Antibody Testing Insights

As we love to share as much information with our patients as possible, we wanted to pass along this great explanation regarding COVID-19 antibody testing. We hope you find it helpful and informative.

The immune system acts the same way in 98 percent of the population. When you are exposed to a virus, your body immediately starts to make antibodies. The body makes two antibodies in response to every viral or bacterial infection: IgM and IgG. The same process occurs each time your body experiences an infection.

The IgM antibody is the first antibody produced by the body and its production peaks at 7 days. After 14 days, the production of IgM has stopped and its presence in your bloodstream is diminished. In most people, IgM antibodies are undetectable 30 to 45 days following exposure to a virus.

Approximately 14 days following exposure to a virus, the body begins to produce the IgG antibody. Production of IgG continues to increase and hits a peak at roughly 30 days after viral exposure.  IgG is the antibody that is with you forever.  If your body were to encounter the same virus, IgG is the antibody that is rushed into production upon re-exposure.  It is your body’s targeted, virus-specific immune response to an infection.  The IgG antibody is the golden ticket.  It is not a perfect immunity, but it is a more rapid and robust response from your immune system if you are subsequently exposed to Covid-19.

For those who tested IgM positive, this result indicates that at some point in the last 5-10 days they were exposed to the Covid-19 virus.  Their body has identified the virus and has started to make antibodies to it.  The CDC currently recommends that anyone who is exposed should self-quarantine for 14 days.  Given what we know about the timeline for the body to begin producing IgM antibodies, self-quarantine for 10 days is recommended, which keeps with the CDC guidelines. For those who test IgM positive, checking in with your doctor is suggested in order for them to provide the best care possible.

For those who tested IgM positive and IgG positive, this result indicates that they are further along in the body’s immune response to the disease.  Their exposure was at least 14-30 days ago.  Enough time has passed that your body is able to start producing IgG, but within a timeframe that IgM antibodies are still detectable in the blood.  It is recommended that these individuals self-quarantine for 5 more days, in an abundance of caution, to prevent the spread of the disease.

For those who were simply IgG positive, their result indicates that they were most likely exposed to Covid-19 30-45 days ago.  They are no longer symptomatic or contagious.  They have had the disease and have developed a degree of immunity to it.  If you were to be re-infected by Covid-19, your immune system will be ready to fight it.

The COVID-19 virus is a novel coronavirus, meaning it is new to humans and therefore there is no existing immunity. The disease stages reflected by the results of the antibody test can be visualized in this highly simplified sketch: