Update of the international multidisciplinary classification of the interstitial pneumonias: an ERS/ATS statement

BACKGROUND: 

The 2013 American Thoracic Society/European Respiratory Society statement on the classification of the idiopathic interstitial pneumonias described six major and two rare subtypes of idiopathic interstitial pneumonia, as well as recognising unclassifiable disease.

OBJECTIVE: 

The objective of this statement is to update the 2013 classification of interstitial pneumonia.

METHODS: 

Five co-chairs identified a committee of 32 experts in the field, as well as two individuals with lived experience. Creation of the document was supported by a series of video meetings, first including the full committee and then subgroups assigned to draft specific sections of the document. The classification scheme was developed by consensus.

RESULTS:

The multidisciplinary committee of experts identified four major advances to the classification of interstitial pneumonia: 1) expansion beyond idiopathic interstitial pneumonias to also include secondary causes; 2) identification of new subcategories and updated terms, including addition of bronchiolocentric interstitial pneumonia as a major pattern as well as changing from acute interstitial pneumonia to idiopathic diffuse alveolar damage and desquamative interstitial pneumonia to alveolar macrophage pneumonia; 3) subclassification of interstitial and alveolar filling disorders, with interstitial disorders further subclassified as fibrotic versus non-fibrotic; and 4) consideration of diagnostic confidence in patient evaluation and management. The committee also provided a comprehensive update on the status of potential molecular tools and identified future research priorities.

CONCLUSIONS: 

This update builds upon the previous classification approach by describing major advances in the classification of interstitial pneumonia over the past decade.