4th wave: what are the available Covid tests and when to do it?

The recent growth in Covid cases has led to an increase in demand for diagnostic tests. Carrying out the test that confirms the infection is important both to guide health care and to take the necessary measures to prevent the virus from spreading.

Currently, there are two types of tests that detect active infection, when the disease is in the transmissible phase. These are the RT-PCR exam and the rapid antigen tests – a modality in which the self-test is included. If the result is positive, the person must initiate the necessary isolation, even if they do not have symptoms.

There is also the rapid antibody test, done with a small sample of blood, but this is only indicated to detect whether the body has produced antibodies after contact with the Sars-CoV-2 virus.


Understand the difference between each of the tests for Covid-19 and the right time to perform them:

Rapid antigen test and self-test

Rapid antigen tests – a group in which self-tests are also included – are an effective way to know if the coronavirus infection is active.

The result comes out between 15 and 20 minutes from a saliva or nasal secretion sample taken with a swab (similar to a cotton swab) in pharmacies, in testing centers or at home, through self-test.

Infectologist Ana Helena Germoglio says that if the test result is negative, but the symptoms persist, it is necessary to perform the test again in 24 or 48 hours.

“The tests of this modality are reliable, have a good sensitivity, but they need to be done well and at the right time”, explains the infectologist.

Rapid antigen tests should be performed between the 1st and 7th day of symptom onset. If the person is asymptomatic, they should be tested five days after contacting the person who tested positive.

RT-PCR test

Considered the gold standard, the RT-PCR test is made from a sample of secretions taken from the nose or mouth in a laboratory and this material undergoes a more careful analysis, confirming, or not, the presence of the virus.

Ideally, this test should be done between the 3rd and 7th day after the onset of symptoms.

antibody test

The antibody test is done by collecting a drop of blood on the finger, to screen for the presence of antibodies – Immunoglobulin M (IgM), released during infection to fight the virus, or Immunoglobulin G (IgG), produced in the most advanced phase. late infection.

The result comes out between 15 and 30 minutes after collection. Rapid antibody testing is not indicated to identify whether a person has developed immunity after vaccination.

Who should take the tests?

Anyone with symptoms corresponding to Covid-19 or who has had recent contact with an infected patient should be tested to contain the spread of the coronavirus. (With information from the portal your health)

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