A coronavirus expert has warned rapid tests might not actually work well on children.
Lateral flow tests have been given to pupils in secondary schools since they reopened on 8 March, nearly four months ago.
However, Jon Deeks, professor of biostatistics at the University of Birmingham and the Cochrane Diagnostic COVID-19 Test Reviews lead, told Sky News on Wednesday that evidence around their effectiveness remains questionable.
“We don’t actually know how well they work in children yet,” he said.
“So all of the use of the tests in schools is based on a presumption that they work in the same way that they work in adults – but that doesn’t seem likely.
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“So a lot of the testing that we’re doing isn’t based on good evidence anyway.”
It comes amid continued disarray surrounding the government’s school bubbles policy.
Concerns have been raised about the interpretation of rules which have resulted in large groups of pupils being sent home for 10 days if another pupil in their bubble tests positive for COVID.
Labour warned 375,000 children were out of school last week as a result of the policy.
Education secretary Gavin Williamson has faced pressure to scrap school bubbles, but told MPs on Wednesday this would only happen in September.
The latest data from the Department for Education, covering England, showed about one in 20 state school pupils did not attend class for COVID-related reasons on 24 June: a record high since the return of schools in March.
How are lateral flow tests currently used on children?
Pupils and teachers are asked to take two tests a week. The tests provide a result in half an hour.
All positive results from lateral flow tests taken by pupils and teachers need to be confirmed with a PCR (polymerase chain reaction) test within two days. These tests are more sensitive to positive cases of the virus.
If the PCR test is negative, students and staff are then able to return to class and stop self-isolating, government advice says.
Prof Russell Viner, a member of the Scientific Advisory Group for Emergencies (Sage), has said he supports lateral flow testing but said “spare” PCR test capacity could be dedicated to schools, “potentially allowing more rapid release of negative contacts from isolation”.
Robert Halfon, chair of the House of Commons education committee, has also called on the government to "update" its guidance and establish mobile testing units at schools to stop entire bubbles being sent home.
Williamson said the school testing policy is "under review".
How accurate are lateral flow tests?
NHS Test and Trace research, published in March, said lateral flow tests provide less than one false positive result in every 1,000 tests taken.
Ministers said at the time that people could be "assured" there is a “minimal chance” the tests will give false positive results.
However, as the BMJ reported in March, the Test and Trace research was based on data at a time when prevalence of COVID was high at 8.7%.
Prof Deeks, who has been assessing medical tests for more than three decades, said that at a lower prevalence of 0.5%, it would mean about half of positive tests would be false positives and therefore pupils would be isolating unnecessarily.
How much is the government spending on lateral flow tests?
It's not known, but health minister Edward Argar told the BBC in April that lateral flow tests – which are also available to the wider public – would be paid for as part of Test and Trace's funding of £37bn over two years.
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