Lateral flow tests detect most people at risk of transmitting Covid-19

Lateral flow tests are more accurate than previously reported and cannot be compared directly to how PCR tests work, finds a new paper led by UCL researchers. The peer-reviewed paper, published today in Clinical Epidemiology, uses a new formula to show that lateral flow tests (LFTs) are likely more than 80% effective at detecting any level of Covid-19 infection and likely more than 90% effective at detecting those who are most infectious when using the test. This level of accuracy is much higher than some previous studies have suggested* and the authors say the tests are a reliable public health tool in stopping the spread of the virus. The researchers from UCL, Liverpool University, Harvard University and the University of Bath highlight that LFTs work in a very different way to polymerase chain reaction (PCR) tests and cannot be compared 'like for like'. LFTs detect material from the surface proteins of the virus and are very likely to give a positive result when someone is infectious whereas PCR tests detect the virus' genetic material, which can be present for weeks after a person is no longer infectious. Lead author, Professor Irene Petersen (UCL Institute of Epidemiology and Health Care), explained: "Previous studies comparing the reliability of lateral flow tests and PCR tests could be potentially misleading because a PCR test is a marker of having been infected at some point within a certain window of time and does not necessarily mean someone is infectious when testing positive.