Utility of Antigen-Based Rapid Diagnostic Test for Detection of SARS-CoV-2 Virus in Routine Hospital Settings

Abstract

Objective: This study aims to evaluate the performance of an antigen-based rapid diagnostic test (RDT) for the detection of the SARS-CoV-2 virus.

Methods: A cross-sectional study was conducted on 677 patients. Two nasopharyngeal swabs and 1 oropharyngeal swab were collected from patients. The RDT was performed onsite by a commercially available immune-chromatographic assay on the nasopharyngeal swab. The nasopharyngeal and oropharyngeal swabs were examined for SARS-CoV-2 RNA by real-time reverse-transcription quantitative polymerase chain reaction (RT-qPCR) assay.

Results: The overall sensitivity of the SARS-CoV-2 RDT was 34.5% and the specificity was 99.8%. The positive predictive value and negative predictive value of the test were 96.6% and 91.5%, respectively. The detection rate of RDT in RT-qPCR positive results was high (45%) for cycle threshold values <25.

Conclusion: The utility of RDT is in diagnosing symptomatic patients and may not be particularly suited as a screening tool for patients with low viral load. The low sensitivity of RDT does not qualify its use as a single test in patients who test negative; RT-qPCR continues to be the gold standard test.

Keywords: COVID-19; RDT; RT-qPCR; rapid antigen test.

Figure 1

Association of Ct values with RTD results in positive RT-PCR results. Ct, cycle threshold; RTD, rapid diagnostic test; RT-PCR, reverse-transcription polymerase chain reaction.

Figure 2

ROC curve using Ct values to estimate Ct cutoff value for RDT to detect SARS-CoV-2 antigen. Ct, cycle threshold; RDT, rapid diagnostic test; ROC, receiver operating characteristic.