Keeping teachers and students in the classroom on the basis of  “unreliable” lateral flow Covid tests is a “recipe for disaster”, a teaching union leader has warned.

Mary Bousted, joint general secretary of the NEU teaching union, has questioned the safety of relying on these tests after an academic estimated they had only picked up around 3 per cent of positive cases at a university campus.

The Department for Education is planning to use these tests to help keep students in schools rather than self-isolating if they have been in contact with a confirmed Covid case at school.

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The plan is for any close contacts to be given a test every day for seven days and to stay in schools if the test results remain negative.

However, Professor Jon Deeks, from the University of Birmingham, has warned that this will result in students with Covid-19 staying in the classroom and infecting others because the tests will return false negatives.

Coronavirus: Fears over the reliability of Covid tests in schools

In response, Dr Bousted said: “This is a recipe for disaster. We are going to be moving from a system where Covid contacts are isolating to one where they stay in school on the basis of tests that have proven to be totally unreliable and with a mutant strain in Covid which is more infectious.

“Schools could end up becoming more of a hotbed for Covid infection than they have been because the only way they have been able to control it this term is through pupils and staff self-isolating when they come into contact with a case. We could be looking at more transmission and more disruption to education next term.”

The Department of Health and Social Care told Tes that the lateral flow tests are reliable. 

But it is being reported today that the government has shelved plans to open rapid-turnaround coronavirus test centres over Christmas amid concerns from public health experts about the accuracy of their test results.

Speaking on Radio 4 this morning, Professor Deeks indicated that the lateral flow tests had only picked up around 3 per cent of positive cases at his university.

Asked what would happen when the tests are used in schools, he said: “Well, we’ll be allowing teachers and students to stay in school who had Covid, we’d be missing people who’ve got Covid.

“The worst thing is actually the proposal that students when they’re in a class where one child has had Covid they stay in the school and are tested with this test until they go positive, because inevitably there’ll be students left in that class who become infectious and infect others, so we’ll end up with outbreaks in the school which wouldn’t happen with our current policy of sending kids home.”

The government is relying on lateral flow tests for a major testing programme in secondary schools and colleges in the new year.

It has asked schools to administer 11 million tests from the start of term with students getting tested twice, three days apart.  

Prof Deeks added: “Anything like this where we’re taking a new unknown test which has very little data as to how it works anywhere, it must be evaluated in its intended use setting before it’s rolled out across the country.”

He went on: “It might possibly be better in schools but the data are emerging that this test isn’t working well anywhere in asymptomatic people… It’s an imperfect test and when you have an imperfect test, you have to use it so carefully to make sure you don’t mislead people and there’s a big risk this test is going to give a lot of false reassurance, which inevitably will lead to more Covid disease.” 

A Department of Health and Social Care spokesperson, commenting on behalf of the government, said: “The country’s leading scientists rigorously evaluated the lateral flow test and confirmed the accuracy of the tests using a sample of over 8,500.

“Latest figures for similar settings showing sensitivity of 57.5 per cent generally and 84.3 per cent in people with high viral loads.

“This means they are accurate, reliable and successfully identify those with Covid-19 who don’t show symptoms and could pass on the virus without realising.

“With up to a third of individuals with Covid-19 not displaying symptoms, broadening testing to identify those showing no symptoms will mean finding positive cases more quickly and break chains of transmission.

“Anyone who tested positive with a lateral flow test during the university testing earlier this month would have been asked to get a confirmatory PCR test.”