There are three types of tests used for COVID-19: polymerase chain reaction (PCR), antigen, and antibody (serology) testing. PCR and antigen tests will tell a person if they are currently infected with the virus that causes COVID-19, and serology detects whether a person had an infection in the past.
PCR Test
Why is the test used?
PCR tests look for pieces of the virus in the nose, throat, or other areas of the respiratory tract to determine if the person has an active infection.
How is the test performed?
In some cases, a nasal or throat swab is taken by a health care provider or self-administered and sent to a lab to be tested. Sometimes the test can be run while you wait.
What does a positive test result mean?
A positive PCR test means the person who was tested has an active COVID-19 infection.
What does a negative test result mean?
A negative PCR test means that person was probably not infected at the time their sample was collected. It does not mean they won’t get sick – it only means they did not have COVID-19 at the time they were tested.
Antigen Test
Why is the test used?
Antigen tests look for pieces of proteins that make up the virus to determine if the person has an active infection.
How is the test performed?
In most cases, a nasal or throat swab is taken by a health care provider and tested. Sometimes the test can be run while you wait, and sometimes the swab is sent to a lab for testing.
What does a positive test result mean?
A positive antigen test means the person who was tested has an active COVID-19 infection.
What does a negative test result mean?
A negative antigen test means that the virus was not detected. However, a negative test does not rule out COVID-19. If there is still a concern that a person has COVID-19 after a negative antigen test, that person should be tested again with a PCR test.
Antibody (Serology) Test
Why is the test used?
Serology looks for antibodies that are formed to fight off the virus in blood to determine if there was a past infection.
How is the test performed?
In most cases, a blood sample is taken and sent to a lab for testing.
What does a positive test result mean?
A positive antibody test means the person who was tested was infected with the virus that causes COVID-19 and their immune system developed antibodies to the virus. The person should also receive a PCR or antigen test to determine if they are still actively infected with the virus.
What does a negative test result mean?
A negative antibody test means that the person may not have had COVID-19 in the past. However, the person could still have a current infection, and the antibody test was collected too soon to give a positive result.