COVID-19 Self-Collection Kits

Antibody testing determines whether you had COVID-19 in the past and now have antibodies against the virus. 

A test to diagnose COVID-19 determines if you currently have the disease. 

COVID-19 antibody testing, also known as serology testing, is a blood test that's done to find out if you've had a past infection with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). An antibody test can't determine whether you're currently infected with the COVID-19 virus. 

Antibodies are proteins produced by your immune system in response to an infection. Your immune system — which involves a complex network of cells, organs and tissues — identifies foreign substances in your body and helps fight infections and diseases. After infection with the COVID-19 virus, it can take two to three weeks to develop enough antibodies to be detected in an antibody test, so it's important that you're not tested too soon.

Antibodies may be detected in your blood for several weeks after you recover from COVID-19. Although these antibodies might provide some immunity to the COVID-19 virus, there's currently not enough evidence to know how long these antibodies last or whether past infection with the virus protects you from getting another infection. Studies on COVID-19 antibodies are ongoing to learn more about immunity.

The FDA approved two types of tests for diagnosing COVID-19 — molecular and antigen.

• Molecular test. This test detects genetic material of the virus using a lab technique called polymerase chain reaction (PCR). Also called a PCR test, a health care worker collects fluid from a nasal or throat swab or from saliva. Results may be available in minutes if analyzed onsite or several days if sent to an outside lab. Molecular tests are considered very accurate when properly performed by a health care professional, but the rapid test appears to miss some cases. The FDA also approved certain COVID-19 at-home test kits, available only with doctor approval: A nasal swab kit and a saliva kit. The sample is mailed to a lab for testing. The FDA warns consumers against buying unapproved home tests, because they may be inaccurate and unsafe.

• Antigen test. This newer COVID-19 test detects certain proteins that are part of the virus. Using a nasal or throat swab to get a fluid sample, antigen tests can produce results in minutes. Because these tests are faster and less expensive than molecular tests are, some experts consider antigen tests more practical to use for large numbers of people. A positive antigen test result is considered very accurate, but there's an increased chance of false negative results — meaning it's possible to be infected with the virus but have negative antigen test results. So antigen tests aren't as sensitive as molecular tests are. Depending on the situation, the doctor may recommend a molecular test to confirm a negative antigen test result.

Results of COVID-19 antibody tests may not always be accurate, especially if the test was done too soon after infection or the test quality is questionable. Many different manufacturers rushed to put antibody tests on the market with little oversight. Now the U.S. Food and Drug Administration posts data online about the performance of certain antibody tests.

COVID-19 antibody testing could lead to false-positive or false-negative test results:

• False-positive result. The test result is positive, but you actually don't have antibodies and you did not have an infection in the past. A false-positive result could give you a false sense of security that you're protected from getting another COVID-19 infection — and even with a true positive result, immunity is questionable.

• False-negative result. You have antibodies to the COVID-19 virus, but the test does not detect them. Or you're tested too soon after infection and your body has not had time to develop antibodies

You should get a COVID-19 antibody test if:

• You are curious to know if you have the antibodies and have not had any symptoms of COVID-19 in the past 14 days;

• Have been diagnosed with COVID-19; it has been at least 14 days since your diagnosis; and you are curious to know if you have the antibodies;

• Have had symptoms of COVID-19 in the past but weren't tested;

• You're about to have a medical procedure, especially if you've had a positive COVID-19 diagnostic test in the past.

COVID-19 antibody test results could be:

• Positive. A positive test means you have COVID-19 antibodies in your blood, which indicates past infection with the virus. It's possible to have a positive test result even if you never had any symptoms of COVID-19. False-positive test results can occur. It may be that the test detected antibodies to a coronavirus closely related to the COVID-19 virus or that the test quality was flawed.

• Negative. A negative test means that you have no COVID-19 antibodies, so you probably were not infected with the COVID-19 virus in the past. Because it takes time for antibodies to develop, false-negative test results can happen if the blood sample is collected too soon after your infection started. In some cases, the test may be flawed.

People who have had COVID-19 or tested positive for antibodies should not assume they're protected from getting a COVID-19 infection again until infectious disease experts learn more about these antibodies. Researchers are trying to determine if antibodies provide some immunity to the COVID-19 virus, what the level of protection is and how long immunity may last.

Until more is known, even if your test results show that you have COVID-19 antibodies, continue to take precautions — including wearing a face mask in public, frequently washing your hands and practicing social distancing — to avoid the risk of spreading the virus.

Do not take the COVID-19 antibody test if you:

• Are showing COVID-19 symptoms;

• Have been diagnosed with COVID-19 within the past 10 days;

• Feeling sick and you think you may have COVID-19.