Quantitative Antibody Test

Antibodies are proteins that the body produces in response (exposure) to an infection or vaccine. Antibodies are believed to be one of the components of the immune systems that provide protection against viral infection - such as COVID-19.

If you’ve been exposed to COVID-19 or received a COVID-19 vaccine, such as the Moderna or Pfizer vaccines, your body may have produced antibodies (anti-spike IgG) as part of the immune system response to the virus or vaccine. 

A clinician may be able to use this test to assess changes in the level of antibodies over time. The test may be appropriate to establish seroconversion (the change from a non-detectable to a detectable level of antibodies in the blood). Seroconversion can occur two to four weeks after exposure to COIVD-19 or vaccination. A clinician may use the numerical value produced by this test to track the long-term duration of an individual’s immune response. Comparison of numerical results will help determine how the immune response develops in an individual and persists over time. The results of this semi-quantitative test should not be interpreted as an indication or degree of immunity or protection from re-infection. 

In a study conducted by ADX Diagnostic Lab, the antibody levels begin to rise two weeks after the first dose and reach their peak between one and two weeks after the second dose. The average antibody level increases after the second dose by about 6 folds and drops to the first dose level approximately 6 months after the first dose. Antibody levels and temporal trends vary greatly between individuals.

How is this test performed? When you arrive at Accel Diagnostics, a phlebotomist will take a blood sample.  You do not need to do anything to prepare for the test. For additional information about COVID-19 testing, visit the FDA website or CDC website.  

What are the limitations of this test? Sometimes false negative or false positive results can occur:

• False negative may happen if tested too soon after being infected or vaccinated. The immune system can take 7-14 days on average to make enough antibodies to be detected. Individuals with weakened immune systems due to a medical condition or certain medications may also not develop detectable levels of antibodies after infection or vaccination.
•  False positive can happen if the test detects antibodies from other coronaviruses you may have been exposed to, like the virus that causes the common cold. If you are concerned about your results, it is important to follow up with a healthcare provider, who can evaluate your medical history. Current research shows that it may be best to get antibody testing 3 to 4 weeks after symptom onset or known exposure to COVID-19 to lower the chance of receiving a false positive or false negative result. Talk to your healthcare provider for more information about whether or not you should get tested.

Can this test help determine my level of immunity? While this test can help identify the level of antibodies developed after exposure to COVID-19 or vaccination, it should not be used to determine the level of immunity you have. Studies are underway to determine the level of antibodies that provide immunity against SARS-CoV-2 (COVID-19).

Can I use this test to track the antibody levels over time? Yes, this test provides a numerical value that helps determine whether or not you have antibodies at the time of testing. However, it is still unknown whether or not it is useful to track antibody levels over time. Follow up with your healthcare provider for additional guidance on how to interpret your test results.

Should I get tested? This test may be right for you if you:

• Have been vaccinated with the Moderna or Pfizer vaccine and want to know if you have detectable antibodies.
• Have previously tested positive for COVID-19 infection and want to know if you have detectable antibodies.
• Have never been diagnosed with COVID-19 and want to know if you have been previously exposed to the virus.

This test may NOT be right for you if you:

• Are feeling sick or have had a fever within the last 24 hours.
• Want to understand if you currently have COVID-19. 
• Have been previously diagnosed or suspect you’ve been exposed to COVID-19. In these cases, you should wait to get an antibody test until it has been at least 10 days after your symptoms started or after testing positive, you have not had a fever for 24 hours, and any symptoms have improved.