Rapid antigen tests for SARS-CoV-2 have low overall rate of false-positive results

A timely new study investigated the incidence of false-positive results in a large sample of rapid antigen tests used to serially screen asymptomatic workers throughout Canada. The study, published in JAMA,an international peer-reviewed general medical journal, showed the overall rate of false-positive results among the total rapid antigen test screens for SARS-CoV-2 was very low.

The study looked at the results from rapid antigen tests that were administrated as an extra layer of protection to control transmission in workplaces throughout Canada by the Creative Destruction Lab Rapid Screening Consortium (CDL RSC). The Consortium is an unprecedented collaboration among businesses, researchers, and government working together to promote the launch of workplace rapid screening across Canada to reopen the economy in a safe way. The Creative Destruction Lab (CDL) delivers a seed-stage program for massively scalable, science-based companies and was founded at the University of Toronto's Rotman School of Management.

Authors of the study were Professor Ajay Agrawal, founder of the CDL and Geoffrey Taber Chair in Entrepreneurship and Innovation at the Rotman School; Professor Joshua Gans, Chief Economist of the CDL and Jeffrey S. Skoll Chair in Technical Innovation and Entrepreneurship at the Rotman School; Professor Avi Goldfarb, Chief Data Scientist at the CDL and the Rotman Chair in Artificial Intelligence and Healthcare at the Rotman School; Sonia Sennik, executive director of CDL and CDL RSC; Professor Janice Stein, vice-president, strategy at CDL RSC and founding director of UofT's Munk School of Global Affairs and Public Policy; and Professor Laura Rosella, vice president, health at CDL RSC and Canada Research Chair in Population Health Analytics at UofT's Dalla Lana School of Public Health.

The study examined rapid antigen tests conducted by employees from January 11 to October 13, 2021, with some workplaces providing at-home screening and others on-site screening programs. Over this period, Canada experienced two significant variant–driven waves from March to June and August to October. The study found only .05% of over 900,000 tests administered had false-positive results.

The study also revealed that a cluster of false-postives at two workplaces was likely the result of manufacturing issues rather than implementation and demonstrate the importance of having a comprehensive data system to quickly identify potential issues. With the ability to identify batch issues within 24 hours, workers could return to work, problematic test batches could be discarded, and the public health authorities and manufacturer could be informed.

The study is available online at JAMA.