. 2021 Mar 16;8:100336. doi: 10.1016/j.ejro.2021.100336

Table 1.

Definition and Subcategories of Interstitial Lung Abnormality (ILA).

Definition
Incidental identification of non-dependent abnormalities, including ground-glass or reticular abnormalities, lung distortion, traction bronchiectasis, honeycombing, and non-emphysematous cysts involving at least 5% of a lung zone (upper, middle, and lower lung zones are demarcated by the levels of the inferior aortic arch and right inferior pulmonary vein) in individuals in whom interstitial lung disease is not suspected.

Definition

Incidental identification of non-dependent abnormalities, including ground-glass or reticular abnormalities, lung distortion, traction bronchiectasis, honeycombing, and non-emphysematous cysts involving at least 5% of a lung zone (upper, middle, and lower lung zones are demarcated by the levels of the inferior aortic arch and right inferior pulmonary vein) in individuals in whom interstitial lung disease is not suspected.

Subcategories of ILA
Non-subpleural: ILAs without predominant subpleural localization
Subpleural non-fibrotic: ILAs with a predominant subpleural localization and without evidence of fibrosis^a
Subpleural fibrotic: ILAs with a predominant subpleural localization and with evidence of pulmonary fibrosis^a

Modified from the Position Paper by the Fleischner Society (Lancet Respir Med 2020, Reference #2).

Fibrosis is characterized by the presence of architectural distortion with traction bronchiectasis or honeycombing (or both).