BENGALURU : Britain on Wednesday approved using a COVID-19 self-test kit endorsed by its state-run health service to detect asymptomatic cases, as it mulls further restrictions to stem the spread of a highly infectious variant of the virus.The government has said it wants to start mass testing people as part of its strategy for tracking and tracing infections with cases spiking and as it battles the new variant.It had launched a mass-testing pilot scheme in the northwest city of Liverpool in November, offering everyone tests whether or not they had symptoms, in an attempt to find a new way to use testing to limit the spread of the coronavirus.The Medicines and Healthcare products Regulatory Agency (MHRA) said that the kit uses an antigen.