Pulmonary CT and MRI markers of asthma remission

On-treatment asthma remission has emerged as a treatment goal in the therapeutic management of severe asthma. Clinical remission of asthma—characterized by sustained symptom control, stable lung function, no oral steroid use or exacerbations—is well-described, but remains a contentious goal of therapy. For example, it is not known if remission is accompanied by the reversal of airway remodeling, nor is it known how long therapy is required for lung structural and functional normalization to occur. In this regard, complete asthma remission considers patients in whom clinical remission and improved airway inflammation (blood and sputum eosinophil counts, fraction of exhaled nitric oxide) and histopathological airway wall and lumen markers (ie, epithelium, basement membrane and smooth muscle) occur. Hence, the Global Initiative for Asthma (GINA) and other frameworks highlight the need to integrate cellular and imaging markers as well as pathology within remission criteria and definitions. Here, we present an overview of current remission definitions and their post-hoc analyses in asthma clinical trials as well as describe retrospective pulmonary imaging data and an image-based index of the reversal of airway and pulmonary vascular remodeling, observed in asthma. The Western-Imaging-Index (WIIN) harnesses the sensitivity and specificity of 129Xe magnetic resonance imaging (MR)I and computed tomography (CT) airway (ventilation-defect-percent, mucus-occlusions, wall thickness, lumen area, total airway count) and pulmonary vascular (small vessel blood volume) measurements. By integrating a novel imaging-index of lung normalization within the definition of asthma remission, we provide a way to untangle the relationship between clinical and complete remission in asthma patients on biologic therapy.