A study by University College London researchers claims that Lateral flow tests (LFTs) are very good at detecting people most likely to spread Covid-19 and positive results should be trusted.
LFTs have long been criticised for being less accurate that PCR tests, where the results come after the material is analysed in a lab, rather than being generated at home.
Prof Irene Petersen, lead study author, said people who get a positive LFT result should continue to “trust them and stay at home”. Government guidelines say that following a positive LFT test, people should confirm the result with a PCR test.
In recent weeks there have been a growing number of cases where a positive LFT result has been followed by a negative PCR test result, which has undermined some confidence in the tests.
Yesterday, Dr Louise Smith, director of public health in Norfolk, told local media that she was aware of “sporadic cases” of this nationally, and heard about it anecdotally locally. She told the Eastern Daily Press:
While we are aware of sporadic cases nationally in which some batches of lateral flow test kits may deliver false positives, these are very rare and when used properly lateral flow tests remain reliable. A PCR test can be arranged to confirm any positive from a lateral flow test.
The UCL study found that LFTs were more than 80% effective at detecting any level of Covid infection, and that they are more than 90% effective at detecting who is most infectious. These figures are higher than previous studies.
Another member of the study team, Prof Michael Mina, from Harvard School of Public Health, said that LFTs will catch nearly everyone who is posing a risk to public health.
“It is most likely that if someone’s LFT is negative but their PCR is positive, then this is because they are not at peak transmissible stage,” he said.
Source : https://www.theguardian.com/world/live/2021/oct/14/coronavirus-live-who-experts-to-revive-virus-origins-inquiry-fiji-prepares-to-welcome-tourists-after-two-years?page=with:block-6167b5ab8f08880f7f055b8a372