25 September 2020

ANU researchers find undetected COVID-19 cases with new blood test

| Michael Weaver
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Person receiving blood test on middle finger.

Antibody blood testing for COVID-19 at the ANU’s John Curtin School of Medical Research. Photo: Jamie Kidston/ANU.

Another weapon in the armoury to combat further waves of the COVID-19 virus has been developed by researchers at the Australian National University (ANU) who have discovered many more people have been exposed to the virus in Australia than have been detected so far.

The new blood test, developed by the ANU research team at the John Curtin School of Medical Research, looks for antibody signatures in the blood to find evidence of previous COVID-19 infection.

The testing was conducted at ANU between 2 June and 17 July – before Melbourne’s second wave outbreak and before testing had increased in response to that second wave – with results now showing how a simple blood test can capture whether someone has been exposed to the virus.

The new highly sensitive test measures the antibodies that follow a previous infection with the SARS-CoV-2 virus, also known scientifically as COVID-19, or novel coronavirus.

Researchers tested 3000 blood samples of healthy people around Australia for antibodies to COVID-19 and found that one in every 350 people had been infected with the virus.

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Associate Professor Ian Cockburn, who co-led the research with Professor Elizabeth Gardiner, said no-one in the study had been previously identified as COVID-19 positive.

“Our best estimate is that around 0.28 per cent of Australians – one in 350 – had been infected with SARS-CoV-2 by that time,” said Associate Professor Cockburn.

“This suggests that instead of 11,000 cases we know about from nasal swab testing, about 70,000 people had been exposed overall.”

The researchers said even with a conservative view of the results, the number translates to potentially around 30,000 people with the virus at that time.

Associate Professor Ian Cockburn and Professor Elizabeth Gardiner standing inside the John Curtin School of Medical Research at ANU.

Associate Professor Ian Cockburn and Professor Elizabeth Gardiner at the ANU’s John Curtin School of Medical Research. Photo: Jamie Kidston/ANU.

They also found another eight in 3000 healthy people were likely to have been previously infected after accounting for false-positive test results.

Associate Professor Cockburn said when someone is infected with SARS-CoV-2, or any virus, their body mounts an immune response which largely consists of producing antibodies.

“Our test measures those antibodies, showing who has previously been exposed to coronavirus,” he said.

“Estimating how many people have had SARS-CoV-2 enables us to better understand the spread of the disease, how effective community testing is, and can determine if there is evidence of herd immunity.”

Hayley McNamara working at ANU's John Curtin School of Medical Research.

PhD candidate and member of the research group Hayley McNamara at the ANU’s John Curtin School of Medical Research. Photo: Jamie Kidston/ANU.

Professor Elizabeth Gardiner said the study enabled the team to rapidly evaluate thousands of samples by a high-throughput robotic capacity which can test up to 100,000 compounds per day.

“This will be important for assessing antibody levels in people receiving SARS-CoV-2 vaccines in the future,” she said.

Professor Graham Mann, director of the John Curtin School of Medical Research, said the blood test provides “another weapon in our armoury to combat further waves of the virus”.

“These highly sensitive ways of detecting antibodies are going to find many uses, especially in surveying for spread in the community, especially among people without symptoms.”

In Canberra, more than 90,000 negative tests for COVID-19 have been conducted.

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