Kumar Gunness, Managing Director – Covid-19: Choosing the best antigenic test for you

What types of Covid-19 tests are available and what are their key features? 

Basically, two types of diagnostic tests are available to detect the Covid (Sars –Cov -2) virus and they work differently, namely the PCR (Polymerase Chain Reaction) tests and Lateral Flow Antigen tests (Rapid Tests).

PCR tests detect the genetic material (RNA) of the virus whereas the Rapid tests detect the presence of a particular protein (antigen) found in the virus.

Both tests require a swab from the back of the nose or throat as a sample. A similar test exists for use with saliva.

In the case of the PCR test, the sample is sent to a laboratory where the process takes hours and requires sophisticated equipment and technicians. The PCR test is almost 100% accurate in spotting infected people.

In contrast, the Rapid Antigen test works by mixing the sample with a solution that unleashes the specific viral protein. The combination is applied to a strip impregnated with an antibody optimized to bind the specific viral protein. If the latter is present, the result is reflected as a band in the strip. The process can be done in about 30 mins. The only drawback of this test is that it has less sensit0ivity and will detect the antigen only if the viral load is high. For example, a recently infected person may not be detected by using this test.

Rapid antigen tests are relatively cheap and may be the most useful to identify outbreaks, or to select people with symptoms for further testing with PCR, allowing self‐isolation or contact tracing, and reducing the burden on laboratory services.

The results we get from the Rapid Antigen tests depend on the person who administers the test and who must strictly follow the guidelines.

 How should we choose Covid-19 tests?

For a quick result, for example after an outbreak in a company, a Rapid Antigen Test will be more appropriate.

In case of a positive result, self-isolation should be immediately implemented and the established protocol followed. For a vulnerable person, a PCR test may be warranted.

In case of a negative result, the test may be repeated in a few days to allow for any potential viral load to build up in the body but while applying barrier methods of protection.

When should we use the tests?

With the current situation of increasing Covid infections in the country and the attitude of the general public regarding the basic protection measures, it is important to regularly do a Rapid Antigen Test if someone has been in contact with infected persons.