
  METHODS
  The study was approved by the institutional review board and informed consent was obtained from all participants. Image review for this study was HIPAA compliant. We reviewed the CT images of 884 cigarette smokers who underwent low-dose CT at a single site in the National Lung Screening Trial. CT findings were categorized as having no evidence of ILA, equivocal for ILA, or ILA. We categorized the type of ILA as nonfibrotic (ground-glass opacity, consolidation, mosaic attenuation), or fibrotic (ground glass with reticular pattern, reticular pattern, honeycombing). We evaluated the temporal change of the CT findings (no change, improvement, or progression) of ILA at 2-year follow-up. A χ(2) with Fisher exact test or unpaired t test was used to determine whether smoking parameters were associated with progression of ILA at 2-year follow-up CT.
  
  
  RESULTS
  The prevalence of ILA was 9.7% (86 of 884 participants; 95% confidence interval: 7.9%, 11.9%), with a further 11.5% (102 of 884 participants) who had findings equivocal for ILA. The pattern was fibrotic in 19 (2.1%), nonfibrotic in 52 (5.9%), and mixed fibrotic and nonfibrotic in 15 (1.7%) of the 86 participants with ILA. The percentage of current smokers (P = .001) and mean number of cigarette pack-years (P = .001) were significantly higher in those with ILA than those without. At 2-year follow-up of those with ILA (n = 79), findings of nonfibrotic ILA improved in 49% of cases and progressed in 11%. Fibrotic ILA improved in 0% and progressed in 37% of cases.
  
  
  CONCLUSIONS
  ILA is common in cigarette smokers. Nonfibrotic ILA improved in about 50% of cases, and fibrotic ILA progressed in about 37%.
authors.affiliation: Department of Radiology, Chonbuk National University Medical School and Hospital, Institute of Medical Science, Research Institute of Clinical Medicine, 634-18 Keumam-Dong, Jeonju, Jeonbuk 561-712, South Korea. gyjin@chonbuk.ac.kr
authors.forename: Gong Yong
authors.initials: GY
authors.lastname: Jin
authors.forename: David
authors.initials: D
authors.lastname: Lynch
authors.forename: Ashish
authors.initials: A
authors.lastname: Chawla
authors.forename: Kavita
authors.initials: K
authors.lastname: Garg
authors.forename: Martin C
authors.initials: MC
authors.lastname: Tammemagi
authors.forename: Hakan
authors.initials: H
authors.lastname: Sahin
authors.forename: Shigeki
authors.initials: S
authors.lastname: Misumi
authors.forename: Keun Sang
authors.initials: KS
authors.lastname: Kwon
mesh_terms: D000368:Aged; D016009:Chi-Square Distribution; D018450:Disease Progression; D005260:Female; D006801:Humans; D016015:Logistic Models; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011857:Radiographic Image Interpretation, Computer-Assisted; D012907:Smoking / Q000453:epidemiology; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014481:United States / Q000453:epidemiology