A SARS-CoV-2 Reference Standard Quantified by Multi-digital PCR Platforms for Quality Assessment of Molecular Tests

SARS-CoV-2 is the seventh coronavirus known to infect humans and has caused an emerging and rapidly evolving global pandemic (COVID-19) with significant morbidity and mortality. To meet the urgent and massive demand for the screening and diagnosis of infected individuals, many in vitro diagnostic assays using nucleic acid tests (NATs) have been urgently authorized by regulators worldwide. The limit of detection (LoD) is a crucial feature for a diagnostic assay to detect SARS-CoV-2 in clinical samples, and a reference standard with a well-characterized concentration or titer is of the utmost importance for LoD studies. Although several reference standards of plasmids or synthetic RNA carrying specific genomic regions of SARS-CoV-2 have already been announced, a reference standard for inactivated virus particles with accurate concentration is still needed to evaluate the complete procedure including nucleic acid extraction and to accommodate customized primer-probe sets targeting different genome sequences. Here, we performed a collaborative study to estimate the NAT-detectable units as viral genomic equivalent quantity (GEQ) of an inactivated whole-virus SARS-CoV-2 reference standard candidate using digital PCR (dPCR) on multiple commercialized platforms. The median of the quantification results (4.6x105 {+/-} 6.5x104 GEQ/mL) was treated as the consensus true value of GEQ of virus particles in the reference standard. This reference standard was then used to challenge the LoDs of six officially approved diagnostic assays. Our study demonstrates that an inactivated whole virus quantified by dPCR can serve as a reference standard and provides a unified solution for assay development, quality control, and regulatory surveillance.

Study on Spatial Dispersal and Migration Events of Japanese Encephalitis Virus / 病毒学报

To explore the spatial distribution mechanism of Japanese encephalitis virus (JEV), PhyML v3.0 was used to build phylogenetic tree using JEV sequences in the dataset. PAUP v4.0 and Migrapyhla softz ware were then used to analyze the migration events. The results showed that a total of 95 migration events were observed during the dispersal of JEV throughout Asia. Further analysis revealed that Thailand, and several Chinese provinces (including Shandong, Shanghai, Sichuan and Yunnan), were the main migration sources of JEV. JEV spread from these migration sources as follows: from Thailand to Australia, Cambodia, Tibet and India; from Shanghai to eastern coastal Asian regions and Yunnan; from Shandong to Korea, Zhejiang, Hubei, Shanxi and Liaoning; from Sichuan mainly to inland regions of China, as well as Vietnam and Japan; and from Yunnan to Zhejiang. This study indicated that frequent migration events occurred during the dispersal of JEV in the Asia and Pacific regions, and that Thailand, Shandong, Shanghai, Sichuan and Yunnan were the sources of JEV dispersal.

Evaluation of radiation dose to working operator in three types of interventional fluoroscopic procedures / 中华放射医学与防护杂志

Objective To assess the level of radiation exposures of operators in three typical types of interventional fluoroscopic procedures.Methods Alderson Radiation Therapy (ART) phantom was used to stimulate the practices of diagnosis and therapy using TLDs for dose measurement.The radiation exposures of eye lens, neck, and breast were measured when the lead shielding of machine was on/off and the equivalent dose and effective dose to the eye lens were estimated.Results Radiation exposure of head was obviously reduced by 85% -90% when the lead shielding was on.The doses in different procedures were different.In cerebral angiography the dose equivalent of eye len was the highest in the three procedures.The annual effective dose for the operators was smaller in peripheral vascular interventions than that in cardiovascular interventional therapy and that in cerebral angiography.Conclusions The operators involved in intervention will receive an annual effective dose of less than 20 mSv as recommended by the ICRP under the protection conditions provided by the current study, except for eye lens.Attention should be paid to the protection of the eyes of operators.