Coronavirus: diagnostic tests from saliva, Japan also chooses them

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Japan has just cleared saliva-based tests for the new coronavirus, a way to increase mass screening and reduce risk for operators.

Adoption in Japan

“We will significantly reduce the burden of prevention measures in the sample collection facilities,” the Health Minister told reporters Tuesday. Japan lags far behind other industrialized nations in terms of the number of swabs made. As of June 1, he had conducted 2.31 swabs per 1,000 people, far below 64.67 in Italy and 51.17 in the US. The ministry then approved two dozen different tests on saliva. More than 30 new infections were reported in Tokyo on Tuesday and the number of daily cases exceeded 30 in 19 days for the first time. The latest cluster of infections is in a hospital, Musashino Central Hospital.

Saliva test, what it is

The saliva test is of the “molecular” type, based on the same technology used for the swabs and produces the same results, only that the sample is not taken with a stick from the nose or throat, but by collecting the saliva in a test tube. This makes thesafer execution also for operators: even in the USA the Food and Drug Administration (FDA) approved a home saliva collection test. It spits into a funnel, saliva slides into a storage liquid and once the liquid turns blue, the sample is shipped in a sealed package to a laboratory, where it is analyzed.

Even more sensitive

According to a study by the University of Yale (not yet published) saliva samples are “an interesting alternative”: a minimally invasive test, less risky for health professionals and above all it also seems more “sensitive” than swabs. In the test carried out by scholars, saliva produced greater detection sensitivity during the course of the infection. In one case, a healthcare professional’s swab was negative for two days before the third turned positive, instead saliva had immediately detected the virus. In a separate research, the Yale University team said that saliva could have detected the virus in only mildly ill people, while a nasopharyngeal swab could not. However, the results are available within 72 hours, then 3 days. Now instead the swabs have faster results there is always the problem of reagents, since diagnostics is based on the same principle.

Rapid test coming to Europe

Lowering the risk for operators and having an equally reliable (if not more) test is the common goal: a rapid test can diagnose from saliva, in one hour, positivity to the new coronavirus. However, it cannot be compared in all respects to the “classic” pad. Every time you read the word “rapid”, in fact, you need to think of a test that is less sensitive and therefore less reliable (such as the type pregnancy test). The name of the rapid salivary test will be “EasyCov”. Large-scale production has already started. It involves the collection of less than 1 ml of saliva under the patient’s tongue. It is expected that it will obtain the CE mark in the first half of June, after which it will be produced in France by Firalis. The cost of the test should be around 20 euros. Marketing will be handled by Skillcell.

In Italy also tests based on antigen

Even in Italy there have been “rapid” swabs for some time, even if based on a rhino-pharyngeal sample. They are tools used by the “first line” in an emergency because they allowed to reduce the response time from 6-7 hours to 60 minutes and travel on small machines that examine 8 samples at a time. It is a kit for triage structures. The tests are entrusted to the Regions which in some cases have decided to use them.
Then there are the rapid tests on saliva not based on molecular analysis (therefore like that of the swabs) but on “antigen”. They have also been studied and tested in Italy by the University of Insubria in collaboration with the Asst dei Sette Laghi. You are looking for the virus with the specific antibody for the spike protein which is the one that is present (pointed) on the surface of the pathogen and there is a reagent that colors the presence of the virus by creating a strip, as in the pregnancy test. The test is awaiting authorizations for more widespread use after a trial on 137 patients.

June 2, 2020 (change June 2, 2020 | 3:48 pm)

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