Tests in the oral cavity could be more effective in detecting omicron

  • Two preliminary studies suggest that the new variant is easier and faster to find in the mouth than in the nostrils

  • Some doctors recommend passing the self-diagnostic swab through the nose but also through the inside of the cheeks and palate

The variant omicron The pandemic is changing at a dizzying pace. So much so that the awkward universal gesture of sticking a stick (called hyssop) by nose to know if a person is infected could be modified in the near future, if what is pointed out by two studies, carried out in South Africa and the United States, which indicate that the samples taken in the oral cavity could be more reliable and detect the virus before those coming from the nasal or nasopharyngeal mucosa (when the swab is inserted deeper, as in PCR or antigen tests in health centers).

The south african study It has been carried out precisely by the same group of researchers who discovered the omicron, who have decided to publish it quickly so that the scientific community knows about it even before it is peer reviewed, which will decide whether or not it is valid for dissemination in a scientific journal. The research has been carried out with nasal and saliva samples from 382 symptomatic and infected patients and indicates that in the delta variant detection was greater in the nose, while with the omicron it is greater in the mouth.

And the american essay, in which 30 people have participated, also points out that virus particles in saliva were found one or two days before being detected by nasal tests. The research has also not yet been peer-reviewed, but both preliminary studies “conform with other published data and indicate that the new variant multiplies more by the upper airways and perhaps that is why it is more infectious, through the voice or the cough”, explains Jesus Perez, Professor of Biochemistry and Molecular Biology and Dean of Biological Sciences at the Complutense University.

the same hyssop

Your department has been carrying out, for more than a year, the covid-lot project, which consists of collecting saliva samples but analyzing them with the PCR technique from thousands of volunteers from the university environment, which has been allowing detection since the sixth wave began “many asymptomatic positives“, according to the professor.

Faced with this situation, some doctors already recommend, through social networks, that they take samples from the oral cavity, in addition to the nose. It would be a matter of using the same swab, introducing it through the two nostrils and then through the inside of the cheeks and gums, above the tongue and palate, and then subjecting it to analysis.

One of them is the cardiologist William Aldama, who advises changing the way the tests are carried out because “for the first time in the pandemic a person can have symptoms and all tests, including PCRs, can be negative“. This occurs because the virus has mutated and the majority of the population is vaccinated, “which can cause the viral load to be lower and undetectable” through a PCR or nasal antigen test.

Doubts with saliva tests

Given this, Dr. Aldama recommends that people who purchase nasopharyngeal tests in pharmacies also pass the swab through their mouth, after a period of more than 30 minutes without smoking, eating or drinking. In your opinion, this may be more effective than saliva self-test, which can also be purchased in pharmacies although there are fewer authorized, since these tests are less tested.

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In fact, the head of infectious diseases at the Germans Trias i Pujol Hospital Bonaventura Clotet warns that saliva “has several inhibitors and performing the test by rubbing the mucosa of the cheeks and the back of the tonsils is complex to do well”. Therefore, the specialist recommends continue with nasal tests, although it warns that, due to vaccination, the maximum viral load peak is not usually reached until between three and six days from the onset of symptoms, so it advises those who have doubts as to whether they have been infected to repeat self-diagnostic tests every 48 hours.


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