Application of digital PCR to determine the reliability of Xpert Xpress SARS-CoV-2 assay with envelope (E) gene negative and nucleocapsid (N2) gene positive results

Wong, Chi Fong; Wong, April S. Y.; Ho, Yolanda Iok-Ieng; Siu, Gilman Kit-Hang; Lee, Lam-Kwong; Leung, Eddie Chi Man; Lai, Robin Kit-Ho

doi:10.1016/j.diagmicrobio.2022.115726

Cited by 4 publications

(5 citation statements)

References 11 publications

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“…Three positive results were also detected with the Xpert assay among ddPCR‐negative specimens, with Ct values above 40.0 in one of the two target genes. The possibility of false‐negative results with Xpert has been reported previously when E or N2 has a Ct value > 38 or when both E and N2 have Ct values > 40 10,11 . Thus, the clinical cut‐off value may need to be adjusted to complement the automatic interpretation of rapid RT‐PCR assays.…”

Section: Discussionmentioning

confidence: 99%

“…Compared with standard or rapid RT‐PCR assays, ddPCR has superior analytical sensitivity, especially for the detection of SARS‐CoV‐2 in samples with a low viral load 11 . Nine discordant results between the STANDARD M10 and Allplex assays were all revealed to be positive, except for one specimen, with ddPCR.…”

Section: Discussionmentioning

confidence: 99%

“…The ddPCR was performed for the specimens with discordant results in the initial STANDARD M10 and Allplex assays. The ddPCR was performed using QX200 system (Bio‐Rad Laboratories), One‐Step RT‐ddPCR Advanced kit for Probes (Bio‐Rad Laboratories), and 2019nCoV CDC ddPCR Triplex Probe Assay (Bio‐Rad Laboratories) according to the manufacturer's recommendations 11 . The frozen nucleic acid samples stored at −70°C after Allplex retest assays were thawed and tested in triplicate.…”

Section: Methodsmentioning

confidence: 99%

“…The ddPCR was performed using QX200 system (Bio-Rad Laboratories), One-Step RT-ddPCR Advanced kit for Probes (Bio-Rad Laboratories), and 2019nCoV CDC ddPCR Triplex Probe Assay (Bio-Rad Laboratories) according to the manufacturer's recommendations. 11 The frozen nucleic acid samples stored at −70°C after Allplex retest assays were thawed and tested in triplicate. The results were analyzed using QuantaSoft Analysis Pro software version 1.0.596 (Bio-Rad Laboratories).…”

Section: Bio-rad Qx200 Ddpcrmentioning

confidence: 99%

“…In the present study, STANDARD M10 detected 118 specimens among 123 positive specimens that were positive with Allplex assay (95.9%), although the positive specimens consisted of 34.1% of specimens with a Ct value ≥ 30 for E gene, which demonstrates acceptable clinical performance based on the criteria by the Korean Ministry of Food and Drug Safety. possibility of false-negative results with Xpert has been reported previously when E or N2 has a Ct value > 38 or when both E and N2have Ct values > 40 10,11. Thus, the clinical cut-off value may need to be adjusted to complement the automatic interpretation of rapid RT-PCR assays.T A B L E 3 (Continued) a The order of RT-PCR results are STANDARD M10, Allplex and Xpert assays.…”

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confidence: 99%

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Clinical performance of the STANDARD M10 SARS‐CoV‐2 rapid RT‐PCR assay in patients visiting an emergency department

Lee,

Han,

Ryu

et al. 2023

Journal of Medical Virology

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In emergency departments, rapid screening of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) was important for arranging limited isolation resources and patient care during the coronavirus disease 2019 (COVID‐19) pandemic. STANDARD M10 SARS‐CoV‐2 (SD Biosensor) is a recently developed cartridge‐based RT‐PCR that provides a turnaround time of 1 h, which is shorter than that for conventional RT‐PCR. This study evaluated the clinical performance of STANDARD M10 in patients visiting an emergency department. From March to June 2022, two specimens were collected from patients visiting an emergency department. Each specimen comprised one nasopharyngeal and one oropharyngeal swab. Respective specimens underwent rapid RT‐PCR using STANDARD M10 and conventional RT‐PCR using Allplex SARS‐CoV‐2 (Seegene). When discordant results occurred, specimens undergoing the STANDARD M10 were retested with the Allplex to exclude specimen variations. Retest results replaced initial results of the Allplex. Clinical performance of STANDARD M10 was compared with Allplex. The study enrolled 1971 patients. COVID‐19 prevalence was 6.2% based on the Allplex. Compared with the Allplex, overall agreement, positive percent agreement, and negative percent agreement of STANDARD M10 were 99.5% (95% CI: 99.1%–99.8%), 95.9% (95% CI: 90.8%–98.3%), and 99.8% (95% CI: 99.4%–99.9%), respectively. Nine discordant results were all positive on droplet digital PCR, except for one specimen that was positive with STANDARD M10. The STANDARD M10 showed reliable diagnostic performance for detecting SARS‐CoV‐2 from patients visiting in emergency departments and is a useful tool in emergency healthcare systems because of its easy‐to‐use cartridge‐based assay and short resulting time for detecting SARS‐CoV‐2.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Bio-rad Qx200 Ddpcrmentioning

confidence: 99%

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confidence: 99%

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