Diagnostic pre-screening method based on N-gene dropout or delay to increase feasibility of SARS-CoV-2 VOC B.1.1.7 detection

Sánchez-Calvo, Juan Manuel; Arboledas, Juan Carlos Alados; Vidal, Luis Ros; de Francisco, José Luis; Prieto, María Dolores López

OBJECTIVES: : To compare the RT-PCR Allplex SARS-CoV-2/FluA/FluB/RSV Assay (Allplex assay) with other methods of detection of VOC B.1.1.7. METHODS: : Suspected and non-suspected cases of VOC B.1.1.7 were defined according to the VirSNiP assay, which detects N501Y and deletion H69-V70. For pre-screening, the Allplex™ and TaqPath assays were used. RESULTS: : One hundred and sixteen suspected and 113 non-suspected cases were included. In the suspected cases, the Allplex assay showed N-gene dropout, or delayed Ct values of 6.27±1.21 and 6.66±1.41 compared with those of the RdRP and S-gene target, respectively. Agreement between the Allplex and TaqPath assays was 100% when the RdRP and S-gene targets had Ct values <35. Agreement between the Allplex and VirSNiP assays was 100% with Ct value <30. CONCLUSIONS: : The Allplex assay showed excellent agreement with the current pre-screening method for VOC B.1.1.7. In addition, its automated processing enhances the feasibility of widespread use in laboratories.