Comparison of BinaxNOW and SARS-CoV-2 qRT-PCR Detection of the Omicron Variant from Matched Anterior Nares Swabs

The COVID-19 pandemic has increased use of rapid diagnostic tests (RDTs). In winter 2021 to 2022, the Omicron variant surge made it apparent that although RDTs are less sensitive than quantitative reverse transcription-PCR (qRT-PCR), the accessibility, ease of use, and rapid readouts made them a sought after and often sold-out item at local suppliers. Here, we sought to qualify the Abbott BinaxNOW RDT for use in our university testing program as a method to rule in positive or rule out negative individuals quickly at our priority qRT-PCR testing site. To perform this qualification study, we collected additional swabs from individuals attending this site. All swabs were tested using BinaxNOW. Initially as part of a feasibility study, test period 1 (n = 110) samples were stored cold before testing. In test period 2 (n = 209), samples were tested immediately. Combined, 102/319 samples tested severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positive via qRT-PCR. All sequenced samples were Omicron (n = 92). We calculated 53.9% sensitivity, 100% specificity, a 100% positive predictive value, and an 82.2% negative predictive value for BinaxNOW (n = 319). Sensitivity would be improved (75.3%) by changing the qRTPCR positivity threshold from a threshold cycle (CT) value of 40 to a CT value of 30. The receiver operating characteristic (ROC) curve shows that for qRT-PCR-positive C-T values of between 24 and 40, the BinaxNOW test is of limited value diagnostically. Results suggest BinaxNOW could be used in our setting to confirm SARS-CoV-2 infection in individuals with substantial viral load, but a significant fraction of infected individuals would be missed if we used RDTs exclusively to rule out infection.

Automated summary

The COVID-19 pandemic has led to increased use of rapid diagnostic tests. While these tests are less sensitive than quantitative reverse transcription-PCR, their accessibility and quick results have made them popular. A study on the Abbott BinaxNOW rapid diagnostic test showed it can accurately confirm SARS-CoV-2 infection in individuals with substantial viral load, but may miss some infected individuals if used exclusively to rule out infection.