Real-world, rapid COVID-19 testing shows few false positives

(HealthDay)—In a Canadian employer screening program, the overall rate of false-positive results using rapid antigen test screens for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is very low, according to a research letter published online Jan. 7 in the Journal of the American Medical Association.

Joshua S. Gans, Ph.D., from the University of Toronto, and colleagues investigated the incidence of false-positive test results in a large sample of rapid antigen tests used to serially screen asymptomatic employees at 537 workplaces throughout Canada. The analysis included 903,408 rapid antigen tests (Jan. 11 to Oct. 13, 2021) conducted by employees through at-home or on-site screening programs.

The researchers identified 1,322 positive results (0.15 percent), of which 1,103 had polymerase chain reaction (PCR) test information. False-positive results were seen for 0.05 percent of screens overall and 42 percent of positive tests with corresponding PCR information. Roughly two-thirds of screens had a trackable lot number. Sixty percent of false-positive results occurred in two workplaces 675 km apart run by different companies between Sept. 25 and Oct. 8, 2021, and all of these false-positive test results were drawn from a single batch of the Abbott Panbio COVID-19 Ag Rapid Test Device.

“The results demonstrate the importance of having a comprehensive data system to quickly identify potential issues,” the authors write. “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.”

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