Approach to the Evaluation and Management of Interstitial Lung Abnormalities. An Official American Thoracic Society Clinical Statement.

There is growing interest in identifying early stages of interstitial lung disease (ILD) to improve patient outcomes. This document reviews updated evidence on interstitial lung abnormalities (ILA), provides suggestions for screening, evaluation, and management, proposes criteria for distinguishing ILA from ILD, and identifies research priorities. A committee of clinical and methodology experts met by video conference to define ILA and ILD by consensus and voted on eleven pre-specified questions after reviewing synthesized evidence from a systematic literature search. Agreement of 70% or more was required to approve each suggestion. ILA is defined as non-dependent bilateral parenchymal CT abnormalities, including ground-glass or reticulations, lung distortion, traction bronchiectasis, and/or honeycombing involving at least 5% of a lung zone. The updated definition removes prior exclusion of high-risk populations. ILD is distinguished from ILA by symptoms (dyspnea/cough) attributable to an interstitial process, abnormal or declining lung function, fibrotic (honeycombing and/or reticulation with traction bronchiectasis involving at least 5% of total lung volume) or progressive imaging abnormalities, and/or specific fibrotic ILD patterns on imaging or pathology. Suggestions include ILA/ILD assessment on imaging acquired for lung cancer screening, screening adults with connective tissue disease and first-degree relatives of patients with familial pulmonary fibrosis, assessing baseline symptoms and pulmonary function among those with ILA, and monitoring ILA with chest CT every 2-3 years. This document presents a comprehensive literature review of ILA with updates to the Fleischner Society ILA definition, establishes a working ILD definition, and provides evidence-based suggestions for ILA evaluation and management.