Clinical Evaluation of Three Sample-to-Answer Platforms for Detection of SARS-CoV-2.

Alexander J Mcadam,Wei Zhen,Gregory J Berry,Elizabeth Smith,Deborah Schron,Ryhana Manji

doi:10.1128/jcm.00783-20

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has now spread across the globe. As part of the worldwide response, many molecular diagnostic platforms have been granted emergency use authorization (EUA) by the Food and Drug Administration (FDA) to identify SARS-CoV-2 positive patients. Our objective was to evaluate three sample-to-answer molecular diagnostic platforms (Cepheid Xpert Xpress SARS-CoV-2 [Xpert Xpress], Abbott ID NOW COVID-19 [ID NOW], and GenMark ePlex SARS-CoV-2 Test [ePlex]) to determine analytical sensitivity, clinical performance, and workflow for the detection of SARS-CoV-2 in nasopharyngeal swabs from 108 symptomatic patients. We found that Xpert Xpress had the lowest limit of detection (100% detection at 100 copies/ml), followed by ePlex (100% detection at 1,000 copies/ml), and ID NOW (20,000 copies/ml). Xpert Xpress also had highest positive percent agreement (PPA) compared to our reference standard (98.3%) followed by ePlex (91.4%) and ID NOW (87.7%). All three assays showed 100% negative percent agreement (NPA). In the workflow analysis, ID NOW produced the lowest time to result per specimen (∼17 min) compared to Xpert Xpress (∼46 min) and ePlex (∼1.5 h), but what ID NOW gained in rapid results, it lost in analytical and clinical performance. ePlex had the longest time to results and showed a slight improvement in PPA over ID NOW. Information about the clinical and analytical performance of these assays, as well as workflow, will be critical in making informed and timely decisions on testing platforms.

Highlights

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread across the globe
LoD was determined by preparing serial dilutions ranging from 20,000 to 5 copies/ml using a known concentration of the Exact Diagnostics SARS-CoV-2 control panel and was defined as the minimum concentration with detection of 100% by positive rate
The LoD established by percent positive rate and the manufacturer’s interpretation algorithm for each assay was determined to be 20,000 copies/ml for ID 1,000 copies/ml for ePlex, and 100 copies/ml for the Xpert Xpress assay (Table 1)

Summary

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread across the globe. ID produced the lowest time to result per specimen (ϳ17 min) compared to Xpert Xpress (ϳ46 min) and ePlex (ϳ1.5 h), but what ID gained in rapid results, it lost in analytical and clinical performance. Available molecular diagnostics platforms include several sample-toanswer platforms that have been issued an emergency use authorization (EUA) by the FDA to qualitatively detect SARS-CoV-2 RNA in symptomatic patients. All three sampleto-answer platforms evaluated in this study are individual cartridge-based tests that are likely to be widely utilized by hospital laboratories Both Xpert Xpress and ID are authorized for use in patient care settings outside the clinical laboratory environment and are highly likely to be considered for patient testing in the outpatient environment

Objectives

Methods

Results

Conclusion