Runny nose ? a sore throat, fever and cough? Covid-19 and nasopharyngitis have many similarities. But can the tests, PCR as antigens be wrong and give false results?
First of all, here’s a little reminder from the WHO: “Coronaviruses (CoV) form a large family of viruses that cause manifestations ranging from the common cold, to more serious illnesses such as Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome, SARS-CoV- 2 (Covid-19) “.
Symptoms sometimes similar but to be differentiated
The symptoms of nasopharyngitis can be very similar to those of Covid-19: fatigue, a runny nose, cough (with a sore throat) and you feel feverish. However, symptoms are specific to Covid-19 such as digestive disorders, skin manifestations or even more problematic, the loss of taste and smell that can occur. Another notable difference is the incubation period. For nasopharyngitis, it usually extends from three to four days while for Covid-19, it usually lasts between three and five days but can go up to 14 days.
Are PCR and antigen tests foolproof?
“The primers that are used in the PCR test are specific for Covid-19“ details at Ouest-France, Line Baisset, biologist at Laborizon Bretagne. A PCR test cannot deceive Covid-19, the purpose of this screening is to determine the genetic material, the RNA of the virus. It is therefore impossible for it to interfere with another virus. On the other hand, the PCR test is not 100% reliable: “If the test was carried out too late, the virus can no longer be isolated from a sample”, says the Haute Autorité de Santé (HAS).
This means that if the screening is not performed when symptoms are felt, the result may be false positive or negative. As for the antigen test, it is relatively the same as a PCR test, although the performance is poorer and therefore the result may be less reliable. However, there is a small percentage of “False positives / negatives”. So, during this period if you have symptoms such as a cold, you are strongly advised to go for a test.
