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Until a few months ago, when the world had not yet entered the era of the pandemic, terms like tampons and test they only brought to mind problems related to physical and psychological well-being. Today, however, we are literally inundated with information about these words and wonder, after coughing or other signs of viral respiratory tract infection, what tests can help us find out if we have contracted, perhaps even completely asymptomatically, Sars Infection- CoV-2.
In short: it is a kind of “jungle” in which getting out is difficult. Having said that the doctor is the reference point for each specific question, here is some useful information.
Searching for the virus with the swab
The classic molecular swab, which is performed by inserting a kind of long cotton swab in the upper part of the nose to collect the material to be analyzed, is today the most effective test to detect the virus. But it is not infallible. Sometimes, in fact, it can be done while the viral incubation is in progress and therefore give a result that is defined as a “false negative”.
On average, the risk of encountering this situation, which is especially at risk when the viral load is very low, is around 10-15 percent. In any case, today the classic nasal swab is not a completely optimal test. is the most effective that is available to search for the presence of the virus’s genetic material, or its RNA.
This is identified by reproducing the extracted material in specific machines that allow the amplification of the viral genetic heritage in the laboratory, until the possible presence of the Sars-CoV-2 genome is identified. However, it must be said that the molecular swab, the scientific term that defines the test (the objective is to perform it not only on nasal secretions, but also on saliva) seems essential to follow the contacts of a person who has tested positive for the virus , even if remembering that today the swabs are made in a different population than in the first months of the pandemic, that is, even in many asymptomatic, and there are also possible variables in the sampling execution methods that can impact the result, from the simple “executor” of the test to the machine to examine the obtained.
Speed with antigen testing
What if you weren’t looking for the full virus, but their biological “footprints” in the form of proteins that SARS-CoV-2 releases? This could be an alternative system, they will say. And this is precisely the goal of antigenic tests, which can be performed much more quickly to give results in a few tens of minutes. These are becoming more and more a control tool, also due to low cost, as is the case for example in some airports. But don’t think they are infallible.
Results and reliability are highly dependent on the amount of virus present and therefore the viral antigens that can be found: when the viral load is very high, the reliability of the test is high, but then it tends to decrease and therefore give “false negative” results which are certainly not optimal in terms of infection control. For this reason, we must never forget that a simple negative antigen test should not be taken at face value in the presence of symptoms and that confirmation of any positivity should be done using the classic molecular swab.
And the antibodies?
Blood testing for the presence of antibodies, in diagnostic terms for the individual, is now considered of little use. In practice, the test looks for the presence of “soldiers” of the immune system that are produced after infection and who have the task of defending us from the “enemy”.
However, from the point of view of infection control, having this information does not seem particularly useful, both because in practice they report what happened in the past and because at a certain stage, at the beginning of the infection, it is still possible that are not present and therefore “deceive”. Therefore, the usefulness of this parameter is linked above all to epidemiological data on the infection: they help to know who has developed a reaction to the coronavirus.
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