Covid Antibody Test

New Report From CDC Claims Half Of All Coronavirus Antibody Tests Are False

The US Centers for Disease Control and Prevention recently listed a compilation of new guidance on their website that stated antibody tests used to determine if an individual has been infected with Covid-19 may be wrong half the time. The tests specifically look for evidence of an immune response in the body to determine, and now the CDC is claiming that they shouldn’t be used to “make decisions about grouping persons residing in or being admitted to congregate settings, such as schools, dormitories, or correctional facilities,” according to their website. 

The CDC is now encouraging health officials not to use these tests to make decisions about when essential workers can return to their workplace if they’ve been infected. Health care providers should also ensure that when they do give patients an antibody test that they’re using the most accurate test possible and are able to test the individual twice to be sure that the result is accurate. 

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“In most of the country, including areas that have been heavily impacted, the prevalence of SARS-CoV-2 antibody is expected to be low, ranging from less than 5% to 25%, so that testing at this point might result in relatively more false positive results and fewer false-negative results. The higher the sensitivity, the fewer false negatives a test will give. The higher the specificity, the fewer false positives. Across populations, tests give more accurate results if the disease being tested for is common in the population. If an infection has only affected a small percentage of people being tested, even a very small margin of error in a test will be magnified,” the CDC said.

One of the biggest concerns is the false positives that some individuals are receiving. A false positive could lead someone to believe that they had the virus and have a certain level of immunity over it when they could’ve actually never had it at all. It’s also extremely important to note that even if the positive test result is accurate, no one is immune from this virus, and you shouldn’t believe that you have no chance at getting it again simply because you have the antibodies. We still don’t know how this virus fully works and mutates, so everyone must continue to ease on the side of extreme caution. 

“It cannot be assumed that individuals with truly positive antibody test results are protected from future infection. Serologic [antibody] testing should not be used to determine immune status in individuals until the presence, durability, and duration of immunity is established,” (CDC). 

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In general, the CDC doesn’t want anyone to use antibody testing as a means of making certain policy decisions. We need to be looking at actual case numbers and rates of infection more than anything when it comes to loosening quarantining measures. They claim that this testing can be wrong so often because of how common the virus is now. 

“For example, in a population where the prevalence is 5%, a test with 90% sensitivity and 95% specificity will yield a positive predictive value of 49%. In other words, less than half of those testing positive will truly have antibodies. Alternatively, the same test in a population with an antibody prevalence exceeding 52% will yield a positive predictive greater than 95%, meaning that less than one in 20 people testing positive will have a false positive test result,” (CDC).

The best way to receive an accurate test result is to take a test with higher sensitivity. High sensitivity antibody tests are much less likely to give a false positive specifically. The Food and Drug Administration has joined the CDC in expressing their hesitation in using antibody results for policy change. For now, both organizations encourage double-testing, and remaining diligent on all other social distancing measures as well.  

COVID Antibody Test

What You Need To Know About Coronavirus Antibody Testing

The Food and Drug Administration (FDA) has been working tirelessly to combat the coronavirus pandemic the world is currently enduring. More recently, they granted emergency authorization to over a dozen kinds of Covid-19 antibody tests to be added to the 200 other kinds of tests that are currently on the market

Roche is one authorized company developing antibody tests that they claim are 100% accurate in finding coronavirus antibodies in the blood and 99.8% accurate at ruling them out as well. For individuals who have gotten sick within the past few months but weren’t tested for Covid-19, or individuals who didn’t get sick, but could also have just been asymptomatic, would likely want to be tested for antibodies to receive possible answers/advancements towards a proper drug treatment or vaccine.  

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Antibodies are defined as the proteins in our bodies that attack foreign viruses when we get sick. For example, if you’ve gotten the common cold before, your body likely has all of the antibodies to fight it off since you’ve gotten sick with the same illness before. These antibodies are what help scientists develop vaccines as well, so it’s imperative that they get as many coronavirus antibodies as possible. 

“Having specific antibodies means you’ve been exposed to that virus, or you’ve had a vaccine for it. However, many antibody tests on the market right now are advertising claims that make no sense. Too little is known about the coronavirus to rely on the results of most of the current antibody tests,” according to CBS News medical contributor Dr. David Agus.

Dr. Agus believes that a lot of these non-authorized tests have a higher rate of false-positive results, and are therefore leading people to believe that they have antibodies when they don’t. Even the latest tests that the FDA approved of and are claiming to be highly accurate could give false-positive results based on the unpredictable nature of this virus in general. 

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It’s also important to note that even if you do test positive for antibodies against Covid-19 and the test itself was accurate, there’s still no guarantee that you’re completely safe from the virus. Again, like the common cold, just because your body has all the antibodies to fight it off, you can still get the cold, and likely will, multiple times throughout your life based on exposure. This is also because sometimes your body creates antibodies just to fight off the infection brought on by the virus, but that doesn’t necessarily mean they can fully neutralize the virus itself. 

For now, however, the antibody tests can at least provide a greater insight into who’s already been exposed/infected, which can help with contact-tracing processes. 

“There is no reason to get a test at the present time unless you’re part of an epidemiologic study, [or] your company wants to know how many people potentially have been exposed. For reasons like that, they’re important. But for personal decisions, right now, they are not to be used, because they do not tell you immunity,” Agus said.

The one universal fact that all medical professionals have agreed upon is the unpredictable nature of this virus, and that applies to its antibodies as well. Until researchers receive more concrete evidence, it’s simply a waiting game, so for now, it’s important to listen carefully to your healthcare professionals and continue to abide by social-distancing policies.