1. Introduction
ince late 2019, with the emergence of Coronavirus Disease 2019 (COVID-19), as a causative agent of a new respiratory disease, there have been many concerns about the spread of this disease and how to deal with it. The virus that causes this severe acute respiratory syndrome is named SARS-CoV-2 and was first reported in Wuhan, Hubei, China [1]. Due to the rapid transmission ability of this virus, diagnosing the infected individuals in the early stages for isolating them is critical. Based on the latest guidelines, Reverse Transcription-Polymerase Chain Reaction (RT-PCR) is the gold standard method for COVID-19 diagnosis [9]. Regarding the limitations of RT-PCR and the importance of early diagnosis of COVID-19 for reducing the morbidity and mortality rates and preventing the further spread, a faster method with higher sensitivity is crucial. The aim of this study is to evaluate the reliability of Computerized Tomography (CT) scan for diagnosing COVID-19.
2. Materials and Methods
In this retrospective study, participants were 212 patients with suspected COVID-19 hospitalized in one of hospitals in Tehran, Iran who had underwent both RT-PCR test and chest CT scan. Demographic information, medical history, symptoms, and the CT scan results were collected and analyzed. Finally, the CT scan results were compared with the RT-PCR test results.
3. Results
According to the results, 57% of patients were male and 43% were female, and most of them (46%) of patients were over 60 years old. Of 212 patients, 189 had positive COVID-19 CT scan results and 23 had negative results. Moreover, of 212 patients, 147 had positive COVID-19 RT-PCR test results and 65 had negative results. The COVID-19 positive rate based on the chest CT scan and initial RT-PCR test results was 89% and 69%, respectively. With RT-PCR test results as the reference, the sensitivity, specificity, Negative Predictive Value (PPV), Negative Predictive Value (NPV), and accuracy of CT scan in diagnosing COVID-19 were 91.83% (95% CI:87.3-93.1%), 23.07% (95% CI:15.9-24.4%), 71.42% (95% CI:68.4-74.4%), 61.11% (95% CI:53.5-67.1%), and 70.75% (95% CI:63.8-71.9%), respectively (Table 1). 


4. Discussion and Conclusion
Several studies have shown that the chest CT scan had higher sensitivity in COVID-19 diagnosis [10]. In our study, sensitivity and specificity of chest CT scan were reported 91.83% and 23.7%, respectively, based on the overall positive RT-PCR test results. Ai et al. [10] reported higher sensitivity (98% and 97%, respectively) for the chest CT scan in COVID-19 diagnosis, but in terms of specificity, our results is close to the results of Ai et al. on 1014 cases [10]. Our results indicated that the chest CT scan had high sensitivity compared to initial RT-PCR test in COVID-19 diagnosis. Furthermore, the results of the initial RT-PCR test may be false-negative, suggesting that the symptomatic patients with or without positive chest CT results should be isolated, and repeated RT-PCR test can help avoid misdiagnosis and finally lead to early treatment, and preventing further spread of COVID-19.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Research Ethics Committee of AJA University of Medical Sciences (Code: IR.AJAUMS.REC.1399.099).

Funding
This study was financially supported by the AJA University of Medical Sciences.

Authors' contributions
Conceptualization, methodology and analysis: Emran Esmailzadeh and Mehrdad Nasrollahzadeh Sabet; Research, references, drafting, editing and finalization: Mohammad Khanalipour, Mohammad Fouad Heidari, Saadatullah Ghaffari, Milad Jafari Ashiani and Sajjad Bigleri.

Conflicts of interest
The authors declared no conflict of interest.


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