A review by an independent global network showed that rapid antigen tests are better at correctly identifying COVID-19 cases in people with symptoms than in people without symptoms.
The updated systematic review from Cochrane, an independent global network, together with leading experts from the University of Birmingham (Birmingham, UK), evaluated rapid tests for the detection of SARS-CoV-2 (COVID-19) infection. . The review showed that there are large differences in the accuracy of the different test brands, with very few meeting the minimum acceptable performance standards of the World Health Organization (WHO).
Tests have been developed to diagnose COVID-19 that can provide results “while you wait.” Two types of rapid “point of care” tests are available, both using nose or throat swabs. Antigen tests identify proteins in the virus and come in disposable plastic cassettes similar to pregnancy tests, with results available in 30 minutes. Molecular tests detect the genetic material of the virus using desktop analyzers or small handheld devices, the results of which are usually available in 30 minutes to two hours. The Cochrane researchers wanted to know how accurate the tests were for determining infection in people with symptoms and in people without symptoms. They identified and summarized studies that measured the accuracy of any point-of-care test used in hospitals or the community compared to the accepted standard laboratory test, RT-PCR, in detecting current SARS-CoV-2 infection.
The first version of this review included 22 studies and was published in August 2020. The updated review now includes evidence from 64 studies. Most of the studies included in the review were from Europe and the USA and assessed the accuracy of rapid antigen tests. Only three studies were conducted exclusively in people without symptoms: two in people who were contacts of confirmed cases and one included staff screening. More than half of the antigen testing studies included samples from people being tested in the community, for example, in testing centers, emergency departments, or as part of contact tracing or outbreak investigations. The molecular testing studies were conducted primarily in laboratories and not in the community where the tests were intended to be used.
The review authors found that antigen tests better identified COVID-19 in people with symptoms than in people without symptoms. In people with symptoms, on average, 72% of people who had COVID-19 were correctly identified as infected; The tests worked best in the first week after symptoms began when they identified 78% of people who had COVID-19. In people without symptoms, on average, antigen tests correctly identified 58% of those infected. Antigen tests correctly ruled out infection in 99.5% of uninfected people with COVID-19-like symptoms and 98.9% of uninfected people without symptoms. The percentage of people with COVID-19 who were correctly identified varied between brands and also depended on whether the manufacturers’ instructions in using the tests were followed.
“Our review shows that some antigen tests may be useful in healthcare settings where COVID-19 is suspected in people with symptoms,” said Dr. Jac Dinnes, Principal Investigator in Public Health, Epidemiology and Biostatistics at the University of Birmingham. . “These tests don’t seem to work as well in people who don’t have COVID-19 symptoms. Confirming a positive rapid test result with an RT-PCR test, particularly when COVID-19 cases are low, can help avoid unnecessary quarantine. “
“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. There is some emerging evidence that the accuracy of the test is affected by who performs it, ”added Dr. Dinnes. “Future studies should look at the relationship between the experience of the person administering the test and the sensitivity of the test. Future research should also evaluate molecular tests in the settings in which they are intended to be used to clarify their performance in practice. “
University of Birmingham