Lateral flow tests ‘detect 80% positive people at high risk of passing on Covid’


Some experts have raised doubts about how effective lateral flow tests are with testing the Omicron variant, with those displaying the ‘milder’ coronavirus symptoms connected to the rapidly spreading strain told to get a PCR test

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Scientists have voiced concerns over whether lateral flow tests are effectively detecting the Omicron Covid variant.

The rapid tests are a key part of the government’s Plan B, with Brits urged to use them before meeting in groups or seeing vulnerable loved ones.

Since Tuesday those who are fully vaccinated are not required to isolate for 10 days if they come into contact with someone with the Omicron variant – as long as they do lateral flow swabs for seven days.

Boris Johnson this week said the approach was brought in to prevent a repeat of the “pingdemic” which brought workplaces and schools to a standstill earlier this year.

But while officials say lateral flows are an effective tool in detecting the virus, questions have been asked about their accuracy with Omicron.

Those with Covid symptoms have been instructed to get a PCR test and not rely on lateral flow swabs, which have been rolled out to identify people with no signs of having the virus.

People with Covid symptoms are told they must get a PCR test, not rely on lateral flows
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Among those voicing concerns is Dr Angelique Coetzee, chair of the South African Medical Association – the nation where the concerning strain was first detected.

She told members of the UK Science and Technology Committee that she was aware of Omicron cases where lateral flow tests were negative, but laboratory-performed PCR tests were positive.

Dr Coetzee said: “The rapid test is still showing false negatives in the early period.

“We do have patients that waited a week and still have a headache and then they do PCR and it’s positive.”

But medical officials stressed it is important that people test regularly – with lateral flow devices detecting the vast majority of positive cases where someone is likely to pass Covid on.

Omicron is ripping through the UK, with 88,376 cases confirmed today – the highest daily figure of the pandemic so far.

Experts say the tests are an important way of tackling Covid – but are not 100% accurate
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Dr Susan Hopkins, who heads the UK Health Security Agency, told MPs that lateral flow tests have a key role to play in fighting the virus.

She said: “They’ve been used very effectively now for almost one year in the UK population.

“What we know is that overall it will detect about 50% of cases compared to PCR, but it will detect about 80% or even more than that of people who have high amounts of virus and therefore are at the highest risk of transmitting to others.”

Dr Hopkins reiterated that people should test before socialising.

Medics have never claimed that lateral flow tests are 100% accurate, and the gov.uk tells people who report a negative report that they are unlikely to pass on the virus – but not certain not to.

The accuracy of lateral flow tests has been questioned by many Britons and health experts
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It still remains to be seen how accurate they are, but experts say their speed compared to lab tests is a distinct advantage.

Dr Alexander Edwards, an expert in biomedical technology at Reading University, told the Mail Online: “They do work very well but are by no means perfect; their great advantage is speed and great convenience, compared to lab-based tests.

“As long as people understand that they don’t always pick up every case, I think they can be very useful.

“The exact accuracy has been measured in a range of settings, and doesn’t seem ideal — lateral flow tests definitely miss some PCR-positive people.”

And criticising a “deadly consensus of inaction”, Independent Sage member Dr Helen Salisbury wrote on Twitter: “The evidence is blindingly clear – Omicron is spreading like wildfire, people may be infected even with negative lateral flow tests.”

Dr Philip Lee said those showing Covid symptoms should not rely on lateral flow results but get a PCR test.

He wrote: “Lateral flows are like a sniff test for milk going off.

“You certainly wouldn’t believe a negative sniff test if the milk had lumps in it ; just like you shouldn’t rely on a lateral flow if you have symptoms.”

Last week, John Edmunds, professor of epidemiology at the London School of Hygiene and Tropical Medicine, defended the tests last week.

He said, The Telegraph reports: “They’re an incredibly useful tool. I think they’ve had a very poor press for some reason.

“It is undoubtedly the case that they are less sensitive than the PCR tests.

“But there’s a strong argument that PCR test is actually over sensitive in many respects.”

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George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.

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