Don’t be fooled by RATs

The strange saga of the missing rapid antigen test kits has preoccupied health authorities, private firms and Opposition MPs of late.

This week we were told two-thirds of the test kits ordered by one unnamed distributor in January had yet to arrive. The distributor was allegedly told the Government requisitioned them, a claim denied by officials.

Just who has what has become a card game where the ante piles up while no one is willing to call. It’s all the more bewildering considering the limitations of the tests.

Coincidentally, around the same time as the war of words, more than 20 aged-care residents tested positive in the Twin Parks Aged Care Centre in Melbourne — where staff highlighted inaccurate results from the tests.

The outbreak began with two infected residents, described as “extremely active” within the facility. Close contacts of the pair were given multiple rapid tests but many registered negative results.

Associate Professor David Anderson, deputy director of the Burnet Institute, told the Sydney Morning Herald the tests were a useful screening tool for quick results but gave people a false sense of security.

He said they detected about 80 per cent of infections among people with symptoms.

However, he said the tests did not detect Covid-19 for one to two days after a person became infected and negative results did not guarantee a person was not infectious.

Australia’s health watchdog has received more than 100 complaints.

The US Food and Drug Administration warns “early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity”.

Dr Ashwin Swaminathan, an infectious diseases physician, told the Guardian the performance of the tests with different variants was “a moving feast”.

It would appear there are many situations needing frequent testing and where fast results are desirable, such as workplaces and travel. Rapid antigen testing developed at a giddying pace to meet this need. But it be foolhardy to become overly reliant on their efficacy.

It should be remembered they are best as a screening tool, rather than a diagnostic one.