To reduce the risk of erroneous test results, patients should not drink, smoke, brush their teeth or blow their nose before sampling biomaterials. Also, physicians must follow all sampling procedures for analysis.
Before taking tests for coronavirus, patients are better off not smoking, blowing their nose, drinking, and laboratories should choose the right time for taking tests and follow the procedure. The interviewed virologists told RBC about this.
then the test will be uninformative,” Tatyana Romanenko, therapist, head physician of the Tvoy Doktor clinic, told RBC …
The same goes for a throat swab, she said. Before the test, the patient should not eat or rinse his mouth with an antiseptic solution. If a person has recently become infected, then the amount of the virus may be low and the test will not catch it. At the same time, if a person has been ill for a long time, he may no longer have a virus in the pharynx or in the nasal passages, since the development of the disease will take place in the lower respiratory tract, the doctor added.
The patient’s actions can also lead to a false-negative test, Galina Kozhevnikova, head of the Department of Infectious Diseases of the RUDN University, told RBC. If he does this, you will not find any pathogens, ”she said.
False negative tests cast doubt on existing incidence statistics, she said. She noted that the tests that are used today are internationally certified, effective and tested on the principles of evidence-based medicine. Then, too, the defect is obtained by medical workers who take these tests, ”she said.
The test results can also be affected by the quality of the preparation of the samples themselves, added in a conversation with RBC a virologist, professor at Moscow State University, Doctor of Biological Sciences Alexei Agranovsky. According to him, the possibility of getting 30% of tests with a false negative result is “an ugly high result.”
Agranovsky noted that viral RNA is a fragile substance that quickly degrades under the action of a number of enzymes, and for a correct test, the RNA must be intact. Any contamination that is completely invisible to the eye, so the slightest introduction of impurities must be avoided, ”said the virologist. He explained that contamination can come from, for example, a dirty pipette tip.
Earlier, Sergei Avdeev, the chief freelance pulmonologist of the Russian Ministry of Health, said that up to 30-40% of tests for COVID-19 may turn out to be erroneous and give a false-negative result. According to him, the problem lies not in the quality of the tests, but in the errors in taking the materials.
In the RBC laboratories, they said that among the errors in taking analyzes could be, for example, taking biomaterial only from the oropharynx or only from the nose, as well as errors directly in the process, for example, violation of sterility. The laboratories also warned that the risk of a false negative result is higher when using kits for self-sampling of biomaterial.