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  • Rapid Evaluation of the Xpe...
    Noble, Lara Dominique; Scott, Lesley Erica; Munir, Riffat; Du Plessis, Mignon; Steegen, Kim; Hans, Lucia; Marokane, Puleng; Da Silva, Pedro; Stevens, Wendy Susan

    Diagnostics (Basel), 12/2022, Volume: 13, Issue: 1
    Journal Article

    The Xpert Xpress SARS-CoV-2 and Xpert Xpress SARS-CoV-2/Flu/RSV tests were rapidly developed and widely used during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. In response to emerging genetic variability, a new SARS-CoV-2 target (RNA-dependent RNA-polymerase) has been added to both tests: Xpert Xpress CoV-2 and Xpert Xpress CoV-2/Flu/RSV test. A rapid evaluation of both tests was performed in South Africa, using residual respiratory specimens. Residual respiratory specimens (n = 125) were used to evaluate the Xpert Xpress CoV-2 test and included 50 genotyped specimens. The Xpert Xpress CoV-2/Flu/RSV test was assessed using 45 genotyped SARS-CoV-2 specimens, 10 influenza A, 10 influenza B and 20 respiratory syncytial virus specimens. Results were compared to in-country standard-of-care tests. Genotyped specimens tested the performance of the test under pressure from circulating SARS-CoV-2 variants of concern. Reference material was included to assess the test limits and linearity. The Xpert Xpress CoV-2 test performance compared to reference results across residual respiratory specimens was good (positive percentage agreement (PPA) = 95.2%, negative percentage agreement (NPA) = 95.0%) The Xpert Xpress CoV-2/Flu/RSV test showed good performance across all residual respiratory specimens (PPA = 100%, NPA = 98.3%). All genotyped variants of concern were detected by both tests. The Xpert Xpress CoV-2 and Xpert Xpress CoV-2/Flu/RSV tests can be used to diagnose SARS-CoV-2, and to diagnose and differentiate SARS-CoV-2, influenza A, influenza B and respiratory syncytial virus, respectively. The NPA was lower than the recommended 99%, but was influenced by the low number of negative specimens tested. The variants of concern assessed did not affect test performance. It is recommended that sites perform their own assessments compared to in-country standard-of-care tests.