The rollout of mass rapid Covid testing in people’s homes across England is “misguided” and unlikely to reduce transmission, public health experts have warned.
Scientists remain divided over the widespread use of lateral flow devices (LFDs), which can return a result within half an hour but are far less accurate than the laboratory-based PCR tests.
Analysis has shown the LFDs correctly identify, on average, 72 per cent of people who are infected with the virus and have symptoms. In those without symptoms, this figure drops to 58 per cent.
Due to the risk of false negatives, critics have warned that many people could be wrongly “reassured” that they are free of Covid, potentially leading to “increases in transmission”.
When a person has coronavirus symptoms – including fever, a continuous cough or a loss of taste or smell – they need to undertake a PCR test, the gold standard of Covid diagnostics.
But under the current mass testing programme, which encourages people to take two rapid tests a week, these individuals might be “tempted” to shun the PCRs in favour of the less accurate LFDs, according to Angela Raffle and Mike Gill, public health consultants with experience in communicable disease control and screening programmes.
In an editorial published in the British Medical Journal, the experts wrote: “The temptation for people with symptoms to opt for unsupervised, rapid, and lower sensitivity self-testing may lead to false reassurance, as happens with other screening, leading to potential increases in transmission.”
The academics said that the cost-benefit for testing the nation twice a week was “not known” and “no plans are in place to measure them”, adding that there is no empirical data to support mass screening.
Indeed, there is little evidence to show how well the rapid tests detect the virus when used as a self-test by someone who has no symptoms.
The experts acknowledge that any response in a pandemic requires speed, but say without training and proficiency testing for those taking samples, plus a robust process for ensuring appropriate actions following a test result, “Sars-CoV-2 self-testing by asymptomatic members of the public is unlikely to reduce transmission”.
They also said that Britain was an “outlier” for putting so much emphasis on asymptomatic mass screening.
Defenders of the scheme have said that the LFDs can help to detect cases that would otherwise have been missed, highlighting that up to one-third of cases are symptomless. But Dr Raffle and Dr Gill said that “evidence is growing that transmission arises overwhelmingly from people with symptomatic infections and their contacts”.
As such, the experts called into question the overall benefit of the programme versus the risks involved – namely, in potentially promoting further onward transmission of people who believe themselves not to be infected.
“Both the laboratories and the rapid tests could be targeted to deliver a substantially more effective and cost-effective testing service founded on the public service principles of sound evaluation, strong ethics, high quality, and full transparency,” they added.
Boris Johnson has put mass testing at the centre of his strategy to lift the UK permanently out of lockdown, alongside the vaccine programme. The government has spent more than £2bn on the rapid tests, as part of the overall £37bn budget for NHS Test and Trace.
Critics have also warned that the lack of financial support for those forced to self-isolate means people with insecure jobs will be discouraged from using the tests out of fear of returning a positive result and losing out on income, thereby rendering the programme irrelevant to certain portions of society.
Paul Hunter, a professor of medicine at the University of East Anglia, who was not involved in the paper, said: “The main issue that we are seeing now is as case numbers are declining across the country, Covid seems to be retreating to areas where it remained a problem last summer (ie the UK’s more deprived areas).
“We know from the Liverpool trial [carried out last year] and elsewhere that it was these more deprived areas where transmission was highest and where uptake of testing was poor.
“So how twice-weekly testing predominantly by middle-class families in areas of low transmission will do anything to affect transmission in our more deprived locations is not clear to me. We would do better by trying to support people in these higher risk areas to self-isolate.”
However, Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh, said that any hope of controlling the spread of Covid-19 “depends crucially on finding cases, and finding them early, ideally before the infection can be passed on”.
“People infected with novel coronavirus are infectious for 24-48 hours before they show symptoms, and this period is thought to account for up to half of all transmission,” he said. “Asymptomatic testing can reveal these crucial pre-symptomatic infections – there is no other way to do this.”
It comes as professor Anthony Harnden, deputy chairman of the Joint Committee on Vaccination and Immunisation (JCVI), said told a parliamentary select committee that people who are vaccinated and using rapid turnaround Covid-19 tests are “not invincible”, adding that “everybody’s got to be cautious”.
A spokesperson for the Department of Health and Social Care said: “There is clear evidence that by using rapid testing we are identifying cases we would otherwise not find, allowing people to isolate, so they can prevent further spread of the disease and save lives.”
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