One in three rapid tests for coronavirus can give false-positive result

PCR tests are considered the gold standard for diagnosing coronavirus, but because of their high cost and time-consuming processing of results, many countries use rapid tests for SARS-CoV-2 coronavirus antigen for screening.

However, a new study published in JAMA Network has shown that such tests are not the most reliable alternative to PCR tests.

As Medportal.ru says, coronavirus antigen tests recognize its specific surface proteins. Such tests are designed to diagnose active SARS-CoV-2 infection. The main advantages of such tests over PCR-tests are the speed of obtaining a result (5 to 15 minutes), relative cheapness and simplicity, since they do not require laboratory equipment.

To assess the potential of rapid tests, scientists at the University of Toronto analyzed more than 900,000 results obtained between January and October 2021. A total of 1,322 positive results were identified, of which 1,103 were confirmed by PCR testing. The scientists estimated that 42% of the rapid test results were false-positive, meaning that the test showed a positive result even though the person did not actually have the coronavirus.

According to the scientists, this could partly be due to improper test administration, but at least 60% of the false-positive results were due to poor quality of the test systems themselves. In particular, 278 false results were obtained with tests from a defective batch.

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