COVID-19 serological tests are designed to determine whether people have been exposed to the new coronavirus, but the U.S. Centers for Disease Control and Prevention (CDC) warns that this could give false hope that false positives are possible in many cases, according tomedia SlashGear. Currently, two types of COVID-19 testing are primarily a measure of the extent of a pandemic, focusing on whether the patient is currently infected with the virus, or whether he has been infected in the past.
Both of these are important tracking factors. Virus detection can find out if a person is currently infected, and it is the first to be deployed when governments are trying to measure the extent of community transmission of the disease with varying urgency.
Antibody testing, also known as serological testing, does not indicate whether a patient is currently infected, but does try to mark whether they have previously been infected with the new coronavirus. They depend on the presence of antibodies — the immune system’s response to infection — antibodies in the body. However, these antibodies can take 1-3 weeks to produce, and it is unclear whether exposure to COVID-19 and subsequent recovery will mean that someone will not be infected again in the future.
Nevertheless, both types of testing are still in progress, using emergency authorization for non-approved diagnostic methods deployed by the FDA during a pandemic. We’ve seen warnings from the FDA that manufacturers of serological testing are overstating the potential benefits of their products, and how the agency enforces stricter rules for these types of testing. Now, the CDC has joined in their own warning.
False positive and false negative s
False positives are tests that show that people have a disease or infection, but they don’t. False negatives are the opposite: in fact, people are infected, but the results are not. For serological tests, false positives can be said to be more dangerous because they can lead to a misguided sense of security. First, there is no guarantee that future infections will be avoided once COVID-19 is infected.
In the updated guidelines, the CDC notes that false positives are likely to exist “in most countries” and “include areas that have been severely affected.” This is because accuracy depends on how many people in the population are infected and therefore produced antibodies.
The CDC recommends that SARS-CoV 2 antibodies are likely to be low prevalence, even in areas severely affected. “Testing at this point may result in relatively more false positive results and fewer false negative results,” the agency cautioned.
“For example, in people with a prevalence rate of 5 percent, tests with 90 percent sensitivity and 95 percent specific tests will produce a 49 percent positive prediction,” the CDC explained. “In other words, less than half of those who tested positive will actually have antibodies. In addition, in people with antibody prevalence of more than 52%, the same test results will produce a positive prediction of more than 95%, that is, less than 1 in 20 people who test positive will have a false positive test results. “
The CDC says the best strategy is to continue testing, but be aware of its limitations. If the positive results from the serological test are preferable, it is best to use a second, different test to ensure that it is not false positive. Even if both tests are positive, this does not automatically guarantee the safety of future coronavirus infections. The CDC recommends: “Asymptomatic people who pass serological tests and have a low risk of historicalactive infection without the most recent COVID-19-compatible disease sit until they are active, and should follow general recommendations to prevent infection with SARS-CoV-2 and other ways to continue with normal activities, including work.” “