Evaluation of analyzers for severe acute respiratory syndrome coronavirus 2 gene: TRCReady-80^®, GeneXpert^®, and TaqPath^®

Abstract

We evaluated the performance of two analyzers, namely, TRCReady-80^® (TOSOH Co., TRC) and GeneXpert^® (Beckman Coulter Inc., GX), and an outsourcing test to detect the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) gene using TaqPath^® reagent (Thermo Fisher Scientific K.K., TaqPath). EDX SARS-CoV-2 Standard^® (Bio-Rad Co.) was used to determine the detection limits. It was diluted with saline and the concentrations of the SARS-CoV-2 gene were determined to be 4.3, 17, 34, 43, 170, 340, and 1,700 copies/mL. Each sample was analyzed using TRC and GX within the day. The detection limits of TRC and GX were 430 and 170 copies/mL, respectively. Nasopharyngeal swab samples were collected from 15 non-infected subjects and 13 infected subjects. Two samples were collected from each subject. The first sample was placed in universal viral transport media for analysis using GX and TaqPath. The second one was stirred well in the dedicated denaturing reagents for TRC. All the samples were measured using TRC or GX within the day and the TaqPath test was performed on the next day. All the results collected from the non-infected subjects were negative. As for the infected subjects’ samples, the SARS-CoV-2 gene was detected using GX but there were three false negatives and ten positives in the analysis using TRC or TaqPath. The samples with the discrepancy between GX and TRC or TaqPath results had high Ct values (> 35). The discrepancies seemed to be caused by the detection limit performance and the fragmentations of the SARS-CoV-2 gene in the samples. We should choose the analyzers on the basis of the difference in their characteristics.