Coronavirus is most common in urine and feces.

Snezana Jovanovic, Photo: Printscreen

Not only is it possible for someone to have coronavirus and test negative, but it is also possible for the test to be negative multiple times and the patient to have bilateral pneumonia. As Snezana Jovanovic, director of the “Fiery Eye” laboratory explains, false negative results occur if the sample is not taken in time, if the transport is inadequate or if a smaller amount of sample is taken.

PCR, antigen and serological tests for coronavirus are performed in Serbia. Each of them has its own sensitivity and specificity, and what will be done in a patient presenting with coronavirus symptoms is decided by the doctor at the Kovid clinic on the basis of clinical examination, biochemical analysis and x-ray of the lungs.

– In a population like ours, when the percentage of transmission of the infection is between 10 and more than 10, the recommendation of the international health institutions is to use an antigen test. A nasopharyngeal swab will be brought to the Kovid clinic for the detection of SARS-CoV-2. If it is negative, and there is still a suspicion that the patient has kovid-19, then a swab is taken and sent for PCR testing to the laboratories that perform those tests, Jovanović explained to RTS.
As he says, there are people who have had all symptoms of kovida-19, and her PCR test was negative.

– Therefore, the diagnosis is made not only on the basis of laboratory tests, but also on the basis of a comprehensive examination, clinical picture and other analyzes. I know of several patients who even had bilateral pneumonia, and that their PCR test was negative three times, “said Jovanović, explaining that it was because the virus stayed in the upper respiratory tract for a short time.

Jovanovic says that false negative results occur if the sample is not taken on time, if the transportation is inappropriate, if a smaller amount of sample is taken, or if an inappropriate sample is taken.

“Here, we are now reading that more of the virus is not found in the nasopharynx, but, let’s say, in feces and urine, and is excreted longer,” he noted.

We do 2,500 tests a day

Snezana Jovanovic points out that the capacity of the “Fire Eye” laboratory is 2,500 PCR tests per day.

– Last week, we did 3,200 samples a day, thanks to the fact that we received two more PCR machines, so it was a little faster – said Jovanović.

In private laboratories only serological tests

Jovanovic explained that there is no point in doing serological tests after the first symptoms appear, because in most people antibodies develop on the sixth or seventh day after the onset of symptoms. In private laboratories, as he emphasized, it is possible to do only serological tests.