Evaluation of Airway Wall Thickness in Severe Asthma with monoclonal antibody therapy

Background: Anti-IgE monoclonal antibody omalizumab, anti-IL-5 antibody mepolizumab and benralizumab have been approved as step 5 treatment. In our previous study, the ratio of bronchial wall thickness to bronchial lumen diameter (T/D), and the percentage of airway wall area (WA%) were significantly decreased after treatment with monoclonal antibodies. However, it is difficult to evaluate airway wall thickness using routine 5-mm slice CT data due to the shortness of breath and heartbeat artifacts. Aims and Objectives: The purpose of this study is to compare two HRCT imaging methods, 5-mm slices quick mode (Q-mode; pitch factor 1.388) and 5-mm slices with electro cardiogram (ECG)-gated mode (ECG-mode), for the evaluation of bronchial thickness in patients with monoclonal antibodies. Methods: T/D and WA% were calculated with Q-mode and ECG-mode CT images. T/D and WA% were calculated at 6 selected levels: superior margin of the aortic arch, 1cm above carina, carina, 1cm below carina, level of inferior pulmonary veins, and 2cm above the diaphragm. Results: Thirty-four subjects (18.5%) required step 5 treatment. Thirty-four bronchi which were able to measure the same bronchus by both modes were evaluated. For T/D and WA%, no statistically significant difference was seen between Q-mode and ECG-mode (p=0.53, p=0.46 respectively). Tracheal walls were clearly visible with both modes. Conclusion: To evaluate the bronchial thickness in severe asthma with monoclonal antibodies, there were no significant differences between Q-mode and ECG-mode. Considering imaging time, image quality and exposure dose, Q-mode was better for evaluating tracheal wall thickness in severe asthma patients with monoclonal antibodies.