Molecular tests that remain a point of reference to have a certainty on the diagnosis, rapid antigenic tests that are the most popular to access the Green pass, and salivaries? After the moment of fame they had on the eve of the reopening of schools, molecular salivary tests are back in the shadows, but they would have many features to become an interesting alternative to rapid antigenic.
“There has been no more talk of salivary tests probably because clear indications have been lacking as to who should have paid for it”, observes virologist Francesco Broccolo, from the University of Milan Bicocca and director of the Cerba laboratory in Milan. In itself, he added, saliva is a good biological matrix for screening, but not for diagnostics. However, for the purpose of requesting the Green pass “it would be possible to replace the rapid antigen test with a particular type of save molecular test, called ‘pooling'”, ie a test that analyzes several samples at the same time and that signals, in each group examined, the possible presence of positive cases for further verification.
Here are the pros and cons of the tests currently used, compared to the types of salivary ests currently available:
QUICK ANTIGEN TESTS: they give the answer within 10 minutes and allow you to obtain the Green pass within an hour and, at controlled prices, cost between 7 and 12 euros; they look for the molecules that are produced following the entry of the virus into the organism (antigens) and it must be considered that the reliability of these tests depends on the viral load. That is, they are able to identify the infection only if the copies of the genetic material of the virus are greater than one million in one milliliter of the biological material taken with the swab. “As a result – Broccoli observes – at least in 50% of cases they give a false negative”.
MOLECULAR TESTS: they give the answer in about eight hours and cost around 50 euros. They search directly for the presence of the genetic material of the SarsCoV2 virus, amplifying it with the polymerase chain reaction (Pcr) technique. Therefore they allow to have a picture of the infection and their certainty and specificity in the diagnosis is 99%.
MOLECULAR SALIVARY TESTS: they look for the genetic material of the virus in the saliva and give the result in about 8 hours, with an average cost of 50 euros.
MOLECULAR SALIVARY TESTS WITH THE POOLING METHOD WITH ANALYSIS IN THE LABORATORY: they are tests that simultaneously analyze several samples (on average 5), thus reducing time and costs, with an average cost of 10 euros, the time used is always eight hours.
MOLECULAR SALIVARY TESTS WITH THE POOLING METHOD WITH REMOTE ANALYSIS: they can also reduce the time for the result to about two hours, with an average cost of 7 euros. At the collection site, the saliva samples are introduced into a device connected to a reference and certified laboratory. Sensitivity and specificity are higher than 99%, but they are not widespread as the set up protocols for saliva screening for public and private laboratories have not been transferred. Some regions, however, are working to adopt them.
Source From: Ansa
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