Diagnostic Accuracy of the Abbott BinaxNOW COVID-19 Antigen Card Test, Puerto Rico

Abstract

Background: The COVID-19 pandemic underscored the need for rapid and accurate diagnostic tools. In August 2020, the Abbott BinaxNOW COVID-19 Antigen Card test became available as a timely and affordable alternative for SARS-CoV-2 molecular testing, but its performance may vary due to factors including timing and symptomatology. This study evaluates BinaxNOW diagnostic performance in diverse epidemiological contexts.

Methods: Using RT-PCR as reference, we assessed performance of the BinaxNOW COVID-19 test for SARS-CoV-2 detection in anterior nasal swabs from participants of two studies in Puerto Rico from December 2020 to May 2023. Test performance was assessed by days post symptom onset, collection strategy, vaccination status, symptomatology, repeated testing, and RT-PCR cycle threshold (Ct) values.

Results: BinaxNOW demonstrated an overall sensitivity of 84.1% and specificity of 98.8%. Sensitivity peaked within 1-6 days after symptom onset (93.2%) and was higher for symptomatic (86.3%) than asymptomatic (67.3%) participants. Sensitivity declined over the course of infection, dropping from 96.3% in the initial test to 48.4% in testing performed 7-14 days later. BinaxNOW showed 99.5% sensitivity in participants with low Ct values (≤ 25) but lower sensitivity (18.2%) for participants with higher Cts (36-40).

Conclusions: BinaxNOW demonstrated high sensitivity and specificity, particularly in early-stage infections and symptomatic participants. In situations where test sensitivity is crucial for clinical decision-making, nucleic acid amplification tests are preferred. These findings highlight the importance of considering clinical and epidemiological context when interpreting test results and emphasize the need for ongoing research to adapt testing strategies to emerging SARS-CoV-2 variants.

Keywords: Omicron; Puerto Rico; SARS‐CoV‐2; diagnostic accuracy; rapid antigen test; sensitivity.

FIGURE 1

Sensitivity and specificity of BinaxNOW Antigen test compared to RT‐PCR by days postonset of symptoms (N = 1181 paired tests from 921 participants with 0 to 16 days postonset). The blue line represents a cubic spline and grey bands indicate 95% confidence intervals of the model fit. Vertical bars are 95% confidence intervals of BinaxNOW sensitivity and specificity for each days postonset subgroup. There were 1181 tests of both BinaxNOW and RT‐PCR.

FIGURE 2

Sensitivity of BinaxNOW Antigen test compared to RT‐PCR for initial tests and repeated tests 7–14 days later by symptom status for the initial and repeated tests (N = 368 paired tests from 184 participants). Additional diagnostic accuracy measures are shown in Table S2. There were 368 tests of both BinaxNOW and RT‐PCR.