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April 30, 2020

Quest Diagnostics offers COVID-19 antibody test for purchase online

But the level of immunity provided by antibodies remains unclear

Quest Diagnostics is now selling COVID-19 antibody tests on its website, allowing consumers to easily purchase the much-hyped tests without going through a health care provider. 

Those interested must order the test online for $119. Once purchased, the company will then prompt users to schedule an appointment to complete a blood draw at one of its labs. Results are provided a day or two afterward. 

People going in for the test will have to wear a face mask and pass a temperature screening. People who have experienced COVID-19 symptoms within the last 10 days are asked to delay testing because it can take 10 to 18 days for the body to produce antibodies detectable in the blood.

Antibody tests measure the amount of antibodies a person has developed against a specific infection. They bind to the virus along with T cells, forming a second level of defense after other cells, like macrophages, are sent to slow the virus. After the body successfully recovers from a virus, those antibodies remain in the blood. 

But the level of protection those antibodies provide against COVID-19 reinfection remains unknown. The antibodies that result from some illnesses, like measles, provide lifetime protection. But others only provide protection for much shorter duration. 

For instance, Columbia University researchers found that immunity against four coronaviruses known to cause the common cold tends to wane quickly. The study found its 191 participants often became reinfected with the same coronavirus. It's not known whether the same is true for the coronavirus that causes COVID-19.

"While the science on COVID-19 is evolving, testing for antibodies may identify people who have likely been exposed to COVID-19 and might have mounted an immune response to the virus," Dr. Jay Wohlgemuth, Senior Vice President and Chief Medical Officer for Quest Diagnostics, said in a statement. "Our goal is to empower individuals and their physicians to make informed decisions about their risk of infection and of spreading the virus." 

Some researchers suggest that antibody tests will prove useful in reopening society by dividing the population into two groups: those at risk and those no longer at risk. This may be particularly beneficial to those who have been exposed to the virus but did not get tested or experience any symptoms. 

The U.S. Food and Drug Administration has allowed companies to sell antibody tests without federal authorization. Companies must validate the tests' accuracy and apply labels stating the products have not received FDA approval and cannot diagnose COVID-19. 

The FDA also is allowing companies to seek emergency use authorization, which requires a lower threshold of evidence than typically required by the federal approval process. 

Only a handful of antibody tests have received emergency use authorization. But more than 100 companies have placed their tests on the marketplace without any regulatory oversight. 

U.S. Rep. Raja Krishnamoorthi, chair of the House Subcommittee on Economic and Consumer Policies, has expressed concerns over the lack of oversight, saying it enables companies to put junk tests on the market. 

The reliability of antibody tests is in doubt. One study evaluated 14 antibody tests and found that only three produced reliable test results. Of those three, only one had no false positives reported.

Quest Diagnostics warns consumers of possible unreliable results on its website, noting the test sometimes detects antibodies from other coronaviruses, including those that cause the common cold. In that scenario, the test results in a false positive. If someone with COVID-19 tests too soon after infection, the immune system may not have produced enough antibodies, leading to a false negative. 

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