Saliva tests, a new weapon against Covid-19
Saliva test carried out in a school near Bordeaux, February 25, 2021. AFP - PHILIPPE LOPEZ
Text by: Cédric de Oliveira
5 mins
While the Covid-19 epidemic is not weakening, especially in France, the massive deployment of saliva tests could significantly improve the virus screening policy.
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Until now, the most common test has been nasopharyngeal PCR.
The one that involves the caregiver will look for traces of the virus deep in the nose using a swab.
Not very pleasant, especially for the person being tested, but it remains the reference method with a 98% reliability rate.
However, it could be stolen from the limelight by
saliva tests
, another, simpler, less painful and less expensive method which has already become democratized in India or the United States, where students are regularly tested.
To carry out the sample, the technique is quite simple, explains Julien Tizot, CEO of BioSpeedia, a company specializing in the diagnosis of infectious diseases: “
You just have to spit into a receptacle which will then be entrusted to a laboratory which will analyze the sample, as in a nasopharyngeal test.
It is much more pleasant for everyone and it decreases the risk for those tested of being able to spread the virus
”.
BioSpeedia offers a saliva test that includes a second step, with a swab, a "nasal enrichment", performed at the edge of the nostril, which improves the reliability of its product.
85% efficient
According to several studies, saliva tests are 85% effective, which is more than the antigen screening method.
In France, the
High Authority of Health therefore authorized their deployment in the territory
on February 11, 2021 after the positive results delivered by three clinical trials.
According to Constance Delaugerre, virologist at Saint-Louis hospital in Paris, who worked on Salicov, one of the trials in question, saliva samples will be very useful for mass screening: “
It's a new health device. public.
The saliva is very easy to collect and the method may be successful in communities where the virus can easily circulate.
Massive testing in schools can allow quick decisions to be made about their closures.
It is truly an epidemiological thermometer
”.
The French government has started rolling out these tests in schools.
He hopes to achieve 200,000 a week soon.
This new modality could also be implemented in accommodation establishments for dependent elderly people (Ehpad) or for caregivers, particularly exposed to Covid-19 and who are therefore obliged to test themselves regularly.
The possibility of self-sampling
The results will not necessarily be faster to obtain.
Just like the nasopharyngeal test, the saliva test is called RT-PCR which must necessarily land in a laboratory to be analyzed.
It will therefore be necessary to wait 24 to 48 hours to be fixed.
But the simplicity of the method should more appeal to the recalcitrant of the swab and make it possible to identify more patients with little symptomatic or asymptomatic, especially in young people.
Constance Delagerre believes that this will considerably change the situation in the management of positive cases: “
The advantage is the rapid rendering.
We know that from the moment the patient knows he is positive, he takes much more precautions with the people with whom he lives, he works ... And this allows him to isolate himself naturally.
This information can be decisive in a public health strategy
”.
For now, screening must be carried out by caregivers but the government could also allow self-sampling, with a rapid result (a quarter of an hour) like what is already done in Germany or United States.
It remains to be reassured about the reliability of these tests.
This is the whole stake of a full-scale experiment which began on Monday February 22, 2021, in Saint-Etienne.
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