Limit of detection in different matrices of nineteen commercially available rapid antigen tests for the detection of SARS-CoV-2

Cubas Atienzar, A. I.; Kontogianni, K.; Edwards, T.; Wooding, D.; Buist, K.; Thompson, C. R.; Williams, C. T.; Baldwin, L.; Patterson, I.; Hughes, G.; Escadafal, C.; Sacks, J.; Adams, E. R.

In the context of the coronavirus disease 2019 (COVID-19) pandemic there has been an increase of the use of antigen-detection rapid diagnostic tests (Ag-RDT). The performance of Ag-RDT vary greatly between manufacturers and evaluating their analytical limit of detection (LOD) has become high priority. Here we describe a manufacturer-independent evaluation of the LOD of 19 marketed Ag-RDT using live SARS-CoV-2 spiked in different matrices: direct culture supernatant, a dry swab, and a swab in Amies. Additionally, the LOD using dry swab was investigated after 7-days storage at -80C of the SARS-CoV-2 serial dilutions. An LOD of {approx} 5.0 x 10^2 pfu/ml (1.0 x 10^6 genome copies/ml) in culture media is defined as acceptable by the World Health Organization. Fourteen of nineteen Ag-RDTs (ActiveXpress, Espline, Excalibur, Innova, Joysbio, Mologic, NowCheck, Orient, PanBio, RespiStrip, Roche, Standard-F, Standard-Q and Sure-Status) exceeded this performance criteria using direct culture supernatant applied to the Ag-RDT. Six Ag-RDT were not compatible with Amies media and a decreased sensitivity of 2 to 20-fold was observed for eleven tests on the stored dilutions at -80C for 7 days. Here, we provide analytical sensitivity data to guide appropriate test and sample type selection for use and for future Ag-RDT evaluations.