The WHAT, HOW, WHO and WHY of Antibody Testing By: Mary Ellen Pratt, FACHE, CEO
COVID-19 was introduced to the world as the “Novel Coronavirus.” Described as novel, new and different, there is still much to learn and understand about COVID-19. New information and new tests are being researched and developed every day.
The CDC is currently evaluating the performance of commercially manufactured antibody tests in collaboration with other government agencies such as the FDA. Due to the state of emergency, these agencies are speeding up the approval process and testing methodologies are being approved for emergency use.
HOW is antibody testing different than diagnostic testing?
The purpose of antibody testing versus diagnostic testing is very different. Diagnostic testing—performed by a nasal or throat swabbing—is done to detect the presence of viral genetic material which helps determine if a person has a current infection. These tests are typically done when patients are symptomatic.
An antibody test is a blood test designed to detect antibodies (immunoglobulins such as IgG and IgM) produced by the immune system in response to an infection such as the coronavirus. Antibody tests are not used to diagnose COVID-19, but simply to indicate whether a person was exposed to the virus. Antibody tests aren’t required and don’t change treatment of COVID-19 or any other medical conditions. IgM and IgG antibody tests may either be ordered together (combination) or separately.
WHY should an antibody test be used?
COVID-19 Antibody testing was initially developed by the CDC for two reasons:
1. As a large scale study to evaluate the overall impact of the pandemic by estimating the total number of people who were infected with SARS-CoV-2—the virus that causes COVID-19
2. As a way to evaluate the performance and accuracy of diagnostic tests
Antibody tests also help to detect previous infections in people with little or few symptoms. Your physician, for example, may decide to order an antibody test if you are asymptomatic, but live with a family member with COVID-19 or if you have been in close contact with someone who has tested positive for COVID-19.
WHEN should a person get tested?
If you are asymptomatic or have mild symptoms, but feel concerned because you have been exposed to someone who tested positive for COVID-19, talk to your physician. Your physician can discuss symptoms to look for and determine if he or she believes a diagnostic or antibody test would be most beneficial.
Generally, antibodies being tested develop between 8 -14 days post exposure, so make sure to tell your doctor when a potential exposure could have happened. If you move forward with antibody testing, it is best to wait 10 days after initial symptoms or exposure.
WHAT do results mean?
If your antibody test is positive:
- You have antibodies that likely resulted from an infection with SARS-CoV-2 (COVID-19) or possibly a related coronavirus.
- It’s unclear if those antibodies can provide protection (immunity) against getting infected again.
- If you have no symptoms, you likely do not have an active infection and no additional follow-up is needed.
- If you have symptoms and meet other guidelines for testing, you will need a diagnostic test (swab test) to confirm if you are positive for COVID-19. An antibody test cannot determine if you are currently sick with COVID-19.
- It’s possible to test positive for antibodies even if you never had symptoms of COVID-19. This is known as an asymptomatic infection.
If you test negative:
- You probably did not have a previous infection that has gotten better. However, you could have a current infection. It’s possible you could still get sick if you have been exposed to the virus recently, since antibodies don’t show up right away. This means you could still spread the virus.
- Remember, some people may take longer to develop antibodies and some people may not develop antibodies.
- But you have symptoms and meet other guidelines for testing, you need a diagnostic test (swab test) to confirm if you have COVID-19. An antibody test cannot determine if you are currently sick with COVID-19.
For now, there is still much to learn about what a positive COVID-19 antibody test really means, so the general consensus for the public is, “Don’t let your guard down.” It’s important to continue to protect yourself and others by following best practices such as social distancing, hand washing, disinfecting high-touch areas and wearing a mask in public.
St. James Parish Hospital is now offering COVID-19 antibody testing with a physician’s order. We remain committed to learning about new tests as they are approved and available.
Visit www.sjph.org/coronavirus often to learn about new testing information and COVID-19 announcements.
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