LAUSR

Abstract Objectives To evaluate the diagnostic and prognostic performance of CT in patients referred for COVID19 suspicion to a French university hospital, depending on symptoms and date of onset. Methods From March 1st to March 28th, 214 patients having both chest CT scan and reverse transcriptase polymerase chain reaction (RT- PCT) within 24 hours were retrospectively evaluated. Sensitivity, specificity, negative and positive predictive values of first and expert readings were calculated together with inter reader agreement, with results of RT-PCR as standard of reference and according to symptoms and onset date. Patient characteristics and disease extent on CT were correlated to short-term outcome (death or intubation at 3 weeks follow-up). Results Of the 214 patients (119 men, mean age 59 ± 19 years), 129 had at least one positive RT-PCR result. Sensitivity, specificity, negative and positive predictive values were 79% (95% CI: 71- 86%), 84%(74- 91%), 72%(63-81%) and 88% (81-93%) for initial CT reading and 81%(74- 88%), 91% (82-96%), 76% (67-84%) and 93% (87-97%), for expert reading, with strong inter-reader agreement (kappa index: 0.89). Considering the 123 patients with symptoms for more than 5 days, the corresponding figures were 90%, 78%, 80% and 89% for initial reading and 93%, 88%, 86% and 94% for the expert. Disease extent exceeded 25% for 68% and 26% of severe and non-severe patients, respectively (p < 0.001). Conclusion CT sensitivity increased after 5 days of symptoms. A disease extent > 25% was associated with poorer outcome.