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Not only is it possible for someone to have the corona virus without having a negative PCR test, but it is also possible for that test to be negative multiple times. There may be several reasons for this.
A false negative result can be the consequence of an incorrect sample selection or an improperly taken sample – said by virologist professor “Kurir”. Dr. Tanja Jovanović, Vice Dean of Regular Classes at Belgrade Medical School.
The choice, he says, depends on the stage at which the person became ill.
– At the beginning of the infection, a nasopharyngeal swab is used, that is, a swab from the nose and throat. And when the virus reaches the lungs and causes pneumonia, sputum is removed. It is also important that the sample does not remain at room temperature for a long time, so as not to destroy its genetic material, says Dr. Jovanović.
When asked when the throat and nose PCR test is already negative, how often sputum is removed from these patients to determine the presence of the virus in the body, Dr. Jovanović said the most important thing is that the patient arrives on time.
– It is important that the patient arrives on time, at the beginning of the disease. If the sample is taken at the right time, from the right place and is transported and processed properly in the laboratory, then there are no errors, the result cannot be false negative, he explains.
But if the disease persists, he adds, if the virus is present in the lower parts of the respiratory system, a swab from the throat and nose may be negative.
– Then it is better to examine the sputum. Also, at the end of the disease, a person can become positive again in a smear from the throat and nose, when the virus is actively excreted from the body. It usually happens after two weeks, says Dr. Jovanović.
He also explained what to do when the PCR test is negative and kovid is suspected.
– As a complementary test in this group of patients, a serological test is carried out, that is, the blood test, and the presence of IgM antibodies is examined. Even if the test is negative, the clinician, based on the blood image and the laboratory and radiological results, assesses whether he will treat a patient as a patient, says Dr. Jovanović.
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