Information for COVID-19 Testing
Up to half of people with COVID-19 do not display symptoms, and a significant proportion of these may be infectious. Tackling the pandemic requires identifying asymptomatic, infectious individuals. Symptomatic individuals should seek PCR testing; given PCR capacity, asymptomatic individuals (except in narrowly defined high risk groups) are not advised to seek PCR testing.
Lateral flow tests have been widely and successfully used to detect COVID19 in asymptomatic individuals. No test is perfect, but the speed and convenience of lateral flow tests supports detection of the virus in asymptomatic individuals who would not otherwise be tested. They are clinically approved and are crucial in the fight against the virus. As the tests are more sensitive with higher viral loads, there is a risk of returning a negative result when viral loads are low (e.g., in the early stages of infection). This is why Public Health England recommend two LFD tests 3 to 5 days apart, or regular testing, to enhance detection by picking up any cases which were not detected during the first test and to catch any new infections.
If you test positive using a LFD, it is likely that you are infectious at that moment, whereas people testing positive on a PCR test could be in the less infectious early or late stages of disease. This means that by using the lateral flow test we can identify people with a high viral load who are the most likely to spread the virus further. A negative LFD result should not be taken as leave to relax or ignore social distancing or other measures intended to reduce transmission – LFD is an additional intervention that contributes to reducing risk.