As the number of cases increases, many people with or without asymptomatic covid-19 have found it difficult to perform tests in laboratories and hospitals due to high demand. In this sense, self-tests are quite useful because the person goes through all the steps of the process, from sampling to interpreting the result, following the instructions for use, without the help of a healthcare professional.
“Self-testing can be done from day 1 to day 7 of symptoms. If the person has no symptoms, they can do self-testing from day 5 onwards with someone who has tested positive for covid-19,” said Ronan Cleiton Loures da Silva of CRF-SP (São Paulo Pharmacy). Regional Council) pharmaceutical consultants.
According to a technical note from the Ministry of Health, self-testing should be understood as a pre-screening tool in the diagnosis of covid-19, which means that it does not provide a definitive diagnosis, indicating a higher chance of developing the disease. in individuals.positive.
What to do when the result is positive?
According to pharmacist Silva, if the result of the self-test is positive (reactive), regardless of the symptoms or not, the diagnosis of covid-19 should be confirmed at a health service, where the person will receive guidance on the time of isolation. and the necessary attention. “Individuals should also be informed of people they have been in contact with because they may be infected,” he says.
It is important to note that a person without symptoms may also be positive. “In the context of SARS-CoV-2 infection, having symptoms is part of the puzzle, but it is not always necessary to make a diagnosis,” says Ana Luíza Gibertoni Cruz, an infectious disease specialist and researcher at the UK Health Security Agency. Department of Population Health, Oxford University, England.
In his view, the absence of symptoms does not mean that it is not possible to transmit it to other people. “Even though the peak viral load is lower and shorter in duration, the risk of transmission to other people is not zero. Transmission of asymptomatic people is one of the factors that has not been able to prevent localized outbreaks from becoming pandemics.” “
Another important point is that if a person has any serious symptoms, such as shortness of breath, persistent high fever, lethargy, mental disorder and dehydration, they should not take a self-test, but seek medical attention immediately, warns Igor Maia. Marinho. , Leforte Dasa São Paulo Hospital Infectious Diseases Coordinator and Infectious Diseases Specialist in the Infectious Diseases Division of Hospital das Clínicas, University of São Paulo Faculty of Medicine (HCFMUSP).
Is it necessary to repeat the self-test in a few days if the first test is negative?
“Since the self-test result is significant and not decisive, it may be necessary to perform another confirmatory test,” says Daniela Caroline de Camargo Veríssimo, CRF-SP Pharmaceutical Guidance Coordinator.
The pharmacist cites as an example a person who has had a positive relationship with someone who has had symptoms and still has a negative self-test result. “In this situation, another self-test may be performed, but the guidance of a physician who may indicate a different type of test would be important.”
When can he give false negatives or false positives?
The self-tests approved by Anvisa are reliable, but the instructions for use must be strictly followed, according to the experts who heard the report. Several factors can interfere with the outcome, leading to a false negative (when the test was negative, but the person may be ill and transmitting the virus). These include errors in the collection procedure, improper storage of the product, or low viral load at the time of testing, impaired detection.
A false positive is also possible (when there is no disease or virus in the respiratory tract when an individual test positive), although this is rarer. This can happen when people do not follow the instructions for use properly in patients with contamination or cross-analysis in patients with other viral diseases similar to SARS-CoV-2 viral particles.
After spending so much time in contact with someone with the virus, is it worth it if you have no symptoms?
If there are no symptoms, it is best to try to maintain isolation and self-test on the 5th day after contact. “This strategy is based on a higher viral load after this initial period of incubation and viral replication, making it easier to detect through testing,” explained Marinho, a researcher at Sírio Libanês Hospital.
Oxford Infectious Disease Specialist Ana Luiza Gibertoni Cruz says that after contact with an infected person, it can take up to 10 days for the infection to show symptoms.
“But even without symptoms, a person can transmit the virus. In this case, for 10 days, the orientation of vaccinated people is to wear a mask every time they are close to other people, the test is done after 5 days. Without vaccination. they would self-test on the 5th day after contact and, if negative, continue to use the mask for another five days, “he said.