Asthma is a major health issue worldwide, and there is a need for noninvasive assessment tools to better understand the disease process and reproducibly quantify the disease burden in relation to the disease severity. Three-dimensional (3D) computed tomography (CT) has a long-standing and proven efficacy to perform this task, as it enables quantification of the bronchial dimensions, which were previously found to correlate with pathological biomarkers of airway remodeling1,2—a key feature that is associated with the development of severe asthma.

The study by Obojski et al3 provides new insights into noninvasive assessment of quantifiable bronchial parameters. In their study, the authors used 3D CT to perform a quantitative measurement of the airways from the third to the ninth bronchial generation. In the analyzed cohort, the bronchial wall was found to be more thickened in asthmatic patients than in healthy controls, especially in the more distal airways, which is in line with the results of previous studies.1

The novelty of the study by Obojski et al3 lies in their comparison of 2 well-characterized asthma subgroups divided according to the Global Initiative for Asthma classification, that is, individuals with severe (n = 22) and nonsevere asthma (n = 48). All patients were in a stable and controlled phase of the disease during examination. Interestingly, there was no significant difference in the bronchial wall or lumen area between these 2 groups, although the results of pulmonary function tests were found to be more altered in the patients with severe asthma.

This finding is novel and deserves to be commented on. Indeed, if airway remodeling was related to the disease severity, a difference in airway wall thickness between the groups could be expected. Conversely, Obojski et al3 postulated that the airway remodeling process could start early in the disease course, which would explain the discrepancy between structural and functional test results. The small distal airways were not analyzed in the study; therefore, it remains unclear whether there is a difference between measurements of central and distal airways, which would clarify the lack of correlation between central airway dimensions and pulmonary function test results. However, regardless of whether the small distal airways were similarly altered in the asthma groups or not, it would not affect the observation that a similar level of bronchial remodeling was found for the central airways.

It is also noteworthy that, despite upgrades in the spatial resolution of CT scans, this modality is still limited in its capacity to characterize the airway wall components. Therefore, this study may promote further attempts to obtain a more specific visualization of the airway wall components with tools such as magnetic resonance imaging (MRI) of the lungs or spectral CT. Lung MRI has recently proven its ability to provide high-resolution morphological imaging in asthma,4 and to enable discrimination between various forms of bronchial inflammatory processes,5 which should be worth evaluating in asthma. Spectral CT may further improve the spatial resolution of CT scans, with a possibility of additional tissue characterization.6 Another research group also proposed to quantify the airway wall attenuation to get an additional insight into the airway wall components.7 Therefore, a key remaining question is, apart from airway dimensions, whether there is a difference in airway wall composition between the groups of patients with varying degrees of asthma severity.

Overall, the result of the study by Obojski et al3 shed additional light on the airway remodeling process and raised new questions. Future investigations should further explore the underlying mechanisms and clinical consequences of airway remodeling, using more specific imaging tools and longitudinal studies.