The British government is to roll out mass community testing across England, to detect people who have Covid-19 but show no symptoms.
The programme, announced on Sunday by health secretary Matt Hancock, will enable all 317 English local authorities to offer rapid testing. They will use "lateral flow" devices, which give results within half an hour but are less accurate than the lab-based PCR tests regarded as the gold standard for diagnosing infection.
Councils will be encouraged to target testing at people who cannot work from home during the lockdown, so they can self-isolate if they are carrying the virus.
The government is also asking businesses – particularly in the food, retail, energy and manufacturing sectors –- to join the asymptomatic testing drive. Companies already running pilot programmes include Apetito, John Lewis, Octopus Energy, Tate & Lyle and Tata Steel.
“With roughly a third of people who have coronavirus not showing symptoms, targeted asymptomatic testing and subsequent isolation is highly effective in breaking chains of transmission,” Mr Hancock said.
“Lateral flow tests have already been hugely successful in finding positive cases quickly – and every positive case found is helping to stop the spread – so I encourage employers and workers to take this offer up,” he added.
But scientific experts gave the testing rollout a mixed reception, with reactions ranging from “this is most welcome and long overdue” to “further rollout of lateral flow testing is very worrying”.
Some expressed concern that lateral flow tests miss too many cases to be a reliable guide – particularly since samples from people who are infected without symptoms are likely to contain less virus than those from people with obvious disease.
Tom Wingfield, senior clinical lecturer at Liverpool School of Tropical Medicine, pointed out that a pilot project using Innova lateral flow tests in Liverpool during November "missed 60 per cent of Covid-19 cases", according to an interim evaluation.
“There was no clear evidence that the strategy independently led to a reduction of cases and hospitalisations locally,” Dr Wingfield said.
Jon Deeks, professor of biostatistics at Birmingham university, said mass testing using the lateral flow technology "brings a real risk that it will increase rather than decrease the spread of Covid. The government only appears to focus on benefits of testing –- that of detecting previously undetected asymptomatic cases – and not the harms which are caused by misinforming people that they do not have Covid-19 infection when in fact they do."
Usual precautions
Adam Finn, professor of paediatrics at the University of Bristol, said authorities would have to make it clear to people being tested that lateral flow produces “red light” results.
“If they come positive that means you are potentially infectious to others and must self isolate,” he said. “They are not ‘green light’ tests. You cannot be sure that if the test is negative you are not infectious, and you must continue to take the usual precautions.”
With that proviso, Prof Finn said, "this provides an important new tool to help to reduce the rapid rise in cases that is paralysing our country."
Prof Lawrence Young, a virologist at Warwick Medical School, also gave the mass testing initiative a cautious welcome.
“Asymptomatic testing of individuals who are unable to stay at home during the current lockdown will help to restrict the spread of infection as long as we ensure that folk who test positive appropriately isolate and that their contacts are traced and also isolate,” he said.
“Repeat testing is essential given the nature and time course of virus infection and concerns about the accuracy of lateral flow tests.” – Copyright The Financial Times Limited 2021