SARS-CoV-2 N-antigenemia dataset

Molecular assays on nasopharyngeal swabs remain the cornerstone of COVID-19 diagnostic. Despite massive worldwide efforts, the high technicalities of nasopharyngeal sampling and molecular assays, as well as scarce resources of reagents, limit our testing capabilities. Several strategies failed, to date, to fully alleviate this testing process (e.g. saliva sampling or antigen testing on nasopharyngeal samples). We assessed the performances of a new ELISA microplate assay, the COVID-19 Quantigene (AAZ France), quantifying SARS-CoV-2 nucleocapsid antigen (N-antigen) in serum or plasma.
The specificity of this assay, determined on 63 non-COVID patients, was 98.4% (95% confidence interval [CI], 85.3 to 100). Sensitivity was determined on 227 serum samples from 167 patients with RT-PCR confirmed SARS-CoV-2 infection included in the French COVID and CoV-CONTACT cohorts. Sensitivity was 93.1% (95% CI, 84.7 to 100) within the first two weeks after symptoms onset. A subset of 73 COVID-19 patients had a serum collected within 24 hours following or preceding a positive nasopharyngeal swab. Among patients with a Ct value below 30 and 33 on the nasopharyngeal swab, only 1/50 and 4/67 tested negative for N-antigenemia, respectively.
To our knowledge, this is the first demonstration of N-antigen blood accumulation during COVID-19. This could provide a valuable new option for COVID-19 diagnosis, only requiring a blood draw and easily scalable in all clinical laboratories.