Lateral flow tests should be trusted, new research suggests

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Wednesday 13th October 2021

Research conducted by a team at University College London (UCL) suggests that lateral flow tests are more accurate than first thought.

Lateral flow tests (LFTs) are used as a rapid test for Covid-19 and have become commonplace in schools, universities and workplaces. Initially, it was thought that lateral flow tests were significantly less accurate than PCR tests, which are analysed in laboratories, but a new study indicates high efficacy rates. 

The team from UCL described lateral flow tests as a “very useful public health tool” and study author, Prof Irene Petersen stressed that test results should be trusted. If a test result is positive, there is no need to do additional PCR tests, Prof Petersen explained. In the vast majority of cases, the result will be accurate. 

Researchers discovered that lateral flow tests had an accuracy rating of over 80% at detecting any level of Covid, which rose to over 90% among the most infectious individuals. Prof Michael Mina suggested that negative lateral flow test results, which are followed by positive PCR tests, are produced when viral load is low and the virus has not yet reached peak transmissibility. By the time the PCR test has been taken, the virus has become more transmissible, increasing the likelihood of a positive test. 

Prof Mina said that lateral flow tests can “catch nearly everyone” who is “a serious risk to public health.” Lateral flow tests were introduced to cut waiting times for test results and make testing more widely accessible. They are used daily by hundreds of businesses and organisations across the UK. Current government guidelines recommend taking a PCR test after receiving a positive lateral flow test. If the result is negative, the individual is able to end self-isolation. Prof Petersen indicated that double testing is not necessary and urged anyone who does get a positive lateral flow test to isolate.