News Coronavirus Why rapid antigen tests won’t become the new coronavirus norm

Why rapid antigen tests won’t become the new coronavirus norm

Watch: Everything you need to know about rapid antigen tests for COVID-19.
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Rapid COVID-19 tests won’t replace the nose-and-throat swab as the gold standard for coronavirus detection in Australia, but they will help us claw back against outbreaks, experts say.

On Wednesday, New South Wales Premier Gladys Berejiklian said rapid antigen tests could be made available for Year 12 students as they resume face-to-face learning on August 16.

The tests, which can produce a result in 10 minutes, have been in use in the government-run Howard Springs facility in the Northern Territory since November.

Federal Liberal and Labor MPs have further called for the tests to be introduced for front-line workers.

Most Australians who have been tested for COVID-19 would have endured the polymerase chain reaction (PCR) test, where results take anywhere from 12 to 24 hours.

Unlike PCR tests, which search for genetic material from the virus, rapid antigen tests detect proteins on the surface of the virus, turning around a result faster. 

But these results aren’t always reliable.

Professor Catherine Bennett, chair in epidemiology at Deakin University, said rapid tests results can be as low as 70 per cent accurate in people displaying symptoms.

That rating drops further to some 60 per cent in populations with low case numbers – including in parts of Sydney – and among asymptomatic people, Professor Bennett said.

That means there is a risk positive cases will be missed.

If a good proportion of positive cases don’t get picked up, and those people mistakenly think they are negative, it can give them greater confidence or reassurance so they might not be as careful in the community, Professor Bennett said.

But rapid antigen tests are not about finding every single positive case, and all their contacts – that’s where you need a diagnostic test like the PCR test.

Antigen tests are more to do with screening to pick up at least a proportion of the positive cases, who can then follow up with a PCR test.

“The problem is if they’re asymptomatic, it’s a bit more hit and miss,” Professor Bennett said.

‘An incredibly useful screening tool’

As a general screening tool, rapid antigen tests could be “incredibly useful”, said Professor Brian Oliver, who heads the Respiratory Molecular Pathogenesis Group at the University of Technology Sydney.

“If we acknowledge that we’re not necessarily going to use them as a form of diagnosing people that are symptomatic, but more as a screening tool, I think they offer lots of advantages,” Professor Oliver told The New Daily.

They are a “really good screening tool” to rule out if someone has COVID-19 who wouldn’t have felt any need to get tested.

“Because there’s enough information known about how sensitive and how specific these tests are, they can be used in multiple different situations now,” Professor Oliver said.

“They offer the advantage of not clogging up our hospital diagnostic labs.”

They can also offer people a less invasive way to get tested.

A study from the Doherty Institute found rapid antigen tests had picked up all COVID-19 cases among people who had symptoms in the previous seven days, but were less accurate in returning positive cases for people with lower viral loads.

Antigen testing suppliers have been contacted about rapid antigen testing on construction sites and in schools.

And they have already been trialled in aged-care facilities in NSW and used by film and television production companies. 

Finance Minister Simon Birmingham says rapid testing would not replace PCR testing, but “complement” it. 

-with AAP

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