scholarly journals Direct diagnostic testing of SARS-CoV-2 without the need for prior RNA extraction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shan Wei ◽  
Esther Kohl ◽  
Alexandre Djandji ◽  
Stephanie Morgan ◽  
Susan Whittier ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Point Of Care ◽  
Diagnostic Testing ◽  
Rna Extraction ◽  
Cost Effective ◽  
Clinical Samples ◽  
Nasopharyngeal Swab ◽  
Percentage Agreement ◽  
Testing Method ◽  
Viral Transport

AbstractThe COVID-19 pandemic has resulted in an urgent need for a rapid, point of care diagnostic testing that could be rapidly scaled on a worldwide level. We developed and tested a highly sensitive and robust assay based on reverse transcription loop mediated isothermal amplification (RT-LAMP) that uses readily available reagents and a simple heat block using contrived spike-in and actual clinical samples. RT-LAMP testing on RNA-spiked samples showed a limit of detection (LoD) of 2.5 copies/μl of viral transport media. RT-LAMP testing directly on clinical nasopharyngeal swab samples in viral transport media had an 85% positive percentage agreement (PPA) (17/20), and 100% negative percentage agreement (NPV) and delivered results in 30 min. Our optimized RT-LAMP based testing method is a scalable system that is sufficiently sensitive and robust to test for SARS-CoV-2 directly on clinical nasopharyngeal swab samples in viral transport media in 30 min at the point of care without the need for specialized or proprietary equipment or reagents. This cost-effective and efficient one-step testing method can be readily available for COVID-19 testing world-wide, especially in resource poor settings.

scholarly journals Direct diagnostic testing of SARS-CoV-2 without the need for prior RNA extraction

2020 ◽  
Author(s):  
Shan Wei ◽  
Esther Kohl ◽  
Alexandre Djandji ◽  
Stephanie Morgan ◽  
Susan Whittier ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Point Of Care ◽  
Low Cost ◽  
Diagnostic Testing ◽  
Rna Extraction ◽  
Nucleic Acid Amplification ◽  
Nasopharyngeal Swab ◽  
Viral Transport ◽  
Extraction Step ◽  
Highly Sensitive

AbstractThe COVID-19 pandemic has resulted in an urgent global need for rapid, point-of-care diagnostic testing. Existing methods for nucleic acid amplification testing (NAAT) require an RNA extraction step prior to amplification of the viral RNA. This step necessitates the use of a centralized laboratory or complex and costly proprietary cartridges and equipment, and thereby prevents low-cost, scalable, point-of-care testing. We report the development of a highly sensitive and robust, easy-to-implement, SARS-CoV-2 test that utilizes isothermal amplification and can be run directly on viral transport media following a nasopharyngeal swab without the need for prior RNA extraction. Our assay provides visual results in 30 min with 85% sensitivity, 100% specificity, and a limit of detection (LoD) of 2.5 copies/μl, and can be run using a simple heat block.

scholarly journals Real-time optical analysis of a colorimetric LAMP assay for SARS-CoV-2 in saliva with a handheld instrument improves accuracy compared to endpoint assessment

2021 ◽  
Author(s):  
Lena M. Diaz ◽  
Brandon E. Johnson ◽  
Daniel M. Jenkins
Keyword(s):  
Nucleic Acid ◽  
Quantitative Method ◽  
Limit Of Detection ◽  
Detection System ◽  
Diagnostic Testing ◽  
Rna Extraction ◽  
Lamp Assay ◽  
Nucleic Acid Amplification ◽  
Clinical Samples ◽  
Ph Indicator

AbstractControlling the course of the COVID-19 pandemic will require widespread deployment of consistent and accurate diagnostic testing of the novel coronavirus SARS-CoV-2. Ideally, tests should detect a minimum viral load, be minimally invasive, and provide a rapid and simple readout. Current FDA-approved RT-qPCR-based standard diagnostic approaches require invasive nasopharyngeal swabs and involve laboratory-based analyses that can delay results. Recently, a loop mediated isothermal nucleic acid amplification (LAMP) test that utilizes colorimetric readout received FDA approval. This approach utilizes a pH indicator dye to detect drop in pH from nucleotide hydrolysis during nucleic acid amplification. This method has only been approved for use with RNA extracted from clinical specimens collected via nasopharyngeal swabs. In this study, we developed a quantitative LAMP-based strategy to detect SARS-CoV-2 RNA in saliva. Our detection system distinguished positive from negative sample types using a handheld instrument that monitors optical changes throughout the LAMP reaction. We used this system in a streamlined LAMP testing protocol that could be completed in less than two hours to directly detect inactivated SARS-CoV-2 in minimally processed saliva that bypassed RNA extraction, with a limit of detection (LOD) of 50 genomes/reaction. The quantitative method correctly detected virus in 100% of contrived clinical samples spiked with inactivated SARS- CoV-2 at either 1X (50 genomes/reaction) or 2X (100 genomes/reaction) of the LOD. Importantly the quantitative method was based on dynamic optical changes during the reaction so was able to correctly classify samples that were misclassified by endpoint observation of color.

scholarly journals Clinical validation of innovative, low cost, kit-free, RNA processing protocol for RT-PCR based COVID-19 testing.

2020 ◽  
Author(s):  
Nikhil Shri Sahajpal ◽  
Ashis K Mondal ◽  
Allan Njau ◽  
Sudha Ananth ◽  
Arvind Kothandaraman ◽  
...  
Keyword(s):  
High Throughput Screening ◽  
Performance Metrics ◽  
Limit Of Detection ◽  
Rna Extraction ◽  
Limited Resource ◽  
Clinical Samples ◽  
Pcr Analysis ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Pcr Assay

The current gold-standard molecular diagnosis for COVID-19 is based on a multi-step assay involving RNA-extraction and RT-PCR analysis for the detection of SARS-CoV-2. RNA-extraction step has been a major rate-limiting step in implementing high-throughput screening for COVID-19 during this pandemic. Moreover, clinical laboratories are facing several challenges that include cost, reagents, instrumentation, turn-around time, trained personnel, and supply-chain constraints to efficiently implement and sustain testing. Cognizant of these limitations, we evaluated the extraction-free methods described in the literature and have developed an innovative, simplified and easy protocol employing limited reagents to extract RNA for subsequent RT-PCR analysis. Nasopharyngeal-swab samples were subjected to the following individual conditions: 65°C for 15 minutes; 80°C for 5 minutes; 90°C for 5 minutes or 80°C for 1 minute, and processed for direct RT-PCR. These groups were also compared with a supplemental protocol adding isopropanol-ethanol-water elution steps followed by RT-PCR assay. The direct RT-PCR assay did not detect SARS-CoV-2 within the various temperature incubation only groups, whereas, the 90°C for 5 minutes-isopropanol-ethanol-water method was found to be comparable to the FDA-EUA method. Evaluation of the performance metrics for 100 clinical samples demonstrated a sensitivity of 94.2% and a specificity of 100%. The limit of detection was ascertained to be ~40 copies/ml by absolute-quantification. The protocol presented for this assay employs limited reagents and yields results with high sensitivity. Additionally, it presents a simplified methodology that would be easier to implement in laboratories in limited resource countries in order to meet the high current COVID-19 testing needs.

Effective optimization of SARS-CoV-2 laboratory testing variables in an era of supply chain constraints

2020 ◽  
Vol 15 (15) ◽  
pp. 1483-1487
Author(s):  
Nikhil S Sahajpal ◽  
Ashis K Mondal ◽  
Allan Njau ◽  
Sudha Ananth ◽  
Kimya Jones ◽  
...  
Keyword(s):  
Supply Chain ◽  
Rna Extraction ◽  
Nasopharyngeal Swab ◽  
Sample Collection ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Short Supply ◽  
Viral Transport ◽  
3D Printed ◽  
Bridging Studies

RT-PCR-based assays for the detection of SARS-CoV-2 have played an essential role in the current COVID-19 pandemic. However, the sample collection and test reagents are in short supply, primarily due to supply chain issues. Thus, to eliminate testing constraints, we have optimized three key process variables: RNA extraction and RT-PCR reactions, different sample types and media to facilitate SARS-CoV-2 testing. By performing various validation and bridging studies, we have shown that various sample types such as nasopharyngeal swab, bronchioalveolar lavage and saliva, collected using conventional nasopharyngeal swabs, ESwab or 3D-printed swabs and, preserved in viral transport media, universal transport media, 0.9% sodium chloride or Amies media are compatible with RT-PCR assay for COVID-19. Besides, the reduction of PCR reagents by up to fourfold also produces reliable results.

scholarly journals DNA aptamer-based detection of prostate cancer

2015 ◽  
Vol 69 (1) ◽  
Author(s):  
Pawan Jolly ◽  
Nello Formisano ◽  
Pedro Estrela
Keyword(s):  
Prostate Cancer ◽  
Point Of Care ◽  
Specific Antigen ◽  
Analytical Techniques ◽  
Cost Effective ◽  
Dna Aptamer ◽  
Clinical Samples ◽  
Gradual Transition ◽  
Long Term Stability ◽  
Promising Tool

AbstractThe use of aptamers in biosensing has attracted considerable attention as an alternative to antibodies because of their unique properties such as long-term stability, cost-effectiveness and adjustability to various applications. Among cancers, the early diagnosis of prostate cancer (PCa) is one of the greatest concerns for ageing men worldwide. One of the most commonly used biomarkers for PCa is prostate-specific antigen (PSA), which can be found in elevated levels in patients with cancer. This review presents the gradual transition of research from antibody-based to aptamerbased biosensors, specifically for PSA. A brief description on aptamer-based biosensing for other PCa biomarkers is also presented. Special attention is given to electrochemical methods as analytical techniques for the development of simple, sensitive and cost-effective biosensors. The review also focuses on the different surface chemistries exploited for fabrication and their applications in clinical samples. The use of aptamers represents a promising tool for the development of point-ofcare biosensors for the early detection of prostate cancer. In view of the unmatched upper hand of aptamers, future prospects are also discussed, not only in the point-of-care format but also in other novel applications.

scholarly journals SARS-CoV-2 Direct Detection Without RNA Isolation With Loop-Mediated Isothermal Amplification (LAMP) and CRISPR-Cas12

2021 ◽  
Vol 8 ◽  
Author(s):  
Alfredo Garcia-Venzor ◽  
Bertha Rueda-Zarazua ◽  
Eduardo Marquez-Garcia ◽  
Vilma Maldonado ◽  
Angelica Moncada-Morales ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Direct Detection ◽  
Direct Method ◽  
Rna Extraction ◽  
Rna Isolation ◽  
High Sensitivity ◽  
High Specificity ◽  
Isothermal Amplification ◽  
Clinical Samples ◽  
Loop Mediated Isothermal Amplification

As to date, more than 49 million confirmed cases of Coronavirus Disease 19 (COVID-19) have been reported worldwide. Current diagnostic protocols use qRT-PCR for viral RNA detection, which is expensive and requires sophisticated equipment, trained personnel and previous RNA extraction. For this reason, we need a faster, direct and more versatile detection method for better epidemiological management of the COVID-19 outbreak. In this work, we propose a direct method without RNA extraction, based on the Loop-mediated isothermal amplification (LAMP) and Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR associated protein (CRISPR-Cas12) technique that allows the fast detection of SARS-CoV-2 from patient samples with high sensitivity and specificity. We obtained a limit of detection of 16 copies/μL with high specificity and at an affordable cost. The diagnostic test readout can be done with a real-time PCR thermocycler or with the naked eye in a blue-light transilluminator. Our method has been evaluated on a small set of clinical samples with promising results.

scholarly journals Saline collection media and an extraction free workflow enables massively scalable, highly sensitive, and cost-effective SARS-CoV-2 testing

2020 ◽  
Author(s):  
Yan Wei Lim ◽  
Nicole Leonetti ◽  
Aakash Amin ◽  
Henrique Machado ◽  
Natasha Bonilla ◽  
...  
Keyword(s):  
Supply Chain ◽  
Sensitivity And Specificity ◽  
Limit Of Detection ◽  
Rna Extraction ◽  
Cost Effective ◽  
Scaling Up ◽  
Consumption Patterns ◽  
Highly Sensitive ◽  
Processing Steps

Abstract The challenges in scaling up SARS-CoV-2 testing capacity include shortages in the supply chain for consumables and reagents. Improvements in consumption patterns can be obtained through removal of key processing steps, including RNA extraction. Here, we present a scalable and validated extraction-free method for the detection of SARS-CoV-2 from swab specimens in saline, with a limit of detection at 1,000 GCE/mL and a sensitivity and specificity of 100%.

scholarly journals Rapid and Extraction-Free Detection of SARS-CoV-2 from Saliva by Colorimetric Reverse-Transcription Loop-Mediated Isothermal Amplification

2020 ◽  
Author(s):  
Matthew A Lalli ◽  
Joshua S Langmade ◽  
Xuhua Chen ◽  
Catrina C Fronick ◽  
Christopher S Sawyer ◽  
...  
Keyword(s):  
Reverse Transcription ◽  
Limit Of Detection ◽  
Colorimetric Assay ◽  
Quantitative Polymerase Chain Reaction ◽  
Rna Extraction ◽  
Lamp Assay ◽  
Isothermal Amplification ◽  
Clinical Samples ◽  
Viral Detection ◽  
Loop Mediated Isothermal Amplification

Abstract Background Rapid, reliable, and widespread testing is required to curtail the ongoing COVID-19 pandemic. Current gold-standard nucleic acid tests are hampered by supply shortages in critical reagents including nasal swabs, RNA extraction kits, personal protective equipment, instrumentation, and labor. Methods To overcome these challenges, we developed a rapid colorimetric assay using reverse-transcription loop-mediated isothermal amplification (RT-LAMP) optimized on human saliva samples without an RNA purification step. We describe the optimization of saliva pretreatment protocols to enable analytically sensitive viral detection by RT-LAMP. We optimized the RT-LAMP reaction conditions and implemented high-throughput unbiased methods for assay interpretation. We tested whether saliva pretreatment could also enable viral detection by conventional reverse-transcription quantitative polymerase chain reaction (RT-qPCR). Finally, we validated these assays on clinical samples. Results The optimized saliva pretreatment protocol enabled analytically sensitive extraction-free detection of SARS-CoV-2 from saliva by colorimetric RT-LAMP or RT-qPCR. In simulated samples, the optimized RT-LAMP assay had a limit of detection of 59 (95% confidence interval: 44–104) particle copies per reaction. We highlighted the flexibility of LAMP assay implementation using 3 readouts: naked-eye colorimetry, spectrophotometry, and real-time fluorescence. In a set of 30 clinical saliva samples, colorimetric RT-LAMP and RT-qPCR assays performed directly on pretreated saliva samples without RNA extraction had accuracies greater than 90%. Conclusions Rapid and extraction-free detection of SARS-CoV-2 from saliva by colorimetric RT-LAMP is a simple, sensitive, and cost-effective approach with broad potential to expand diagnostic testing for the virus causing COVID-19.

scholarly journals Direct-RT-qPCR Detection of SARS-CoV-2 without RNA Extraction as Part of a COVID-19 Testing Strategy: From Sample to Result in One Hour

Diagnostics ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 605 ◽  
Author(s):  
Eva Kriegova ◽  
Regina Fillerova ◽  
Petr Kvapil
Keyword(s):  
High Throughput Screening ◽  
High Speed ◽  
Limit Of Detection ◽  
Point Of Care ◽  
Rna Extraction ◽  
Rna Isolation ◽  
High Sensitivity ◽  
Ease Of Use ◽  
Diagnostic Tools ◽  
Heat Inactivation

Due to the lack of protective immunity in the general population and the absence of effective antivirals and vaccines, the Coronavirus disease 2019 (COVID-19) pandemic continues in some countries, with local epicentres emerging in others. Due to the great demand for effective COVID-19 testing programmes to control the spread of the disease, we have suggested such a testing programme that includes a rapid RT-qPCR approach without RNA extraction. The Direct-One-Step-RT-qPCR (DIOS-RT-qPCR) assay detects severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in less than one hour while maintaining the high sensitivity and specificity required of diagnostic tools. This optimised protocol allows for the direct use of swab transfer media (14 μL) without the need for RNA extraction, achieving comparable sensitivity to the standard method that requires the time-consuming and costly step of RNA isolation. The limit of detection for DIOS-RT-qPCR was lower than seven copies/reaction, which translates to 550 virus copies/mL of swab. The speed, ease of use and low price of this assay make it suitable for high-throughput screening programmes. The use of fast enzymes allows RT-qPCR to be performed under standard laboratory conditions within one hour, making it a potential point-of-care solution on high-speed cycling instruments. This protocol also implements the heat inactivation of SARS-CoV-2 (75 °C for 10 min), which renders samples non-infectious, enabling testing in BSL-2 facilities. Moreover, we discuss the critical steps involved in developing tests for the rapid detection of COVID-19. Implementing rapid, easy, cost-effective methods can help control the worldwide spread of the COVID-19 infection.

scholarly journals Rapid isothermal amplification and portable detection system for SARS-CoV-2

2020 ◽  
Vol 117 (37) ◽  
pp. 22727-22735 ◽  
Author(s):  
Anurup Ganguli ◽  
Ariana Mostafa ◽  
Jacob Berger ◽  
Mehmet Y. Aydin ◽  
Fu Sun ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Detection System ◽  
Alternative Pathway ◽  
Rna Extraction ◽  
Lamp Assay ◽  
Isothermal Amplification ◽  
Clinical Samples ◽  
Complete Agreement ◽  
Rt Pcr ◽  
Viral Transport Medium

The COVID-19 pandemic provides an urgent example where a gap exists between availability of state-of-the-art diagnostics and current needs. As assay protocols and primer sequences become widely known, many laboratories perform diagnostic tests using methods such as RT-PCR or reverse transcription loop mediated isothermal amplification (RT-LAMP). Here, we report an RT-LAMP isothermal assay for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and demonstrate the assay on clinical samples using a simple and accessible point-of-care (POC) instrument. We characterized the assay by dipping swabs into synthetic nasal fluid spiked with the virus, moving the swab to viral transport medium (VTM), and sampling a volume of the VTM to perform the RT-LAMP assay without an RNA extraction kit. The assay has a limit of detection (LOD) of 50 RNA copies per μL in the VTM solution within 30 min. We further demonstrate our assay by detecting SARS-CoV-2 viruses from 20 clinical samples. Finally, we demonstrate a portable and real-time POC device to detect SARS-CoV-2 from VTM samples using an additively manufactured three-dimensional cartridge and a smartphone-based reader. The POC system was tested using 10 clinical samples, and was able to detect SARS-CoV-2 from these clinical samples by distinguishing positive samples from negative samples after 30 min. The POC tests are in complete agreement with RT-PCR controls. This work demonstrates an alternative pathway for SARS-CoV-2 diagnostics that does not require conventional laboratory infrastructure, in settings where diagnosis is required at the point of sample collection.

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