title: Identification of occult parechymal disease such as emphysema or airway disease using screening computed tomography.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) is a major public health problem. This study was performed to determine whether the low attenuation area (LAA) and visual score provided by low-dose computed tomography (CT) can be used to detect occult parenchymal disease, such as insidious COPD.
  
  
  METHODS
  Each participant underwent low-dose CT scan and pulmonary function tests. The LAA% of the corresponding lung area was calculated. The cut-off level between the normal lung density area and LAA was defined as -960 HU, and the severity of emphysematous change (visual score) and LAA% were evaluated on three same chest CT slices obtained at full inspiration.
  
  
  RESULTS
  Forty-eight of 2,247 individuals including 1058 non-smokers and 1189 smokers were diagnosed with COPD. Chest CT findings in individuals diagnosed with COPD showed centrilobular emphysema (50%), however, 17 of the subjects diagnosed with COPD had normal screening CT findings. Thirty-one subjects diagnosed with COPD showed a positive visual score, and 27 individuals with COPD showed LAA% of more than 30. Nine of 17 subjects with a negative visual score showed LAA% of more than 30. The visual score in smokers was significantly higher than that of non-smokers. The lung function in smokers was lower than that of non-smokers. Smokers also showed higher frequencies of chest CT abnormalities.
  
  
  CONCLUSIONS
  Low-dose CT scans detected LAA and a positive visual score before COPD associated with an impaired lung function develops. Smokers with normal spirometry had a potential to develop an airflow obstruction accompanied with abnormal CT findings.
authors.affiliation: Azumi General Hospital, Kitaazumi-gun, Japan. tsushimakenji@yahoo.co.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Tsushima
authors.forename: Shusuke
authors.initials: S
authors.lastname: Sone
authors.forename: Keisaku
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Keishi
authors.initials: K
authors.lastname: Kubo
authors.forename: Satoshi
authors.initials: S
authors.lastname: Morita
authors.forename: Misa
authors.initials: M
authors.lastname: Takegami
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuhara
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging*; D011656:Pulmonary Emphysema / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging*; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed / Q000379:methods*