The Role of Chest CT in Deciphering Interstitial Lung Involvement: Systemic Sclerosis Versus COVID-19

Background: In clinical practice, the striking similarities observed at computed tomography (CT) between diseases make it difficult to distinguish a COVID-19 pneumonia from progression of interstitial lung disease (ILD) secondary Systemic sclerosis (SSc). The aim present study was identify main CT features that may help distinguishing SSc-ILD pneumonia. Methods: This multicentric included 22 international readers divided in radiologist group (RAD) and non-radiologist (nRAD). A total 99 patients, 52 with 47 SSc-ILD, were study. Findings:  Fibrosis inside focal ground glass opacities (GGO) upper lobes; fibrosis lower lobe GGO; reticulations lobes (especially if bilateral symmetrical or associated signs fibrosis) most frequently SSc-ILD.  COVID- 19 were: consolidation (CONS) lobes, CONS peripheral (both central/peripheral patchy distributions), anterior posterior rounded-shaped GGOs lobes. After multivariate analysis, presence (p <0.0001) GGO remained independently respectively. predictive score weas created which resulted positively diagnosis (96.1% sensitivity 83.3% specificity). Interpretation: differential is possible through combination our radiologic expertise. If an overlap both suspected, suggest while indicate SSc-ILD. Funding: No Funding received for this study. Declaration Interests: SC reports personal fees NOVARTIS-SANOFI-LILLY-CELTHER-PFIZER-JANSSEN; MK grants Boehringer-Ingelheim, Corbus, Chugai, Ono Pharmeceuticals, Tanabe-Mitsubishi, Astellas, Gilead, Mochida; ST Boehringer Ingelheim, Roche, outside submitted work; GS Ingelheim; CB Actelion, Eli Lilly, European Scleroderma Trial Research (EUSTAR) group, New Horizon Fellowship, Foundation Rheumatology (FOREUM), Fondazione Italiana per la Ricerca sull'Artrite (FIRA); CV F. Hoffmann-La Roche Ltd.; FL lectures fee Boehringer- CPD GSK, Boerhinger Servier, Inventiva, Arxx Therapeutics, Sanofi, Roche; Orion Pharma, AstraZeneca, MSD, HIKMA, Trudell International, Chiesi Farmaceutici, Novartis Pharma; MH Speaking lilly Pfizer; D K Bayer, Ingelhem, CSL Behring, Horizon, Pfizer, BMS, Dr Khanna Chief Medical officer Eicos Sciences Inc has stock options. All mentioned authors declared previous feed work. other declare no competing interests. Ethics Approval Statement: retrospective, observational, multicentric, approved by Institutional Ethics Committee Florence Careggi hospital (protocol number 17104_oss).