ABSTRACT
Coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China, in December 2019 as an out-break of pneumonia of unknown origin. Previous studies have suggested the utility of chest computed tomography (CT) in the diagnosis of COVID-19 because of its high sensitivity (93%-97%), relatively simple procedure, and rapid test results. This study, performed in Japan early in the epidemic when COV1D-19 prevalence was low, evaluated the diagnostic accuracy of chest CT in a population present-ing with lung diseases having CT findings similar to those of COVID-19. We retrospectively included all consecutive patients (18 years old) presenting to the outpatient department of Keio University Hospital between March 1 and May 31, 2020, with fever and respiratory symptoms. We evaluated the perfor-mance of diagnostic CT for COVID-19 by using polymerase chain reaction (PCR) results as the refer-ence standard. We determined the numbers of false-positive (FP) results and assessed the clinical utility using decision curve analysis. Of the 175 patients, 22 were PCR-positive. CT had a sensitivity of 68% and a specificity of 57%. Patients with FP results on CT diagnosis were mainly diagnosed with diseases mimicking COVID-19, e.g., interstitial lung disease. Decision curve analysis indicated that the clinical utility of CT imaging was limited. The diagnostic performance of CT for COVID-19 was inadequate in an area with low COV ID-19 prevalence and a high prevalence of other lung diseases with chest CT findings similar to those of COVID-19. Considering this insufficient diagnostic performance, CT findings should be evaluated in the context of additional medical information to diagnose COVID-19.