Mass testing for Covid could increase transmission – experts

People with symptoms of Covid-19 may be “tempted” to bypass the laboratory-assessed coronavirus tests and use the at-home kits instead, experts have warned.

Public health consultants said that this could potentially lead to “increases in transmission” and people with symptoms could be “falsely reassured” by the rapid turnaround tests.

When a person has symptoms of Covid-19 – including fever, a new and continuous cough or a loss or change of sense of taste or smell – they need to get a coronavirus test which is assessed in a lab – known as a PCR test.

But they might be “tempted” to instead to use the lateral flow tests which people across the nation are being encouraged to use as part of the mass screening efforts, experts warned.

Watch: What is the UK's future on testing, travel and vaccine passports?

All adults in England can now get regular #COVID19 Test Kits from their local lateral flow test sites.

The tests give a result within 30 minutes.

Find out where you can get yours here 👇https://t.co/DhLEY5Y9QS pic.twitter.com/Wx9vcgIs1x

— Southern Health NHS (@Southern_NHSFT) April 23, 2021

Angela Raffle and Mike Gill, public health consultants with experience in both communicable disease control and screening programmes, argued that the mass screening, also known as Operation Moonshot, is a “misguided policy, unlikely to reduce transmission”.

They 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”.

In an editorial published in the BMJ, they argued that there is no empirical data to support mass screening.

And home self-testing “has not been evaluated”, they added.

They said that Britain was an “outlier” for putting so much emphasis on asymptomatic mass screening.

Pointing to the justification of the screening programme due to people who have Covid-19 but are not displaying symptoms, the academics said that evidence is growing that transmission arises “overwhelmingly” from people with symptoms, and their contacts.

Meanwhile they argued that the asymptomatic testing was “skewing” nationwide statistics on test numbers, cases and positivity rates.

They said that the UK should learn from the experience of the last year, adding: “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.”

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On Wednesday, Professor Anthony Harnden, deputy chairman of the Joint Committee on Vaccination and Immunisation (JCVI), said people who are vaccinated and using rapid turnaround Covid-19 tests are “not invincible”.

“If you’ve got a positive lateral flow test, that’s quite helpful in the sense that you know that you need to have a PCR and you may well have the infection and you may be infectious to other people,” he told the Science and Technology Committee.

“The problem is with a negative lateral flow test, (it) doesn’t mean to say necessarily you’ve not got the infection.

“I think everybody’s got to be cautious and just because you’ve been vaccinated, and just because you have a negative lateral flow test, (it) does not mean you’re invincible because these tests are not perfect.

“Of course, as the prevalence infection goes down in the population, the predictive value of all these tests becomes problematic as well, so I would say they’re helpful as part of the arsenal of tests and investigations and vaccine and everything else, but they shouldn’t be just taken in isolation.”

Responding to the editorial, Dr Susan Hopkins, Covid-19 strategic response director to Public Health England and chief medical adviser to NHS Test and Trace, said: “Around one in three people with Covid-19 experience no symptoms and there is clear evidence that rapid testing detects cases quickly, meaning positive cases can isolate immediately.

“After building a testing system from scratch, we have now carried out over 149.2 million coronavirus tests – more than any other comparable European country.

“These tests have helped enable children to return to school, businesses to reopen and the latest easing of national restrictions.

“Meanwhile, the NHS Test and Trace app has already prevented an estimated 600,000 Covid-19 cases since its launch.

“Protecting communities and saving lives is always our first priority and every pound spent on testing is contributing towards our efforts to keep people safe.”