For one who wishes to be compliant with the rules and up to date on Covid-19 in Italy, finding trusted sources is not an easy task. With news running wild in all directions, steady information sources are much needed.
Our team at DoctorsinItaly has chosen to rely on the Technical-Scientific Committee of the National Emergency Management Agency, at the Presidency of the Council.
Periodic updates are issued by the Committee in the form of Circulars of the Ministry of Health.
We have collected the most relevant information regarding testing options for Covid-19 from these sources.
There are three common types of tests that are used for diagnostic purposes and for monitoring of coronavirus: the PCR swab test, the rapid antigenic swab test and the blood test.
There are different methodological approaches to each of these testing strategies, but this categorization can help make sense of the alternatives in layman’s terms.
The so called “swab test”, may refer to a RT-PCR test looking for viral RNA, or to a rapid antigenic swab. Both are performed on a nose/throat swab sample but one is a molecular test (detects virus’s genetic material) while the other is not (it only looks for particular virus’s proteins).
They are used to detect the presence of an infection, and can only detect the virus during the infection. This means these tests cannot detect whether a person was infected and then subsequently recovered.
If you have flu-like symptoms or signs of a respiratory infection, these are the tests you need to get to diagnose if you have Covid-19 or not.
The PCR swab test transcribes and replicates RNA traces present in a biological sample, allowing to detect the virus even when the viral load is low.
This test can be used on people who have signs of infection, and on those who have no symptoms at all.
The antigen swab test is faster than the PCR swab (15 – 30 minutes) positive results are usually accurate, but negative results may need to be confirmed with a RT-PCR test.
[January 9th 2021 update] On January 8th, 2021, the Italian Ministry of Health has recognized the validity of the latest generation of rapid antigenic tests (immunofluorescence with microfluidic reading) which have shown results that are comparable to PCR swabs, especially if used within the first week of infection.
The blood test for Covid-19 is used to identify a person who has been exposed to the virus and has developed specific antibodies.
This type of test for coronavirus is currently available at some private labs and it can be done by anyone who requests it.
This test is not useful for acute cases, such as patients who have developed symptoms, nor it can be used to rule out an infection. If you have been sneezing and can’t get tested through the official health centres, this test won’t help you either.
Serology tests are blood-based tests that can be used to identify whether people have been exposed to a particular pathogen by looking at their immune response and identifying specific antibodies. They all focus on proteins made by your immune system in response to an infection. The immune system keeps you healthy by producing antibodies, particles that destroy foreign invaders, such as viruses, by attaching to the antigens and deactivating them.
If your blood contains antibodies that are specific to Covid-19, it means that your system has responded to its presence, thus you have been in contact with the virus.
Serology testing for SARS-CoV-2 is at increased demand in order to better quantify the number of cases of COVID-19, including those that may be asymptomatic or have recovered, and inform public health policies.
The rapid tests for Covid-19, used to find IgM and IgG antibodies, can verify that a person has been infected, but it cannot confirm what is their current status.
Specifically, a positive serology test for coronavirus would confirm the presence of specific antibodies, showing that the subject has been infected. However, this is not sufficient to understand if the person is still infected and contagious, or if they have overcome the disease and are no longer contagious.
A negative result, on the other hand, is even more uncertain: it may mean that the person is healthy and has not been in contact with the virus, or it could mean that the person is currently infected, but has not yet developed a detectable quantity of antibodies.
For this reason, serology tests cannot substitute the swab test used for diagnosing an ongoing infection and they cannot be used on subjects with symptoms to identify their status.
So why are these tests even done, you may ask.
From the perspective of public health authorities, policymakers, and researchers, it makes a lot of sense to get a more accurate estimate of how many people have been infected with Covid-19.
Additionally, if herd immunity were to be possible this kind of test could prove very useful to detect all those who have the antibodies and can be considered immune.
A word of caution is in order here: it’s still unclear for how long might immunity to the coronavirus last.
Another shortcoming of the serology test is that it may show false positive results due to cross-reaction to similar viral strains, such as other common types of coronavirus. A person may result positive and be considered immune, while having actually had a different type of infection.
What is the Covid-19 blood test for?
The test is used to determine whether a SARS-Cov-2 infection has occurred. This infection, in fact, may have occurred without any symptom or with mild symptoms you may not have given importance. It’s a way to find out if you have had the infection without knowing. The test can give useful indications about a possible contact of the patient with the virus, by measuring IgM and IgG in the blood.
What happens when IgM and IgG are both negative?
The test is able to detect infections that occurred within 10 days preceding the moment of detection. In the current state of knowledge the window period of SARS-Cov-2 is estimated in 10 days from the presumed infection. A negative result therefore cannot exclude that there is no current infection, as the patient may still be in the 10-day window period.
What happens when only the IgM are positive?
If the IgM result is positive (therefore in the report the IgM are indicated as “positive”) the patient must be able to access the confirmation test for Covid-19 (swab), in agreement with the NHS doctor or local health authorities.
In any case, the positive result of the IgM cannot give indications on the course of the infection.
What happens when IgG are positive and IgM negative?
If the IgG result is positive (therefore in the report the IgG are indicated as “positive”) it means that the patient is likely to have recovered from Covid-19 infection, but in any case it is recommend an assessment with a doctor.
When to take the test?
The test can be always performed, except in the presence of symptoms (as indicated by the Ministry of Health, for example fever, flu syndrome, cough, breathlessness, etc.). In this case the swab test is the most appropriate and it is recommended to contact the local health authorities, to obtain the appropriate evaluation and adequate assistance.
When to repeat the test?
If the IgM and IgG in the report are indicated as “negative”, the test has to be repeated 7 days after the first sampling.
Can the test give “wrong” answers?
Like any other test, there is a possibility that the test will produce false positives or false negatives. The tests in use at most reputable laboratories are marked CE-IVD but there is still paucity of data to estimate the sensitivity of this new test.
How could the test provide “wrong” answers?
Case 1: IgM could be negative because the test was performed too early, during the window period.
Case 2: IgG could be positive due to a different type of Coronavirus (there are several in nature), very “similar” to SARS-COV-2.
What is the use of a positive IgG result?
Given that a false positive is a rare occurrence, this test remains important for the prevention of transmission of viruses, epidemiologically, to map the territory and protect a given population, determining the relationship between people who developed antibodies and people who haven’t yet developed them.
Are all blood tests for Covid-19 the same?
There are 2 types of tests: qualitative and quantitative. Initially most labs use the qualitative one, which just informs about presence or absence of antibodies. Amidst Coronavirus emergency, qualitative test is simpler, faster and allows to take the correct actions. At the end of the emergency, if it will be very likely more useful to switch to a quantitative test, which measures the exact concentration of IgG in the blood.
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There is much discussion within the scientific community on how likely are people without symptoms to spread the disease. With SARS and MERS-CoV the risk of transmission before exhibiting symptoms was considered low.
However, evidence suggests that Covid-19 is contagious even when symptoms are not present in the carrier, therefore seemingly healthy people can transmit the virus.
These carriers are commonly divided into three categories:
While post-symptomatic individuals fall into the mandatory self-quarantine as defined by the recent decrees, the pre-symptomatic and asymptomatic may well be among those who go to the supermarket, or work as a cashier, or carry your food at home.
The masks are meant not so much to protect you from getting infected, but rather to reduce the chance that you spread the virus, in case you have it and don’t know it.
Universal use of face mask outdoors, until we are all vaccinated (or a novel treatment becomes available), may reduce community spreading by asymptomatic individuals and will be very likely adopted in every country. For this to be possible, mask manufacturing capacity will have to ramp up until sufficient units become available for public use.
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For one who wishes to be compliant with the rules and up to date on Covid-19 in Italy, finding trusted sources is not an easy