Interpreting a lateral flow SARS-CoV-2 antigen test.

### What you need to know Lateral flow devices (LFDs) are being used to test asymptomatic people for covid-19 as part of the approach in the UK and elsewhere to control the spread of the disease and to enable society to reopen.1234 The risks and benefits of using LFDs for widespread testing of asymptomatic people are the subject of ongoing uncertainty and debate.1567 Despite concerns about accuracy, LFD tests continue to be widely used. In the week ending 19 May, 4.9 million registered tests were undertaken in England.8 People taking a test receive advice on what their result means and what they should do; however, the widespread use of these tests means doctors may increasingly be asked about them (for example, when patients with a recent result present to services). This practice pointer considers how to interpret and communicate results from LFD tests based on our current understanding of the tests’ performance. Lateral flow devices can detect the presence of a target substance in a liquid, typically in a single use disposable …