Rapid Antigen Test

Subject – Science and Tech

Context – States/UTs directed to ramp up rapid antigen tests

Concept –

The test is done on swabbed nasal samples that detect antigens that are found on or within the SARS-CoV-2 virus.
- Antigens are foreign substances that induce an immune response in the body.
It is a point-of-care test, performed outside the conventional laboratory setting, and is used to quickly obtain a diagnostic result.

RT-PCR vs Rapid antigen test:

RT-PCR is currently the gold standard frontline test for the diagnosis of Covid-19.
Like RT-PCR, the rapid antigen detection test too seeks to detect the virus rather than the antibodies produced by the body.
While the mechanism is different, the most significant difference between the two is time. RT-PCR test takes a minimum of 2-5 hours including the time taken for sample transportation. In a reliable rapid antigen detection test, the maximum duration for interpreting a positive or negative test is 30 minutes.

Limitations of an antigen test’s results –

These tests are very specific for the virus, but are not as sensitive as molecular PCR tests. This means that positive results from antigen tests are highly accurate, but there is a higher chance of false negatives, so negative results do not rule out infection.
Negative results from an antigen test may need to be confirmed with a PCR test prior to making treatment decisions or to prevent the possible spread of the virus due to a false negative.
Once the sample is collected in the extraction buffer, it is stable only for one hour. Therefore, the antigen test needs to be conducted at the site of sample collection in the healthcare setting.