A rapid antigen test, or rapid antigen detection test is one of the two main tests – the other being the Reverse Transcriptase Polymerase Chain Reaction (RC-PCR) test – used to detect the presence of the SARS-CoV2 virus. An antigen is a foreign substance, present in the novel coronavirus, that triggers the body’s immune system, which responds by releasing antibodies. More specifically, the test is designed to detect the protein in the virus that triggers the immune response.
How it works
The rapid antigen test is typically a point-of-care test, meaning that it is performed at the time and place of patient care, outside a conventional laboratory environment. It is a nasopharyngeal swab test – secretions are collected along the length of the passageway that connects the back of the nose to the back of the throat.
Advantages and limitations of antigen testing
Rapid antigen tests offer several benefits, the most important being speed. It takes just 10 to 30 minutes to generate results. They offer high specificity, meaning that a positive result needs no further confirmation, allowing patients to isolate themselves quickly if they test positive. They also offer convenience, having been designed for both near-patient use as well as laboratory use. Additionally, they are relatively inexpensive compared to RT-PCR tests.
Accuracy is one of the main limitations of rapid antigen tests. While they offer high specificity, they are not as sensitive as RT-PCR tests, thereby resulting in false negatives. Negative results need to be confirmed by an RT-PCR test before any treatment decisions. Further, antigen testing can reveal whether a patient is infected with the novel coronavirus only at the time of testing. It is because there will be no traces of antigens before or after the infection.
