Experts are calling on the UK government to halt or pause its mass testing programme for people without symptoms in care homes, schools, communities and potentially at home, warning that the lateral flow devices it has bought are inaccurate and can do more harm than good. Prof Jon Deeks, of Birmingham University and the Royal Statistical Society, and colleagues say the public is being misled. “The UK government is widening the rollout of the Innova lateral flow test without supporting evidence, and we understand that this may soon extend to further home use,” they write in the BMJ. “This may cause serious harm. We call on the government urgently to change course.” The lateral flow tests were used in Liverpool’s mass testing exercise and failed to pick up 60% of Covid infections, they say. The tests also failed to detect 30% of people with high viral loads, who are the most infectious. “Among students in Birmingham, only 3% of those who would have tested positive on PCR [lab tests] were detected. The government continues to claim that the test detects 77% – a figure from an unrealistic study using laboratory scientists and experienced nurses running tests on symptomatic people,” write Deeks, Angela Raffle of the University of Bristol , a consultant to the national screening programme, and Mike Gill, a former regional director of public ealth. They are concerned that people who have a negative test will presume they are safe to get involved in activities with others or visit vulnerable and elderly people. “The government has championed the use of negative tests to enable visiting relatives in care homes, returning to work or staying in school despite known exposure to an infectious case, safe travel home for Christmas, and participation in sporting events, weddings and funerals. We know of at least one confirmed outbreak caused when a healthcare worker with symptoms continued to work due to false reassurance from a negative Innova test result. “Low test accuracy would be less dangerous if people being tested and the public at large received accurate information about the risks and implications of a false negative result. Instead they are being misled. Results from government studies have been selectively reported and some have not been reported at all,” they say. But the government has paid £1bn for pregnancy test-style devices from Innova, which are stacked in warehouses. “The message has gone out that ‘they have to be used’, or ‘as long as testing detects otherwise unknown cases, the whole exercise will be worthwhile’,” say the authors. A Department of Health and Social Care spokesperson said: “Lateral flow devices (LFDs) used by the UK government go through a rigorous evaluation by the country’s leading scientists. With up to a third of individuals not displaying symptoms, broadening asymptomatic testing is essential. LFDs detect cases with high levels of virus, making them effective in finding individuals who are the most likely to transmit the disease, including those not showing symptoms. “Some 14,800 Covid-19 carriers have already been detected using LFDs who would have otherwise not been identified. Many of these individuals have subsequently self-isolated, therefore preventing the onward transmission of the disease.”