Retrospective comparison of high-resolution computed tomography of eosinophilic granulomatosis with polyangiitis with severe asthma

Background Eosinophilic granulomatosis with polyangiitis (EGPA) is often misdiagnosed as severe asthma due to their similar clinical presentations. We compared the pulmonary radiologic features of EGPA to those of severe asthma by high-resolution computed tomography (HRCT) in order to early diagnose EGPA. Methods We retrospectively reviewed clinical records and HRCT findings of 96 patients with EGPA and 82 patients with severe asthma who were seen at our hospital from 2011 to 2017. We used a semi-quantitative grading system to evaluate radiological findings. A radiological only and a clinical-radiological model were used to differentiate EGPA from severe asthma. Results Bronchial wall thickening, air trapping, tree-in-bud opacities, bronchial mucus plugging, bronchiectasis, diffuse ground-glass opacities (GGOs), consolidation, and increased small vascular markings were more common in EGPA patients than in severe asthmatics (P<0.05). The gradings of GGO (grade 2 vs. grade 1) and tree-in-bud opacities (grade 2 vs. grade 0) were higher in EGPA patients than in severe asthmatics. The total image score of EGPA patients was significantly higher than that of severe asthmatics (P<0.05). In the radiological only and the clinical-radiological model, the area under the receiver operating characteristic (ROC) curves (AUCs) for the identification of EGPA and severe asthma were 0.904 [95% confidence interval (CI): 0.860 to 0.948] and 0.974 (95% CI: 0.955 to 0.993), respectively. Conclusions Lung HRCT scan is useful in differentiating EGPA from severe asthma. In patients with difficult-to-treat asthma, an HRCT scan of the thorax should be performed should there be features that raise the suspicion of EGPA.