Evaluation of CT Scan Diagnostic Value in the Novel Coronavirus Disease and Presenting a Corona CT Severity Index

Abstract

Background: Several diagnostic methods have been proposed and evaluated for the COVID-19 disease. However, the published studies have reported different diagnostic values for these methods. Aims: The present study aimed to evaluate the diagnostic performance and accuracy of CT in the novel corona virus disease (COVID-19) and to develop and present a Corona CT severity index. Methods: The CT diagnostic performance was measured based on sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy, and RT-PCR was regarded as a standard. Patients’ CT reports were evaluated by a radiologist, and scoring and calculating of the CT severity index were performed. Results: Of 208 patients, 82 showed positive and 126 showed negative RT-PCR results with a positive frequency of 39.4% (95% CI, 32.7-46.4). The chest CT scan related to 136 patients indicated COVID-19, whereas their initial RT-PCR assays of 56 patients were negative. Considering RT-PCR results as reference standard, the sensitivity, specificity, and accuracy of chest CT to indicate COVID-19 infection was 100%, 55.6% (95% CI 46.4-64.4%), and 72.8% (95% CI 66.2-78.8%), respectively. The severity of pulmonary involvement was assigned with different grades. For 60.7% of patients with severity grades of 2 to 6, who showed the involvement of at least one lung lobe in CT, PCR retrieved negative results. Conclusion: CT scan represents an appropriate sensitivity as well as a consistently higher specificity to diagnose COVID-19 pneumonia than PCR. It can be regarded as a primary tool to detect the current COVID-19 in epidemic regions.