What is Rapid Antigen Test for COVID-19?

The Rapid Antigen Detection Test (RADT) for COVID-19 is a rapid point-of-care nasopharyngel swab test that directly detects the presence or absence of coronavirus antigen in the patient’s body, generating diagnosis results within 30 minutes. These tests are designed to detect a specific protein in the virus that elicits the body’s immune response.

RT-PCR, though highly accurate, requires complex bio safety compliant set ups and takes longer to give a result. We are thus seeing longer turnaround times as the number of cases rise. The antigen testing solves this problem to an extent as apart from being fast, it is highly specific and thus positive results are highly accurate.

How does an antigen test work?

An antigen is a molecule capable of stimulating an immune response. They may be proteins, polysaccharides, lipids or nucleic acids. Each antigen has distinct surface features that are recognized by the immune system.

SARS-CoV-2, the virus that causes COVID-19, has several known antigens, including its nucleocapsid phosphoprotein and spike glycoprotein, which are the visible protrusions on its surface.

An antigen test reveals if a person is currently infected with a pathogen such as the SARS-CoV-2 virus. Once the infection has gone, the antigen disappears. Unlike nucleic acid based tests such as PCR, which detect the presence of genetic material, antigen tests detect proteins or glycans, such as the spike proteins found on the surface of the SARS-CoV-2. They usually provide test results rapidly, are relatively cheap, and can be more amenable to point-of-care use, which could make them more suitable for testing in the community and in remote regions.