Identification of occult parechymal disease such as emphysema or airway disease using screening computed tomography

Abstract

Rationale: 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. Conclusion: 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. © Copyright © 2010 Informa Healthcare USA, Inc.