Simple to perform and painless, the saliva detection tests for Covid-19 are eagerly awaited by doctors and epidemiologists who see them as a weapon against the spread of the virus. Less intrusive than taking a sample deep in the nasal cavity with a long cotton swab, they also require less equipment and reduce the risk of contamination of caregivers. "If their reliability is demonstrated, they will make it easier to test vulnerable groups such as children, the elderly or those with psychiatric disorders ," indicates Professor Dominique Le Guludec, President of the Haute Autorité de Santé (HAS).In addition, they can be carried out repeatedly in the same person, for example if they have been exposed to the virus, to check over time that they are not infected. ”
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In an open letter published on Wednesday, the French Pediatric Association thus requests, as the start of the school year approaches, the provision of saliva tests. The repetition of nasopharyngeal samples in children with fever, respiratory or digestive signs (frequent in winter) would have "a modest return, a certain cost and exposes us to rejection from children and / or parents" , plead the pediatricians.
Being evaluated
Already used in the United States, screening by saliva sampling will not take place for several weeks in France, however, because the reliability of this method is still being evaluated. "The question of the sensitivity of these tests (their ability to detect the virus) has not yet been decided ," said Dr Vincent Enouf, deputy head of the National Reference Center (CNR) for respiratory viruses at the Institut Pasteur. We must verify on the one hand that saliva is a good model for screening, on the other hand that the different analysis techniques are as efficient as the reference RT-PCR test. "
The test will identify most patients in the early phase
Prof. Jacques ReynesScientific studies on saliva tests carried out so far in France or abroad show variable results. “Overall, saliva seems to be a less efficient medium than the current nasopharyngeal sample ,” notes Professor Le Guludec. It remains to measure the extent of this difference. Even with a lower sensitivity, saliva tests can indeed retain an interest given their other advantages. "
Pressed to accelerate the pace, the HAS granted on August 10 an innovation package allowing the Cayenne hospital to launch a large clinical study aimed at evaluating the effectiveness of diagnosis by saliva: 1,200 patients, divided into four groups of age, must be recruited. The Assistance Publique-Hôpital de Paris has undertaken to participate in the study. The first results are expected in September.
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The performance of the EasyCov saliva detection test, developed by the CNRS, should be known at around the same time. This device tested in Montpellier uses a faster analysis technique than conventional RT-PCR. He displayed a sensitivity (ability to detect a positive case) of 73% in a preliminary study in June. Head of the infectious diseases department at the Montpellier University Hospital, Prof. Jacques Reynes, who coordinates the test, is quite confident: “The test will make it possible to identify most of the patients in the early phase, with a high viral load, at the time when they are the most contagious. ”
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