Sep 9, 2021

PCR, antigenic, salivary tests: when and for which Covid-19 screening test to choose in your child?

 From the first outbreak of fever of his child, should you push the doors of a laboratory? A contaminated friend in his class, should he be tested immediately? The answers of Dr Fabienne Kochert, pediatrician and president of the French Association of Ambulatory Pediatrics.

PCR, antigenic, salivary tests when and for which Covid-19 screening test to choose in your child


Saliva tests for the coronavirus are currently being rolled out in schools. It is not easy to navigate the complexity of current recommendations and between the different screening tests. When to test your child and where to turn?

PCR or antigenic test, what is the difference?

The antigen test detects the presence of sars-Cov-2 virus antigens, it is a rapid diagnostic orientation test (TROD). The advantage: you get the results in 10 minutes. On the other hand, it is less sensitive than PCR: for it to be positive, it requires a high viral load. The latter is therefore useful when a child has symptoms and we need to know quickly if he is a carrier of Sars-Cov-2. On the other hand, if the child has no symptoms and a screening test is necessary, it is better to favor the PCR test, a genomic amplification test, therefore more sensitive.


This Monday, April 26, the High Authority of Health (HAS) has also authorized the use of antigenic tests in the youngest. Until now reserved for those over 15 years of age, antigenic tests and self-tests, which are carried out by nasal swabs, are now possible in both adults and children.


"Feasible in rapid diagnostic tests (TDR), rapid diagnostic orientation tests (TROD) or self-tests, antigenic tests on nasal swabs appear relevant to break chains of contamination, especially in schools," said the statement of the HAS.


The Public Authority recalls, like the Directorate General of Health, that a positive result "must thus be confirmed by an RT-PCR test, in particular, to identify the variant in question". And that in case of a negative result, the person tested can still be a carrier of the virus, and must continue to respect the barrier gestures.



My child is sick, do I have to get him tested?

No question of multiplying the tests in the face of a simple cold. The action to be taken is different depending on the age of the child. "Rhinoviruses continue to circulate in children even if, thanks to barrier gestures, they are less sick than in previous winters. Runny nose, fever, before 6 years, the probability that the child has Covid is tiny', reassures Dr Fabienne Kochert, pediatrician and president of the French Association of Ambulatory Pediatrics. "If the child has a fever, we isolate him, we do not put him in community. If this lasts beyond three days, the usual pediatrician or doctor is consulted. He will check if it is not angina, laryngitis or otitis that can cause these symptoms. He will decide whether to test if no cause of the fever is found.' In case of fever, the action to be taken is the same as outside the Covid period: if it is poorly tolerated (amorphous child, bad coloring, unusual behavior), it is necessary to consult.


If the child is over 6 years old, it is different. "In general, after 6 years, the child has made his immunity, he is armed against seasonal viruses," explains the pediatrician. In case of fever after 6 years, it is necessary to be vigilant, even if, in the absence of contact at risk, the probability of having Covid is low. "With the circulation of variants today, we must be extra careful. In case of cough accompanied by fever, it is necessary to consult quickly. ' In children, it is advisable to start with a clinical examination at the doctor's office. "Paediatricians are not in favour of 'all coming' PCR without prior clinical examination," says Dr Fabienne Kochert. 'Imagine the child has meningitis, if their condition worsens, we waste time waiting for the COVID test result.'


It is then up to the parents to judge according to the child's condition: if he has a fever peak in the morning, then nothing afterwards, keep him under observation. But if the fever lasts more than 24 hours, it is necessary to consult. In this case, a screening test is recommended: antigen test (at the doctor's office if possible) or PCR test. "Paediatricians have a preference for carrying out the antigen test in the doctor's office, on the one hand, because they are used to taking the samples, on the other hand, because they can explain the conclusions of the test and the action to be taken to the parents," adds Dr Fabienne Kochert.


Finally, whatever his age, your child has a runny nose and he must be looked after by his grandparents? If you have any doubt and need reassurance, performing an antigen test can be helpful. It must be done the same day because it has value only in a very short period of time.



My child is case contact, when to do a test?

If a member of the household is infected, it is necessary to follow the advice of the 'contact tracing' of the Health Insurance. Protocols evolve according to variants. Today, the child is isolated 10 days, and then 7 days after the person is cured. The child is tested immediately, then retested 17 days later, upon leaving isolation. In this case, it is the PCR test that is indicated.


If the child is under 6 years of age, he is isolated, but he will not necessarily be tested. If he is small and healthy, there is no need to take a sample.


Precautions to take: The infected person in the household must wear a mask and isolate himself, especially at mealtimes.


Finally, if the child is a case of contact with a sick person outside the home, it is necessary to isolate him 7 days after the last contact and then make a PCR test after 7 days


A child has tested Covid in his class, how to react?

In nursery or nursery school, in the absence of wearing a mask by children, all classmates are considered as contact cases, they are then placed in isolation. A test is not necessarily necessary if the child has no symptoms.


In primary school, as all students wear masks, their peers are not considered to be at risk contact. "But if there have been contacts without a mask, for example, during a lunch in the canteen, a screening test will be necessary," adds the pediatrician.


Are there any risks to doing a PCR or antigen test in children?

"Whether it's a PCR or antigenic test, the sampling technique is the same," explains Dr Fabienne Kochert. 'The sample is taken where the virus is present, namely at the nasopharynx. This is the same type of sampling as that taken for influenza viruses. Paediatricians in particular master the gesture and there are no risk for children.'


Can I request a saliva test?

Salivary tests are analyzed in 'RT-PCR' (Reverse Transcriptase - Polymerase Chain Reaction), it is just the sampling technique that changes: the PCR is performed on a saliva sample and not on a nasopharyngeal sample. They are currently reserved for studies in schools. Currently, they are not used for diagnostic purposes in sick children or contact cases even if their indications will probably evolve.


My child has tested positive, what is the procedure to follow?

"Covid is not a risky disease in children," reassures Dr Fabienne Kochert. "The main risk of doing a severe form is to be over 65 years old. Most children are asymptomatic carriers: they were screened because they were contact cases most often within their family. They no longer go to the community and stay at home.' As for the Kawasaki like inflammatory syndrome (PIMS) described at the beginning of the epidemic, it corresponds to a runaway immune response following contamination by the virus. It concerns only a minority of children. In any case: if a child has been diagnosed positive for Sars-Cov-2 and his condition deteriorates, it is necessary to consult again.

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