Antibody Testing for COVID-19 and Why it’s Important

By now everybody knows that the SARS-CoV-2 virus and the disease it causes, COVID-19, has caused unprecedented global turmoil.

Just recently testing has become available that allows us to differentiate between people who are suspected of having an active COVID-19 infection, and those people who may have had a prior exposure.  This testing, often referred to as antibody testing, doesn’t really tell whether or not a person is “positive” or “negative” for carrying the virus” but provides information about how a person’s body is responding to the virus.  

This test provides a good deal of important information.  Questions such as these can be answered with antibody testing:

  • Do I have COVID?

  • I was previously ill for several weeks, could it have been COVID?

  • Am I an asymptomatic carrier?

This is crucial information to know as it can be used to help determine those who may need quarantine and close medical surveillance, and those who do not.  

It’s worth mentioning that even though viral testing is available, most people aren’t getting it done.  As of this writing, April 13 2020, the number of people in the US who have actually been tested has been estimated by the US Centers for Disease Control (CDC) to be roughly 250,000.  This is just a tiny fraction (0.0007%) of the 327 million people living in the United States. 

It is highly likely that many more people have been exposed to the virus than those who have been tested.  In fact, the CDC estimates that at least 25% of people who have the virus do not have any symptoms.  These people, despite being exposed to the virus, have been able to successfully defend themselves from the infection without getting sick.  There are many potential explanations for this, most notably by being a generally healthy person.  When a person is exposed to a virus or THE virus, their body responds by activating their immune system.  The immune system is comprised of cells, such as T-cells, B-cells, and NK cells.  These cells work together to identify and destroy invaders such as viruses, bacteria, molds, cancer cells, etc.  This is what antibody testing is all about.

In the case of viruses, the B-cells are important because of their ability to defend us by making something called antibodies.  An antibody is a little chunk of protein that basically sticks to foreign matter in the body, an antigen, like a virus.  Antibodies are specific towards each invader to which they are directed.  For example, the B-cells will create specific antibodies for the SARS CoV-2 virus that differ from the antibodies made by the immune system for the Herpes Zoster virus.  

In addition to having virus specific antibodies, there are also different types of antibodies.  When a virus initially invades the body, the immune system creates a IgM antibodies.  IgM antibodies are made rapidly and are the first to show up to defend the body.  They are like the Special Forces; get in fast and neutralize the enemy.  The IgM response typically fades off after a couple of weeks, and is therefore typically associated with a recent or current infection.

Shortly after the IgM response the immune cells begin making IgG antibodies.  Eventually the IgG antibodies will be more prevalent than the IgM’s and this called seroconversion.  IgG antibodies are the most common type of antibody and, once made, often persist for life.  Therefore, IgG antibodies can be used to assess if a person has been previously exposed to an infective agent, such as a virus. For example, if test results show the absence of IgM antibodies to SARS CoV-2 and the presence of IgG antibodies it would mean that a person was previously infected, but they are not actively fighting a current infection. In some viral diseases the presence of IgG antibodies suggest that the person is then immune to that virus. 

Currently, there is a lack of data about whether or not the presence of SARS CoV-2 IgG antibodies will convey immunity.  It’s just too new of a virus for us to have enough data to know for sure.  In the case of SARS-CoV, the Severe Acute Respiratory Syndrome virus, the presence of IgG antibodies conveyed a roughly 3-year immunity.  

At Chambers Clinic we are committed to providing excellence to our patients, and the COVID antibody testing we are offering is no exception.  We have chosen to partner with Vibrant America for virus antibody testing.  Vibrant America has validated their testing and found it to be 97.14% sensitive and 98.36% specific.  Furthermore, samples are checked for four different COVID viral antigens- not just two antigens as is done by many other laboratories. This is a big deal.  It allows the test to be very specific and prevents false positives.

For more information call our office today at 480-389-3265

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