While some people have severe symptoms of Covid-19, others don’t even realize they have been infected and are therefore asymptomatic. So how to find out if you have a Sars-CoV-2 infection in progress or not?
The only way to be sure that you have been infected by the virus is to obtain a positive result from the molecular or throat swab. This procedure consists in taking, using a cotton swab attached to a stick, a sample of mucus from the mucous membrane of the pharynx passing through the nose or throat. To check for the presence of the virus, the sample taken is then taken to a specialized laboratory to be treated with special detergents in order to inactivate the virus and prevent it from infecting operators. Subsequently, the viral genome is extracted and amplified using a technique called RT-PCR, which allows for the amplification of any RNA present in the sample even in small traces.
There are two different types of tests (antigenic and salivary) that allow you to check if the patient, when the test is performed, is positive for the virus. Antigenic tests aim to search for viral antigens, proteins expressed on the surface of the viral particle. These antigens are specific to the virus and, if found, they identify an infection in progress. Salivary tests, on the other hand, offer more versatility, as they facilitate and speed up the sampling phase: in fact, the collection of saliva does not require a throat swab and can be performed independently by the individual patient. The actual analysis, which detects the presence of genetic material of the virus, must in any case be performed by experienced personnel in the laboratory. At the moment, however, there are no validated salivary tests yet. In both cases the test response may be available approximately 6 hours after collection.
If it isn’t possible to swab, another way to verify Covid-19 positivity is to carry out serological tests, based on the search for specific antibodies produced by our immune system in response to the encounter with the coronavirus. These tests look for two specific types of antibodies: IgM, which form in the early stages of the disease and disappear a few weeks after healing, and IgG, which develop about two weeks after the first symptoms appear and circulate in our body much longer. Serological tests, which are normally performed with a blood sample followed by laboratory analysis, can be of two types: rapid (they provide a qualitative result – yes / no – and are performed on a drop of blood taken from a fingertip, therefore they are less reliable) or classic (they provide a quantitative result corresponding to the number of antibodies present in our body). However, we remind you that the final interpretation of the data must take into account not only the result itself, but also the patient’s clinical history; so serological tests alone are not sufficient as diagnostic tests.