The chief medical adviser to the NHS has defended the mass use of rapid Covid-19 testing amid concerns a high number of “false negatives” is falsely reassuring the public.
Government figures released earlier this week from Liverpool – where the mass rollout of the lateral flow tests was first piloted – showed they missed half of all cases and a third of those with a high viral load who were likely to be the most infectious.
It led to calls from some scientists for their use to be suspended amid fears some people who tested negative would go on to mix with others who may be more vulnerable because they wrongly believed they did not have the disease.
But Dr Susan Hopkins, chief medical adviser to NHS Test and Trace, said the tests had enabled them to find many cases of infection in people without Covid-19 symptoms that would otherwise have been missed.
“What we are doing here is case detection. We are not saying people do not have the disease if their test is negative,” she told the BBC Radio 4 Today programme.
“We are trying to say (to people who test positive) ‘You do have the disease and now we want you to go and isolate for ten days’. That is a whole different game-changer.”
With other local authorities looking to roll out the lateral flow tests, Hopkins stressed their use did not end the need for social distancing.
“We have been very clear that this test finds people we couldn’t otherwise find. We are also very clear that until we get a much lower prevalence of disease in this country that we shouldn’t be changing our behaviours.”
She was backed by Professor Calum Semple, of Liverpool University and a member of the government’s Scientific Advisory group for Emergencies (Sage), who said their deployment in the city meant 85% of the population were just a 15-minute walk from a testing centre.
“This means we have broken over a thousand transmission chains in those hotspot areas,” he told Today.
“We are increasing the safety of an activity that is going to happen anyway. In this case we are breaking transmission chains and that is really important.”
But Professor Jon Deeks, of Birmingham University, said the tests were being used in ways for which they were never intended with potentially dangerous consequences.
“They are a low-tech test, they can’t detect low levels of the virus. The World Health Organisation has said ‘Don’t use it for this purpose,’ the manufacturer said ‘Don’t use it for this purpose’,” he told Today.
“We can’t see why the government is progressing with using this test when it is missing so many people.
“They have been sold to people with the idea that if you are negative you will be able to go and visit people, you will be able to be clear that you haven’t got Covid, and that it really dangerous.”
Liverpool City Council defended the use of the tests on Friday, telling the Liverpool Echo the scheme had “always been a pilot, not only to identify where the virus is in the city, but also to learn about different testing technologies and different testing strategies.”