In addition, the doctors interviewed by RBC recommended not to eat before testing, not to rinse your mouth with antiseptic agents, and not to brush your teeth.
There are also certain rules on how to take a nasal swab. In particular, it is recommended to deeply penetrate the nasal passage with a stick, otherwise the test with a shallow smear may show an incorrect result. The time of the test also affects the effectiveness of the test. If a person has been sick very recently, the test may not yet catch particles of the virus, just as if the person has been sick for a long time, the test will give a negative result as the virus descends into the lungs.
It was previously noted that in a third of cases, tests for coronavirus can give a false negative result. This is due to the wrong material intake. A curious incident, in particular, happened with the founder of SpaceX, billionaire Elon Musk. In one day, he passed four tests for coronavirus, two of which tested positive, two negative.