Currently, only PCR tests can detect the presence of coronavirus. But screening for the disease is not systematic in case of symptoms. Who can be tested? What does it consist of? What is the difference with a serological test?
New so-called serological tests (still under evaluation) will soon increase screening capacity and will make it possible to check whether the virus is still circulating in the population. They should be available at the end of April. There are two types of tests:
Only two types of health professionals are allowed to do this: nurses and biologists - whether they are pharmacists or doctors.
In addition, to avoid false negatives, health professionals remind people that it is necessary to explore both nostrils when taking the sample. Finally, in the case of a severe patient, a sampling of the trachea or bronchial tubes may be more appropriate, since the virus migrates progressively to the respiratory tract. After a few days, the viral load in the nose of a patient with Covid-19 could be zero.
Covid-19 coronavirus test
Screening for COVID-19 disease is currently based on PCR (polymerase chain reaction) tests, which are only available on medical prescription. At stage 3 of the epidemic, people with potential symptoms of COVID-19 are no longer routinely screened.New so-called serological tests (still under evaluation) will soon increase screening capacity and will make it possible to check whether the virus is still circulating in the population. They should be available at the end of April. There are two types of tests:
- Conventional serological tests using the Elisa (enzyme-linked immunosorbent assay) method, which can be carried out on automatic machines capable of performing hundreds of tests per day;
- Rapid unit tests (TRODs), which detect antibodies from a single drop of blood in a few minutes. These individual tests could be reserved as a priority for people at high risk of severe forms of the disease (residents of EHPADs, patients with chronic illnesses, etc.) and people working in exposed professions (medical and nursing staff, care assistants, etc.).
What is the difference between a PCR test and a serological test?
The PCR test looks for the direct presence of the virus by nasopharyngeal swabbing. It confirms whether the person is infected with the virus at the time of testing. The serological test looks for IgM and IgG class antibodies specific to Sars CoV-2 through a blood sample. It is used to determine the immune status of individuals against the virus, i.e. whether a person is immune even if he or she has not shown any symptoms of covid-19.What is the Covid-19 PCR test?
The PCR test is a non-invasive test that takes only a few seconds and can be more or less painful depending on the sensitivity of each person," says Dr François Blanchecotte, President of the Union of Biologists. "The aim is to detect a strand of RNA belonging to the SARS-CoV-2 coronavirus that causes Covid-19". To confirm or deny the presence of the virus, deep nasal cells are taken with a swab, a kind of long cotton swab that is inserted into the nasal cavities, up to about 15 cm.Only two types of health professionals are allowed to do this: nurses and biologists - whether they are pharmacists or doctors.
In addition, to avoid false negatives, health professionals remind people that it is necessary to explore both nostrils when taking the sample. Finally, in the case of a severe patient, a sampling of the trachea or bronchial tubes may be more appropriate, since the virus migrates progressively to the respiratory tract. After a few days, the viral load in the nose of a patient with Covid-19 could be zero.
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