Antigen tests: What are they and do they work?

The European Commission has a  document on its website which lists antigen tests whose results are “mutually recognised”
Antigen tests: What are they and do they work?

Also referred to as rapid self-tests, antigen tests do not require a laboratory to process the sample and issue results in a short period of time, usually under 30 minutes. Photo: Gareth Chaney/Collins

Also referred to as rapid self-tests, antigen tests do not require a laboratory to process the sample and issue results in a short period of time, usually under 30 minutes.

Why have they been in the news in recent days?

Last week, supermarket chain Lidl announced it was selling kits of five tests for €24.99. They went on sale on Friday and 10,000 kits were sold across the country. 

That’s good news, isn’t it?

Not according to some public health officials, who fear they create a false sense of security among members of the public.

Prof Philip Nolan, chairman of the Irish Epidemiological Advisory Group, had particularly staunch criticism when the retailer advertised the product alongside an image of sausages and charcoal in a post on Twitter.

Tweeting in response to the post, Prof Nolan said: “Can I get some snake oil with that? It makes for a great salad dressing with a pinch of salt and something acerbic. Stay safe when socialising outdoors over the next few weeks. Small numbers, distance, masks. These antigen tests will not keep you safe.” 

Is there political support for them?

The Government supports the wider use of antigen testing as an additional health and safety measure but warns they cannot replace any other public health measure.

Tánaiste Leo Varadkar also criticised the way in which the Lidl tests were marketed online, adding they give an incorrect message that a negative test means people have the "all-clear" to go to a BBQ and socialise.

Are all antigen tests the same?

Public health chiefs have specifically referred to supermarket-bought antigen tests in their criticism.

The European Commission, however, has a publicly available document on its website which lists antigen tests whose results are “mutually recognised”.

How accurate are they?

Antigen tests are less accurate than PCR tests, and individuals who test positive through an antigen test would be required to undergo a confirmatory PCR test.

Prof Mark Ferguson, chief scientific advisor to the Government, recently said they have a false positivity rate of one in 1,000, and also have false-negative results.

Prof Ferguson said the tests are capable of detecting whether someone is infectious, and so are most accurate on people who have high viral loads.

He added there are videos online to help educate the public on the proper procedure to increase accuracy.

Are we currently using antigen tests in our fight against Covid-19?

There are pilot antigen testing programmes in the higher education sector, but they have not yet been rolled out community-wide.

However, Transport Minister Eamon Ryan last week said rapid antigen tests could play a significant role in reopening society.

Immunologist Kingston Mills also believes they could be an extra layer of protection against Covid-19.

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