Podcast: How accurate are rapid tests for diagnosing COVID-19?

Within our growing collection of reviews relevant to COVID-19, we have several relating to its diagnosis. One of these, on the use of rapid point-of-care tests was updated in March 2021. Here's lead author Jacqueline Dinnes from the University of Birmingham in the UK to tell us what they found for antigen tests.

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Monaz: Hello, I'm Monaz Mehta, editor in the Cochrane Editorial and Methods department. Within our growing collection of reviews relevant to COVID-19, we have several relating to its diagnosis. One of these, on the use of rapid point-of-care tests was updated in March 2021. Here's lead author Jacqueline Dinnes from the University of Birmingham in the UK to tell us what they found for antigen tests.

Jac: Tests for diagnosing COVID-19 are an incredibly important tool to help reduce the spread of infection in our communities, schools and workplaces. Tests are not perfect measures of whether or not someone has the condition of interest and it's important to estimate how often a test will give an incorrect result. Whether this is a false positive or a false negative, knowing how often this might occur allows us to weigh up the possible benefits and harms from using that test.
Our review of rapid point-of-care tests looks at the evidence for two types of test: rapid antigen, or lateral flow tests, and rapid molecular tests. Both use samples taken from the nose or throat, can be done outside of a specialist laboratory and provide results much more quickly than the PCR test, which can take up to 24 hours to provide a result. In this podcast, I'll focus on the rapid antigen tests, which provide a result in less than half an hour and are cheaper and easier to use than the molecular tests.
We included 48 studies, evaluating 16 different lateral flow tests, where the findings were available before 16 November 2020. These studies included samples from just over 20,000 people, including around 5500 who had COVID-19 infection confirmed by a PCR test. 
The studies mainly included people with symptoms of COVID-19 who presented for testing at a COVID-19 test centre or other community setting, but some included anonymised samples left over after PCR tests and did not provide detailed information about who the participants were. In the studies, the tests were not always done in the way that the test manufacturers recommend or were carried out in laboratories by specialist personnel, which means that different results might be seen when the tests are used in routine practice.
Turning to our results, in people with COVID-19 confirmed by PCR, lateral flow tests correctly identified the infection in an average of 72% of people with symptoms, compared to 58% of people without symptoms. For people with symptoms, tests correctly identified more people with infection when they were used within a week of the symptoms appearing. This is likely to be because people have the most virus in their system in the first days after they are infected.
In people who did not have COVID-19 or who had negative results on PCR tests, lateral flow tests correctly ruled out infection in 99.5% of people with symptoms and 98.9% of people without symptoms.
However, there was a lot of variation in the sensitivity of different brands of tests and our overall results combine findings from different studies that evaluated the same tests. However, when we limited the analyses to studies that followed the manufacturer's instructions, only one test met international standards of 'acceptable' accuracy when used in people with symptoms of COVID-19.
In summary, rapid antigen tests will continue to be an attractive and potentially important tool for managing the spread of COVID-19. Most of the evidence available so far is from people with symptoms and we are much less certain as to how well these tests perform in people with no symptoms. However, we know that more studies are now available and are already working on the next version of the review to add in this latest evidence.

Monaz: If you would like to read the current version of the review and to watch for future updates, it's available free on Cochrane Library dot com. If you go to the website, and type in a search for 'antigen tests for COVID-19', you'll find it.

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