Lateral flow tests detect ‘most infectious’ COVID-19 cases, Oxford researchers find

Lateral flow tests can detect COVID-19 in people with high viral loads – who are the most infectious – according to researchers from the University of Oxford.

The researchers, working alongside Public Health England and NHS Test and Trace, used data from the Test and Trace service to identify why some individuals pass COVID-19 on to their contacts more easily than others.

They also set out to discover whether or not lateral flow tests can sufficiently detect the most infectious cases of COVID-19.

Although lateral flow tests – also known as finger-prick tests – are less sensitive compared to the gold-standard PCR test, they could allow more people to be tested in a shorter time-frame.

Lateral flow tests, according to the researchers, are more effective depending on the viral load an individual possesses. The higher the viral load, the more likely it is that a lateral flow test will detect the presence of COVID-19.

The researchers found that those who are best detected by lateral flow tests – those with high viral loads – are also the most infectious, according to Test and Trace data.

They found that lateral flow kits would be effective in detecting up to 90% of COVID-19 infections that these individuals passed on to their contacts.

“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,” said Tim Peto, professor of medicine at the University of Oxford and senior author on the study.

“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,” commented David Eyre, co-leader of the study and associate professor at Oxford’s Big Data Institute and Nuffield Department of Population Health.

“This would allow people to get back to work, school and their normal activities and still stay safe,” he added.

Earlier this week, Imperial College London researchers released updated results from its REACT-1 study, which is charting how COVID-19 is spreading across England.

This study found that during the first ten days of the third COVID-19 lockdown in England, which commenced on 6 January, virus levels were ‘very high with no evidence of decline’.

'Until prevalence in the community is reduced substantially, health services will remain under extreme pressure and the cumulative number of lives lost during this pandemic will continue to increase rapidly,' added the REACT-1 study authors.