The role of chest ct in understanding interstitial lung disease (ILD): Systemic sclerosis (SSC). versus COVID-19

ABSTRACT

Background: COVID-19 pandemic is a global emergency which may overlap on the clinical and radiological scenario of ILD in SSc. In clinical practice, the striking similarities observed at computed tomography (CT) between the diseases make it difficult to distinguish a COVID-19 superinfection from a progression of SSc-ILD. Objectives: The aim of our study was to identify the main CT features that may help distinguishing SSc-ILD from COVID-19 pneumonia. Methods: 22 international readers were included and divided in the radiologist group (RAD) and non-radiologist group (nRAD). The RAD group included nonchest RAD and chest-RAD. A total of 99 patients, 52 with COVID-19 and 47 with SSc-ILD, were included in the study. Results: Fibrosis inside focal ground glass opacities (GGO) in the upper lobes;fibrosis in the lower lobe GGO;reticulations in lower lobes (especially if bilateral and symmetrical or associated with signs of fibrosis) were the CT parameters most frequently associated with SSc-ILD. The CT parameters most frequently associated with COVID-19 pneumonia were consolidation (CONS) in the lower lobes, CONS with peripheral (both central/peripheral or patchy distributions), anterior and posterior CONS and rounded-shaped GGOs in the lower lobes. After multivariate analysis, the presence of CONS in the lower lobes (p <0.0001) and signs of fibrosis in GGO in the lower lobes (p <0.0001) remained independently associated with COVID-19 pneumonia or SSc-ILD, respectively. These two variables were combined in a predictive score which resulted positively associated with the COVID-19 diagnosis, with 96.1% sensitivity and 83.3% specificity 3 different risk class for COVID-19 pneumonia may be identified high risk for COVID-19 pneumonia (5-9 points);probable overlap COVID-19 pneumonia in SSc-ILD (4 points);low risk for COVID-19 pneumonia (0-3 points). Conclusion: The CT differential diagnosis between COVID-19 Pneumonia and SSc-ILD is possible and may be fostered in practice by the use of a radiological score. In the case where an overlap of both diseases is suspected, the presence of consolidation in the lower lobes may suggest a COVID-19 pneumonia while the presence of fibrosis inside GGO may indicate a SSc-ILD.