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 (460000 ±65000 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.

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A Highly Automated Mobile Laboratory for On-site Molecular Diagnostics in the COVID-19 Pandemic

Clinical Chemistry ◽

10.1093/clinchem/hvab027 ◽

2021 ◽

Vol 67 (4) ◽

pp. 672-683

Author(s):

Wanli Xing ◽

Jiadao Wang ◽

Chao Zhao ◽

Han Wang ◽

Liang Bai ◽

...

Keyword(s):

Infectious Disease ◽

Nucleic Acid ◽

Limit Of Detection ◽

Disease Outbreaks ◽

Clinical Samples ◽

Acid Extraction ◽

Robot Arm ◽

Mobile Laboratory ◽

Infectious Disease Outbreaks ◽

Specimen Collection

Abstract Background Infectious disease outbreaks such as the COVID-19 (coronavirus disease 2019) pandemic call for rapid response and complete screening of the suspected community population to identify potential carriers of pathogens. Central laboratories rely on time-consuming sample collection methods that are rarely available in resource-limited settings. Methods We present a highly automated and fully integrated mobile laboratory for fast deployment in response to infectious disease outbreaks. The mobile laboratory was equipped with a 6-axis robot arm for automated oropharyngeal swab specimen collection; virus in the collected specimen was inactivated rapidly using an infrared heating module. Nucleic acid extraction and nested isothermal amplification were performed by a “sample in, answer out” laboratory-on-a-chip system, and the result was automatically reported by the onboard information platform. Each module was evaluated using pseudovirus or clinical samples. Results The mobile laboratory was stand-alone and self-sustaining and capable of on-site specimen collection, inactivation, analysis, and reporting. The automated sampling robot arm achieved sampling efficiency comparable to manual collection. The collected samples were inactivated in as short as 12 min with efficiency comparable to a water bath without damage to nucleic acid integrity. The limit of detection of the integrated microfluidic nucleic acid analyzer reached 150 copies/mL within 45 min. Clinical evaluation of the onboard microfluidic nucleic acid analyzer demonstrated good consistency with reverse transcription quantitative PCR with a κ coefficient of 0.979. Conclusions The mobile laboratory provides a promising solution for fast deployment of medical diagnostic resources at critical junctions of infectious disease outbreaks and facilitates local containment of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) transmission.

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422. Performance Evaluation of a Rapid and Easy-to-Use COVID-19 Test

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa439.616 ◽

2020 ◽

Vol 7 (Supplement_1) ◽

pp. S278-S278

Author(s):

Corike Toxopeus ◽

Brian Jones ◽

Jessica Brown ◽

Mark Gurling ◽

Cynthia Andjelic ◽

...

Keyword(s):

Nucleic Acid ◽

Research Study ◽

Limit Of Detection ◽

Scientific Research ◽

Cross Reactivity ◽

External Control ◽

Clinical Samples ◽

Acid Extraction ◽

Clinical Specimens ◽

Study Investigator

Abstract Background The BioFire® COVID-19 Test is a qualitative test for use on the FilmArray® 2.0 and Torch systems for the detection of SARS-CoV-2 RNA in nasopharyngeal swabs (NPS) in transport media. This test received Emergency Use Authorization from the FDA. A closed, disposable pouch contains all the necessary reagents for sample preparation, nucleic acid extraction, reverse transcription, polymerase chain reaction (PCR), and amplified nucleic acid detection to identify RNA from SARS-CoV-2 virus in an NPS specimen. Internal controls monitor all stages of the test process. Once an NPS sample (0.3 mL) is loaded into the system disposable pouch (Figure 1), the fully automated test returns results within an hour. As an additional resource, the BioFire® COVID-19 Test External Control Kit (+) includes positive external control material that may be used for quality control and laboratory verification. Figure 1. BioFire COVID-19 Test Disposable Pouch Methods The following were evaluated: • Limit of Detection (LoD) • Positive and Negative Percent Agreement (PPA and NPA, respectively) for clinical contrived samples and a limited number of clinical specimens • Exclusivity Results • LoD The LoD was evaluated using live SARS-CoV-2 virus (cultured from the USA_WA1/2020 strain obtained from World Reference Center for Emerging Viruses and Arboviruses (WRCEVA)). The LoD was determined to be 3.3E+02 GC/mL (2.2E-02 TCID50/mL). • Clinical Contrived Accurate detection of virus in clinical matrix was demonstrated at various LoD levels using thirty contrived individual unique clinical samples (PPA), and 66 individual unique negative clinical specimens (NPA). • Clinical Samples Positive samples were collected from patients presenting with signs or symptoms of COVID-19, and who were previously identified as positive for SARS-CoV-2 by another EUA test. Negative samples were collected in 2018, and therefore presumed negative for SARS-CoV-2. • Exclusivity The potential for cross-reactivity was evaluated for six viruses from the same genetic family as SARS- CoV-2, and for an additional 30 high priority organisms/viruses. No cross-reactivity was observed. Table 1. SARS-CoV-2 Virus Test Results at 1× and 0.1× LoD for the BioFire COVID-19 Test Table 2. Clinical Contrived and Negative Testing with the BioFire COVID-19 Test Table 3. BioFire COVID-19 Test Performance Summary Conclusion The BioFire COVID-19 Test reliably detects SARS-CoV-2 virus RNA in clinically relevant samples. Disclosures Corike Toxopeus, PhD, BioFire Defense, LLC. (Employee, stock owner) Brian Jones, PhD., BioFire Defense, LLC (Employee, own stock) Jessica Brown, BS, BioFire Defense (Employee, Stock owner) Mark Gurling, PhD, BioFire Defense, LLC (Employee) Cynthia Andjelic, PhD., BioFire Defense (Employee, Other Financial or Material Support, Own stocks) Cynthia L. Phillips, PhD, BioFire Defense (Employee, Scientific Research Study Investigator, Shareholder)BioFire Defense (Employee, Scientific Research Study Investigator, Shareholder)

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Inactivation of SARS-CoV-2 virus in saliva using a guanidium based transport medium suitable for RT-PCR diagnostic assays

PLoS ONE ◽

10.1371/journal.pone.0252687 ◽

2021 ◽

Vol 16 (6) ◽

pp. e0252687

Author(s):

Sukalyani Banik ◽

Kaheerman Saibire ◽

Shraddha Suryavanshi ◽

Glenn Johns ◽

Soumitesh Chakravorty ◽

...

Keyword(s):

Limit Of Detection ◽

Viral Rna ◽

Clinical Samples ◽

Sample Collection ◽

Rt Pcr ◽

Diagnostic Assays ◽

Guanidinium Thiocyanate ◽

Upper Respiratory ◽

Polymerase Chain ◽

The Stability

Background Upper respiratory samples used to test for SARS-CoV-2 virus may be infectious and present a hazard during transport and testing. A buffer with the ability to inactivate SARS-CoV-2 at the time of sample collection could simplify and expand testing for COVID-19 to non-conventional settings. Methods We evaluated a guanidium thiocyanate-based buffer, eNAT™ (Copan) as a possible transport and inactivation medium for downstream Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) testing to detect SARS-CoV-2. Inactivation of SARS-CoV-2 USA-WA1/2020 in eNAT and in diluted saliva was studied at different incubation times. The stability of viral RNA in eNAT was also evaluated for up to 7 days at room temperature (28°C), refrigerated conditions (4°C) and at 35°C. Results SARS-COV-2 virus spiked directly in eNAT could be inactivated at >5.6 log10 PFU/ml within a minute of incubation. When saliva was diluted 1:1 in eNAT, no cytopathic effect (CPE) on VeroE6 cells was observed, although SARS-CoV-2 RNA could be detected even after 30 min incubation and after two cell culture passages. A 1:2 (saliva:eNAT) dilution abrogated both CPE and detectable viral RNA after as little as 5 min incubation in eNAT. SARS-CoV-2 RNA from virus spiked at 5X the limit of detection remained positive up to 7 days of incubation in all tested conditions. Conclusion eNAT and similar guanidinium thiocyanate-based media may be of value for transport, stabilization, and processing of clinical samples for RT-PCR based SARS-CoV-2 detection.

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Defining the analytical and clinical sensitivity of the ARTIC method for the detection of SARS-CoV-2

10.1101/2021.10.09.21264695 ◽

2021 ◽

Author(s):

Nabil-Fareed Alikhan ◽

Joshua Quick ◽

Alexander J. Trotter ◽

Samuel C. Robson ◽

Matthew Bashton ◽

...

Keyword(s):

Performance Metrics ◽

Limit Of Detection ◽

Diagnostic Testing ◽

Virus Detection ◽

Detection Methods ◽

Clinical Samples ◽

Sequencing Data ◽

Clinical Sensitivity ◽

Diagnostic Assays ◽

Sequencing Method

The SARS-CoV-2 ARTIC amplicon protocol is the most widely used genome sequencing method for SARS-CoV-2, accounting for over 43% of publicly-available genome sequences. The protocol utilises 98 primers to amplify ~400bp fragments of the SARS-CoV-2 genome covering all 30,000 bases. Understanding the analytical performance metrics of this protocol will improve how the data is used and interpreted. Different concentrations of SARS-CoV-2 control material were used to establish the limit of detection (LoD) of the ARTIC protocol. Results demonstrated the LoD was a minimum of 25-50 virus particles per mL. The sensitivity of ARTIC was comparable to the published sensitivities of commercial diagnostics assays and could therefore be used to confirm diagnostic testing results. A set of over 3,600 clinical samples from three UK regions were then evaluated to compare the protocols performance to clinical diagnostic assays (Roche Lightcycler 480 II, AusDiagnostics, Roche Cobas, Hologic Panther, Corman RdRp, Roche Flow, ABI QuantStudio 5, Seegene Nimbus, Qiagen Rotorgene, Abbott M2000, Thermo TaqPath, Xpert). We developed a Python tool, RonaLDO, to perform this validation (available under the GNU GPL3 open-source licence from https://github.com/quadram-institute-bioscience/ronaldo). Positives detected by diagnostic platforms were generally supported by sequencing data; platforms that used RT-qPCR were the best predictors of whether the sample would subsequently sequence successfully. To maximise success of sample sequencing for phylogenetic analysis, samples with Ct <31 should be chosen. For diagnostic tests that do not provide a quantifiable Ct value, adding a quantification step is recommended. The ARTIC SARS-CoV-2 sequencing protocol is highly sensitive, capable of detecting SARS-CoV-2 in samples with Cts in the high 30s. However, to routinely obtain whole genome coverage, samples with Ct <31 are recommended. Comparing different virus detection methods close to their LoD was challenging and significant discordance was observed.

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Single Tube qPCR detection and quantitation of hotspot mutations down to 0.01% VAF

10.1101/2021.08.12.456178 ◽

2021 ◽

Author(s):

Kerou Zhang ◽

Luis Rodriguez ◽

Lauren Yuxuan Cheng ◽

David Yu Zhang

Keyword(s):

Rare Variants ◽

Limit Of Detection ◽

Digital Pcr ◽

Clinical Samples ◽

Peripheral Blood Mononuclear ◽

Clinical Sensitivity ◽

Sequencing Technologies ◽

Median Error ◽

Allele Specific ◽

Dna Sequence Variants

Clinically and biologically, rare DNA sequence variants are significant and informative. However, existing detection technologies are either complex in workflow, or restricted in the limit of detection (LoD), or do not allow for multiplexing. Blocker displacement amplification (BDA) method can stably and effectively detect and enrich multiple rare variants with LoD around 0.1% variant allele fraction (VAF). Nonetheless, the detailed mutation information has to be identified by additional sequencing technologies. Here, we present allele-specific BDA (As-BDA), a method combining BDA with allele-specific TaqMan (As-TaqMan) probes for effective variant enrichment and simultaneous SNV profiling. We demonstrated that As-BDA could detect mutations down to 0.01% VAF. Further, As-BDA could detect up to four mutations with low to 0.1% VAF per reaction using only 15 ng DNA input. The median error of As-BDA in VAF determination is approximately 9.1%. Comparison experiments using As-BDA and droplet digital PCR (ddPCR) on peripheral blood mononuclear cell (PBMC) clinical samples showed 100% concordance for samples with mutations at 3 0.1% VAF. Hence, we have shown that As-BDA can achieve simultaneous enrichment and identification of multiple targeted mutations within the same reaction with high clinical sensitivity and specificity, thus helpful for clinical diagnosis.

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One-Tube SARS-CoV-2 Detection Platform Based on RT-RPA and CRISPR/Cas12a

10.21203/rs.3.rs-96229/v1 ◽

2020 ◽

Author(s):

Yangyang Sun ◽

Lei Yu ◽

Chengxi Liu ◽

Wei Chen ◽

Dechang Li ◽

...

Keyword(s):

Nucleic Acid ◽

Limit Of Detection ◽

Lateral Flow ◽

Lateral Flow Assay ◽

N Gene ◽

Clinical Samples ◽

Nucleic Acid Detection ◽

Detection Process ◽

Human Coronaviruses ◽

Negative Controls

Abstract Background: COVID-19 has spread rapidly around the world, affecting almost every person. When lifting certain mandatory measures for an economic restart, robust surveillance must be established and implemented, with nucleic acid detection for SARS-CoV-2 as an essential component. Methods: We designed RT-RPA (Reverse Transcription and Recombinase Polymerase Isothermal Amplification) primers of RdRp gene and N gene according to the SARS-CoV-2 gene sequence. We optimized the components in the reaction so that the detection process could be carried out in one tube. The specificity was demonstrated through detecting nucleic acid samples from seven human coronaviruses. Clinical samples were used to validate the platform and all results were compared to rRT-PCR. RNA standards diluted by different gradients were used to demonstrate the limit of detection. Furthermore, we have developed a lateral flow assay based on OR-DETECTR for the detection of COVID-19. Results: We have developed a o ne-tube detection platform based on R T- R PA and DNA Endonuclease-Targeted CRISPR Trans Reporter ( DETECTR ) technology, termed OR-DETECTR, to detect SARS-CoV-2. The detection process is completed in one tube, and the time is 50min. The method can specifically detect SARS-CoV-2 from seven human coronaviruses with a low detection limit of 2.5 copies/µl input. Results from six SARS-CoV-2 patient samples, eight samples from patients with fever but no SARS-CoV-2 infection, and one mixed sample from 40 negative controls showed that OR-DETECTR is 100% consistent with rRT-PCR. Furthermore, we have developed a lateral flow assay based on OR-DETECTR for the detection of COVID-19. Conclusions: OR-DETECTR detection platform is rapid, accurate, tube closed, easy-to-operate, and free of large instruments for COVID-19 detection.

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SalivaDirect: A simplified and flexible platform to enhance SARS-CoV-2 testing capacity

10.1101/2020.08.03.20167791 ◽

2020 ◽

Cited By ~ 14

Author(s):

Chantal B.F. Vogels ◽

Anne E. Watkins ◽

Christina A. Harden ◽

Doug Brackney ◽

Jared Shafer ◽

...

Keyword(s):

Supply Chain ◽

Nucleic Acid ◽

Large Scale ◽

Limit Of Detection ◽

Proteinase K ◽

Acid Extraction ◽

Sample Collection ◽

Reverse Transcription Pcr ◽

August 15Th ◽

Frequent Sampling

Current bottlenecks for improving accessibility and scalability of SARS-CoV-2 testing include diagnostic assay costs, complexity, and supply chain shortages. To resolve these issues, we developed SalivaDirect, which received Emergency Use Authorization (EUA) from the U.S. Food and Drug Administration on August 15th, 2020. The critical component of our approach is to use saliva instead of respiratory swabs, which enables non-invasive frequent sampling and reduces the need for trained healthcare professionals during collection. Furthermore, we simplified our diagnostic test by (1) not requiring nucleic acid preservatives at sample collection, (2) replacing nucleic acid extraction with a simple proteinase K and heat treatment step, and (3) testing specimens with a dualplex quantitative reverse transcription PCR (RT-qPCR) assay. We validated SalivaDirect with reagents and instruments from multiple vendors to minimize the risk for supply chain issues. Regardless of our tested combination of reagents and instruments from different vendors, we found that SalivaDirect is highly sensitive with a limit of detection of 6-12 SARS-CoV-2 copies/μL. When comparing SalivaDirect to paired nasopharyngeal swabs using the authorized ThermoFisher Scientific TaqPath COVID-19 combo kit, we found high agreement in testing outcomes (>94%). In partnership with the National Basketball Association (NBA) and Players Association, we conducted a large-scale (n = 3,779) SalivaDirect usability study and comparison to standard nasal/oral tests for asymptomatic and presymptomatic SARS-CoV-2 detection. From this cohort of healthy NBA players, staff, and contractors, we found that 99.7% of samples were valid using our saliva collection techniques and a 89.5% positive and >99.9% negative test agreement to swabs, demonstrating that saliva is a valid and noninvasive alternative to swabs for large-scale SARS-CoV-2 testing. SalivaDirect is a flexible and inexpensive ($1.21-$4.39/sample in reagent costs) option to help improve SARS-CoV-2 testing capacity. Register to become a designated laboratory to use SalivaDirect under our FDA EUA on our website: publichealth.yale.edu/salivadirect/.

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Evaluation of real-time nucleic acid sequence-based amplification for detection of Chikungunya virus in clinical samples

Journal of Medical Microbiology ◽

10.1099/jmm.0.010736-0 ◽

2009 ◽

Vol 58 (9) ◽

pp. 1168-1172 ◽

Cited By ~ 14

Author(s):

J.-N. Telles ◽

K. Le Roux ◽

P. Grivard ◽

G. Vernet ◽

A. Michault

Keyword(s):

Nucleic Acid ◽

Real Time ◽

Chikungunya Virus ◽

False Negative ◽

Nucleic Acid Sequence ◽

Clinical Samples ◽

Acid Extraction ◽

Plasma Samples ◽

Rt Pcr ◽

Nucleic Acid Extraction

The Chikungunya virus (CHIKV) is a member of the genus Alphavirus that is transmitted to humans by Aedes mosquitoes. In 2005 and 2006, the Indian Ocean island of La Réunion was hit with an unprecedented CHIKV fever outbreak that infected 300 000 people. In the present study, we describe the evaluation of real-time nucleic acid sequence-based amplification (RT-NASBA) for the detection of CHIKV in clinical samples. A co-extracted and co-amplified chimerical CHIKV RNA sequence was used as an internal control to eliminate false-negative results. The detection threshold of the assay was determined from quantified CHIKV-positive plasma, and estimated to be 200 copies per NASBA reaction. The specificity of the assay was determined using blast analyses and non-cross-reactivity using an O'nyong-nyong virus culture and 250 CHIKV RT-PCR-negative plasma samples. A 100 % specificity was found and no invalid result was obtained, showing the good quality of the nucleic acid extraction. The assay was then evaluated using 252 CHIKV-positive RT-PCR plasma samples. The samples were all tested positive, including those with low viral load. This evaluation showed that the RT-NASBA is a rapid (5 h from sample nucleic acid extraction to detection), sensitive, specific and reliable method for the routine diagnosis of CHIKV in clinical samples.

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Towards a “Sample-In, Answer-Out” Point-of-Care Platform for Nucleic Acid Extraction and Amplification: Using an HPV E6/E7 mRNA Model System

Journal of Oncology ◽

10.1155/2012/905024 ◽

2012 ◽

Vol 2012 ◽

pp. 1-12 ◽

Cited By ~ 16

Author(s):

Anja Gulliksen ◽

Helen Keegan ◽

Cara Martin ◽

John O'Leary ◽

Lars A. Solli ◽

...

Keyword(s):

Nucleic Acid ◽

Sample Preparation ◽

Clinical Sample ◽

Point Of Care ◽

Fluorescent Detection ◽

Clinical Samples ◽

Microfluidic Channels ◽

Acid Extraction ◽

Nucleic Acid Extraction ◽

Hpv E6

The paper presents the development of a “proof-of-principle” hands-free and self-contained diagnostic platform for detection of human papillomavirus (HPV) E6/E7 mRNA in clinical specimens. The automated platform performs chip-based sample preconcentration, nucleic acid extraction, amplification, and real-time fluorescent detection with minimal user interfacing. It consists of two modular prototypes, one for sample preparation and one for amplification and detection; however, a common interface is available to facilitate later integration into one single module. Nucleic acid extracts (n=28) from cervical cytology specimens extracted on the sample preparation chip were tested using the PreTect HPV-Proofer and achieved an overall detection rate for HPV across all dilutions of 50%–85.7%. A subset of 6 clinical samples extracted on the sample preparation chip module was chosen for complete validation on the NASBA chip module. For 4 of the samples, a 100% amplification for HPV 16 or 33 was obtained at the 1 : 10 dilution for microfluidic channels that filled correctly. The modules of a “sample-in, answer-out” diagnostic platform have been demonstrated from clinical sample input through sample preparation, amplification and final detection.

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Semi-Quantitative, Duplexed qPCR Assay for the Detection of Leishmania spp. Using Bisulphite Conversion Technology

Tropical Medicine and Infectious Disease ◽

10.3390/tropicalmed4040135 ◽

2019 ◽

Vol 4 (4) ◽

pp. 135 ◽

Cited By ~ 3

Author(s):

Ineka Gow ◽

Douglas Millar ◽

John Ellis ◽

John Melki ◽

Damien Stark

Keyword(s):

Limit Of Detection ◽

Quantitative Polymerase Chain Reaction ◽

World Health ◽

Clinical Samples ◽

Acid Extraction ◽

Analytical Sensitivity ◽

Internal Transcribed Spacer Region ◽

Leishmania Spp ◽

Sensitivity Data ◽

Conversion Technology

Leishmaniasis is caused by the flagellated protozoan Leishmania, and is a neglected tropical disease (NTD), as defined by the World Health Organisation (WHO). Bisulphite conversion technology converts all genomic material to a simplified form during the lysis step of the nucleic acid extraction process, and increases the efficiency of multiplex quantitative polymerase chain reaction (qPCR) reactions. Through utilization of qPCR real-time probes, in conjunction with bisulphite conversion, a new duplex assay targeting the 18S rDNA gene region was designed to detect all Leishmania species. The assay was validated against previously extracted DNA, from seven quantitated DNA and cell standards for pan-Leishmania analytical sensitivity data, and 67 cutaneous clinical samples for cutaneous clinical sensitivity data. Specificity was evaluated by testing 76 negative clinical samples and 43 bacterial, viral, protozoan and fungal species. The assay was also trialed in a side-by-side experiment against a conventional PCR (cPCR), based on the Internal transcribed spacer region 1 (ITS1 region). Ninety-seven percent of specimens from patients that previously tested positive for Leishmania were positive for Leishmania spp. with the bisulphite conversion assay, and a limit of detection (LOD) of 10 copies per PCR was achieved, while the LOD of the ITS1 methodology was 10 cells/1000 genomic copies per PCR. This method of rapid, accurate and simple detection of Leishmania can lead to improved diagnosis, treatment and public health outcomes.

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