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COVID-19 Antibody Test

Does this test have other names?

SARS-CoV-2 serology test; COVID-19 serology test; COVID-19 semi-quantitative test

What is this test?

This blood test checks if you had a COVID-19 infection in the past. COVID-19 is caused by a coronavirus called SARS-CoV-2. The test looks for proteins in your blood (antibodies) that show up if you had the infection. The test doesn’t show if you’re infected with COVID-19 right now. That’s a different type of test called a viral test, which is done to diagnose a current COVID-19 infection. An antibody test is done to see if you had a previous COVID-19 infection.

It can take your body 1 to 3 weeks to make antibodies as a response to an infection. This test checks for two types of antibodies, called IgM and IgG, that develop after a person is infected. IgM antibodies show up first. IgG antibodies can show up a few days after that. Your test results may show you have one or both of these types of antibodies in your blood.

Newer COVID-19 antibody tests, called semi-quantitative tests, estimate the amount of SARS-CoV-2 antibodies in your blood. At this time, no antibody test can predict whether you are immune from COVID-19, because experts are still learning about the virus.

Why do I need this test?

You may have this test if your healthcare provider thinks you may have had COVID-19. This is not a test for people who may have a current infection or symptoms.

What other tests might I have along with this test?

In some cases, a healthcare provider may also test for an active COVID-19 infection. This is called a viral test. This type of testing is done with a nasal or throat swab. Or you may have tests for another type of infection, such as influenza or bronchitis. You may have another blood test, lung sputum test, or a chest X-ray.

What do my test results mean?

A positive test result means the test may have found antibodies in your blood from a previous COVID-19 infection, or possibly from a related coronavirus infection. You may test positive even if you didn’t feel sick. Some people who had COVID-19 had no symptoms or mild symptoms.

A negative test result means the test did not find these antibodies in your blood. This means you likely did not have a COVID-19 infection in the past. Or it could mean you had or have an infection, and your body hasn’t created antibodies yet.

If you had a semi-quantitative test, the results may show an estimate of the amount of SARS-CoV-2 antibodies in your blood.

Ask your healthcare provider when to expect to learn your results. The timing is based on whether you have a rapid test that can show results in 30 minutes, or a test sent to a lab for results. The type of test you have varies by what is available in your area.

No matter what your test results are, it’s important to follow CDC and your state and local instructions about wearing face masks and social distancing. Also practice good handwashing. This is to protect others. It’s also because researchers don’t know yet if having antibodies for COVID-19 mean that you are protected from getting the virus again. If the antibodies do protect a person, experts don’t know how long that lasts. They also don’t know how long a person who had COVID-19 may be able to infect others.

How is this test done?

The test is done with a blood sample. The tip of your finger may be pricked with a small sharp device. Or a needle may be used to draw blood from a vein in your arm or hand.

Does this test pose any risks?

Having a blood taken from a vein with a needle has some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What might affect my test results?

The accuracy of the test varies. It depends on several factors. This type of test is new, and there are tests from many testing companies right now. Some tests are approved by the FDA, but many are not. Because of this, the proven accuracy of their results varies. Some tests are more reliable than others. This means your test results may not be correct. You may test positive without having COVID-19 in the past. You may test negative even if you were infected.

Also, because it takes 1 to 3 weeks for antibodies to show up, the test results also depend on when you have the test. Having this test too soon after infection means it may not show COVID-19 antibodies.

Because your test results may not be accurate, you still need to follow your state and local instructions about wearing face masks and social distancing.

How do I get ready for this test?

You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.

Last modified date: 8/4/2020

Medical Reviewers:

  • Daniel Federman, MD
  • L Renee Watson, RN, BSN