Indian Journal of Health Sciences and Biomedical Research KLEU

: 2020  |  Volume : 13  |  Issue : 3  |  Page : 175--177

Chest computed tomography in relation to reverse-transcription polymerase chain reaction in diagnosis of coronavirus disease 2019

Rajendra B Nerli1, Shridhar C Ghagane2,  
1 Department of Urology, JN Medical College, KLE Academy of Higher Education and Research, JNMC Campus, Belagavi, Karnataka, India
2 Department of Urology, Urinary Biomarkers Research Centre, KLES Dr. Prabhakar Kore Hospital and Medical Research Centre, Belagavi, Karnataka, India

Correspondence Address:
Dr. Shridhar C Ghagane
Department of Urology, Urinary Biomarkers Research Centre, KLES Dr. Prabhakar Kore Hospital and Medical Research Centre, Belagavi - 590 010, Karnataka

How to cite this article:
Nerli RB, Ghagane SC. Chest computed tomography in relation to reverse-transcription polymerase chain reaction in diagnosis of coronavirus disease 2019.Indian J Health Sci Biomed Res 2020;13:175-177

How to cite this URL:
Nerli RB, Ghagane SC. Chest computed tomography in relation to reverse-transcription polymerase chain reaction in diagnosis of coronavirus disease 2019. Indian J Health Sci Biomed Res [serial online] 2020 [cited 2021 Jan 25 ];13:175-177
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Full Text

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified from Wuhan city, Hubei province, China, in December 2019. SARS-CoV-2 is a part of the Coronavirdae family that includes the common cold, SARS, and Middle East respiratory syndrome. COVID-19 is the seventh member of the coronavirus family which infects humans.[1],[2] These viruses can cause acute respiratory distress syndrome (ARDS), bilateral pneumonia, and pulmonary failure, leading to severe morbidity and at times even death.[1],[2],[3] As of now, there is no highly effective pharmacological therapy identified for COVID-19, further highlighting the importance of early detection and isolation of COVID-19 patients to prevent the spread of the disease.

Several previous studies have shown that the vast majority of patients with COVID-19 had clinical symptoms, including fever and cough. Reverse-transcription polymerase chain reaction (RT-PCR) test is currently the gold standard diagnostic tool for COVID-19. The RT-PCR assays can be performed on the nasopharyngeal and/or oropharyngeal swabs, sputum, blood samples, body fluids, stool samples, and bronchoalveolar lavage fluid.[4] Because of strong infectivity of COVID-19, rapid and accurate diagnostic methods are urgently required to identify, isolate, and treat the patients as soon as possible, which could reduce mortality rates and the risk of public contamination. However, real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) results often require a long time for reports to be made. Initially, due to increased load, the time taken for reporting was 2–3 days.

Computed tomography (CT) of the chest has become a standard of care in the diagnosis and assessment of a variety of respiratory conditions, such as interstitial lung disease and lung cancer, and optimizes the management process. Although CT scans are not routinely used to diagnose ARDS, certain complications relating to mechanical ventilation including pneumonia, pneumothorax, and emphysema are sometimes identified by CT but not by chest radiography. In addition, CT imaging has been used to identify lung atelectasis due to poor positioning of the endotracheal tube as well as potentially directing ventilation to achieve optimal pressures and air recruitment. This is important in relation to COVID-19 since patients in intensive care units (ICUs) require optimization of ventilatory settings, and it is increasingly recognized that prone ventilation appears favorable. Nevertheless, in the clinical setting, the benefits of routine CT imaging must be weighed against the considerable practicalities and risks, including that of infection transmission associated with transporting a patient from the ICU, or elsewhere in the hospital, to the radiology department.

The Royal College of Radiologists, the American Society of Emergency Radiology, and the Society of Thoracic Radiology do not recommend the use of CT scanning as a diagnostic tool for COVID-19. As a negative CT finding does not rule out COVID-19 infection.[5],[6] Fang et al.[7] retrospectively analyzed the patient's data at Taizhou Enze Medical Center from January 19, 2020, to February 4, 2020. During this period, chest CT and RT-PCR were performed for consecutive patients who presented with (a) a travel history to or residential history in Wuhan or local endemic areas or contact with individuals from these areas with fever or respiratory symptoms within 14 days and (b) fever or acute respiratory symptoms of unknown cause. In case of an initial negative RT-PCR test, repeat testing was performed at intervals of 1 day or more. The average time from initial symptom onset to CT was 3 days ± 3 (standard deviation); the average time from initial symptom onset to RT-PCR testing was 3 days ± 3. Of the 51 patients, 36 had initial positive RT-PCR findings for COVID-19. COVID-19 was confirmed in 12 of the 51 patients with two RT-PCR nucleic acid tests (1–2 days), in two patients with three tests (2–5 days), and one patient with four tests (7 days) after initial onset. Fifty of the 51 patients (98%) had evidence of abnormal CT findings compatible with viral pneumonia at baseline; one patient had a normal CT scan. In this patient sample, the detection rate for initial CT (50 of 51 patients [98%]; 95% confidence interval: 90%, 100%) was greater than that for the first RT-PCR (36 of 51 patients [71%]; 95% confidence interval: 56%, 83%) (P < 0.001).

Ai et al.[8] investigated the diagnostic value and consistency of chest CT when compared with RT-PCR assay in COVID-19. They included 1014 patients in Wuhan, who underwent both chest CT and RT-PCR tests between January 6 and February 6, 2020. With the use of RT-PCR as the reference standard, the performance of chest CT in the diagnosis of COVID-19 was assessed. In addition, for patients with multiple RT-PCR assays, the dynamic conversion of RT-PCR results (negative to positive, positive to negative) was analyzed as compared to serial chest CT scans for those with a time interval between RT-PCR tests of 4 days or more. Of the 1014 patients, 601 of 1014 (59%) had positive RT-PCR results and 888 of 1014 (88%) had positive chest CT scans. The sensitivity of chest CT in suggesting COVID-19 was 97% (95% confidence interval: 95%, 98%; 580 of 601 patients) based on the positive RT-PCR results. At analysis of serial RT-PCR assays and CT scans, the mean interval between the initial negative and positive RT-PCR results was 5.1 days ± 1.5; the mean interval between initial positive and subsequent negative RT-PCR results was 6.9 days ± 2.3. Of the 1014 patients, 60% (34 of 57) to 93% (14 of 15) had initial positive CT scans consistent with COVID-19 before (or parallel to) the initial positive RT-PCR results. Twenty-four of 57 patients (42%) showed improvement on follow-up chest CT scans before the RT-PCR results turned negative. The authors concluded that chest CT had a high sensitivity for the diagnosis of COVID-19. Chest CT may be considered as a primary tool for the current COVID-19 detection in epidemic areas.

Gietema et al.[9] investigated the diagnostic accuracy of CT using RT-PCR for SARS-CoV-2 as the reference standard and investigated reasons for discordant results between the two tests. In a single-center study in the Netherlands, all adult symptomatic emergency department (ED) patients had both a CT scan and an RT-PCR upon arrival at the ED. CT results were compared with the PCR test(s). Between March 13 and March 24, 2020, 193 symptomatic ED patients were included. In total, 43.0% of patients had a positive PCR and 56.5% had a positive CT, resulting in a sensitivity of 89.2%, a specificity of 68.2%, a likelihood ratio (LR)+ of 2.81, and an LR− of 0.16. Sensitivity was higher in patients with high-risk pneumonia (CURB-65 score ≥3; n = 17, 100%) and with sepsis (SOFA score ≥2; n = 137, 95.5%). Of the 35 patients (31.8%) with a suspicious CT and a negative RT-PCR, nine had another respiratory viral pathogen, and in seven patients, COVID-19 was considered likely. One of nine patients with a nonsuspicious CT and a positive PCR had developed symptoms within 48 h before scanning. The authors concluded that the accuracy of chest CT in symptomatic ED patients was high; however, when used as a single diagnostic test, CT could not safely diagnose or exclude COVID-19. However, CT can be used as a quick tool to categorize patients into “probably positive” and “probably negative” cohorts.

Long et al.[1] evaluated the diagnostic value of CT and rRT-PCR for COVID-19 pneumonia. The study included all patients with COVID-19 pneumonia suspicion and who were examined by both CT and rRT-PCR at initial presentation. A total of 36 patients were finally diagnosed with COVID-19 pneumonia. Thirty-five patients had abnormal CT findings at presentation, whereas one patient had a normal CT. Using rRT-PCR, 30 patients were tested positive, with six cases initially missed. Among these six patients, three became positive in the second rRT-PCR assay (after 2, 2 days, and 3, respectively), and the other three became positive only in the third round of rRT-PCR tests (after 5, 6, and 8 days, respectively). At presentation, CT sensitivity was therefore 97.2%, whereas the sensitivity of initial rRT-PCR was only 83.3%. The authors concluded that rRT-PCR may produce initial false-negative results. They suggested that patients with typical CT findings but with negative rRT-PCR results should be isolated, and rRT-PCR should be repeated to avoid misdiagnosis.


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