PCR, antigen or serological: everything you need to know about Covid-19 tests

As a player in COVID-19 screening, SOS MEDECINS Casablanca informs you about the benefits and limitations of tests today thanks to our home doctors offering a result in 15 minutes. 

• What is the Covid-19 antigen test?

The rapid antigen test (RAT) looks for the presence of Sars-Cov-2 virus proteins in the sample and requires the same nasopharyngeal swab as the PCR test but involves a simplified analysis technique. 

The antigen test is a manual test, with a direct reading on a small plastic device, similar to pregnancy tests sold in pharmacies. The result appears within 15 to 20 minutes as lines on the device.

• What is the purpose of the Covid-19 antigen test?

The antigen test confirms the presence of the virus when the test is positive. Its advantage lies in the speed with which results are available; however, it has a lower sensitivity than the PCR test, which is why it is only recommended for symptomatic cases with a high viral load. 

• When should I get a Covid-19 antigen test?

The Rapid Antigen Test is useful when dealing with a person who presents symptoms related to theCOVID (cough, fever), because it allows for a rapid diagnosis of infection. SARS-CoV-2It can be carried out at a doctor's office, in a pharmacy, at a nurse's office, or in an emergency department.

It is useless in people without symptoms as an individual screening tool.

What is the meaning of a positive antigen test?

A positive result confirms infection, indicating a significant viral presence. The person is therefore infected and infectious. The rapid antigen test (RAT) has very high specificity, meaning there are no false positives. A positive RAT does not need to be confirmed by a home PCR test.

What is the meaning of a negative antigen test?

On an individual level, a negative rapid antigen test (RAT) does not rule out the possibility that the person is carrying SARS-CoV-2, due to the low sensitivity of these tests. On a collective level, it is absolutely essential to continue protecting oneself and others by respecting preventative measures. 

In case of symptoms suggestive of Covid-19, it is necessary to carry out a PCR test which is more sensitive.

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