There’s a lot of discussion lately about antibody testing for Covid-19. In many instances, people want to know if it’s safe to re-open and go back to work or school.
Some want to know if they currently have the virus. Others want to know could they have had the virus.
As scientists learn more about the novel Covid-19 virus (SARS-CoV-2), it is helpful to understand what antibody testing is and how it may be a useful tool in re-opening public activities.
Antibody testing is not the same as Covid-19 diagnostic testing.
Diagnostic testing is performed to determine whether or not there is an active infection. If a patient has any symptoms of Covid-19, such as fever, body aches, headache, fatigue, cough, then the diagnostic test tells them if they have active Covid-19 or not.
Antibody testing is performed to determine if one had an infection in the past and has built up antibodies. Antibodies, also known as an immunoglobulin, are proteins produced by the body that are used by the immune system to fight infections such as bacteria and viruses.
Antibodies are produced in COVID-19 virus infection. One type of antibody called IgM can be detected in a blood test during active infection. The other antibody detected in the blood is called IgG which can be detected by 14-18 days after exposure. Therefore, the Covid-19 antibody test that is performed by Atlanta Urgent Care looks for this IgG antibody. If positive, there is a strong chance that you had a Covid-19 infection in the past.
Atlanta Urgent Care offers both Diagnostic Testing and Antibody Testing for COVID-19.
The diagnostic Covid-19 (corona virus) test is a nasal swab assay test. The antibody test is done by a simple blood draw. Results are available in 2-3 days.
The FDA originally allowed antibody tests for Covid-19 to come to market even though they had not been tested or scrutinized as much as normally required. This was part of the Emergency Use Act and was designed to make things readily available during the pandemic. As a result, the market was flooded with tests that are misleading, if not faulty. The result was that when consumers would go for an antibody test, they may end up getting one that picks up viruses other than SARS-CoV-2 (coronavirus/Covid-19). We at Atlanta Urgent Care did not take this route. We waited till the proper test came along.
The Labcorp and Quest IgG antibody test used by Atlanta Urgent Care reportedly have a very high specificity and sensitivity. The sensitivity (or true positive rate) correctly identifies people with the disease. The specificity (or true negative rate) identifies people who do not have the disease.
There is an assumption that a positive antibody test means that one not only had the disease, but also is immune to it and won’t get re-infected. While there isn’t much data on this due to the fact that it is a novel virus, Dr. Anthony Fauci, the US director of the National Institute of Allergy and Infectious Diseases, and others are optimistic (based on SARS data and low mutation rates of SARS-CoV-2). About 2 weeks after exposure to SARS-CoV-2, IgG antibodies begin to develop and stay in the system-hopefully to help with immunity.
It is to note by many virologists and immunologists that immunity can be implied based on the fact that immunoglobulin plasma (Covid-19 antibodies from those who recovered from the illness) is being used to treat patients with the active Covid-19 infection. Second, based on other types of corona virus antibodies found in the body, it has been found that these antibodies do help with immunity.
As of today, more studies are needed to prove whether Covid-19 antibodies imply immunity.
The CDC and WHO still recommend using clinical criteria in making decisions on back to work/school. The guidelines that govern infection control and contact tracing state that 14 days after symptoms abate a person is no longer contagious.
The bigger question is what to recommend for people who appear healthy. In the coming days and weeks, government officials will begin to develop more guidelines and recommendations for schools and places of work.
Until there is clear direction, people will have to discern the risk in their individual circumstances. Until there is a vaccine, people can minimize their risk of infection by frequent hand washing, avoiding confined indoor public spaces with other people, and wearing a mask in public.