|Year : 2021 | Volume
| Issue : 1 | Page : 89-91
The yield of screening for COVID-19 in asymptomatic patients before elective or emergency surgery using chest computed tomography and reverse transcription polymerase chain reaction
Suvendu Sekhar Jena, Ravi Chandra Reddy Obili, Samiran Nundy
Department of Surgical Gastroenterology and Liver Transplantation, Sir Ganga Ram Hospital, New Delhi, India
|Date of Submission||17-Jan-2021|
|Date of Acceptance||06-Feb-2021|
|Date of Web Publication||25-Apr-2021|
Dr. Suvendu Sekhar Jena
Department of Surgical Gastroenterology and Liver Transplantation, Sir Ganga Ram Hospital, Room Number 1469, New Delhi - 110 060
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Jena SS, Obili RC, Nundy S. The yield of screening for COVID-19 in asymptomatic patients before elective or emergency surgery using chest computed tomography and reverse transcription polymerase chain reaction. J Med Evid 2021;2:89-91
|How to cite this URL:|
Jena SS, Obili RC, Nundy S. The yield of screening for COVID-19 in asymptomatic patients before elective or emergency surgery using chest computed tomography and reverse transcription polymerase chain reaction. J Med Evid [serial online] 2021 [cited 2022 Aug 12];2:89-91. Available from: http://www.journaljme.org/text.asp?2021/2/1/89/314636
Puylaert CA, Scheijmans JC, Borgstein AB, Andeweg CS, Bartels-Rutten A, Beets GL, et al. Yield of Screening for COVID-19 in asymptomatic patients before elective or emergency surgery using chest CT and RT-PCR (SCOUT). Ann Surg 2020;272:919-24.
| Article Information|| |
Since its origin in Wuhan, China, the COVID-19 virus has affected the entire globe. To accommodate the vast load of infected patients, the rest of the world has increased the number of hospital beds and halted many other medical services because much of the available manpower and resources has been directed towards managing patients with COVID-19 infection. As a result, most hospitals have had to stop all elective and some emergency operations.
However, after some time, it became apparent that patients waiting for surgery 'who did not have COVID-19' might suffer from a substantial amount of morbidity and mortality if left untreated so hospitals worldwide started to increase the number of elective operations performed. However, it was important to detect asymptomatic patients already infected with COVID-19 who were not only at an increased risk of post-operative morbidity and mortality but could also spread their infection to health-care workers (HCWs) as well as to their fellow patients. To prevent this, various hospitals across the world developed protocols to screen asymptomatic patients before surgery or even hospital admission. The Infectious Diseases Society of America guidelines on COVID–19 diagnosis recently advised pre-operative screening using SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) in all asymptomatic individuals undergoing surgery. However, the low sensitivity of SARS-CoV-2 RT-PCR (30%–50%) is a limiting factor in screening. To reduce the false-negative rate of the RT-PCR, computed tomography (CT) of the chest was introduced, which then began to play an important role in detecting lung abnormalities and facilitated early identification of COVID-19 infection. However, CT scanning of the chest is expensive and there is a risk of ionising radiation.
Therefore, the authors conducted a multicentre study in the Netherlands to compare the yield of a CT scan of the chest and RT-PCR for routine screening of patients scheduled for elective, emergency or other interventional procedures.
| Background|| |
The study was conducted at 3 academic and 11 non-academic hospitals across the Netherlands and its observational nature obviated the need for a formal ethical approval. Patients aged 18 years or older who were planned for surgical intervention were included and incapacitated emergency patients, in whom COVID-19 infection could not be ruled out, were excluded. They were divided into two groups, one had both a chest CT and COVID-19 RT-PCR and the other had a chest CT alone. Asymptomatic patients were identified by a specifically designed questionnaire, the CT chest was classified according to the CO-RADS classification (CO-RADS developed by the Dutch Radiological Society assesses the suspicion for pulmonary involvement of COVID-19 on a scale from 1 (very low) to 5 (very high)). RT-PCR was done using nasopharyngeal and/or oropharyngeal swab specimens and was performed using RT-PCR assays targeted at the viral envelope, RNA-dependent RNA polymerase and/or nucleocapsid genes and in those who came positive, the cycling threshold values were reported.
| Patients and Methods|| |
The primary study outcome was the yield of detected COVID-19 infection by the chest CT and RT-PCR, while the secondary outcomes were individual yields of chest CT and RT-PCR along with their relationship differences in community prevalence and operative management after screening. They collected 2-week follow-up data for all patients, which included the post-operative diagnosis of COVID-19-related complications and intensive care unit admissions. The relationship between community prevalence and screening results was established by collecting the prevalence data from the Dutch National Institute for Public Health and separately comparing the screening results for each.
| Outcomes Analysed|| |
A total of 2093 patients were included across 14 centres, out of which 1224 were screened by both CT and RT-PCR, while 869 by CT only. In the combined group, surgery was postponed in 17 patients (1.4%), while it was postponed in 2 patients (0.2%) in the CT chest only group. The combined diagnostic yield was 1.5%, of which RT-PCR had a yield of 1.1%. The incremental yield of the CT chest was found to be 0.4%. RT-PCR had a diagnostic yield of ~ 6% in areas of high community prevalence (>1.5/100,000), while it was low in areas of low prevalence (<1.5/100,000), but no relationship was observed in the CT chest group with community prevalence. Later, 3 patients in the CT chest only group and none from the combined group developed symptomatic COVID-19.
| Results|| |
Patients who have asymptomatic COVID-19 infection are now becoming a major area of concern. They not only expose HCW to the infection but other patients as well. According to the Centers for Disease Control (CDC), USA, 55% of HCWs from 9282 COVID-19 cases had had exposure in the hospital setting. In India, a recent study by Chatterjee et al. demonstrated that HCWs such as dentists who were exposed to the airways and oral cavities of patients for prolonged periods were at the greatest risk of infection. Hence, diagnosing asymptomatic cases is a major area of concern. Various studies have shown an increase in the morbidity and mortality in COVID-19-positive patients following surgery. To prevent this, many nations have devised protocols for screening asymptomatic patients based on the local transmission rate, type of surgery being done and the amount of presumed exposure. In June 2020, the Indian Council of Medical Research proposed that testing for COVID-19 should be done on asymptomatic patients coming for elective neurosurgery, ear–nose–throat surgery, dental procedures, gastrointestinal (GI) surgeries, orthopaedic procedures and for non-surgical interventions such as bronchoscopy, upper GI endoscopy, colonoscopy, endotracheal intubation and dialysis.
Whether the screening for COVID-19 infection should be done by RT-PCR or a chest CT is not yet clear. This is the first multicentre study to compare the yield of pre-operative screening for COVID-19 using RT-PCR and chest CT/RT-PCR. Although the addition of chest CT may have increased the yield of diagnosing asymptomatic cases, its routine use as a pre-operative screening test is questionable in view of the risk of radiation exposure, cost and the false-positive findings. Chest CT findings may be non-specific and share commonalities with other infections such as influenza and H1N1 due to which the CDC does not recommend its routine use for diagnosing COVID-19 patients. This might explain the false-positive rate of CT chest in the current study. The Royal College of Radiologists in the UK also concurred that there was no current role for CT in suspected COVID-19 in March 2020 but later stated that chest CT may be used in the absence of rapid access to other COVID-19 tests in acutely ill patients requiring an abdominal CT and possibly needing emergency surgery. Although they used the low-dose CT chest, the radiation exposure is still higher than after a chest X-ray. Another limiting factor in CT chest is its cost to utility ratio. In a study by Sriwijitali and Wiwanitkit from Thailand, the cost to utility ratio is higher for CT chest in comparison to RT-PCR and was 96.6 versus 71.53. The availability of CT chest facilities is also a major limiting factor in any third world country.
However, RT-PCR also has its own limitations like a false-negative rate when used too early or too late in the disease. It has been shown that the probability of a false-negative RT-PCR test on day 1 after infection is 100% and it decreases to 67% on day 4, 20% on day 8 and increases again to 66% on day 21. The sampling error rate of RT-PCR is also high.
The authors had concluded that CT chest should not be used as a routine screening tool to detect asymptomatic patients before elective surgery. It has the disadvantages of radiation exposure, a high false-positive rate, a high cost to utility ratio and a lack of 24 h availability. This high cost to utility ratio and poor availability is important for developing countries which generally have limited health resources.
Therefore, according to this study, RT-PCR which is cheaper, available and nearly as accurate as a chest CT should be routinely used as a screening tool to detect COVID-19 infection in asymptomatic patients before elective operations. CT chest may be used in special circumstances like emergency procedures.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| Commentary|| |
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