scholarly journals Nested pool testing strategy for the reliable identification of individuals infected with SARS-CoV-2

2021 ◽  
Author(s):  
Inés Armendáriz ◽  
Pablo A. Ferrari ◽  
Daniel Fraiman ◽  
José M. Martínez ◽  
Hugo G. Menzella ◽  
...  
Keyword(s):  
Gold Standard ◽  
Large Scale ◽  
Optimal Path ◽  
False Negative ◽  
Cost Effective ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Infection Prevalence ◽  
Rna Detection ◽  
Pool Sizes

AbstractThe progress of the SARS-CoV-2 pandemic requires the design of cost-effective testing programs at large scale. To this end, pooling multiple samples can provide a solution. Defining a cost-effective strategy requires the establishment of an efficient deconvolution and re-testing procedure that eventually allows the identifcation of the carrier. Based on Dorfman’s algorithm, we developed an adaptive nested strategy for which we have, for a given prevalence, simple analytic expressions of the optimal number of samples in the starting pool, of the number of partitioning steps (stages) in the optimal path, of the pool sizes in each of these stages and of the expected average number of tests needed to identify the infected individuals. In this paper we analyze the strategy in detail focusing on its practical implementation when there are restrictions that prevent the use of the optimum. More specifically, we analyze how to proceed when the infection prevalence is poorly known a priori or when the optimal requires starting with pool sizes that are too large for the reliable detection of an infected sample. The sensitivity of the RT-qPCR assay, the gold standard RNA detection method, is a major concern in the case of SARS-CoV-2: it is estimated that half of the infected individuals give false negative results. Recently, droplet digital PCR (ddPCR) was shown to be 10 − 100 times more sensitive than RT-qPCR, making this technology suitable for pool testing. ddPCR has the added value of providing the direct quantification of the RNA content at the end of the test. In the paper we show how this feature can be used for verification purposes. The analyses and strategies presented here should be useful to those considering the adoption of a pooling approach for RNA detection, particularly, for the identification of individuals infected with SARS-CoV-2.Author summaryThe progress of the SARS-CoV-2 pandemic requires the design of cost-effective testing programs at large scale. Running tests on pooled samples can provide a solution if the tests sensitivity is high enough. In the case of SARS-CoV-2, the current gold standard test, RT-qPCR, has shown some limitations that only allow the use of pools with relatively few samples. In this regard, Droplet digital PCR (ddPCR) has been shown to be 10 − 100 times more sensitive than RT-qPCR, making it suitable for test pooling. In this paper we describe a nested pool testing method in which the properties that make it optimal are simple analytic functions of the infection prevalence. We discuss how to proceed in practical implementations of the strategy, particularly when there are constraints that prevent the use of the optimal. We also show how its nested nature can be combined with the direct RNA quantification that the ddPCR test provides to identify the presence of unviable samples in the pools and for self-consistency tests. The studies of this paper should be useful for those considering the adoption of test pooling for RNA detection.

scholarly journals Superiority of MALDI-TOF Mass Spectrometry over Real-Time PCR for SARS-CoV-2 RNA Detection

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 730
Author(s):  
Magda Rybicka ◽  
Ewa Miłosz ◽  
Krzysztof Piotr Bielawski
Keyword(s):  
Mass Spectrometry ◽  
Gold Standard ◽  
Viral Genome ◽  
False Negative ◽  
Rt Pcr ◽  
Rna Detection ◽  
Maldi Tof ◽  
Negative Results ◽  
False Negative Results ◽  
Pcr Test

At present, the RT-PCR test remains the gold standard for early diagnosis of SARS-CoV-2. Nevertheless, there is growing evidence demonstrating that this technique may generate false-negative results. Here, we aimed to compare the new mass spectrometry-based assay MassARRAY® SARS-CoV-2 Panel with the RT-PCR diagnostic test approved for clinical use. The study group consisted of 168 suspected patients with symptoms of a respiratory infection. After simultaneous analysis by RT-PCR and mass spectrometry methods, we obtained discordant results for 17 samples (10.12%). Within fifteen samples officially reported as presumptive positive, 13 were positive according to the MS-based assay. Moreover, four samples reported by the officially approved RT-PCR as negative were positive in at least one MS assay. We have successfully demonstrated superior sensitivity of the MS-based assay in SARS-CoV-2 detection, showing that MALDI-TOF MS seems to be ideal for the detection as well as discrimination of mutations within the viral genome.

scholarly journals Direct Quantitation of SARS-CoV-2 Using Droplet Digital PCR in Suspected Samples With Very Low Viral Load

2021 ◽  
Author(s):  
Michela Deiana ◽  
Chiara Piubelli ◽  
Antonio Mori ◽  
Gian Paolo Chiecchi ◽  
Giulia La Marca ◽  
...  
Keyword(s):  
Viral Load ◽  
Real Time ◽  
False Negative ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Hospitalized Patients ◽  
Lower Sensitivity ◽  
Rt Pcr ◽  
Viral Genes ◽  
Viral Target

Background: The reference test for SARS-CoV-2 detection is the reverse transcriptase real time PCR (real time RT-PCR). However, evidences reported that real time RT-PCR has a lower sensitivity compared with the droplet digital PCR (ddPCR) leading to possible false negative in low viral load cases. Methods: We used ddPCR for viral genes N1 and N2 on 20 negative (no detection) samples from symptomatic hospitalized COVID-patients presenting fluctuating real time RT-PCR results and 10 suspected samples (Ct value>35) from asymptomatic not hospitalized subjects. Results: ddPCR performed on RNA revealed 65% of positivity for at least one viral target in the hospitalized patients group of samples (35% for N1 and N2, 10% only for N1 and 20% only for N2) and 50% in the suspected cases (30% for N1 and N2, while 20% only for N2). On hospitalized patients’ samples, we applied also a direct ddPCR approach on the swab material, achieving an overall positivity of 83%. Conclusion: ddPCR, in particular the direct quantitation on swabs, shows a sensitivity advantage for the SARS-CoV-2 identification and may be useful to reduce the false negative diagnosis, especially for low viral load suspected samples.

scholarly journals Droplet-Digital PCR Provides a Rapid, Accurate and Cost-Effective Method for Identification of Biomarker FcγRIIIa-F158V Genotypes

2017 ◽  
Vol 06 (02) ◽  
Author(s):  
Paul Griffith ◽  
David Sun ◽  
Sarah R Tritsch ◽  
Caroline Jochems ◽  
James L Gulley ◽  
...  
Keyword(s):  
Cost Effective ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Cost Effective Method

scholarly journals Droplet digital PCR for identifying copy number variations in patients with primary immunodeficiency disorders

2021 ◽  
Author(s):  
See-Tarn Woon ◽  
Julia Mayes ◽  
Alexander Quach ◽  
Hilary Longhurst ◽  
Antonio Ferrante ◽  
...  
Keyword(s):  
Primary Immunodeficiency ◽  
Copy Number ◽  
Sanger Sequencing ◽  
Cost Effective ◽  
Digital Pcr ◽  
Copy Number Variations ◽  
Droplet Digital Pcr ◽  
Inborn Errors ◽  
Primary Immunodeficiency Disorders ◽  
Large Deletions

Abstract Primary immunodeficiency disorders comprise a rare group of mostly monogenic disorders caused by inborn errors of immunity. The majority can be identified by either Sanger sequencing or Next Generation Sequencing. Some disorders result from large insertions or deletions leading to copy number variations (CNV). Sanger sequencing may not identify these mutations. Here we present droplet digital PCR as an alternative cost-effective diagnostic method to identify CNV in these genes. The data from patients with large deletions of NFKB1, SERPING1 and SH2D1A are presented.

scholarly journals Nested pool testing strategy for the diagnosis of infectious diseases

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Inés Armendáriz ◽  
Pablo A. Ferrari ◽  
Daniel Fraiman ◽  
José M. Martínez ◽  
Hugo G. Menzella ◽  
...  
Keyword(s):  
Large Scale ◽  
Cost Effective ◽  
Digital Pcr ◽  
Practical Implementation ◽  
Testing Procedures ◽  
Effective Strategies ◽  
Rna Quantification ◽  
Pooling Strategy ◽  
Definition Of ◽  
Self Consistency

AbstractThe progress of the SARS-CoV-2 pandemic requires the design of large-scale, cost-effective testing programs. Pooling samples provides a solution if the tests are sensitive enough. In this regard, the use of the gold standard, RT-qPCR, raises some concerns. Recently, droplet digital PCR (ddPCR) was shown to be 10–100 times more sensitive than RT-qPCR, making it more suitable for pooling. Furthermore, ddPCR quantifies the RNA content directly, a feature that, as we show, can be used to identify nonviable samples in pools. Cost-effective strategies require the definition of efficient deconvolution and re-testing procedures. In this paper we analyze the practical implementation of an efficient hierarchical pooling strategy for which we have recently derived the optimal, determining the best ways to proceed when there are impediments for the use of the absolute optimum or when multiple pools are tested simultaneously and there are restrictions on the throughput time. We also show how the ddPCR RNA quantification and the nested nature of the strategy can be combined to perform self-consistency tests for a better identification of infected individuals and nonviable samples. The studies are useful to those considering pool testing for the identification of infected individuals.

scholarly journals Droplet Digital PCR – A Superior Complementary Technique for SARS-CoV-2 Detection

2020 ◽  
pp. 12-15
Author(s):  
I. M. Hussaini ◽  
S. Gide ◽  
B. Musa ◽  
M. A. Sulaiman ◽  
A. Usman
Keyword(s):  
Sensitivity And Specificity ◽  
False Negative ◽  
Standard Technique ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Reference Standard ◽  
Rt Pcr ◽  
Negative Results ◽  
False Negative Results ◽  
Current Reference Standard

Accurate and timely SARS-CoV-2 detection in suspected persons is crucial in the fight against its spread. Many techniques have been developed to meet up with the continuously growing demand, however some of these techniques lack the required accuracy, sensitivity and specificity. The current reference standard technique for SARS-CoV-2 detection is RT-PCR, but studies have shown that false-negative results are inevitable and data can be non-reproducible when samples and primers are not appropriately verified and validated. Droplet digital PCR (ddPCR) is a newly introduced technique that performs precise nucleic acid quantification. Researchers have evaluated the efficacy of ddPCR and the technique has shown promising results even in specimens with low viral load. ddPCR has shown increased accuracy, precision, sensitivity and specificity. Furthermore, it is less affected by annealing and amplification inhibitors. This suggests that ddPCR can be used as a complementary detection technique especially in convalescent cases.

scholarly journals Large-scale Testing for SARS-CoV-2 using Tapestry Pooling

2020 ◽  
Author(s):  
Anirudh Chakravarthy ◽  
Srikar Krishna ◽  
Sumana Ghosh ◽  
Ajay Tomar ◽  
Sriram Varahan ◽  
...  
Keyword(s):  
Prevalence Rate ◽  
Large Scale ◽  
False Negative ◽  
Pool Size ◽  
Prevalence Rates ◽  
Recovery Algorithm ◽  
Viral Loads ◽  
Large Scale Testing ◽  
The Individual ◽  
Pool Sizes

AbstractWe have previously described Tapestry Pooling, a scheme to enhance the capacity of RT-qPCR testing, and provided experimental evidence with spiked synthetic RNA to show that it can help to scale testing and restart the economy. Here we report on validation studies with Covid19 patient samples for the Tapestry Pooling scheme with prevalence in the range of 1% to 2%. We pooled RNA extracted from patient samples that were previously tested for Covid19, sending each sample to three pools. Following three different pooling schemes, we pipetted 320 samples into 48 pools with pool size of 20 at prevalence rate of 1.6%, 500 samples into 60 pools with pool size of 25 at prevalence rate of 2%, and 961 samples into 93 pools with pool size of 31 at prevalence rate of 1%. Of the 191 RT-qPCR experiments that we performed, only one pool was incorrect (false negative). Our recovery algorithm correctly called results for the individual samples, with a 100% sensitivity and a 99.9% specificity, with only one false positive across all the 1,781 blinded results required to be called. We show up to 10X savings in number of tests required at a range of prevalence rates and pool sizes. These experiments establish that Tapestry Pooling is robust enough to handle the diversity of sample constitutions and viral loads seen in real-world samples.

scholarly journals Screening Newborn Blood Spots for 22q11.2 Deletion Syndrome Using Multiplex Droplet Digital PCR

2015 ◽  
Vol 61 (1) ◽  
pp. 182-190 ◽  
Author(s):  
Dalyir Pretto ◽  
Dianna Maar ◽  
Carolyn M Yrigollen ◽  
Jack Regan ◽  
Flora Tassone
Keyword(s):  
Newborn Screening ◽  
Large Scale ◽  
Wide Spectrum ◽  
Delayed Diagnosis ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Deletion Syndrome ◽  
Population Total ◽  
Total N ◽  
Blood Spot

Abstract BACKGROUND The diagnosis of 22q11 deletion syndrome (22q11DS) is often delayed or missed due to the wide spectrum of clinical involvement ranging from mild to severe, often life-threatening conditions. A delayed diagnosis can lead to life-long health issues that could be ameliorated with early intervention and treatment. Owing to the high impact of 22q11DS on public health, propositions have been made to include 22q11DS in newborn screening panels; however, the method of choice for detecting 22q11DS, fluorescent in situ hybridization, requires specialized equipment and is cumbersome for most laboratories to implement as part of their routine screening. We sought to develop a new genetic screen for 22q11DS that is rapid, cost-effective, and easily used by laboratories currently performing newborn screening. METHODS We evaluated the accuracy of multiplex droplet digital PCR (ddPCR) in the detection of copy number of 22q11DS by screening samples from 26 patients with 22q11DS blindly intermixed with 1096 blood spot cards from the general population (total n = 1122). RESULTS Multiplex ddPCR correctly identified all 22q11DS samples and distinguished between 1.5- and 3-Mb deletions, suggesting the approach is sensitive and specific for the detection of 22q11DS. CONCLUSIONS These data demonstrate the utility of multiplex ddPCR for large-scale population-based studies that screen for 22q11DS. The use of samples from blood spot cards suggests that this approach has promise for newborn screening of 22q11DS, and potentially for other microdeletion syndromes, for which early detection can positively impact clinical outcome for those affected.

scholarly journals Comparison of real-time PCR and droplet digital PCR for the detection of Xylella fastidiosa in plants

2019 ◽  
Author(s):  
Enora Dupas ◽  
Bruno Legendre ◽  
Valérie Olivier ◽  
Françoise Poliakoff ◽  
Charles Manceau ◽  
...  
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Limit Of Detection ◽  
Xylella Fastidiosa ◽  
False Negative ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Detection Sensitivity ◽  
Plant Sample ◽  
The European Union

AbstractXylella fastidiosa (Xf) is a quarantine plant pathogen bacterium originating from the Americas and that has emerged in Europe in 2013. Xf can be detected directly on plant macerate using molecular methods such as real-time PCR, which is a sensitive technique. However, some plants may contain components that can act as PCR reaction inhibitors, which can lead to false negative results or an underestimation of the bacterial concentration present in the analyzed plant sample. Droplet digital PCR (ddPCR) is an innovative tool based on the partitioning of the PCR reagents and the DNA sample into thousands of droplets, allowing the quantification of the absolute number of target DNA molecules present in a reaction mixture, or an increase of the detection sensitivity. In this study, a real-time PCR protocol, already used for Xf detection in the framework of official surveys in the European Union, was transferred and optimized for Xf detection using ddPCR. This new assay was evaluated and compared to the initial real-time PCR on five plant matrices artificially inoculated and on naturally infected plants. In our conditions, this new ddPCR enabled the detection of Xf on all artificially inoculated plant macerates with a similar limit of detection, or a slight benefit for Quercus ilex. Moreover, ddPCR improved diagnostic sensitivity as it enabled detection of Xf in samples of Polygala myrtifolia or Q. ilex that were categorized as negative or close to the limit of detection using the real-time PCR. Here, we report for the first time a ddPCR assay for the detection of the bacterium Xf.

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