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How testing works for COVID-19

17 January 2022

COVID-19 is the disease caused by the SARS-CoV-2 coronavirus.

To detect if a person has COVID-19, there are two kinds of tests. The tests can either detect:

  1. the presence of the SARS-CoV-2 virus in the body. This is usually done by testing if the virus is present in the throat, nose, nasal secretions (snot) or sputum (saliva/spit)
  2. if the body has produced antibodies to the SARS-CoV-2 virus. This is usually done by taking a blood sample to test for specific antibodies.

Detecting the presence of SARS-CoV-2 virus

Two types of tests that can detect the presence of the SARS-CoV-2 virus are nucleic acid and rapid antigen tests.

Nucleic acid tests

Nucleic acid tests detect the presence of nucleic acids (the genetic material) of the SARS-CoV-2 virus. Such tests are good at detecting the virus early in the infection, sometimes before a person feels unwell. Several types of nucleic acid tests can be used, including polymerase chain reaction (PCR) tests and isothermal nucleic acid amplification tests (such as loop-mediated isothermal amplification (LAMP) tests).

PCR tests are generally better at detecting the presence of the SARS-CoV-2 virus than rapid antigen tests.

Nucleic acid tests are complicated to do and usually need to be run by specialist scientists in a laboratory to get an accurate result. The laboratory scientists run these tests on automated machines that can do many tests at once. This means lots of people can be tested quickly.

Some nucleic acid tests for SARS-CoV-2 can be used outside of a laboratory by trained people. Most of these systems give results quickly but cannot do many tests at once.

Rapid antigen tests

Rapid antigen tests detect the presence of specific proteins of the virus. They are most accurate when used to test symptomatic individuals. They are not as good at detecting the virus as a nucleic acid test.

Rapid antigen tests are generally best performed within the first 7 days from when symptoms first appear. They are not as accurate if you do not have symptoms and can produce false negative or false positive results. Most tests produce a result within 10-20 minutes.

  • Point-of-care tests

    Rapid antigen point-of-care tests are performed by health practitioners, or trained persons under their supervision. This ensures an adequate sample is collected, the results are interpreted correctly and clinical advice and treatment can be provided, if required.

    For more information see rapid antigen point-of-care tests.

  • Rapid Antigen self-tests (home-use tests)

    Rapid antigen self-tests can be used unsupervised anywhere, such as at home or work, without the involvement of a health practitioner. The person taking the test will collect the sample, perform the test and interpret the results.

    For more information see rapid antigen self-tests.

Detecting antibodies to the SARS-CoV-2 virus

Antibody tests look in our blood to see if our body has produced specific antibodies. These antibodies help fight a current infection or helped to fight a past infection. Antibody tests do not detect the SARS-CoV-2 virus itself.

It takes time for our bodies to make antibodies. A person could be infected with the SARS-CoV-2 virus and be spreading it to other people before we can detect their antibodies.

Scientists usually run viral antibody tests in laboratories. However, since the beginning of the COVID-19 pandemic, some manufacturers have developed tests that can be used outside of the laboratory at the point of care. These are called point-of-care antibody tests. They can also be called serology or IgG or IgM tests. IgG and IgM are different kinds of antibodies made by our bodies to fight infection.

These point-of-care antibody tests are not intended for self-testing. They are designed to be used by a health professional. The supply of COVID-19 rapid antibody tests for self-testing is prohibited in Australia.