Analytical Sensitivity of the Abbott BinaxNOW COVID-19 Ag CARD

ABSTRACT

Multiple rapid antigen tests for SARS-CoV-2 have recently received Emergency Use Authorization (EUA) from the United States Food and Drug Administration (FDA). Although less sensitive than molecular detection methods, rapid antigen testing offers the potential for cheap, quick, decentralized testing. Robust analytical sensitivity data in comparison to qRT-PCR is currently lacking for many rapid antigen tests. Here, we evaluated the analytical sensitivity of Abbott BinaxNOW COVID-19 Ag CARD using SARS-CoV-2 positive clinical specimens quantified by RT-ddPCR and multiple FDA EUA qRT-PCR platforms using RNA standards. Initial and confirmatory limits of detection for the BinaxNOW COVID-19 Ag CARD were determined to be equivalent to 4.04 – 8.06x10⁴ copies/swab. We further confirmed this limit of detection with 72 additional clinical samples positive for SARS-CoV-2 in either phosphate-buffered saline or viral transport media.100% of samples with viral loads >40,000 copies/swab were detected by rapid antigen testing. These data indicate that the BinaxNOW COVID-19 Ag CARD has the approximate analytical sensitivity equivalent to a generic qRT-PCR C_T of 29-30.