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Local lockdowns have been imposed because infections are deemed dangerously high, but research by experts at Oxford University suggests as many as half of the “positive” tests relied upon could actually be false. This is because the current test is so sensitive it can pick up dead and harmless viral particles that are shed once the infection has passed.
People are infectious only for about a week, but particles continue to be emitted from the body for up to 74 days, their research has indicated, leading to an over-estimate of the pandemic.
The warnings over false positives come as Leeds, South Tyneside, Middlesbrough, Corby and Kettering were placed on the Government’s “areas of concern” watchlist on Friday following a spike in Covid-19 cases. This means tougher restrictions could be imposed if cases keep rising.
Dame Anne Johnson, a leading epidemiologist of University College London, warned the country is at a “critical moment” as students prepare to return to universities.
And concerns were raised that returning university students could add to the infection numbers as they socialise or throw house parties.
Leeds council leader Judith Blake urged youngsters to “recognise their own responsibility” as it was revealed £10,000 fines were issued to seven illegal rave organisers in the city last weekend.
Also warned pubs and restaurants which put “profits before people” by failing to enforce social distancing rules risk being closed as public health officials policed them last night.
Yesterday there were 12 deaths and 1,813 news cases. Last night Labour joined calls more extensive testing to be rolled out at airports to reduce travellers’ self-isolation periods.
But Professors Tom Jefferson and Carl Heneghan warned that the tests were flawed because they were so sensitive they could skew the infection results.The pair, who reviewed 25 papers on Covid tests, found in one area of Italy over half of all positive tests were “false positives” as a result of the problem.
Researchers called for the current PCR – polymerase chain reaction – test to be re-calibrated and questioned the rationale behind plans by the Health Secretary to introduce mass testing of which will see weekly tests for thousands.
The rapid expansion of testing may have also led to less stringent testing practices and poor quality results due to contaminated kit, they said.
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The flaws could explain why despite seeing rising numbers of cases, the UK and Italy – the nations worst hit by Covid-19 – have not seen a parallel number of deaths even weeks after cases started rising again.
Lead author Professor Jefferson, from the Centre of Evidence-Based Medicine, said: “I agree we need to find out who is infected but there is currently no way to distinguish people who are testing positive because they have ongoing infection or whether they have had a previous infection and are no longer infectious.
“For this reason you cannot lock down a whole region based on the infection levels as a result of testing.
“Nor do I understand the rationale behind mass testing. We need to refine testing to find infectious people as a matter of urgency – not people who have remnants of a previous disease. “This needs to be done now and these tests standardised across the world because this is a global problem.”
He added: “At the moment we should not be using this test as a yes or no as to whether someone is infectious.
“This may be one of the reasons why we are not seeing a rise in deaths nor a rise in hospital admissions alongside the recent increase in cases in the UK.”
Co-author Professor Heneghan said: “We are potentially locking down thousands of people on the basis of false positive tests. The government needs to follow the evidence which is now clear that the test results are not reliable.”
Professor Heneghan’s work has led to a change in the way deaths were calculated after it was discovered cases were being counted if a person died of other causes following an infection.
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