Abstract
This case reports the result of a positive nasal swab for the SARS Antigen FIA Quidel, during the start of the realization of the antigen test, in a 26 years old asymptomatic nurse without any factors of risk who had been in contact with a COVID-19 patient three days ago. The result of the antigen test was not confirmed by the RT PCR test, which had been practiced twice. This leads us to discuss the Positive Predictive Value of the rapid tests for guidance, depending on the prevalence of the disease in the population on which they are used. This has many practical consequences for performing this test in an asymptomatic population or when used in mass screening. Care should be taken to use this test according to the correct indications.