David Augustine Lynch MD, Presenter: Consultant, Actelion Ltd, Allschwil, Switzerland Consultant, InterMune, Inc, Brisbane, CA Research support, Siemens AG Consultant, Gilead Sciences, Inc, Brisbane, CA

Ashish Chawla MD, Abstract Co-Author: Nothing to Disclose

Hakan Sahin MD, Abstract Co-Author: Nothing to Disclose

Kavita Garg MD, Abstract Co-Author: Nothing to Disclose

To determine the prevalence of infiltrative lung disease (ILD) in a population of cigarette smokers included in the National Lung Screening Trial (NLST)

Participants in the NLST were required to be between the ages of 55 and 74 years, with a current or former cigarette smoking history of at least 30 pack-years, and were randomized to chest radiograph or chest CT. The CT images of 400 NLST participants, obtained at a single site, were randomly selected for review for the presence of features suggestive of ILD. The scans were anonymized, and any link to lung cancer data for these participants will not be established prior to the release of lung cancer data for the NLST. Initial review was performed by a single observer. Abnormal or equivocal scans were reviewed by a second reviewer and consensus was reached regarding the presence of ILD. Abnormality suspicious for ILD was diagnosed if there was nondependent ground glass abnormality affecting more than 5% of any lung zone, nondependent reticular abnormality, diffuse centrilobular nodularity with ground glass abnormality, honeycombing, traction bronchiectasis, nonemphysematous cysts, or architectural distortion in any part of the lung. Abnormality equivocal for ILD was diagnosed if there was focal or unilateral ground glass attenuation, focal or unilateral reticulation, or mild patchy ground glass abnormality.

Abnormalities suspicious for ILD were identified in 39 (9.8%) of CT scans, while abnormalities equivocal for ILD were identified in a further 45 (11%). Among those with abnormalities suspicious for ILD, the most prevalent pattern was ground glass abnormality (n=31), thought to represent desquamative interstitial pneumonia or respiratory bronchiolitis interstitial lung disease. Other patterns included fibrotic abnormality,(n=3), cystic lung disease (n=2) and nodular lung disease (n=2).

Features of ILD are common in participants in the NLST, and probably largely represent smoking-related lung disease. However, fibrotic lung disease is also found.

The prevalence of ILD in this study is higher than anticipated.

Lynch, D, Chawla, A, Sahin, H, Garg, K, Prevalence of Infiltrative Lung Disease Identified on CT in Participants in the National Lung Screening Trial.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6016453.html