In a study of more than 1,000 patients published in the journal Radiology, researchers from Tongji Hospital- Wuhan in China, concluded that CT should be used as the primary screening tool for COVID-19.
According to the researchers, in the absence of specific therapeutic drugs or vaccines for COVID-19, it is essential to detect the disease at an early stage and immediately isolate an infected patient from the healthy population.
“Early diagnosis of COVID-19 is crucial for disease treatment and control. Compared to RT-PCR, chest CT imaging may be a more reliable, practical and rapid method to diagnose and assess COVID-19, especially in the epidemic area,” the authors wrote.
According to the latest guidelines published by the Chinese government, the diagnosis of COVID-19 must be confirmed by reverse-transcription polymerase chain reaction (RT-PCR) or gene sequencing for respiratory or blood specimens, as the key indicator for hospitalisation.
However, with limitations of sample collection and transportation, as well as kit performance, the total positive rate of RT-PCR for throat swab samples have been reported to be about 30 per cent to 60 per cent at initial presentation.
In the current public health emergency, the low sensitivity of RT-PCR implies that a large number of COVID-19 patients won’t be identified quickly and may not receive appropriate treatment.
In addition, given the highly contagious nature of the virus, they carry a risk of infecting a larger population.
According to the researchers, recent research found that the sensitivity of CT for COVID-19 infection was 98 per cent compared to RT-PCR sensitivity of 71 per cent.
For the current study, researchers, set out to investigate the diagnostic value and consistency of chest CT imaging in comparison to RT-PCR assay in COVID-19.
Included in the study were 1,014 patients who underwent both chest CT and RT-PCR tests between January 6 and February 6.
With RT-PCR as reference standard, the performance of chest CT in diagnosing COVID-19 was assessed.
For patients with multiple RT-PCR assays, the dynamic conversion of RT-PCR test results (negative to positive, and positive to negative, respectively) was also analysed as compared with serial chest CT scans.
The results showed that 601 patients (59 per cent) had positive RT-PCR results, and 888 (88 per cent) had positive chest CT scans.
The sensitivity of chest CT in suggesting COVID-19 was 97 per cent, based on positive RT-PCR results.
In patients with negative RT-PCR results, 75 per cent (308 of 413 patients) had positive chest CT findings.
Of these, 48 per cent were considered as highly likely cases, with 33 per cent as probable cases.
By analysis of serial RT-PCR assays and CT scans, the interval between the initial negative to positive RT-PCR results was four to eight days.
“About 81 per cent of the patients with negative RT-PCR results but positive chest CT scans were re-classified as highly likely or probable cases with COVID-19, by the comprehensive analysis of clinical symptoms, typical CT manifestations and dynamic CT follow-ups,” the authors wrote.