A large-scale testing campaign in Canadian workplaces shows that the regular use of rapid antigen tests is highly effective at ferreting out asymptomatic SARS-CoV-2 infections1.

Rapid antigen tests identify proteins on the virus’s surface and are faster and cheaper than more-sensitive polymerase chain reaction (PCR) tests, which can pinpoint tiny amounts of the virus by detecting its RNA. To determine the usefulness of rapid antigen tests, Laura Rosella at the University of Toronto in Canada and her colleagues studied a programme that implemented twice-a-week COVID-19 screening at Canadian companies that ranged from fewer than 100 employees to more than 10,000.

From January 2021 to June 2021, nearly 322,000 rapid tests were conducted at 73 workplaces. Testing yielded 604 positives; 473 of those were confirmed by PCR to be true positives. Only about one in 4,300 rapid-test results was confirmed by PCR as a false positive, which the authors note was not enough to disrupt workplace operations.

Of the 116 workplace-testing organizers who responded to a survey, 99% said they were either satisfied or very satisfied with the programme.