This Is When You Should Get a COVID-19 Antibody Test

Antibody tests for COVID-19 have been available for months, but the medical community has been largely unsure of when and how to use them. Now, a panel of experts hopes to change that with newly-released recommendations.

The recommendations, which were published in the journal Clinical Infectious Diseases on September 12, were created under the guidance of the Infectious Diseases Society of America. The recommendations acknowledge that there are concerns about the accuracy of antibody tests—also known as serology tests—noting that the accuracy “has not been well-defined.”

However, the panel wrote, there are specific instances when the use of antibody testing may be warranted:

• In patients with a “high clinical suspicion for COVID-19” when testing for the virus is negative and at least two weeks have passed since the patient first experienced symptoms.
• In cases where medical providers suspect multisystem inflammatory syndrome in children (MIS-C), a complication of COVID-19 that causes different body parts to become inflamed.
• For surveillance studies, to help track the portion of the population exposed to COVID-19.

The researchers made it clear that the tests are not helpful in diagnosing COVID-19.

Antibody Test Basics

A COVID-19 antibody test involves a blood test to look for antibodies or proteins that indicate a person may have had a past infection with SARS-CoV-2, the virus that causes COVID-19, according to the Centers for Disease Control and Prevention (CDC). Antibodies are disease-specific and can provide protection against getting a particular illness again.

These tests should not be used to diagnose a current COVID-19 infection, except in situations where viral testing is delayed, the CDC says. An antibody test also may not show if a person has a current COVID-19 infection because it can take up to three weeks after infection for the body to make antibodies.

Research suggests that antibodies to COVID-19 may wane over a period of a few months, making it unclear whether developing antibodies to the virus can provide lasting protective immunity.

Timing Matters with Testing

Antibody tests for COVID-19 aren’t perfect. One meta-analysis of 54 studies conducted by Cochrane found that antibody tests performed a week after COVID-19 patients first developed symptoms only detected 30% of people with the virus. After two weeks, testing detected antibodies in 70% of those patients and, after three weeks, antibodies were detected in more than 90% of those tested.

“Timing matters because, if you get tested too early after being infected, you may have a negative antibody test in your blood, and it is a waste of time and money to get tested,” Janet Englund, MD, a professor of pediatric infectious diseases at Seattle Children’s Hospital and University of Washington, who co-authored the recent recommendations on antibody testing, tells Verywell.

The actual test you use “doesn’t matter,” Englund says, adding, “getting tested too early may not be helpful.” 

As for the perfect timing to get a test, it’s “up for debate,” Jamie Alan, PhD, an assistant professor of pharmacology and toxicology at Michigan State University, tells Verywell. “We can take our best guess at timing but, until we know more, we are still at the ‘best educated guess’ stage,” she says.

There Is No ‘Best’ Antibody Test

There are a lot of antibody tests available, including some that can be done at home. But it’s unclear at this point which is the best.

“I don’t know what the best antibody test is, and I do not know who knows that,” Englund says. “There are multiple tests out there and many approaches to testing for antibodies, and many are very good.”  

However, your doctor may be able to give you more guidance. “Most clinicians who work at a hospital or clinic know what type of test their institution uses and can find out how ‘good’ the test is,” Englund says. And, while the Food and Drug Administration (FDA) recently granted emergency use authorization for a rapid antibody test for COVID-19, Englund says the information antibody tests can provide “is not urgent.”

“The antibody test is done to see if you were infected with SARS-CoV-2 in the past,” she says. “This test usually doesn’t become positive until at least about 10 to 12 days after infection, so it typically is not important to get done rapidly.”

Ultimately, if you have symptoms of COVID-19 or suspect you recently were infected with the virus, it’s a good idea to talk to your doctor about next steps. “If you still have symptoms and were sick or exposed for less than 10 days, you should not get an antibody test,” Englund says. “You should discuss this with a healthcare provider and likely get a diagnostic viral test like a PCR test or an antigen test to actually see if you are infected.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.