Stop the spread of COVID-19 with rapid antigen testing and get results in 3-15 minutes, not 3 days.

Updated: Sep 18, 2021

Widespread testing for SARS–CoV–2, the virus that causes COVID-19, is critical to knowing if, when and how people can start to return to their normal lives.

Rapid antigen testing for COVID-19 can be a huge help in reducing the spread of COVID-19 by expanding testing and detecting virus, even in asymptomatic cases.

In Australia, the TGA have approved a number of rapid antigen and antibody tests.

What is an antigen?

The human immune system work on a simple idea: Any protein in your body that is not encoded by your own genes is most likely from a pathogen and should be captured and destroyed.

When the immune system detects a foreign protein, your white blood cells, create antibodies to trap and destroy these proteins. Antibodies are Y-shaped proteins that use their arms as grabbers for foreign proteins. The first round of antibodies is not particularly well matched to the shape of a new invading protein, but every time white blood cells make new antibodies, they modify the shape of the antibody grabber until it fits the protein.

The foreign protein that triggers this process is referred to as an “anti–gen” because it is an antibody generator.

How does an antigen test work?

Antigen tests are well named: They look for antigens. To identify these antigens, antigen tests use antibodies.

You may have performed one yourself if you’ve ever used a home pregnancy test, which uses tests for an antigen called human chorionic gonadotropin in urine that is produced by the cells that surround a fetus when a woman becomes pregnant.

Like the test that diagnoses influenza, the SARS–CoV–2 antigen test uses antibodies to hunt for proteins embedded in the coronavirus’s surface. If the antibodies detect viral proteins in a sample, the person most likely has the coronavirus.

An antigen test for SARS-CoV-2 starts with a medical professional collecting a sample of mucus from the back of a persons throat or nose using a swab. They then dip the swab into a liquid to dissolve the mucus and release the virus.

The liquid is then applied to the surface of the test slide that is coated with antibodies. These antibodies are stuck to the slide and “grab onto” any coronavirus proteins that are in the sample.

A second mixture of antibodies is then applied to the slide. These antibodies have been chemically modified with a dye that makes them visible to the naked eye or detectable by fluorescent light.

If the sample contains viral antigen proteins, those antigens are now sandwiched by two antibodies: one that attaches them to the test kit and another that makes them visible. The more coronavirus antigen there is, the more dye will be visible, indicating that the patient is infected with SARS-CoV-2.

If there is no detectable dye, this would mean the person does not have SARS-CoV-2 or that the sample did not have enough viral proteins.

What are the benefits of antigen tests?

The main benefits of antigen tests are that they are far faster and easier to perform than reverse transcriptase-polymerase chain reaction (PCR) tests. PCR tests – the swab tests that look for viral RNA – are currently the most common way to test for an active SARS-CoV-2 infection and can take up to four days to perform.

By contrast, the most time-consuming part of the antigen test process is waiting for the antibody mixtures and the sample to mix completely. This process takes mere minutes, given the small volumes typically used in an antigen test.

Similar tests are done routinely in clinics for influenza all the time. In contrast, PCR tests swabs must be sent to diagnostic laboratories to be performed by experienced technicians as of right now.

While rapid antigen tests are not quite as accurate as PCR, studies have shown that repeat rapid antigen testing, and rapid response, is more effective at reducing viral transmission than single sample testing.

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