Testing for COVID-19 – Frequently Asked Questions

Health Street provides answers to COVID-19 testing questions to help companies and staff understand the types of tests available and how to interpret results of COVID-19 tests.

Antibody Test-Specific FAQs

What is the purpose of COVID-19 antibody testing?

An antibody test looks for antibodies in the blood. Your immune system makes antibody proteins to help fight infections. COVID-19 antibody tests will show whether or not you’ve developed antibodies against SARS-CoV-2, the virus that causes COVID-19, as a result of being exposed to that virus. An antibody test cannot tell you whether you have a current COVID-19 infection.

Antibody testing is also valuable because researchers can get a sense of how many people in a population have been exposed to and infected by COVID-19. In the future, antibody testing may show whether someone has immunity against COVID-19, meaning that they cannot get infected again. If antibodies make people immune to COVID-19, it can help inform leaders and public health officials about whether the population has reached herd immunity. Herd immunity is when a l​arge percentage of a population has become immune to COVID-19, which can protect those people who are not immune.

What are the different types of antibodies? Do they offer different types of immunity?

There are three different types of antibodies: IgM, IgG, and IgA.

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Immunoglobulin M (IgM) is usually produced as the body’s first response to an infection. However, for COVID-19, IgM antibodies are produced around the same time as IgG antibodies. Generally, IgM may provide short-term protection and can help tell if an individual has been recently infected
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Immunoglobulin G (IgG) is the most common type of antibody. It’s usually made several days to weeks after most infections. However, for COVID-19, IgM antibodies are produced around the same time as IgG antibodies. Generally, IgG remains in the body and may provide long-term protection against future exposure.
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Immunoglobulin A (IgA) is found in the blood, sinuses, lungs, and stomach. Generally, IgA helps protect these areas from infection. However, it is unknown what role these antibodies play in determining exposure or immunity to COVID-19.

There is not enough evidence at this time to suggest that people who have these antibodies are protected against future COVID-19 infections.

When do antibodies develop?

Based on the most current research, antibodies develop around 1 to 3 weeks after infection from COVID-19. However, this varies by individual, and some people may take a longer time to develop antibodies.

Do all COVID-19 antibody tests look for the same types of antibodies? ​Is there any advantage in getting one type of antibody test over another?

All COVID-19 antibody tests look for antibodies in the blood specific to the virus. There are antibody tests that look for ​one ​specific antibody (such as ​an​ IgG ​test). Other antibody tests look for the presence of ​any type of​ multiple​ antibod​ies​. Both types of tests are used to help identify if someone has been exposed to the virus.​ However, it has not yet been established whether tests that look for specific antibodies are more or less useful than tests that look for muliple antibodies. ​However, at this time, IgM and IgG antibodies are the most useful for assessing antibody response to COVID-19 because little is known about IgA antibody response in the blood.

Can antibody tests be used to diagnose a COVID-19 infection?

Antibody tests do not show whether a person is currently infected. A molecular (PCR) test is a more reliable indicator of current COVID-19 infection.

My COVID-19 antibody test was positive, but I’m still having symptoms. What should I do?

If you’re having symptoms of COVID-19, contact your healthcare provider or local health department to get tested for active infection. The antibody test can only tell you if you’ve been exposed and have developed an immune response, but it cannot say whether you have an active infection.

My COVID-19 antibody test was negative, but I previously tested positive for COVID-19 or was exposed. Is my result incorrect?

Getting an antibody test too soon after being infected may cause a false negative result. It usually takes around​ ​1 to 3 weeks after being infected with COVID-19 for your body to produce enough antibodies to be detected in the blood. Some people may take even longer to develop antibodies or may not develop enough antibodies to be detected by the test. If you get a negative result for COVID-19 antibodies but you feel that you were exposed, it is recommended that you contact your healthcare provider or local health department to see if retesting is needed.

If my COVID-19 antibody test is positive, can I get sick again with COVID-19?

If your test results show that you’re positive for COVID-19 antibodies in the blood, it means you’ve likely been exposed to COVID-19. Although having antibodies usually gives immunity from further infection, there is not enough evidence at this time to suggest that people who have these antibodies are protected against future COVID-19 infections.

What is the chance that my COVID-19 antibody test result was a false positive?

False positives occur when a person tests positive even though they DO NOT have the antibodies for COVID-19. There is a small chance that the result could be a false positive. Manufacturers must demonstrate a high specificity of approximately 99% to 100% to ensure validation of their test. ​If you have additional questions, please contact the lab directly for more information.

If I had more severe symptoms of COVID-19, will I have a higher antibody level?

Some studies have shown that individuals with more severe symptoms develop higher antibody levels. However, although having antibodies usually gives immunity from future infection, there is not enough evidence at this time to suggest that people who have higher amounts of these antibodies are better protected against future COVID-19 infections.

Can I have antibodies if I did not have any symptoms of COVID-19?

You can have antibodies from an asymptomatic COVID-19 infection. An asymptomatic infection is when you are infected but do not show any symptoms.

Can my antibody value change over time?

It usually takes 1 to 3 weeks for antibodies to be detected in your blood. Because antibodies develop over time, it’s possible that your antibody levels can change depending on when you tested.

My antibody value is low. Should I get retested to see if my result will change?

It usually takes 1 to 3 weeks for antibodies to be detected in your blood. Because antibodies develop over time, it’s possible that your antibody levels can change depending on when you tested. However, this varies by individual. Talk with your healthcare provider or local health department about your results to see if retesting is advised.

What does an indeterminate COVID-19 antibody test result mean?

If your test result is indeterminate for COVID-19 antibodies in the blood, this means that the results were neither positive nor negative. You will likely need to be retested in order to confirm whether or not you have antibodies in the blood. An indeterminate result can happen if you do not have enough antibodies in your blood for the test to detect, such as if you test too soon after becoming infected. This result can also happen if there was a problem with your sample or the test itself.

Based on the results of my antibody test, do I need to continue social distancing and/or wearing a mask? Can I visit someone who is at risk for severe symptoms of the virus?
At this time, there is no test that can tell you when to stop social distancing or isolating. Be sure to check with your healthcare provider about next steps and continue to follow federal, state, and local government guidance regarding social distancing and COVID-19 safety precautions. You should also use caution or avoid visiting at-risk individuals like those above the age of 65 or with pre-existing medical conditions.

If I have antibodies, am I a good candidate for donating plasma?

People who have fully recovered from COVID-19 and have antibodies are encouraged to consider donating plasma. You must be completely recovered from symptoms for at least 14 days prior to donation. If you have additional questions, please contact the donation center directly for more information.

What guidance does the FDA provide regarding COVID-19 antibody testing?

Antibody testing can play a critical role in the fight against COVID-19. It can help identify individuals who may have been exposed to COVID-19 and have developed an immune response. Using antibody tests and clinical follow-up can also provide more information on immunity against COVID-19 for research and medical developments for the virus.

General Test FAQs

How do I know if the COVID-19 test is accurate and reliable?

Health Street only offers COVID-19 antibody tests that have received Emergency Use Authorization (EUA). These approved tests minimize the chance of inaccurate, false positive, or false negative results. The FDA has found that tests that meet certain standards are of superior quality and have high sensitivity and specificity (measurements of accuracy). Actual sensitivity and specificity may vary between test manufacturers. A sample that is not properly collected may also result in an inaccurate result.

What is the difference between an antibody test and a PCR test?

An antibody test checks to see if you’ve developed antibodies against COVID-19, which occurs after being exposed to the virus. Antibody tests do not show whether a person is currently infected.

PCR tests check for genetic material (viral RNA) produced by the virus. It determines if you’re currently infected and can spread COVID-19 to others.

When would I get an antibody test vs. a PCR test?

You should get an antibody test if you’ve been previously exposed or believe you’ve been exposed to COVID-19 and want to see if you have developed antibodies.

You should get a PCR test if you think you have an active COVID-19 infection. Visit the ​CDC website​ for more information.

If I’m having symptoms of COVID-19 or believe I’ve been exposed to it, what type of test should I get?

If you’re currently having symptoms of COVID-19 or have recently been exposed, you should get a PCR test to see if you’re currently infected.

Can an antibody test be used instead of a PCR test to diagnose COVID-19?

Antibody tests do not show whether a person is currently infected. Therefore, they should not be used in place of a PCR test to diagnose a current infection.

Can an antibody test be used together with a PCR test?

Antibody tests can complement PCR tests by providing information about exposure and how the immune system responds to ​COVID-19​ infections.

Can a COVID-19 test tell me when I can visit someone who is at risk for severe symptoms of the virus?

There is no test that can tell you when you can visit someone who is at risk for more severe symptoms of COVID-19. Check with your primary healthcare provider or local health department to help determine when the time is right to make such visits. Be sure to continue to follow federal, state, and local government guidance regarding social distancing and COVID-19 safety precautions.

What is the difference between Emergency Use Authorization (EUA) and Food and Drug Administration (FDA) approval?

The FDA has the authority to grant Emergency Use Authorization (EUA) to diagnostic tests that have not yet received formal approval in times of a public health emergency. The FDA has granted EUA for certain tests during the COVID-19 pandemic to help detect or diagnose COVID-19.

Like full FDA approval, EUA relies on strict standards. However, EUA is completed more quickly based on the limited data that is available, unlike full FDA approval.

For more information, please visit the ​FDA website​.

Have COVID-19 tests been approved by the Food and Drug Administration (FDA)?

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The antibody tests and the molecular tests (together referred to as “tests”) have not been cleared or approved by the Food and Drug Administration (FDA).
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The FDA has authorized the use of some tests by certain laboratories under Emergency Use Authorization (EUA).
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The antibody tests have been authorized for the detection of antibodies against SARS-CoV-2 only, and not for the detection of any other viruses or pathogens.
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The molecular (PCR) tests have been authorized for the detection of nucleic acid from SARS-CoV-2 only, and not for the detection of any other viruses or pathogens.
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Tests are only authorized for as long as the circumstances exist to justify the authorization of emergency use of in vitro diagnostics for detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Act, 21 U.S.C. § 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner.

What guidance does the FDA provide regarding Antibody Testing for COVID-19?

Having antibodies usually gives immunity from further infection. However, there is not enough evidence at this time to suggest that people who have these antibodies are protected against future COVID-19 infection. Nevertheless, experience with other viruses suggests that people with antibodies may be able resume work and other activities, as long as they are recovered and not currently infected.

What does “sensitivity” mean? What does “specificity” mean?

Sensitivity and specificity are different and complementary measures to inform doctors and patients about the accuracy of a test. A good test has both high sensitivity and high specificity.

Sensitivity​ is a measure of how well a test is able to detect people who are infected (positive cases). If a person has an infection, a test with 100% sensitivity can accurately detect it with a positive result.

Specificity​ is a measure of how well a test can detect people who are NOT infected (negative cases). If a person does not have an infection, a test with 100% specificity can accurately detect it with a negative result.

What are false positives and false negatives?

A positive result that is incorrect is called a false positive. False positives occur when a person tests positive even though they do not have the infection.

A negative result that is incorrect is called a false negative. False negatives occur when a person tests negative even though they do have the infection.

False negatives and positives can worsen the COVID-19 pandemic by providing false reassurance to those who have the infection or by causing those who do not have it to use critical resources.