French scientists review Covid-19 saliva testing

PCR saliva tests are already being used in the US, but are not currently available in France where their reliability is still being studied by scientists. 

21 August 2020
a scientist in a lab holding test tubes. French scientists are reviewing Covid-19 PCR saliva tests.Saliva tests are less painful than nasal-swab tests, but are not as reliable.
By Joanna York

In France, PCR tests are currently taken by nasal swab. This process can be painful for the person being tested as samples are taken by inserting a long cotton bud deep into the nasal cavity.

Saliva tests, by contrast, are pain-free and reduce the risk of contamination for medical staff.

Dominic Le Guludec, president of health body the Haute Autorité de Santé (HAS) told news source Le Figaro: “If [saliva tests’] reliability is proven they will allow us to test vulnerable members of the public more easily.

“In addition, they could be done repeatedly on the same person, for example, to verify they have not been infected if they have been exposed to the virus.” Nasal and saliva PCR tests reveal whether the person being tested is infected with Covid-19 at the time of testing. 

The French Association of Paediatricians (l’Association Française de Pédiatrie) have also called for saliva tests to be made available as children return to school in September. 

They say taking nasal swabs from children with common winter illnesses such as fevers, respiratory difficulties or digestive issues will yield “modest productivity” as children or their parents may refuse the painful tests.

Reliability still being assessed in France

However scientists in France have doubts over whether saliva tests are sensitive enough to reliably detect positive cases of Covid-19. 

Dr Vincent Enouf from research centre Centre National de Référence (CNR) des Virus Respiratoires at Institut Pasteur said: “We have to check, on one hand, that the saliva is a good model for testing, and, on the other hand, that the different test analysis techniques perform well enough.”

Mr Le Guludec added: “Overall, saliva testing seems to be a less high-performing method than nasal testing at the moment. We still need to measure the significance of this difference.”  

Increase in research in France

HAS is now organising large-scale hospital tests in order to speed up access to saliva testing in France. 

Since August 10 they have been running a large study in Cayenne hospital (French Guiana) testing 1,200 patients from all age groups. Parisian hospital group Assistance Publique-Hôpitaux de Paris also plans to take part in the study.

Results should be available in September. 

Tests being done by the CNRS should yield results around the same time. The centre is currently running tests in Montpellier (Occitanie) using test analysis tools that are faster than those currently in use. Initial studies in June showed the tests had a 73% capability of detecting positive cases of Covid-19. 

However, Mr Le Guludec said that French authorities should consider making saliva tests available, even if they do prove to be less reliable than nasal PCR tests. He said: “Even with weaker sensitivity, saliva tests could still be useful, considering their other benefits.”

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