Rapid antigen tests unreliable in asymptomatic COVID-19 cases: study

“While-you-wait” tests for COVID-19 that detect proteins on the virus are better at diagnosing the disease in patients with symptoms than in those without symptoms, according to data pooled from 64 studies.

The analysis, published on Wednesday by The Cochrane Library, found that on average, “antigen tests” correctly identified 72 per cent of symptomatic COVID-19 cases but only 58 per cent of cases in people without symptoms.

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The best-performing test – the SD Biosensor STANDARD Q – correctly identified the virus in 88 per cent of symptomatic patients and in 69 per cent of those with no symptoms.

For screening purposes, among 10,000 people with no symptoms, where 50 people had COVID-19, this test would correctly identify 35, miss 15 cases, and incorrectly give positive results to 90 people who were not infected, the authors estimated.

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“Confirming a positive result from a rapid test with a RT-PCR test, particularly where cases of COVID-19 are low, may help avoid unnecessary quarantine,” coauthor Jac Dinnes of the University of Birmingham in the UK said in a statement.

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“All antigen tests will miss some people with infection, so it is important to inform people who receive a negative test result that they may still be infected.”

Coauthor and Dinnes colleague Jon Deeks noted that repeated rapid antigen tests are being used to screen school pupils, teachers, and healthcare workers. “These testing policies have been implemented without any supporting real-world evidence,” he said.

© 2021 Reuters

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