serological, PCR, which will change on May 11

Serological, virological, PCR, blood, saliva tests … The screening strategy for coronavirus will change in France from May 11, the date of deconfinement. Who can then be tested? With what types of tests? Can we be reimbursed?

[Mise à jour le mercredi 6 mai 2020 à 11h17] From May 11 “there’s going to be a significant change in testing policy, explains Jean Castex, coordinator of the deconfinement of France, heard by the Senate Wednesday May 6. As soon as a person feels a symptom that resembles Covid-19, they should immediately contact a doctor and be systematically tested. “ France will therefore test its population much more what Prime Minister Edouard Philippe put forward on April 28 before the National Assembly: “At the end of confinement, we set ourselves the objective of carrying out 700,000 virological tests per week because the Scientific Council tells us that epidemiological models predict between 1000 and 3000 new cases every day from May 11 “. A difficulty nevertheless: Rlink individuals with symptoms to platforms performing tests ” said Professor Arnaud Fontanet of the Institut Pasteur on April 30. Since transition to stage 3 of the coronavirus epidemic in France, only those most at risk and caregivers can benefit from the tests.

The goal is to test all people with respiratory symptoms from May 11.

The coronavirus screening strategy in France is changing as the epidemic evolves. “The first tests were distributed at the end of January-beginning of February to hospitals” recalls Professor Arnaud Fontanet. At the very beginning, it was decided to test people who presented symptoms of respiratory disorders (cough, fever, shortness of breath, acute respiratory distress syndrome) and if there was contact with China or with a person returning from China. But faced with the increase in cases and in the midst of an influenza epidemic, testing all people with such symptoms became impossible. France lacked tests since the start of the coronavirus epidemic, in particular because their manufacture requires products imported from China and the United States, which were no longer delivered in sufficient quantity. From March 14 when France went to stage 3 of the epidemic, only people at risk were tested (caregivers …). Screening was prioritized and extended to residents of nursing homes and the personnel accompanying them on April 6. “We we are at more than 165,000 tests (PCR) per week “ indicates the general director of Health Jérôme Salomon Thursday April 23 at a hearing before the National Assembly with the objective ofreach 700,000 tests per week by May 11 for test people with symptoms and their contacts.

Why not test everyone on May 11?It is not possible and above all it has no use. We should retest everyone 8 days later and retest another 15 days later “, replied Professor Delfraissy on April 30, who recognizes than “the provision of 700,000 tests per week is a prerequisite (on deconfinement). If we don’t have all of that, it’s not going to do it on May 11. “

In the current context of public health emergency, laboratories and research institutes are developing diagnostic solutions to detect the SARS-Cov-2 virus, responsible for the Covid-19 epidemic. Among the proposed solutions:

PCR test

It is the screening test used in France since the beginning of the epidemic. The diagnostic test says “PCR” or “virological” (“polymerase chain reaction“) consists of nasopharyngeal swab (throat, nose, nasopharynx) which is done using a small swab (brush) inserted in the nose. It must be carried out by a doctor or nurse. The result is available after 3 to 4 hours. In addition, screening for coronavirus can be sought by other methods: a sample from the lower respiratory tract (sputum …). The sample is then analyzed by a specialized laboratory to search for the presence of the coronavirus genetic material and thus confirm the diagnosis of the infection. This is an easy test to perform, non invasive but unpleasant for the patient. A Chinese study published on April 19 on the site Clinical Infectious Diseases and reported by Inserm on 56 Covid-19 patients hospitalized with mild to moderate symptoms shows that “virus shedding can last up to 6 weeks after symptoms appear. PCR tests were positive in the majority of patients during the first 3 weeks, and from the fourth, the number of negative tests gradually increased. Finally, the median duration between the onset of symptoms and the end of viral excretion was evaluated at 24 days. However, it is not known whether patients can transmit the virus during the entire period of viral shedding. The study suggests that an extended observation period may be necessary for older patients. ”

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Quick test

New rapid and ultra-rapid molecular tests (45 and 15 minutes respectively) are being evaluated by the National Reference Center for respiratory infection viruses. We speak of “rapid diagnostic orientation tests” or “TRODs“They are presented in a unitary format, detecting antibodies from a single drop of blood in a few minutes. Their analytical performance (sensitivity and specificity) is not yet known.

Saliva test

SARS-CoV-2 EasyCov diagnostic saliva test with a closed 0.5 ml tube containing all the reagents necessary to reveal the presence of the virus. © SkillCell

EasyCov, the quick-reading salivary test for Covid-19 (in 30 minutes), with simplified reading, developed by the Sys2Diag laboratory (CNRS-Alcediag and SkillCell) indicates having obtained “very good performance” in the preliminary phase of its clinical studies in the field. The tests carried out on 180 people: patients tested positive for the virus and on the medical staff assumed to be negative at the Montpellier University Hospital demonstrated that they are “easily achievable, without laboratory. Simply take saliva – one of the main vectors of the virus – and place it with the reagents at 65 ° C for 30 minutes. The nursing staff can then read the result with the naked eye ” indicates the laboratory on April 27. “At the same time, the development, production and distribution chain is being organized for rapid and massive deployment of health personnel test as of May “ specifies the laboratory. This new test has already been tested and validated with viral RNA isolated in the Sys2Diag laboratory, and with active virus at the Center for Infectious Diseases and Anti-Infectious Pharmacology Studies (CNRS / University of Montpellier). The researchers now aim to develop a consumer version of Easycov.

Serological tests could arrive in May.

Serological test

Unit serological tests with the testing for antibodies to the coronavirus in the blood that testify to a past infection are still being evaluated, as are automated serological tests such as ELISA (enzyme linked immunosorbent assay). “There have been a lot of disillusionment with the first tests offered. Our Spanish and English colleges have paid the price. These tests will improve. I’m pretty hopeful that sometime in May we will have tests that become reliable “ says Professor Fontanet, April 30. The realization of a serological diagnosis allows the detection of the humoral post-infectious immune response (detection of antibodies IgM, IgG and possibly IgA).

“We don’t know if the antibodies you have are protective.”

What do they say ? “They say: you have been in contact with the virus but today we are not able to say if this contact with the virus is accompanied by protection so if you can consider yourself protected from reinfection. We don’t know if the antibodies you have are protective. The other problem is that with the available tests, they still have a high level of 5% false positives when we know that the proportion of French people infected on the territory is also around 5% so we cannot trust it today. ”

What is serology? The serology is a biological method using serum to make medical diagnoses. Serum is a constituent of blood plasma. During a blood test, the biologist will analyze the serum. Serology makes it possible to make a diagnosis of infectious diseases, autoimmune diseases, to determine the blood groups, to follow the evolution of certain diseases, to check the vaccinations. This test method is the subject ofa first device developed by NG Biotech in France: the test takes a drop of blood – rapid diagnostic orientation tests (TRODs) – (on the same principle as a diabetes test) and identifies in 15 minutes the specific antibodies produced by the body during infection with SARS-Covid-19. The test, developed with the support of the AP-HP (Public Assistance -Hospitals of Paris) and the CEA-Saclay is clinically validated in France. It could be proposed soon. These tests “still in the evaluation phase by the National Reference Center for respiratory infection viruses (…) can be performed in most medical analysis laboratories“said the National Academy of Medicine in a statement on April 10.

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Detecting the coronavirus makes it possible to follow the evolution of the epidemic in the country and the circulation of the virus during the deconfinement of the population. According to Inserm: “Deconfinement will not be effective without screening and systematic isolation of people carrying Covid-19.” Several types of coronavirus are capable of causing respiratory infections whose manifestations range from a simple cold to respiratory distress. “In the most severe cases, a biological sample will identify the responsible pathogen. In addition, performing a CT or chest x-ray assesses the extent of lung damage and determines the person’s care“, specifies the specialist.

Currently, it is not because we have symptoms similar to those caused by the coronavirus that we will be able to benefit from a diagnostic test. The PCR test is thus reserved for:

People with criteria related to severity:

  • Patients with respiratory symptomatology hospitalized in intensive care (in particular acute respiratory distress syndrome ARDS);
  • Patients with symptoms suggestive of Covid-19 hospitalized for pneumonia with signs of severity (hypoxaemic pneumonia).
  • Healthcare workers with symptoms suggestive of Covid-19 which should be screened first in order to limit nosocomial spread.

In hospitals, as of March 24, 2020, 101,046 tests have been performed and 20,068 are positive for SARS-CoV-2.

Criteria related to comorbidity:

  • People at risk of severe forms as defined above and presenting symptoms suggestive of Covid-19.
  • Symptomatic pregnant women regardless of the term of pregnancy.

Criteria related to a situation:

  • Residents in nursing homes and medico-social establishments (since April 7, 2020).
  • Professionals working in nursing homes and medico-social establishments (since April 7, 2020).
  • Patient hospitalized for another cause and becoming symptomatic (cough or fever or dyspnea).
  • Donors of hematopoietic organs, tissues or stem cells.
  • Monitoring of viral excretion in severe resuscitation patients to guide treatment.
  • Exploration of a source of possible cases (in particular in communities of the elderly). Within this type of community, the number of tests is limited to 3 per unit.

If one does not belong to any of these categories, a doctor performs the diagnosis on clinical signs. Outpatient testing is possible.

Initially, this test was carried out only in reference centers because they had the researchers and all the necessary technologies. Most major hospitals are now equipped with it so that they can respond more quickly in the event of suspected coronavirus infection “, comments Marie-Françoise Gros. The city ​​laboratories have been authorized to carry out the coronavirus testing.

In no case should you go directly to the biological laboratories, but call them beforehand.

  • For patients diagnosed in hospital or with signs of severity, these tests will be performed in hospitals.
  • For other patients meeting the screening criteria, it is possible to be tested in laboratories in town, after contact with the attending physician and medical prescription. The samples will be taken at home. In no case should you go directly to biological laboratories, but call them beforehand, and only if you have a medical prescription, because there is a great risk of infecting other patients, especially the most fragile. Certain hospitals such as the Henri-Mondor AP-HP hospital in Créteil (Val-de-Marne) have set up a outpatient coronavirus screening which welcomes patients without having to go through hospital services. Sent by 15 they are patients who do not go through the emergency room but who will come specifically with symptoms, a potential suspicion of infection by the coronavirus. Finally, more and more laboratories are setting up “drive” screenings where patients with a medical prescription are screened while staying in their car.
covid-19 test positive or negative
Screening procedure envisaged by the government from May 11, 2020. © Twitter Ministry of Health

Until May 11: If I test positive or if I am clinically diagnosed : I stay strictly at home, if I have an essential medical appointment I wear a mask to get there. In case of breathing difficulty, I call 15. I am prescribed an initial work stoppage lasting 7 to 14 days, between the 6th and the 8th day I have a medical opinion, remotely, to make watch my symptoms. Depending on my condition, I renew this stop for an additional 7 days. My isolation will be lifted 48 hours after the complete resolution of the symptoms. As of March 24, the average age of patients tested positive for SARS-CoV-2 is 70 years. The data confirm the low number of children affected in the city and in the hospital.

From May 11, “Once the person has tested positive, all contact cases will be tested and asked to isolate“. The objective is to isolate carriers as quickly as possible to break the chain of transmission of the virus. “Isolation is not a punishment but a shelter measure” said Edouard Philippe. The person will be able to isolate himself at home which will entail the confinement of the whole home for 14 days or in requisitioned hotels.

If I test negative, my isolation at home is lifted, I apply barrier gestures (I wash my hands very regularly, I cough and sneeze in my elbow, I use disposable tissues, I greet without shaking hands and I ‘avoid hugs).

Depending on the symptoms presented, a patient may be suspected of having the Sars-Cov-2 virus, possibly infected or confirmed.

  • Possible case: Anyone with clinical signs of acute respiratory infection with a fever or feeling of fever, AND Having traveled or stayed in a hazardous exposure zone within 14 days before the date of onset of clinical signs.

OR Anyone, even without the notion of travel / stay in a risk exposure area or close contact with a confirmed case of COVID-19, presenting with pneumonia for which another etiology has been previously excluded on the basis of clinical criteria , radiological and / or virological and the clinical condition of which requires hospitalization OR signs of acute respiratory distress up to ARDS (Acute Respiratory Distress Syndrome) in a context possibly viral and without any obvious etiology.

  • Probable case: Anyone with clinical signs of acute respiratory infection within 14 days of close contact with a confirmed case of COVID-19.
  • Confirmed case: patients, symptomatic or not, with a biological sample confirming the presence of SARS-CoV-2.
  • Contact case: person having been in contact with a “confirmed case” with different levels of risk: negligible, low and moderate / high. Close contact is a person who, from the 24 hours preceding the onset of symptoms of a confirmed case, has shared the same place of life (family, same room) or had direct contact with him, face to face , less than 1 meter from the case and / or for more than 15 minutes, during a discussion; flirt; close friends; class or office neighbors; neighbors of the case in a prolonged means of transport; person providing care to a confirmed case or laboratory personnel handling biological samples from a confirmed case, in the absence of adequate means of protection.

The time to get a PCR test result is between three and five hours. The result of this examination is returned to the patient and the prescribing doctor, with information to the intervention unit of Public Health France in the region, to the regional health agency and to the crisis center of the General Directorate of Health. With the new tests expected, the results can be given in less than an hour.

From May 11, yes. As the Prime Minister explained to the National Assembly on April 28, the tests for Covid-19 will be 100% covered by Health Insurance.


Opinion of the Scientific Council COVID-19 April 2, 2020 Inventory of containment and exit criteria.

Publication of the Institut Pasteur, results of serological tests, April 23, 2020.

Thanks to Marie-Françoise Gros, Director of Medical Affairs at bioMérieux, French specialist in medical diagnosis.

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