Scientists defend use of rapid lateral flow Covid test as government steps up UK rollout

The devices are seen as crucial for targeting asymptomatic cases, enabling different sectors of society, such as care and entertainment, to reopen their doors. Having spent more than £700m on the kits, the government hopes they will provide the bedrock for its mass-testing strategy.

Scientists have defended the government’s rollout of a rapid coronavirus test amid concerns it is inaccurate and unsafe to use.

Health officials have also brought forward plans for care home staff to receive bi-weekly tests using the device, developed by the US-based company Innova, as concerns grow about the rapid spread of a new coronavirus variant.

However, research released by the government’s Scientific Advisory Group for Emergencies (Sage) has shown that the tests are capable of picking up only 48.9 per cent of active infections.

A separate study conducted by the University of Liverpool during the city’s recent mass testing pilot showed the device identified only 40 per cent of asymptomatic cases.

This meant 1,300 people who were unaware they had the virus were diagnosed as positive and told to self-isolate. The research also showed that that the lateral flow tests detected two-thirds of people with higher viral loads.

Some experts have warned that the tests are not fit for purpose, amid concern people would be encouraged to change their behaviour on the back of a false negative result.

But a group of scientists, including professor Sir John Bell, a member of the government’s Scientific Advisory Group for Emergencies, have insisted that the devices have a role to play in tackling the spread of Covid-19.

Identifying every positive case “is a win”, Sir John told a press briefing held on Wednesday. “You need to remember the counterfactual that these are people who are not going to get tested at all. You have to think of what the benefits are of finding even a majority of people but not everybody, that’s a key element to this.”

He pointed to the example of the NHS, which has been piloting the lateral flow tests for a number of weeks now.

“In the first wave, a failure to test for asymptomatic carriers among healthcare workers was a major driver of infections in hospitals,” he said.

“There’s a million people from NHS using these on a twice-weekly basis and identified 3,500 positives. These are people who would never have been identified before: 3,500 healthcare workers, wandering around wards with vulnerable people. How many people do you think they’d have infected if they hadn’t been caught? It’s a very big number.”

A total of 123 council areas have agreed to roll out rapid community testing using the lateral flow devices, including some region which are now in tier 4.

Public Health England scientists at Porton Down have also confirmed the tests “successfully detected samples” of the new coronavirus variant, which is spreading across London and the southeast of England.

Although the scientists acknowledged the tests are far from perfect, they argued that they remain a “really good public health intervention”.

“There isn’t a magic bullet or a golden ticket,” said professor Louise Kenny, executive vice chancellor at the University of Liverpool. “We’re gathering evidence on the hoof, more will be available, but you have an array of academics in front of you now convinced of the utility of this intervention.

“I think some of the negative discourse we’ve seen in recent weeks is very unhelpful. It’s this or nothing… the alternative is we don’t pick up anybody.”

Prof Kenny said it was vital that people regularly tested themselves using the devices. This, she argued, would counteract the risk of returning a one-off false negative. “It’s called serial testing and the key is serial. It’s more successful with a serial approach.”

Her colleague Iain Buchan, a professor of public health at the University of Liverpool, said that two tests a week “should be the rhythm of life”, while Tim Peto, a professor of medicine at Oxford University, said repetition and experience of using the tests – which involves taking a nasal swab – would help to increase the accuracy of the results.

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