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

Background: Several diagnostic methods were proposed and evaluated for the COVID-19 disease. However, 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 coronavirus disease (COVID-19) and developed and presented a Corona CT severity index. Methods: In this retrospective study, 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 the initial RT-PCR assays of 56 patients were negative. Considering RT-PCR results as the reference standard, the sensitivity, specificity, and accuracy of chest CT to indicate COVID-19 infection were 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 shows an acceptable sensitivity as well as a consistently better specificity to identify COVID-19 pneumonia than PCR. It may be considered a major method to identify COVID-19 in epidemic locations.