Chest CT scans recommended for COVID‑19 screening

Monday, 02 March, 2020

Chest CT scans recommended for COVID‑19 screening

Chinese researchers have found that computed tomography (CT) of the chest demonstrates better sensitivity than reverse-transcription polymerase chain reaction (RT-PCR) when it comes to diagnosing the 2019 novel coronavirus disease (COVID-19).

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. According to the latest guidelines published by the Chinese Government, the diagnosis of COVID-19 must be confirmed by 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 has been reported to be about 30–60% at initial presentation. The low sensitivity of RT-PCR thus 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.

With this in mind, researchers at Tongji Hospital in Wuhan set out to investigate the diagnostic value and consistency of chest CT imaging in comparison to RT-PCR assay in COVID-19. Their study of 1014 patients, who underwent both chest CT and RT-PCR tests between 6 January and 6 February, was published in the journal Radiology.

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 study authors wrote.

The researchers concluded that CT should be used as the primary screening tool for COVID-19, writing, “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.”

Meanwhile, scientists at The University of Queensland (UQ) have met a key milestone in their fast-tracked research to develop a vaccine for COVID-19, as part of the Coalition for Epidemic Preparedness Innovations (CEPI) rapid response program. In just three weeks, the team has created their first vaccine candidate in the laboratory and will move immediately into further development before formal preclinical testing.

The work in the lab shows the feasibility of using UQ’s ‘molecular clamp’ technology to engineer a vaccine candidate that could be more readily recognised by the immune system, triggering a protective immune response. The next stage is to produce this on a larger scale needed for additional testing, to determine its effectiveness against the virus.

“There is still extensive testing to ensure that the vaccine candidate is safe and creates an effective immune response, but the technology and the dedication of these researchers means the first hurdle has been passed,” said UQ Vice-Chancellor and President Professor Peter Høj.

The scientists said the early research had gone “as expected” and the material created had the properties that allowed the team to proceed with vaccine development. The group continues to work to a much-accelerated timetable to keep on track for investigational clinical testing after the middle of the year.

Image caption: UQ scientists are busy in the lab, as part of an international collaboration to develop a vaccine for the recent coronavirus outbreak.

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