Comparative Evaluation of Rapid Isothermal Amplification and Antigen Assays for Screening Testing of SARS-CoV-2.

Nol Salcedo,Xiying Qu,Brena F Sena,Bobby Brooke Herrera

doi:10.3390/v14030468

Abstract

Human transmission of SARS-CoV-2 and emergent variants of concern continue to occur globally, despite mass vaccination campaigns. Public health strategies to reduce virus spread should therefore rely, in part, on frequent screening with rapid, inexpensive, and sensitive tests. We evaluated two digitally integrated rapid tests and assessed their performance using stored nasal swab specimens collected from individuals with or without COVID-19. An isothermal amplification assay combined with a lateral flow test had a limit of detection of 10 RNA copies per reaction, and a positive percent agreement (PPA)/negative percent agreement (NPA) during the asymptomatic and symptomatic phases of 100%/100% and 95.83/100%, respectively. Comparatively, an antigen-based lateral flow test had a limit of detection of 30,000 copies and a PPA/NPA during the asymptomatic and symptomatic phases of 82.86%/98.68% and 91.67/100%, respectively. Both the isothermal amplification and antigen-based lateral flow tests had optimized detection of SARS-CoV-2 during the peak period of transmission; however, the antigen-based test had reduced sensitivity in clinical samples with qPCR Ct values greater than 29.8. Low-cost, high-throughput screening enabled by isothermal amplification or antigen-based techniques have value for outbreak control.

Highlights

Alongside widespread vaccine campaigns, strategies continue to be implemented to reduce the human transmission of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) [1–4]
We show that the RT-recombinase polymerase amplification (RPA) assay allows for detection of SARS-CoV-2 down to 10 RNA copies per reaction compared to folds higher with the antigen test
We demonstrate that the reverse transcription RPA (RT-RPA) assay has increased sensitivity in nasal swab specimens, in quantitative polymerase chain reaction (qPCR) cycle thresholds (Ct) values greater than 29.8, regardless of if the sample was collected during the asymptomatic or symptomatic phases

Summary

Introduction

Strategies continue to be implemented to reduce the human transmission of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) [1–4]. In particular, has played an important role throughout the coronavirus disease 2019 (COVID-19) pandemic in detecting the virus and emergent variants of concern, enabling responses at the national, community, and individual levels [5,6]. Most testing occurs in centralized settings that utilize quantitative polymerase chain reaction (qPCR) assays [7–9]. While these molecular techniques can detect minute amounts of viral RNA and are most appropriate for clinical diagnosis, they cannot be scaled to meet demands for extensive public health surveillance or frequent screening of individuals, especially in resource-limited settings. Diagnostic testing for COVID-19 focuses on establishing the presence or absence of SARS-CoV-2 in symptomatic or asymptomatic individuals [9,10]. The respiratory specimens are processed by centralized high-complexity laboratories with specialized equipment

Methods

Results

Conclusion