Dear NP

Dear NP,

Can you talk about the COVID-19 antibody test? Specifically, who should get the test, what does it mean if I have a positive or negative test, and how long do antibodies last?

Dear Reader,

Now that the COVID-19 pandemic shows signs of resolution, at least locally, COVID-19 antibody bloods tests are becoming more readily available. When it comes to COVID-19 testing, you’ll find two main options: diagnostic tests and antibody tests.

A diagnostic test will show if you have an active COVID-19 infection and help determine if quarantining from others is necessary. Antibody testing can determine evidence of past infection with COVID-19.

If you are having symptoms and want to know if you have COVID-19, a diagnostic test is the right test to get. There are currently two types of diagnostic tests – molecular and antigen tests. Molecular tests, such as an RT-PCR test, look for the genetic material of the virus.

Antigen tests detect specific proteins of the coronavirus. With an antigen test, you will get quicker results, but they have a higher chance of missing an active infection. If your antigen test is negative, your provider may order a molecular test to confirm the result.

Antibody tests are not used to diagnose COVID-19. These tests detect antibodies made by your immune system to fight infection after exposure to a virus. A positive test would mean that you have been exposed to or had an infection with coronavirus in the past, while a negative test would indicate that you have not had an infection.

Your body may need several days to weeks to make antibodies after exposure, and these antibodies will stay in your blood for several weeks or longer after infection. Because of these, an antibody test cannot diagnose active COVID-19 and is not recommended for deciding if you are currently infected. Researchers are also unsure if coronavirus antibodies mean that you are immune to COVID-19 in the future or how long you will continue to have antibodies after infection.

An issue with current antibody testing is that it is not specific to the COVID-19 virus. If you’ve had an infection with another variant of coronavirus that may have given you symptoms like the common cold, your test may show positive.

You may also test positive even if you’ve never had symptoms of COVID-19. This can happen if you had an infection without becoming ill, which we call an asymptomatic infection.

While some people want an antibody test to see if they have already had COVID-19, organizations such as the Centers for Disease Control are not recommending antibody testing as the results do not provide meaningful information. Do not rely on a positive antibody test to protect against catching COVID-19 again or being able to pass the infection on to others. In the future, antibody tests may help determine response levels in those that have received a COVID-19 vaccine.

If you are concerned that you may have COVID-19 and desire testing, seek out a diagnostic test. Rapid testing is available for both molecular and antigen tests, which will give you a quick result.

A positive result means you have a current infection and will need to quarantine as directed by your health care provider. Unfortunately, no test is 100% accurate, and false negatives do occur. If you have symptoms of COVID-19 and a negative test, quarantine may still be recommended until you are feeling well again.

The best defense against COVID-19 is protective measures. Avoid large crowds, continue to socially distance whenever possible and wear a face covering. Frequently wash or sanitize your hands. If you feel ill, stay home and avoid exposing others. For more severe symptoms, contact your healthcare provider for recommendations.

Dr. Wesley Davis is an Emergency Nurse Practitioner at Crook County Medical Services District and Coordinator of the Family and Emergency Nurse Practitioner program at the University of South Alabama. He encourages readers to send their questions to [email protected]