I've heard about antibody testing for COVID-19. What is antibody testing? Is it the same as testing to diagnose COVID-19?

Antibody testing shows whether you have antibodies to the virus that causes COVID-19, also called coronavirus disease 2019.

Having antibodies suggests you've either had an infection with the virus in the past or you've had the COVID-19 vaccine. Antibody testing is not used to diagnose COVID-19.

What are antibodies and why are antibody tests done?

Antibodies are proteins. The body makes antibodies when there are things in the body that shouldn't be there, such as viruses. The antibodies help clear out the virus. Having antibodies to a virus may give some protection from the disease caused by the virus for a time.

A blood test can show whether you have antibodies to the COVID-19 virus within days to weeks of having the infection or the vaccine. But antibody testing, also called serology testing, is not done routinely.

A healthcare professional might use an antibody test to diagnose complications of COVID-19. These include multisystem inflammatory syndrome, a rare condition linked to COVID-19.

If you've gotten over COVID-19, you might be able to help others who have COVID-19. If testing shows that you have a high level of antibodies, you might donate part of your blood called plasma. This is called convalescent plasma. It may help others with severe disease who have a weakened immune system.

What tests are used to diagnose COVID-19?

Two types of tests can help diagnose COVID-19.

  • Molecular tests. These tests look for genetic material from the COVID-19 virus.

    Polymerase chain reaction tests, shortened to PCR tests, are molecular tests. You may also hear this type of test called an NAAT test, short for nucleic acid amplification test.

    PCR tests are more accurate than the other type of COVID-19 test, called an antigen test. You can do PCR tests at home. But they are more likely to be done by a healthcare professional and processed in a lab.

  • Antigen tests. These tests look for viral proteins called antigens.

    Antigen tests also may be called rapid COVID-19 tests or at-home COVID-19 tests. These tests are useful if you need quick results.

    Antigen tests are accurate. But they're less accurate than PCR tests. If you have symptoms and an antigen test is negative for COVID-19, take another antigen test after 48 hours to get the best result.

    If you don't have symptoms and get a negative result, test again after 48 hours. If the result is still negative and you think you have COVID-19, you can test a third time after another 48 hours. Or you can get a molecular test or call your healthcare professional.

How do I get a COVID-19 diagnostic test?

In the United States, at-home COVID-19 tests are available from several sources. Free tests can be mailed to U.S. addresses, or you can buy tests in stores and pharmacies or online. The U.S. Food and Drug Administration (FDA) approves the tests. On the FDA website, you can find a list of the tests that are validated and when they expire.

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May 14, 2024 See more Expert Answers

See also

  1. Antibiotics: Are you misusing them?
  2. Convalescent plasma therapy
  3. Coronavirus disease 2019 (COVID-19)
  4. Coronavirus infection by race
  5. COVID-19 and pets
  6. COVID-19 and vitamin D
  7. COVID-19 and your mental health
  8. COVID-19 antibody testing
  9. COVID-19 drugs: Are there any that work?
  10. COVID-19 in babies and children
  11. COVID-19 tests
  12. COVID-19 travel advice
  13. COVID-19 vaccine: Should I reschedule my mammogram?
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  16. COVID-19 variant
  17. COVID-19 vs. flu: Similarities and differences
  18. COVID-19, cold, allergies and the flu
  19. COVID-19: How can I protect myself?
  20. COVID-19: Who's at higher risk of serious symptoms?
  21. Debunking coronavirus myths
  22. Diarrhea
  23. Different COVID-19 vaccines
  24. Extracorporeal membrane oxygenation (ECMO)
  25. Fever
  26. Fever treatment: Quick guide to treating a fever
  27. Fever: First aid
  28. Fight coronavirus (COVID-19) transmission at home
  29. Herd immunity and coronavirus
  30. Honey: An effective cough remedy?
  31. How to measure your respiratory rate
  32. How to take your pulse
  33. How to take your temperature
  34. How well do face masks protect against COVID-19?
  35. Is hydroxychloroquine a treatment for COVID-19?
  36. Long-term effects of COVID-19
  37. Mayo Clinic Minute: How dirty are common surfaces?
  38. Mayo Clinic Minute: You're washing your hands all wrong
  39. Multisystem inflammatory syndrome in children (MIS-C)
  40. Pregnancy and COVID-19
  41. Safe outdoor activities during the COVID-19 pandemic
  42. Safety tips for attending school during COVID-19
  43. Sex and COVID-19
  44. Stool color: When to worry
  45. Thermometers: Understand the options
  46. Thrombocytopenia
  47. Treating COVID-19 at home
  48. Undigested food in stool
  49. Unusual symptoms of coronavirus