Coronavirus: What part could rapid antigen tests play in the fight against COVID-19?

Plans to roll out 120 million rapid-diagnostic tests in the fight against coronavirus were revealed on Monday.

The tests will provide results in approximately 15 to 30 minutes, rather than hours or days, according to the World Health Organization (WHO).

The agency said the tests aimed to help lower- and middle-income countries make up ground with richer countries.

But what role could they have to play in the fight against COVID-19?

Rapid COVID-19 tests that give results 'in minutes' to be rolled out in poorer countries
How accurate are they?
The rapid tests look for antigens, or proteins found on the surface of the virus. They are generally considered less accurate than higher-grade genetic tests, known as PCR tests.

"Those tests are pretty specific, they, like all rapid antigen tests, are not as sensitive, so you run more of a risk of a false negative, than a false positive," Dr Gigi Gronvall, Senior Scholar at the Johns Hopkins Center for Health Security, told Euronews.

The chance of the tests giving a false negative is higher at the start of a person's infection, according to Gronvall.

"The test will have a certain percentage of false negatives, regardless of where it’s being used and there’s also the potential for false positives," he added.

He argued "all testing is good" but tests are just one strand in a complete approach and there has to be a strategy behind their use.

What are the benefits and drawbacks of the rapid tests?
"The speed is really the big advantage of these tests," Gronvall said. "If it (a test) takes 48 hours to get a result sometimes, it’s like what’s the point?"

PCR tests require processing with speciality lab equipment and chemicals and have a turnaround that typically takes several days to deliver results to patients.

But the scholar argues: "There’s no reason why PCR has to take as long as it’s been taking in some places, no reason why you couldn’t have results in 24 hours or less.

"It’s just the infrastructure behind it and getting samples to where the test can be done because it is a laboratory test."
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