scholarly journals Assessment of the direct quantitation of SARS-CoV-2 by droplet digital PCR

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Michela Deiana ◽  
Antonio Mori ◽  
Chiara Piubelli ◽  
Salvatore Scarso ◽  
Mosè Favarato ◽  
...  
Keyword(s):  
Direct Method ◽  
Rna Extraction ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Direct Approach ◽  
Heat Inactivation ◽  
Nasopharyngeal Swab ◽  
Clinical Value ◽  
Care Needs ◽  
North East

Abstract Droplet digital PCR (ddPCR) is a sensitive and reproducible technology widely used for quantitation of several viruses. The aim of this study was to evaluate the 2019-nCoV CDC ddPCR Triplex Probe Assay (BioRad) performance, comparing the direct quantitation of SARS-CoV-2 on nasopharyngeal swab with the procedure applied to the extracted RNA. Moreover, two widely used swab types were compared (UTM 3 mL and ESwab 1 mL, COPAN). A total of 50 nasopharyngeal swabs (n = 25 UTM 3 mL and n = 25 ESwab 1 mL) from SARS-CoV-2 patients, collected during the pandemic at IRCCS Sacro Cuore Don Calabria Hospital (Veneto Region, North-East Italy), were used for our purpose. After heat inactivation, an aliquot of swab medium was used for the direct quantitation. Then, we compared the direct method with the quantitation performed on the RNA purified from nasopharyngeal swab by automated extraction. We observed that the direct approach achieved generally equal RNA copies compared to the extracted RNA. The results with the direct quantitation were more accurate on ESwab with a sensitivity of 93.33% [95% CI, 68.05 to 99.83] and specificity of 100.00% for both N1 and N2. On the other hand, on UTM we observed a higher rate of discordant results for N1 and N2. The human internal amplification control (RPP30) showed 100% of both sensitivity and specificity independent of swabs and approaches. In conclusion, we described a direct quantitation of SARS-CoV-2 in nasopharyngeal swab. Our approach resulted in an efficient quantitation, without automated RNA extraction and purification. However, special care needs to be taken on the potential bias due to the conservation of samples and to the heating treatment, as we used thawed and heat inactivated material. Further studies on a larger cohort of samples are warranted to evaluate the clinical value of this direct approach.

scholarly journals Assessment of the direct quantitation of SARS-CoV-2 by droplet digital PCR

2020 ◽  
Author(s):  
Michela Deiana ◽  
Antonio Mori ◽  
Chiara Piubelli ◽  
Salvatore Scarso ◽  
Mose Favarato ◽  
...  
Keyword(s):  
Direct Method ◽  
Rna Extraction ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Direct Approach ◽  
Heat Inactivation ◽  
Nasopharyngeal Swab ◽  
Clinical Value ◽  
Care Needs ◽  
North East

Abstract Droplet digital PCR (ddPCR) is a sensitive and reproducible technology widely used for quantitation of several different viruses. The aim of this study was to compare the 2019-nCoV CDC ddPCR Triplex Probe Assay (BioRad) performance on the direct quantitation of SARS-CoV-2 on nasopharyngeal swab respect to the procedure applied to the extracted RNA. Moreover, the two widely used swab types were compared (UTM 3mL and ESwab 1mL, COPAN). A total of 50 nasopharyngeal swabs (n=25 UTM 3mL and n=25 ESwab 1mL) from SARS-CoV-2 patients collected during the pandemic from IRCCS Sacro Cuore Don Calabria Hospital (Veneto Region, North-East Italy) were used for our purpose. After heat inactivation, an aliquot of swab medium was used in order to perform the direct quantitation. Then, we compared the direct method with the quantitation performed on the RNA purified from nasopharyngeal swab by automated extraction. We observed that the direct approach achieved generally equal RNA copies compared to the RNA extracted. The results with the direct quantitation were more accurate on ESwab with a sensitivity of 93.33% [95% CI, 68.05 to 99.83] and specificity of 100.00% for both N1 and N2. On the other hand, on UTM we observed a higher rate of discordant results for N1 and N2. The human internal amplification control (RPP30) showed 100% of both sensitivity and specificity independent of swabs and approaches.In conclusion, we described a simple and fast approach for the quantitation of SARS-CoV-2 in nasopharyngeal swab. Our approach resulted in an efficient quantitation, without automated RNA extraction and purification. However, special care needs to be taken on the potential bias due to the conservation of samples as we used thawed material and to the heating treatment. Further studies on a larger cohort of samples are warranted to evaluate the clinical value of this direct approach.

scholarly journals Heat Inactivation of Clinical COVID-19 Samples on an Industrial Scale for Low Risk and Efficient High-throughput qRT-PCR Diagnostic Testing

2021 ◽  
Author(s):  
Oona Delpuech ◽  
Julie Douthwaite ◽  
Thomas Hill ◽  
Dhevahi Niranjan ◽  
Nancy Malintan ◽  
...  
Keyword(s):  
Large Scale ◽  
Diagnostic Testing ◽  
Rna Extraction ◽  
Heat Inactivation ◽  
Nasopharyngeal Swab ◽  
Standard Testing ◽  
Manual Handling ◽  
Near Future ◽  
Level 2 ◽  
Operator Safety

Abstract We report the development of a large scale process for heat inactivation of clinical COVID-19 samples prior to laboratory processing for detection of SARS-CoV-2 by RT-qPCR. With more than 120 million confirmed cases, over 3.8 million deaths already recorded at the time of writing, COVID-19 continues to spread in many parts of the world. Consequently, mass testing for SARS-CoV-2 will remain at the forefront of the COVID-19 response and prevention for the near future. Due to biosafety considerations the standard testing process requires a significant amount of manual handling of patient samples within calibrated microbiological safety cabinets. This makes the process expensive, effects operator ergonomics and restricts testing to higher containment level laboratories. We have successfully modified the process by using industrial catering ovens for bulk heat inactivation of oropharyngeal/nasopharyngeal swab samples within their secondary containment packaging before processing in the lab to enable all subsequent activities to be performed in the open laboratory. As part of a validation process, we tested greater than 1200 clinical COVID-19 samples and showed less than 1 Cq loss in RT-qPCR test sensitivity. We also demonstrate the bulk heat inactivation protocol inactivates a murine surrogate of human SARS-CoV-2. Using bulk heat inactivation, the assay is no longer reliant on containment level 2 facilities and practices, which reduces cost, improves operator safety and ergonomics and makes the process scalable. In addition, heating as the sole method of virus inactivation is ideally suited to streamlined and more rapid workflows such as ‘direct to PCR’ assays that do not involve RNA extraction or chemical neutralisation methods.

scholarly journals Extraction-free protocol combining proteinase K and heat inactivation for detection of SARS-CoV-2 by RT-qPCR

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0247792
Author(s):  
Valeria Genoud ◽  
Martin Stortz ◽  
Ariel Waisman ◽  
Bruno G. Berardino ◽  
Paula Verneri ◽  
...  
Keyword(s):  
Rna Extraction ◽  
Standard Technique ◽  
Proteinase K ◽  
Clinical Samples ◽  
Heat Inactivation ◽  
Nasopharyngeal Swab ◽  
Reverse Transcription Pcr ◽  
Extraction Step ◽  
Commercial Kits ◽  
Inexpensive Procedure

Real-time reverse transcription PCR (RT-qPCR) is the gold-standard technique for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection in nasopharyngeal swabs specimens. The analysis by RT-qPCR usually requires a previous extraction step to obtain the purified viral RNA. Unfortunately, RNA extraction constitutes a bottleneck for early detection in many countries since it is expensive, time-consuming and depends on the availability of commercial kits. Here, we describe an extraction-free protocol for SARS-CoV-2 detection by RT-qPCR from nasopharyngeal swab clinical samples in saline solution. The method includes a treatment with proteinase K followed by heat inactivation (PK+HID method). We demonstrate that PK+HID improves the RT-qPCR performance in comparison to the heat-inactivation procedure. Moreover, we show that this extraction-free protocol can be combined with a variety of multiplexing RT-qPCR kits. The method combined with a multiplexing detection kit targeting N and ORF1ab viral genes showed a sensitivity of 0.99 and a specificity of 0.99 from the analysis of 106 positive and 106 negative clinical samples. In conclusion, PK+HID is a robust, fast and inexpensive procedure for extraction-free RT-qPCR determinations of SARS-CoV-2. The National Administration of Drugs, Foods and Medical Devices of Argentina has recently authorized the use of this method.

scholarly journals Accurate Detection of Methicillin-Resistant Staphylococcus aureus in Mixtures by Use of Single-Bacterium Duplex Droplet Digital PCR

2017 ◽  
Vol 55 (10) ◽  
pp. 2946-2955 ◽  
Author(s):  
Jun Luo ◽  
Junhua Li ◽  
Hang Yang ◽  
Junping Yu ◽  
Hongping Wei
Keyword(s):  
Staphylococcus Aureus ◽  
Limit Of Detection ◽  
Direct Method ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Clinical Samples ◽  
Methicillin Resistant ◽  
Content Type ◽  
Accurate Detection ◽  
Nasal Swabs

ABSTRACT Accurate and rapid identification of methicillin-resistant Staphylococcus aureus (MRSA) is needed to screen MRSA carriers and improve treatment. The current widely used duplex PCR methods are not able to differentiate MRSA from coexisting methicillin-susceptible S. aureus (MSSA) or other methicillin-resistant staphylococci. In this study, we aimed to develop a direct method for accurate and rapid detection of MRSA in clinical samples from open environments, such as nasal swabs. The new molecular assay is based on detecting the cooccurrence of nuc and mecA markers in a single bacterial cell by utilizing droplet digital PCR (ddPCR) with the chimeric lysin ClyH for cell lysis. The method consists of (i) dispersion of an intact single bacterium into nanoliter droplets, (ii) temperature-controlled release of genomic DNA (gDNA) by ClyH at 37°C, and (iii) amplification and detection of the markers ( nuc and mecA ) using standard TaqMan chemistries with ddPCR. Results were analyzed based on MRSA index ratios used for indicating the presence of the duplex-positive markers in droplets. The method was able to achieve an absolute limit of detection (LOD) of 2,900 CFU/ml for MRSA in nasal swabs spiked with excess amounts of Escherichia coli , MSSA, and other mecA -positive bacteria within 4 h. Initial testing of 104 nasal swabs showed that the method had 100% agreement with the standard culture method, while the normal duplex qPCR method had only about 87.5% agreement. The single-bacterium duplex ddPCR assay is rapid and powerful for more accurate detection of MRSA directly from clinical specimens.

scholarly journals Concentration of the cellular material in the nasopharyngeal swabs increases the clinical sensitivity of SARS-CoV2 RT-PCR

2020 ◽  
Author(s):  
Priya Kannian ◽  
Pasuvaraj Mahanathi ◽  
Veeraraghavan Ashwini
Keyword(s):  
Direct Method ◽  
Rna Extraction ◽  
Direct Methods ◽  
N Gene ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Clinical Sensitivity ◽  
Concentration Method ◽  
Viral Transport Medium ◽  
Analytical Variable

SummarySevere acute respiratory syndrome - coronavirus 2 (SARS-CoV2) is detected by a highly sensitive molecular method, reverse transcriptase-polymerase chain reaction (RT-PCR) from nasopharyngeal swab (NPS) samples collected in 2-3ml of viral transport medium (VTM). Unlike body fluids, NPS samples are undermined by high variability in the amount of cells that get suspended into the VTM. Hence, the cell density used for RNA extraction becomes an important analytical variable that contributes to the overall sensitivity of the RT-PCR. In this study, we compared the sensitivity of SARS-CoV2 RT-PCR in 50 NPS samples collected from in-patients of the COVID wards using the concentration and direct methods. The concentration method detected the viral RNA in all 50 samples, while the direct method was positive in only 41 (82%) samples (p=0.003). Additionally, the Ct values were lower in the direct method compared to concentration method among the 41 positive samples (p=0.03 for N gene and p=0.04 for RdRp gene). The mean CV% was also ≥10%. Thus, the concentration of the cells prior to RNA extraction drastically improves the sensitivity of detection of SARS-CoV2 in NPS samples.

scholarly journals Efficacy of a novel SARS-CoV-2 detection kit without RNA extraction and purification

2020 ◽  
Author(s):  
Tatsuya Fukumoto ◽  
Sumio Iwasaki ◽  
Shinichi Fujisawa ◽  
Kasumi Hayasaka ◽  
Kaori Sato ◽  
...  
Keyword(s):  
Rapid Detection ◽  
Human Error ◽  
Direct Method ◽  
Rna Extraction ◽  
Virus Detection ◽  
Nasopharyngeal Swab ◽  
Direct Pcr ◽  
Extraction And Purification ◽  
Novel Coronavirus ◽  
Time Required

AbstractRapid detection of SARS-CoV-2 is critical for the diagnosis of coronavirus disease 2019 (COVID-19) and preventing the spread of the virus. A novel “2019 Novel Coronavirus Detection Kit (nCoV-DK)” halves detection time by eliminating the steps of RNA extraction and purification. We evaluated concordance between the nCoV-DK and direct PCR. The virus was detected in 53/71 fresh samples by the direct method and 55/71 corresponding frozen samples by the nCoV-DK. The overall concordance rate of the virus detection between the two methods was 94.4% (95% CI, 86.2-98.4). Concordance rates were 95.2% (95% CI, 83.8-99.4), 95.5% (95% CI, 77.2-99.9), 85.7% (95% CI, 42.1-99.6) in nasopharyngeal swab, saliva, and sputum samples, respectively. These results indicate that the nCoV-DK effectively detects SARS-CoV-2 in all types of the samples including saliva, while reducing time required for detection, labor, and risk of human error.

scholarly journals Effect of Heat inactivation on Real-Time Reverse Transcription PCR of the SARS-COV-2 Detection

2020 ◽  
Author(s):  
yanxia liu ◽  
zhengan cao ◽  
mei chen ◽  
Yan zhong ◽  
yuhao luo ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Real Time ◽  
Reverse Transcription ◽  
Statistical Difference ◽  
Rna Extraction ◽  
Heat Inactivation ◽  
Nasopharyngeal Swab ◽  
Reverse Transcription Pcr ◽  
Nucleic Acid Isolation ◽  
Heat Treated

Background: Real-time reverse transcription PCR (rRT-PCR) is commonly used to diagnose SARS-CoV-2 infection. Heat inactivation prior to nucleic acid isolation may allow safe testing, while the effects of heat inactivation on SARS-CoV-2 rRT-PCR detection result need to be determined. Methods: 14 positive nasopharyngeal swab specimens were inactivated at 56°C for 30min, 56°C for 60min, 60°C for 30min, 60°C for 75min, and 100°C for 10min, and another 2 positive nasopharyngeal swab specimens were also inactivated at 100°C for 10min, 100°C for 30min, 100°C for 60min, after which the samples were isolated and detected by rRT-PCR. Results: All 14 heat treated samples remained positive. The range of threshold cycle (Ct) values observed when detecting ORF1a/b was 27.228-34.011 in heat-treated samples, while 25.281-34.861 in unheated samples, and the range of threshold cycle (Ct) values observed at the time of detecting N was 25.777-33.351 in heat-treated samples, while 24.1615-35.433 in unheated samples, on basis of which it showed no statistical difference otherwise a good correlation of Ct values between the heat-inactivated samples and the untreated samples. However, the 2 samples inactivated at 100°C 30min, 100°C 60min turned into negative. Conclusions: Heat inactivation at 56°C for 30min, 56°C for 60min, 60°C for 30min, 60°C for 75min, and 100°C for 10min shall not affect the detection results of Real-Time Reverse Transcription PCR of the SARS-COV2. Furthermore, it is recommended to inactive nasopharyngeal swab specimens 10min at 100°C before RNA extraction in consideration of efficiency and reliable results. Key Words: SARS-CoV-2, Heat Inactivation, rRT-PCR, Comparison

scholarly journals ANALYSIS OF FOUR DIFFERENT TRANSPORT AND PRESERVATION MEDIUM KITS FOR SARS-COV-2 DIAGNOSIS FROM NASOPHARYNGEAL SWAB BY REAL-TIME PCR: ADAPTING TO THE CONSTANTLY INCREASING DEMAND OF SAMPLING PROCESSING AND STOCK-OUTS DURING THE PANDEMIC

2021 ◽  
Author(s):  
Carlos Barrera-Avalos ◽  
Roberto Luraschi ◽  
Eva Vallejos-Vidal ◽  
Maximiliano Figueroa ◽  
Esteban Arenillas ◽  
...  
Keyword(s):  
Thermal Inactivation ◽  
Rna Extraction ◽  
Rnase P ◽  
Heat Inactivation ◽  
Nasopharyngeal Swab ◽  
Limited Information ◽  
Virus Transport ◽  
High Demand ◽  
Transport Medium ◽  
Worldwide Population

The high demand for supplies during the COVID19-pandemic has generated several stock-out of material and essential reagents needed to meet the current high demand for diagnosis in the worldwide population. In this way, there is limited information regarding the performance of different virus transport medium (VTM) for nasopharyngeal swab sampling (NPS) aimed for SARS-CoV-2 detection. We compared the RT-qPCR amplification profile of four different commercial transport medium kits, including DNA/RNA Shield, NAT, VTM, and Phosphate-buffered saline (PBS) transport medium, for NPSs samples from Central Metropolitan Health Service, Santiago, Chile. The RT-qPCR showed a slight lower RNase P Cq value of the samples preserved and transported in DNA/RNA Shield compared to NAT medium. By contrast, a marked increase in the RNase P Cq value was registered in the samples transported with VTM compared to DNA/RNA Shield medium. For PBS-preserved NPS, the performance of two strategies were assessed due to the potential presence of any remaining active virus in the sample: (1) thermal inactivation; and (2) thermal inactivation treatment followed by RNA extraction. The heat inactivation showed a significantly lower Cq value for RNase P and viral ORF1ab Cq compared to the followed by RNA extraction. This study indicates that new medium alternatives could be used if supplies run out to diagnose COVID19

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