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Lung India Official publication of Indian Chest Society  
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Year : 2021  |  Volume : 38  |  Issue : 7  |  Page : 11-21

Diagnostic accuracy of chest computed tomography in improving the false negative rate as compared to reverse transcriptase polymerase chain reaction in coronavirus disease 2019 pneumonia: A cross sectional analysis of 348 cases from India

Department of Radiology, St. John's Hospital, Kattappana, Kerala, India

Correspondence Address:
Dr. Reddy Ravikanth
Department of Radiology, St. John's Hospital, Kattappana - 685 515, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/lungindia.lungindia_410_20

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Background: Early differentiation between emergency department (ED) patients with and without coronavirus disease 2019 (COVID-19) is very important. The diagnosis of COVID-19 depends on real-time reverse transcriptase polymerase chain reaction (RT-PCR). On imaging, computed tomography (CT) manifestations resemble those seen in viral pneumonias, with multifocal ground-glass opacities and consolidation in a peripheral distribution being the most common findings. Although these findings lack specificity for COVID-19 diagnosis on imaging grounds, CT could be used to provide objective assessment about the extension of the lung opacities, which could be used as an imaging surrogate for disease burden. We set out to investigate the diagnostic accuracy of chest CT scanning in detecting COVID-19 in a population with suspected COVID-19 patients. Materials and Methods: In this cross-sectional single-center study performed on 348 cases with clinical suspicion of COVID-19, all adult symptomatic ED patients had both a CT scan and a PCR upon arrival at. CT results were compared with PCR test (s) and diagnostic accuracy was calculated. Results: Between February 15, 2020, and June 30, 2020, 348 symptomatic patients were included. In total, 62.3% of patients had a positive PCR and 69.8% had a positive CT, resulting in a sensitivity of 94.2%, specificity of 76.7%, likelihood ratio (LR) of +2.94 and (LR) −0.18. The sensitivity of the CT tended to be higher in those with acute respiratory distress syndrome (100.0%, P = 0.017) and severe COVID-19 (98.5%, P = 0.027) than in patients with mild (82.5%, P = 0.047) and moderate COVID-19 (89.3%, P = 0.039). The diagnostic ability of chest CT was found to be high with 86.3% concordance between findings of CT and PCR. In 48 (13.7%) patients, discordant findings between CT and PCR were observed. In most cases, the CT scan was considered suspicious for COVID-19, while the PCR was negative (37/48, 77.0%). In the majority of these, the diagnosis at discharge was pulmonary infection (n = 26; 54.1%). Conclusion: The accuracy of chest CT in symptomatic COVID suspect patients is high, but when used as a single diagnostic test, CT cannot accurately diagnose or exclude COVID-19. Therefore, we recommend a combination of both CT and RT-PCR for future follow-up, management, and medical surveillance.

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