Study suggests chest CT to diagnose COVID-19

A Chinese study of more than 1000 patients has found that chest CT outperformed lab testing in the diagnosis of COVID-19. Publishing their findings in Radiology, the researchers from Tongji Hospital in Wuhan, China, concluded that CT should be used as the primary screening tool for COVID-19.

Without specific treatments or vaccines for COVID-19, it is essential to detect the disease at an early stage and immediately isolate infected patients from the healthy population.

According to the latest guidelines published by the Chinese government, a 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 is reported at 30–60% at initial presentation.

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.

“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 said.

Recent research found that the sensitivity of CT for COVID-19 infection was 98% compared with 71% for RT-PCR.

To assess the performance of chest CT in diagnosing COVID-19 in the current study, 1014 patients underwent both chest CT and RT-PCR tests, with RT-PCR as the reference standard.

The results showed that 59% of patients had positive RT-PCR results and 88% had positive chest CT scans. The sensitivity of chest CT in suggesting COVID-19 was 97%, based on positive RT-PCR results.

In patients with negative RT-PCR results, 75% had positive chest CT findings. Of these, 48% were considered as highly likely cases, with 33% 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 4–8 days.

“About 81% 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.

Image credit: ©stock.adobe.com/au/Dmytro Flisak