Important information to consider about testing
There are two main types of tests for COVID-19 currently available. Each has its own limitations, and no test is 100% accurate all the time. If you and your healthcare provider think you have COVID-19, you should take appropriate precautions to avoid spreading it to others even if the test suggests you do not have it. More information about testing is available from the CDC.
Types of tests
Swab test, Polymerase Chain Reaction (PCR), or Nucleic acid amplification test (NAAT)
This type of testing, also called viral testing, is done by swabbing the nose or mouth. A positive test is generally a very reliable indicator that the virus is present and is the recommended test to determine if someone is currently infected. CDC provides further information on this type of testing.
- Positive test = test suggests you have the illness
- Negative test = test suggests you do not have the illness, but other factors must be considered such as the timing that the test is done
- There must be enough virus present for the test to detect it. The virus level may not be high enough for a test to be positive for several days after the person was exposed. People with symptomatic COVID-19 typically have high enough levels of virus in their bodies for a test to be positive.
- A negative test does not guarantee that a person doesn’t have the virus. A person who is tested immediately after they are exposed and infected, when the amount of virus in their body is still low, will have a negative test. That person will have enough virus to infect others soon after, even before they develop symptoms of COVID-19. If you are instructed to quarantine after an exposure to a person with COVID-19, you must remain isolated for the entire quarantine period, even if you test negative.
- Testing is generally not recommended in the clinical setting for people without risk factors for or symptoms of COVID-19 infection. Public health testing clinics in the community will test everyone, regardless of risks or symptoms.
Blood test, antibody or serology testing
This testing is done using a sample of blood collected by a venipuncture or a finger prick and detects antibodies produced as the body fights off the virus. These tests are most useful for determining if someone has been infected with COVID-19 in the past. Antibody tests are NOT recommended to determine if someone is currently infected. Further information about these types of tests can be found on the CDC and DHEC websites.
- Positive test = test suggests you had COVID-19 in the past
- Negative test = test suggests you have not been infected with COVID-19 in the past, but other factors must be considered such as the timing that the test is done
- It can take 1 to 3 weeks after infection occurs for your body to produce enough antibodies for the test to detect them. You may be currently infected even if you have a negative antibody test.
- We are still learning about antibody tests. At the present time, doctors and scientists do not know whether the antibodies detected by these tests will protect people against becoming infected again in the future. Until we learn more, no one should consider themselves immune to COVID-19 infection based on these results. You should still take precautions to protect yourself against future infections, even if your antibody test is positive.
Antigen testing, which detects a protein on the virus itself, is not yet widely available for COVID-19 testing.