Last modified on Thu 15 Apr 2021 16.01 EDT Everyone in England is now able to take a free Covid-19 lateral flow test (LFT) twice a week, but experts have raised concerns about accuracy. We take a look at the issues. What is a lateral flow test? LFTs are a rapid way of testing for Covid-19. A swab is taken from the back of the nose or throat, mixed with an extraction fluid, and a drop of this mixture is placed in a well on a small device. The fluid is then drawn into the device and along a strip of test paper. Should coronavirus proteins be detected, a red line will appear, in addition to a second line that indicates the test is working. It works a little like a pregnancy test, but instead of looking for certain hormones, the test contains antibodies that bind to coronavirus proteins.