Evaluating the Effect of a Modified Sample Preparation on SARS-CoV-2 Detection in a Cartridge-Based Platform

Abstract

Introduction: The ePlexVR SARS-CoV-2 emergency use authorization (EUA) test is a cartridge-based assay for the detection of SARS-CoV-2 in nasopharyngeal specimens. Since performance data has been previously published on this platform, the manufacturer has modified the workflow design in order to improve assay performance. Evaluation of the new workflow, which eliminated the sample delivery device (SDD), led to a dramatic improvement of assay performance while saving time and making cartridge loading more convenient. Methods: 145 confirmed positive nasopharyngeal swab specimens were used to evaluate the assay analytical sensitivity, accuracy, and overall time-saving for the 2 workflows that is with and without the use of SDD on the ePlex SARS-CoV-2 test. Results: Elimination of the SDD step led to a dramatic increase in accuracy and the overall limit of detection when using 145 previously defined and valid SARS-CoV-2 positive specimens with relatively low, medium, and high cycle thresholds (CT). This simple workflow change led to an overall detection from 94/145 (64.8%) to 131/ 145 (90.3%), with an additional 37 specimens being detected. CT value ranges revealed that 90% of the specimens in the 33 CT < 35.3 CT range were detected, whereas with the SDD workflow, only 30% of positive specimens were detected in this same range. Hands-on time for each specimen also improved and showed overall time savings. Conclusion: The simple workflow modification eliminating the SDD led to an overall improvement in the detection of positive specimens and also simplified workflow and reduced hands-on time.