Lateral flow devices can detect the most infectious cases of COVID-19, meaning they could help with a safe relaxation of lockdown, say experts.
New research from the University of Oxford, Public Health England, and NHS Test and Trace, has looked at the Test and Trace programme data and determined that lateral flow devices are sufficient in detecting COVID-19 cases in people that are most likely to pass on the virus.
The scientists used data from over a quarter of a million people who have taken part in the programme and determined for the first time in a large scale study that, in all groups, the higher the viral load in the nose and throat, the more infectious an individual is, explaining part of why some people pass COVID-19 on and others do not.
The data showed that only six in 100 contacts of infected cases went on to get the virus themselves.
Lateral flow tests
To reduce the spread of the COVID-19 infection, highly contagious people are identified and isolated. The researchers say that COVID-19 tests that are less sensitive than the standard PCR but, easier to make widely available, such as the lateral flow tests, could offer a solution to ensure that those who are highly infectious are aware they need to isolate much sooner, therefore allowing an easing of lockdown restrictions.
While lateral flow tests do not detect as many cases as the standard PCR test, there has been debate over whether they are efficient enough to catch the most infectious cases of COVID-19. This new research demonstrates that the lateral flow devices are able to detect cases with the highest viral load, and therefore the most infectious, with modelling from the study showing that they would be effective at detecting up to 90% of the infections that were then passed on to their contacts.
Tim Peto, Professor of Medicine at the University of Oxford and senior author on the study, 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.
“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.”
The researchers also found that contacts in the same household were more likely to become infected than contacts at work, school, or elsewhere, and that children were less likely to infect someone else, in particular, contact in schools with an infected child had a lower risk of transmission.
The team also demonstrated that amongst household visitors, those in their 20s and over 65 years were more infectious.
Dr David Eyre, of Oxford’s Big Data Institute and Nuffield Department of Population Health, who co-led the study, said: “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.”