Abstract
The nasopharyngeal swab is currently the main testing method used to diagnose COVID-19. The principle is to collect respiratory cells infected by the virus and to use the RT-PCR (Reverse Transcription - Polymerase Chain Reaction) technique to detect the RNA of the virus. The false negative rate is high, about 30%, which can mainly be explained by an incorrect execution of the technique may increase the false negative rate and decrease the test's sensitivity. The aim of this note is to help healthcare providers to perform this test correctly in adults and children.