Michel Prost
Objective: The aim of this work was to explore reliability and performance of an antigen rapid test device on random clinical specimens routinely collected for SARSCoV- 2 diagnosis.
Method: Run a rapid in vitro diagnostic test device for detection of SARS-CoV-2 antigen in nasal specimens taken among those routinely analyzed by RT-PCR in two different sites.
Results:
Site 1: Concordance for SARS-CoV-2 negative results was 100% between Ag rapid test and RT-PCR.
Concordance for SARS-CoV-2 positive results was 91% in our series (Ct range from 11 to 32). Concordance for positive results was 97,8% if we consider only specimens with Ct<25.
Site 2: The test results of RT-PCR reagent and the COVID-19 Antigen Detection Kit are summarized as follows: The sensitivity of the positive sample was 97.3%, and the specificity of the negative sample is 99.5%. The total accuracy achieved 98.3%.
Conclusion: Rapid Ag test devices are convenient devices to aid in the rapid diagnosis of SARS-CoV-2 infections. Molecular diagnosis based upon viral RNA amplification is better because of its lower limit of detection. Specimens should be positive by rapid Ag testing if viral burden corresponds to Ct of around 28 or less by RT-PCR. This is very frequent with virus-producing patients. As this device targets N Ag, molecular variations within S gene did not influence performance of the test.
