Are COVID-19 Antibody Tests Accurate?

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Are COVID-19 Antibody Tests Accurate?

(AscendHealthy.com) – With over 3.7 million US residents having contracted COVID-19 as of July 17 and no signs of the virus letting up anytime soon, health experts believe it’s more important than ever to keep accurate statistics. Testing has been problematic, and many officials have questioned the reported numbers. The implications could be nearly as scary as the pandemic itself.

Quick Read:
COVID-19 antibody testing has some problems: Antibodies can take weeks to show up in the blood, causing false-negative results until then, and other coronaviruses, like the ones that cause the common cold, may cross-react with COVID-19 tests, causing false-positive results. It’s also hard to say how long the antibodies might remain in a person’s system. We have all the details on COVID-19 antibody testing below.

Get the Full Story on COVID-19 Antibody Testing Accuracy.

How Antibody Tests Work

We have different types of antibodies in our blood. The CDC reports that different kinds crop up at different times after an intruder tries to take hold. IgM antibodies usually show up first, with IgG antibodies usually developing later and persisting much longer. Doctors use a few different kinds of tests to detect viral infections, but the tests typically rely on the presence of proteins specific to the virus. COVID-19 IgM and IgG antibody tests generally look for two proteins: spike glycoprotein and nucleocapsid phosphoprotein.

Pitfalls of Current COVID-19 Testing

COVID-19 antibody testing is riddled with issues, making accuracy questionable, at best. First, it can take time to develop antibodies once someone’s caught the infection. In one study, antibody tests failed to detect 70% of cases 1 week into infection, and it failed to catch 30% of cases 2 weeks in. After 3 weeks, antibody tests only missed about 10% of positive cases, but the unfortunate fact is that many legitimately sick people will have negative antibody tests until that time.

Another potential issue is cross-reactivity with other coronaviruses, like the ones that cause the common cold, causing false-positive results. COVID-19 has a lot in common with these other viruses, making it easy to confuse an antibody test. There’s also the question as to how long COVID-19 antibodies remain in the system. Researchers are still trying to determine if recovered patients actually have any type of long-term immunity against reinfection.

Unless the issues with antibody testing for COVID-19 are addressed, the results have little practical use in most cases. The test can serve as one of many tools to connect the dots in cases where severe complications are present, but the results can’t be considered diagnostic for COVID-19. RNA testing for the virus itself, which requires a nasal swab, is far less likely to cause false-positives, although false-negatives, at a rate of about 20%, do also exist with this test as well.

~Here’s to Your Healthy Ascension

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