Will miss cases: Doctor highlights flaws in Covid lateral flow tests amid new strain

Coronavirus: UK cases surpass ten million during pandemic

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The World Health Organisation (WHO) has designated a new South Africa variant of coronavirus a “variant of concern” and has named it Omicron. The variant, which has now been detected in Belgium, has an unusually large number of mutations. This raises the spectre of it breaching the immune defences erected by the vaccines. More than ever, picking up cases will be key to informing decisions that contain the threat of coronavirus and its emergent strains.

Unfortunately, lateral flow tests, which are integral to tracking the virus, are flawed in a number of ways, warned doctor Chris Smith on BBC Breakfast today.

Rapid tests help to check if someone has COVID-19. If people test positive and self-isolate, it helps stop the virus spreading.

You can get rapid lateral flow tests if you do not have symptoms of coronavirus (COVID-19).

However, doctor Chris Smith highlighted the fact that the tests are not “perfect”.

Doctor Chris was responding to a question posed by a viewer.

They asked: “Is there a problem with the lateral flow tests, as we repeatedly get a positive result with them followed by negative PCR results?”

To which doctor Chris replied: “No test is perfect. The lateral flow tests will miss cases. They will miss up to half of cases of coronavirus as opposed to a PCR.”

He continued: “They also generate a false positive. And that happens one time in a thousand. So if you tested a thousand people and none of them had coronavirus. One of them would test positive for coronavirus.”

According to doctor Chris, those are average numbers.

The TV doc also pointed to the problems associated with sticking swabs in our noses and throats.

“That’s a pretty mucky place to stick a swab. You can imagine why it is hard to make a test that works perfectly with what is a mucky sample.”

He continued: “We like to test pristine samples in laboratories. These are not pristine samples. Anything you put into your mouth or nose can affect the performance of the test.”

According to doctor Chris, it’s possible things people have eaten and drunk can change the chemistry of the mouth, saliva and throat for a short period of time and that can throw some of these tests.

“That’s one possibility.”

All this is not to say PRC tests are foolproof.

“PCR is a very reliable test platform normally but as we saw earlier this year one testing place had a problem with their PCR testing and people were told they did not have coronavirus but their lateral flow test was telling them that they did,” noted doctor Chris.

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