Rapid antigen tests: How do they work and when should we use them?

They’re the fast and cheap COVID-testing alternative. How do they work and when should we use them?

Dr Ian Norton, a specialist emergency physician at Respond Global, who is overseeing a trial of rapid antigen testing at the Sydney aged-care centre Whiddon, says rapid antigen tests are most useful when there is substantial community spread. In that case, he says, the aim of testing is to identify people who have high viral load and are most likely to spread the virus.

“Rapid tests are very effective at picking up super spreaders. This is where they are most useful,” he says.

“When we’re chasing elimination in Australia, that’s where PCR is the test to use, because we want to catch every single person with the virus.”

But sensitivity is only one marker of a good test, says Norton. Speed, accessibility and cost are crucial traits to consider during outbreaks because, he says, the strategy is more about limiting community transmission than tracing every single case.