By Beth Lawrence
Antibody tests to detect previous COVID-19 infection have become a hot topic lately.
Though there are tests out there, not enough is known about their reliability for Jackson County Department of Public Health to recommend taking one right now, Deputy Health Director Melissa McKnight said.
Experts are predicting there have been numerous undiagnosed cases of COVID-19 because in the early stages of the pandemic testing capability was insufficient and there were narrow guidelines for who could be tested.
To get a better picture of how widespread the disease was, many experts have begun recommending antibody testing.
The National Institute of Health commenced a study in April to measure the number of undiagnosed SARS-CoV-2 cases. The testing will check for antibodies which indicate a person was previously infected with a disease.
To understand how antibody testing works, it helps to know what antibodies are and the purpose they serve.
“Antibodies are specific proteins that your body makes in response to infections,” McKnight said.
Antibodies are also specific to the infection. The immune system produces antibodies which work by attaching to germs. They may block the germ’s ability to attach to the body’s other cells and spread the infection, or they may identify the germ to be destroyed by the immune system.
Allergies are an example of antibodies and the immune system at work, although allergic reactions are the body’s immune system working in overdrive.
Antibodies are prevalent in the blood after an infection has run its course.
“An antibody test checks your blood by looking for antibodies which generally show if you have had a previous infection with a virus and an immune response to that infection,” McKnight said.
There are several antibody tests commercially available right now, but evidence has proven some to be unreliable.
The Centers for Disease Control and Prevention is working to develop a standard.
“It is very important to know that the CDC is still evaluating the performance of the COVID-19 commercial antibody tests,” McKnight said.
CDC has its own blood test to specifically test for antibodies related to COVID-19.
The goal is “to determine how much of the U.S. population has been infected with SARS-CoV-2, the virus that causes COVID-19,” the CDC said. “Antibody test results are especially important for detecting previous infections with few or no symptoms.”
The CDC is also using its test to check the accuracy of commercial antibody tests.
The antibody tests for SARS-CoV-2 can only predict whether or not a person has been infected with COVID-19. There is not yet enough information available to determine whether or not infection and the presence of antibodies will prevent future infection or for how long.
There has been concern that some antibody tests are testing for the presence of coronaviruses not specifically related to COVID-19, and that those results could skew COVID-19 case counts.
“While there are seven different types of coronaviruses that infect humans, only four are common in humans,” McKnight said. “People around the world commonly get infected with these four and they are not reportable to the Health Department.
“Other human coronaviruses include MERS, SARS, and the new COVID-19. These three are rare and are reportable to the Health Department. Healthcare providers can test patients for coronaviruses other than COVID-19 based on their clinical discretion. However, they are only required to report lab confirmed cases of COVID-19 to the Health Department. Our case counts and communicable disease investigation is based on COVID-19 positive lab reports only.”
The tests should not be taken as proof of immunity. Not enough is known right now to definitively answer that question, McKnight said. Experts also don’t know the amount of antibodies needed to protect against this disease or how long they will provide immunity.
Antibodies may provide lifetime immunity after an infection such as with a person who has contracted measles or received a vaccine for it. Or the antibodies may provide limited protection, such as with flu and colds.