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.
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One of the strategies to face the Covid-19 pandemic is epidemiological surveillance, with the systematic recording and observation of suspected or confirmed cases of the disease, based on tests.Getty Images
According to experts, in order to control the disease and contain the spread of the virus, it is important to increasingly test the population.Aline Massuca/Metropolis
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Health Department says there is no shortage of Covid-19 tests in DFBreno Esaki/Agência Saúde-DF
RT PCR: considered the “gold standard” for its high sensitivity, the test is used for the diagnosis of Covid-19. It detects the viral load up to the 12th day of the patient’s symptoms, when the virus is still active in the body. The result is delivered in approximately three daysVinícius Schmidt/Metropolis
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The test uses molecular biology to detect the Sars-CoV-2 virus in respiratory secretions, through a sample obtained by swab (swab)Rafaela Felicciano / Metropolis
Salivary test by RT-PCR: uses the same methodology as swab RT-PCR and has an accuracy of more than 90% for the diagnosis of active disease. The procedure should be performed within the first seven days of illness in patients with symptoms Disclosure
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PCR Lamp or Antigen Test: commonly found in pharmacies, the test evaluates the presence of the active virus by collecting the secretion from the nose using a swab. The result takes only 30 minutes to be ready, so it is indicated for situations where the diagnosis needs to be fast.Getty Images
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According to the company that provides the exam, it is 80% confident. The method used in the test is also used for other infectious diseases, such as H1N1RAFAELA FELICCIANO/METROPOLES
Serology test: reveals whether the patient has had contact with the coronavirus in the past. It detects the presence of IgM, IGg or IgA antibodies separately, created by the body of infected people to fight Sars-CoV-2, from a blood collection test.Shutterstock / SoonThorn Wongsaita
The exam should be carried out from the 10th day of symptoms. The accuracy of the result is lower than in RT-PCR type tests. Also, false negatives may appear more often.National Cancer Institute/Disclosure
quick test: The method is similar to diabetes control tests, with a prick in the finger. The blood sample is placed in a reagent that gives the result quicklyRafaela Felicciano / Metropolis
The rapid immunological test detects the presence of antibodies and the positive result signals that the patient has already suffered infection by the new coronavirus. The reliability of the result varies greatly, as the method has a high rate of false negatives.Vinícius Schmidt/Metropolis
Total antibody test: detects the production of IgM and IgG in the body, from a single blood collection test, and does not distinguish the present values of each antibody. The accuracy of the result reaches 95% iStock
Neutralizing antibody test: the procedure is indicated for immunological evaluation. The test detects antibodies and sees the proportion that blocks the virus from binding to the cell’s receptorDisclosure
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.
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.
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)