when should it be done? The guide- Corriere.it

The tests (rapid or molecular) must be done from 48-72 hours from the presumed risk contact to five days later, or immediately before an opportunity to meet, but the vaccinated in the latter case should not do them. Absolute no to do-it-yourself tests at home

Why do the swab (rapid or molecular)?

There are three reasons for taking a swab: suspicion of a contact at risk, the onset of symptoms that suggest Covid and prevention, in view of an encounter with other people, perhaps fragile.

When should I get tested after having a risky contact?

The swab (rapid or molecular) must be done from 48 hours after contact with a positive to 5 days later, the ideal would be to do it at 48 hours and then repeat it at 5 days in case of suspected risk contact (as is the case for tracking school). If the test is done too early, the danger of having a false negative: as you can see from the graph below, in the first two days the virus is undetectable, from 48 to 72 hours only detectable by molecular swabs and from 72 hours also by swabs quick.
Recall that, if we are close contacts of a positive (WHO the characteristics that define close contact, ed
) will be the ATS to take charge of our test, if instead we are not close contacts, therefore low risk, we do not have to take the test.

When should I get tested if I have symptoms?

In case of symptoms I can do the test immediately: the incubation period is over because the symptoms start later, so the swab can detect any positivity.

When to swab in view of an opportunity to meet?

To understand if we are negative when we go, for example, to a dinner, it is better to take the test as close as possible to the event. The tampon, in fact, is the photograph of the moment in which I do it: I could leave the pharmacy and get infected on public transport, so it is valid for hours, certainly not days. By law, the quick swabs used for the basic green pass are considered valid 48 hours from the time of execution, the molecular ones last 72 hours, but it has been discussed several times in recent times whether it was appropriate to reduce their duration. A rapidly replicating virus, such as Omicron might be, can go from undetectable to highly detectable within hours (morning to night).

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Who has to do the tampons?

Recall that vaccinated people should not swab to meet others. They can become infected, but, in percentage, much less than the unvaccinated, they can infect, but in an even lower percentage, and are 90% protected from symptomatic disease. So in the absence of symptoms or tracking required by the ATS it is not necessary for them to take a test. This would also avoid clogging the buffer points. You can have extra attention if there is a fragile person in the family, for example transplanted or in chemotherapy: but masks and spacing would be enough.

Why is it necessary to avoid the quick swab at home (the do-it-yourself)?

Do-it-yourself tests sold in pharmacies are believed to be dangerous by experts, because they are not tracked (therefore theoretically a person could hide their positivity), for the quality of the sample, which risks being inadequate (many people are not able to perform a nasopharyngeal sampling independently), finally, because they are less sensitive and specific. While it is not easy to make an appointment for a swab (rapid or molecular, but performed by special personnel), do-it-yourself is not a shortcut because it risks generating false security: a result that will not be valid and could put people at risk. that we encounter, that it doesn’t help us if we have symptoms (and we need to know as soon as possible how to treat ourselves) and that it is not valid for the contact tracing required by law.

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Which test to do? What are the differences?
The swab can be rapid or molecular, the important thing is that it is done by specialized personnel. A very high sensitivity test, such as the molecular swab, protects against false negatives, which are the real risk. The molecular has a sensitivity higher than 99%, the rapid ones slightly exceed 90%, the do-it-yourself is always not recommended. As can be seen from the graph above, the rapid swab does not detect the incubation period, the pre-infectious one.

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