Multidisciplinary assessment of the Abbott BinaxNOW SARS-CoV-2 point-of-care antigen test in the context of emerging viral variants and self-administration

Abstract

While there has been significant progress in the development of rapid COVID-19 diagnostics, as the pandemic unfolds, new challenges have emerged, including whether these technologies can reliably detect the more infectious variants of concern and be viably deployed in non-clinical settings as "self-tests". Multidisciplinary evaluation of the Abbott BinaxNOW COVID-19 Ag Card (BinaxNOW, a widely used rapid antigen test, included limit of detection, variant detection, test performance across different age-groups, and usability with self/caregiver-administration. While BinaxNOW detected the highly infectious variants, B.1.1.7 (Alpha) first identified in the UK, B.1.351 (Beta) first identified in South Africa, P.1 (Gamma) first identified in Brazil, B.1.617.2 (Delta) first identified in India and B.1.2, a non-VOC, test sensitivity decreased with decreasing viral loads. Moreover, BinaxNOW sensitivity trended lower when devices were performed by patients/caregivers themselves compared to trained clinical staff, despite universally high usability assessments following self/caregiver-administration among different age groups. Overall, these data indicate that while BinaxNOW accurately detects the new viral variants, as rapid COVID-19 tests enter the home, their already lower sensitivities compared to RT-PCR may decrease even more due to user error.

Figure 1

Concordance of LFA and RT-PCR results. Qualitative results from the 3 LFA assays: BD, Sofia and BinaxNOW were compared to the RT-PCR results based on the Ct values. Ct values were divided in 4 groups and displayed on the x-axis. The total number of samples tested as positive by each LFA assay is displayed at the top of the graph, with the total number of samples tested underneath. Percent (%) positive agreement of each LFA assay to the RT-PCR assay is represented on the y-axis.

Figure 2

BinaxNOW agreement versus gold standard PCR decreases with rising Ct values and self collected samples. (A) Collection of diagnostic samples from the anterior nares was completed by either trained healthcare workers (blue) or individual participants (red). Results of quantitative RT-PCR are presented as Ct scores and used to stratify the presented data. % Agreement was calculated as the percentage of concordant test results per group. (B) Pictures of BinaxNOW results for positive and negative findings.

Figure 3

Evaluation for the independent use of BinaxNOW. Usability assessment following self-administration, with parent/caregiver (n = 17) or oneself (adolescent) (n = 3) and adult self-collected sample (n = 42). Self-collection reflects confidence in sample collection. Self-administration reflects confidence in completing assay (assay development, interpretation, etc.).