Lateral flow tests: Do nasal swabs pick up Omicron? Expert’s NYE warning

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UK Covid infections may have hit a pandemic record high of 189,213 in the previous 24 hour period but Prime Minister Boris Johnson has urged Britons to go ahead with their New Years Eve parties tonight. He said: “Everybody should enjoy New Year but in a cautious and sensible way – take a test, ventilation, think about others but, above all, get a booster.”

Health Secretary Sajid Javid added people must “remain cautious” and take a lateral flow test before attending any bash today.

But as well as a major lack of LFT availability, it seems there’s another issue to contend with, as anecdotal evidence suggests tests that require only a nasal swab are less effective at detecting some forms of COVID-19 – including the new Omicron variant.

Some Brits have reported testing negative on lateral flow tests when only swabbing the inside of their nose, despite a recent positive PCR test.

Now, scientists are beginning to question the efficacy of nose-only tests. Professor Irene Petersen, of University College London, said she had been “trying to get an understanding of what’s going on” after infected people picked up on the possible defect with LFTs.

The epidemiologist believes only swabbing the nose could be less effective at picking up coronavirus in its early infection stages than a throat swab.

She said this could be because the virus “may replicate in your throat and then your nose”.

Professor Petersen said: “To me, it seems as though some people may have an infection in their throat before they get an infection in their nose.

“It seems a question about how Omicron establishes itself in your body and that appears to be different than previous variants.”

Professor Tim Spector, lead scientist for the Zoe Covid study, agreed, saying: “As well as knowing about cold-like symptoms – always swab both your throat as well as your nose if you want an accurate LFT.

Professor Peterson added it was a “good idea” to take a sample from both the throat and nose to get an accurate result.

She said: “When you are really infectious you have millions of copies of the virus in different tissue in your body, and nasal swabs should be able to pick this up.

“It may be less of a problem at the other side of infection than at the beginning. Most people would not be infectious after seven days.”

The accuracy of LFTs has been called into question several times this year, long before Omicron even graced British shores.

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In March, an independent review found that the rapid antigen tests correctly identified 72 percent of people infected with the virus and have symptoms, on average.

But when it came to people with no symptoms, that number saw a significant drop, down to just to 58 percent of people getting a correct reading.

The evidence comes as a mass shortage of lateral flow and PCR tests hampers parts of the UK just before one of the biggest social events of the year.

Right now, the public are being urged to take LFTs before heading out to mass gatherings or social settings, as well as these tests being used to release people from self-isolation. But with none available online, tonight could risk becoming a super spreader event.

On Thursday there were no PCR tests at walk-in sites across England, with “very few available” in all regions of Northern Ireland.

There are now walk-in PCR in all regions of England, but a number of areas still have very few or no tests available at all.

Home testing kits have also been in sparse supply in the run-up to New Year’s Eve, despite the Government’s pleas for the public to test themselves before they socialise on the night in question.

On Wednesday, an industry body revealed that pharmacies in England did not receive any deliveries of LFTs for four days over Christmas.

A Department for Health spokesperson told Express.co.uk this morning: “All lateral flow devices used by NHS Test and Trace have gone through rigorous validation and are proven to be highly effective at detecting COVID-19 in people.

“We are currently seeing high numbers of positive LFD [LFT] tests reported. This means we are detecting tens of thousands of cases that may otherwise have gone undetected.”

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