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Rapid testing 'not quite at the level' to identify all COVID-19 cases

A senior member of NPHET has said rapid result testing could be a useful extra tool but is not li...
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Newsroom

14.49 25 Oct 2020


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Rapid testing 'not quite at th...

Rapid testing 'not quite at the level' to identify all COVID-19 cases

Newsroom
Newsroom

14.49 25 Oct 2020


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A senior member of NPHET has said rapid result testing could be a useful extra tool but is not likely to replace PCR tests.

Dr Cillian De Gascun, Director of the National Virus Reference Laboratory and Chair of NPHET's COVID Expert Advisory Group, said 'Antigen' tests are not as sensitive as the polymerase chain reaction (PCR) test which is the standard diagnostic tool for the virus in most countries.

This would mean that by using such rapid result testing, people may need to be tested more frequently.

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It comes as The Sunday Times reported today that Antigen tests have been considered for schools to reassure parents and teachers.

Dr De Gascun told On The Record with Gavan Reilly there is a possibility of using the two types of testing regimes together.

He said: "If you want to identify all cases, then Antigen testing might not be quite at that level yet.

"However there may be a role for it to be used in the context of an outbreak, a rapid investigation.

"But equally, the people who aren't identified by the Antigen test as being cases in an outbreak setting, they would still have to on to have PCR testing to facilitate the contact tracing."

Rapid testing 'not quite at the level' to identify all COVID-19 cases

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Dr De Gascun added: "The test we have at the moment, the PCR, is the most accurate, the most sensitive and the most specific test.

"Antigen testing, by definition, is less sensitive, and in certain circumstances that might not necessarily be a bad thing, but you have to compensate for that lack of sensitivity."

He said that this compensation could be done by testing a larger number of people.

He explained: "So for example, in an outbreak setting, Antigen testing may well have a role purely because if you're testing 20 people with symptoms, you're very unlikely to get 20 false negatives.

"Similarly, the other alternative if you want to compensate for the reduced sensitivity is perhaps to increase the frequency of testing.

"That's the principle that on a serial basis, you're unlikely to get repeated false negatives."

Dr De Gascun added that this principle "hasn't really been proven at this point in time but it's speculative".

He said he would be "very happy to look at new technologies as they come to the market" and that Antigen testing will improve.

Main image: File photo of COVID-19 testing in a lab. Credit: Amy Beth Bennett/Sun Sentinel/TNS/Sipa USA)

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