COVID-19 Antibody Testing Explained
What is an Antibody Test?
A COVID-19 antibody test will help determine if you were previously infected with SARS-CoV-2 (the strand of coronavirus that causes COVID-19). Antibodies are the physical immune response to the presence of an antigen (toxin) that enters the body. When the antibody comes in contact with the SARS-CoV-2 virus, hypervariable regions at the antigen-binding site contribute to the specificity of the antibody. In the variable region, segments of protein chains fold together to form an antigen-binding pocket. Using this binding system, an antibody can tag an infected cell for attack by other parts of the immune system, or can neutralize the target directly.
- Patients of all ages should get tested to break the exposure cycle in our community (antibody test available for ages 13+)
- The test helps patients make safer, more informed decisions about their personal health
- Many patients who are asymptomatic or presymptomatic can spread the virus without knowing it
Coronavirus Antibody Testing FAQs
When should you get tested for antibodies?
Antibody testing offers information about whether you have been previously infected by SARS-CoV-2. Antibody testing may be right for you if the following is applicable to you.
- You are not currently experiencing symptoms consistent with COVID-19
- You have not experienced a fever in at least three days, and if you have not have had or suspect you have had COVID-19, but have not experienced any new symptoms in the past 10 days.
Who should get tested for antibodies?
Antibody testing is available to anyone over the age of 13 that does not suspect themselves of being actively infected with COVID-19. Antibody testing is available to anyone who is not feeling sick or has had not had a fever within the last three days or if you have been diagnosed with COVID-19 in less than 10 days, or if you have been directly exposed to COVID-19 in the last 14 days. Antibody testing is also not right for you if you have a condition that weakens your immune system.
How accurate is antibody testing?
There are several different methods for antibody testing and they vary widely in accuracy. There are two different major categories of antibody testing. Lateral flow kits or “rapid” antibody kits and antibody analyzers that are ELISA, CLIA, and CMIA. The lateral flow kits are significantly less accurate than the analyzers. The lateral flow kits range from 40% to 84% PPV at prevalence.
Antibody analyzers tend to be much more sensitive and accurate. The main types of antibody analyzers are ELISA (Enzyme-Linked Immunosorbent Assay), CLIA (Chemiluminescence Immunoassay), CMIA (Chemiluminescent Microparticle Immunoassay). All of these types of analyzers operate on the same basic principles. In their most simple forms, antigens are attached to a surface, then, a matching antibody is applied over the surface so that it can bind to the antigen. If there was a binding, the subsequent reaction produces a detectable signal that is used to measure the antibodies in the system.
These systems can then be categorized by the protein that they are targeting. Antibody analyzer systems that are detecting antibodies to SARS-CoV-2 target N, S1/S2, or S1 proteins. The most specific being the S1-RBD (Receptor Binding Domain) protein. Depending on which of these proteins that analyzer targets determines the specificity of the analyzer.
The Genalyte analyzer is a completely different type of anybody analyzer. The Genalyte MaverickTM SARS-CoV-2 Multi-Antigen Serology Panel uses photonic ring resonance to detect IgG and IgM antibodies.
How do antibody tests differ from PCR/Viral test?
After exposure to an antigen, antibodies continue to circulate in the blood providing protection from future exposure. The most prevalent and long-lasting antibody is IgG which can remain in the blood serum for over 6 months. The presence of IgG indicates recovery from the virus. The next most abundant is IgM which indicates an initial exposure to the antigen. Most antibody testing platforms with FDA EUA’s are testing for Pan-Ig or Ig (total immunoglobins) while many intend to extend their platform to include IgM or differentiate between IgM and IgG, IgM has been documented to only remain in the blood for as little as four days. IgM has been determined by many to have little clinical value; however, from a patient perspective differentiation of antibodies especially in tandem with viral testing, can offer a lot of information regarding their infection. 
How Your Antibody Testing Process Works
Sample Collection
One of our technicians will collect and register your sample in a private office in order to perform the test. The COVID-19 antibody test requires a small blood sample. If you believe you currently have COVID-19, the PCR test will require a nasal swab for analysis.
Antibody Testing
In traditional antibody testing methods, antigens are attached to a surface and then the matching antibody is applied over the surface, so it binds to the antigen. This antibody is linked to an enzyme and then the unbound antibodies are removed. If the antibody binds to the antigen, the subsequent reaction produces a detectable signal which can be used to measure the presence of antibodies.
At Bloom, we have partnered with Genalyte to bring a new and innovative solution to COVID-19 antibody testing. Genalyte has designed a revolutionary system using the Maverick SARS-CoV-2 Multi-Antigen Serology Panel v2. The Maverick system is a multiplex photonic ring immunoassay (PRI) for the semi-quantitative detection of IgG and IgM antibodies. This system utilizes the principles of photonic ring resonance to detect antibodies using only a microchip. Photonic ring resonance is a property of light wherein certain circumstances specific wavelengths are trapped in a ring resonator. Sensors based on silicon photonic ring resonators function by detecting the interaction between light circulating inside the sensor and matter deposited on the sensor surface. Binding of biological material results in a localized change in the refractive index on sensor surface. The patient sample flows over the microchip and a capture immunoassay measures the change of resonant wavelength.
What do your COVID-19 antibody test results mean?
If you are positive for Coronavirus Antibodies:
According to the CDC, a positive test result shows you may have antibodies from an infection with the virus that causes COVID-19. Having antibodies to the virus that causes COVID-19 may provide protection from getting infected with the virus again. You should continue to protect yourself and others since you could get infected again. You may test positive for antibodies even if you have never had symptoms for COVID-19. This can happen if you had an infection without symptoms, which is called an asymptomatic infection.
If you are negative for Coronavirus Antibodies:
Are you immune to COVID-19 if you have antibodies?
With other viruses, the human immune system fights off infection by creating antibodies and memory cells that recognize the virus if the individual is exposed again. This generally confers immunity once the person recovers. The immunity question is still to be determined with COVID-19, and many experts believe it is possible that people who have been infected with the virus once can get sick again and infect others.
However, some scientific research has provided evidence that antibodies to SARS-CoV-2 can protect from reinfection with greater protection resulting in symptomatic patients. This creates unique challenges for research in developing a vaccine.