Rapid-turnaround Covid tests that could hasten an easing of restrictions are able to catch nine out of 10 infectious cases, the first major study has found.
Contradicting weeks of scepticism, the research by Oxford University and Public Health England (PHE) strongly suggests that 30-minute lateral flow tests could be a viable means of reopening schools and workplaces.
It follows a bitter row within the scientific community after some academics alleged the technology had missed 60 per cent of positive cases during the Liverpool pilot scheme in which the kits were introduced for mass community use.
They accused ministers of “misleading” the public about lateral flow’s ability to make workplaces safe.
This week, the Government put plans to roll out the kits in schools when they reopen on hold over accuracy concerns.
However, the new study has used big data analysis of roughly a quarter of a million people recorded by NHS Test and Trace to determine exactly what characteristics of a Covid infection make carriers infectious to others. This was found to be high levels of virus in the nose and throat.
The Oxford/PHE team’s modelling found that 90 per cent of these patients tested positive using lateral flow tests.
Mass repeated use of the kits is hoped to be particularly useful at picking up asymptomatic carriers of Covid, thought to make up one in three cases.
Tim Peto, professor of medicine at the University of Oxford and the senior author on the study, said: “We know that lateral flow tests are not perfect, but that doesn’t stop them being a game-changer for helping to detect large numbers of infectious cases sufficiently rapidly to prevent further onward spread.”
Dr David Eyre, who co-led the study at Oxford’s Big Data Institute, added: “When the time comes to relax the current lockdown restrictions, by rapidly identifying the most infectious people using these lateral flow tests we can potentially relax the lockdown much more safely.
“This would allow people to get back to work, school and their normal activities and still stay safe.”
The study found that, overall, six in 100 contacts of infected cases went on to get infected themselves. It also showed that contacts in the same household were more likely to become infected than contacts at work, school or elsewhere.
Children were the least likely to infect someone else, while among household visitors it was people in their 20s and those over 65 who were the most infectious.
Before the latest lockdown, the Government announced that it would roll out lateral flow testing in workplaces in a bid to stamp out asymptomatic infections. They are already in use in hospitals.
Professor Peto said: “Lateral flow tests have been very popular with staff at our hospitals in Oxford, with over 60,000 tests done since November. We’ve been able to detect asymptomatic infected staff who would not have been otherwise diagnosed, protecting patients and staff.
“The tests can be done at home before coming to work, with a result available within 30 minutes.”
The new study coincides with a broadside of criticism against scientists who have argued against the efficacy of the Linva lateral flow tests based on the claim that they “missed infection in 60 per cent of people”.
Led by names such as Sir John Bell, Regius professor of medicine at Oxford, and Professor Matthew Ashton, the Liverpool Director of Public Health, the rebuttal, published on Monday, says: “The authors confuse ‘missed infection’ with infectiousness.
“It is well known that PCR detects non-viable RNA fragments as well as viable virus, meaning that large proportions of PCR test positive individuals will not be infectious.”
