ddPCR: a more sensitive and accurate tool for SARS-CoV-2 detection in low viral load specimens

AbstractReal time fluorescent quantitative PCR (RT-PCR) is widely used as the gold standard for clinical detection of SARS-CoV-2. However, due to the low viral load in patient throats and the limitations of RT-PCR, significant numbers of false negative reports are inevitable, which results in failure to timely diagnose, early treat, cut off transmission, and assess discharge criteria. To improve this situation, an optimized droplet digital PCR (ddPCR) was used for detection of SARS-CoV-2, which showed that the limit of detection of ddPCR is significantly lower than that of RT-PCR. We further explored the feasibility of ddPCR to detect SARS-CoV-2 nucleic acid from 77 clinical throat swab samples, including 63 suspected outpatients with fever and 14 supposed convalescents who were about to discharge after treatment, and compared with RT-PCR in terms of the diagnostic accuracy. In this double-blind study, we tested, surveyed subsequently and statistically analyzed 77 clinical samples. According to our study, 26 samples from COVID-19 patients with RT-PCR negative were detected as positive by ddPCR. No FPRs of RT-PCR and ddPCR were observed. The sensitivity, specificity, PPV, NPV, NLR and accuracy were improved from 40% (95% CI: 27–55%), 100% (95% CI: 54–100%), 100%, 16% (95% CI: 13–19%), 0.6 (95% CI: 0.48–0.75) and 47% (95% CI: 33–60%) for RT-PCR to 94% (95% CI: 83–99%), 100% (95% CI: 48–100%), 100%, 63% (95% CI: 36–83%), 0.06 (95% CI: 0.02–0.18) and 95% (95% CI: 84–99%) for ddPCR, respectively. Moreover, 14 (42.9 %) convalescents still carry detectable SARS-CoV-2 after discharge. Overall, ddPCR shows superiority for clinical diagnosis of SARS-CoV-2 to reduce the false negative reports, which could be a powerful complement to the current standard RT-PCR. It also suggests that the current clinical practice that the convalescent after discharge continues to be quarantined for at least 2 weeks is completely necessary which can prevent potential viral transmission.

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SARS-CoV-2 detection using digital PCR for COVID-19 diagnosis, treatment monitoring and criteria for discharge

10.1101/2020.03.24.20042689 ◽

2020 ◽

Cited By ~ 14

Author(s):

Renfei Lu ◽

Jian Wang ◽

Min Li ◽

Yaqi Wang ◽

Jia Dong ◽

...

Keyword(s):

Viral Load ◽

Limit Of Detection ◽

False Negative ◽

Digital Pcr ◽

Detection Sensitivity ◽

Rt Pcr ◽

Pharyngeal Swab ◽

Clinical Specimens ◽

Positive Results ◽

Negative Detection

SummaryBackgroundSARS-CoV-2 nucleic acid detection by RT-PCR is one of the criteria approved by China FDA for diagnosis of COVID-19. However, inaccurate test results (for example, high false negative rate and some false positive rate) were reported in both China and US CDC using RT-PCR method. Inaccurate results are caused by inadequate detection sensitivity of RT-PCR, low viral load in some patients, difficulty to collect samples from COVID-19 patients, insufficient sample loading during RT-PCR tests, and RNA degradation during sample handling process. False negative detection could subject patients to multiple tests before diagnosis can be made, which burdens health care system. Delayed diagnosis could cause infected patients to miss the best treatment time window. False negative detection could also lead to prematurely releasing infected patients who still carry residual SARS-CoV-2 virus. In this case, these patients could infect many others. A high sensitivity RNA detection method to resolve the existing issues of RT-PCR is in need for more accurate COVID-19 diagnosis.MethodsDigital PCR (dPCR) instrument DropX-2000 and assay kits were used to detect SARS-CoV-2 from 108 clinical specimens from 36 patients including pharyngeal swab, stool and blood from different days during hospitalization. Double-blinded experiment data of 108 clinical specimens by dPCR methods were compared with results from officially approved RT-PCR assay. A total of 109 samples including 108 clinical specimens and 1 negative control sample were tested in this study. All of 109 samples, 26 were from 21patients reported as positive by officially approved clinical RT-PCR detection in local CDC and then hospitalized in Nantong Third Hospital. Among the 109 samples, dPCR detected 30 positive samples on ORFA1ab gene, 47 samples with N gene positive, and 30 samples with double positive on ORFA1ab and N genes.ResultsThe lower limit of detection of the optimize dPCR is at least 10-fold lower than that of RT-PCR. The overall accuracy of dPCR for clinical detection is 96.3%. 4 out 4 of (100 %) negative pharyngeal swab samples checked by RT-PCR were positive judged by dPCR based on the follow-up investigation. 2 of 2 samples in the RT-PCR grey area (Ct value > 37) were confirmed by dPCR with positive results. 1 patient being tested positive by RT-PCR was confirmed to be negative by dPCR. The dPCR results show clear viral loading decrease in 12 patients as treatment proceed, which can be a useful tool for monitoring COVID-19 treatment.ConclusionsDigital PCR shows improved lower limit of detection, sensitivity and accuracy, enabling COVID-19 detection with less false negative and false positive results comparing with RT-PCR, especially for the tests with low viral load specimens. We showed evidences that dPCR is powerful in detecting asymptomatic patients and suspected patients. Digital PCR is capable of checking the negative results caused by insufficient sample loading by quantifying internal reference gene from human RNA in the PCR reactions. Multi-channel fluorescence dPCR system (FAM/HEX/CY5/ROX) is able to detect more target genes in a single multiplex assay, providing quantitative count of viral load in specimens, which is a powerful tool for monitoring COVID-19 treatment.

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Microfluidic Nano-Scale qPCR Enables Ultra-Sensitive and Quantitative Detection of SARS-CoV-2

Processes ◽

10.3390/pr8111425 ◽

2020 ◽

Vol 8 (11) ◽

pp. 1425

Author(s):

Xin Xie ◽

Tamara Gjorgjieva ◽

Zaynoun Attieh ◽

Mame Massar Dieng ◽

Marc Arnoux ◽

...

Keyword(s):

Viral Infections ◽

Limit Of Detection ◽

False Negative ◽

False Negative Rate ◽

Clinical Samples ◽

Quantitative Detection ◽

Rt Pcr ◽

Viral Loads ◽

Nano Scale ◽

Negative Rate

A major challenge in controlling the COVID-19 pandemic is the high false-negative rate of the commonly used RT-PCR methods for SARS-CoV-2 detection in clinical samples. Accurate detection is particularly challenging in samples with low viral loads that are below the limit of detection (LoD) of standard one- or two-step RT-PCR methods. In this study, we implemented a three-step approach for SARS-CoV-2 detection and quantification that employs reverse transcription, targeted cDNA preamplification, and nano-scale qPCR based on a commercially available microfluidic chip. Using SARS-CoV-2 synthetic RNA and plasmid controls, we demonstrate that the addition of a preamplification step enhances the LoD of this microfluidic RT-qPCR by 1000-fold, enabling detection below 1 copy/µL. We applied this method to analyze 182 clinical NP swab samples previously diagnosed using a standard RT-qPCR protocol (91 positive, 91 negative) and demonstrate reproducible and quantitative detection of SARS-CoV-2 over five orders of magnitude (<1 to 106 viral copies/µL). Crucially, we detect SARS-CoV-2 with relatively low viral load estimates (<1 to 40 viral copies/µL) in 17 samples with negative clinical diagnosis, indicating a potential false-negative rate of 18.7% by clinical diagnostic procedures. In summary, this three-step nano-scale RT-qPCR method can robustly detect SARS-CoV-2 in samples with relatively low viral loads (<1 viral copy/µL) and has the potential to reduce the false-negative rate of standard RT-PCR-based diagnostic tests for SARS-CoV-2 and other viral infections.

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Distribution of SARS-CoV-2 PCR Cycle Threshold Values Provide Practical Insight Into Overall and Target-Specific Sensitivity Among Symptomatic Patients

American Journal of Clinical Pathology ◽

10.1093/ajcp/aqaa133 ◽

2020 ◽

Vol 154 (4) ◽

pp. 479-485 ◽

Cited By ~ 4

Author(s):

Blake W Buchan ◽

Jessica S Hoff ◽

Cameron G Gmehlin ◽

Adriana Perez ◽

Matthew L Faron ◽

...

Keyword(s):

Viral Load ◽

Limit Of Detection ◽

False Negative ◽

Age Group ◽

Rt Pcr ◽

Patient Age ◽

Cycle Threshold ◽

Negative Results ◽

Patient Âgé ◽

False Negative Results

Abstract Objectives We examined the distribution of reverse transcription polymerase chain reaction (RT-PCR) cycle threshold (CT) values obtained from symptomatic patients being evaluated for coronavirus disease 2019 (COVID-19) to determine the proportion of specimens containing a viral load near the assay limit of detection (LoD) to gain practical insight to the risk of false-negative results. We also examined the relationship between CT value and patient age to determine any age-dependent difference in viral load or test sensitivity. Methods We collected CT values obtained from the cobas severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) assay corresponding to 1,213 combined nasopharyngeal-oropharyngeal specimens obtained from symptomatic individuals that were reported as positive or presumptive positive for SARS-CoV-2. CT values were stratified by SARS-CoV target and patient age group. Results In total, 93.3% to 98.4% of specimens demonstrated CT values greater than 3× the assay LoD, at which point false-negative results would not be expected. The mean of CT values between age groups was statistically equivalent with the exception of patients in age group 80 to 89 years, which demonstrated slightly lower CTs. Conclusions Based on the distribution of observed CT values, including the small proportion of specimens with values near the assay LoD, there is a low risk of false-negative RT-PCR results in combined nasopharyngeal-oropharyngeal specimens obtained from symptomatic individuals.

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

10.20944/preprints202104.0688.v1 ◽

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.

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Microfluidic nano-scale qPCR enables ultra-sensitive detection of SARS-CoV-2

10.1101/2020.08.28.20183970 ◽

2020 ◽

Author(s):

Xin Xie ◽

Tamara Gjorgjieva ◽

Zaynoun Attieh ◽

Mame Massar Dieng ◽

Marc Arnoux ◽

...

Keyword(s):

Viral Infections ◽

Limit Of Detection ◽

False Negative ◽

False Negative Rate ◽

Clinical Samples ◽

Nasopharyngeal Swab ◽

Rt Pcr ◽

Viral Loads ◽

Nano Scale ◽

Negative Rate

Background: A major challenge in controlling the COVID-19 pandemic is the high false-negative rate of the commonly used standard RT-PCR methods for SARS-CoV-2 detection in clinical samples. Accurate detection is particularly challenging in samples with low viral loads that are below the limit of detection (LoD) of standard one- or two-step RT-PCR methods. Methods: We implement a three-step approach for SARS-CoV-2 detection and quantification that employs reverse transcription, targeted cDNA preamplification and nano-scale qPCR based on the Fluidigm 192.24 microfluidic chip. We validate the method using both positive controls and nasopharyngeal swab samples. Results: Using SARS-CoV-2 synthetic RNA and plasmid controls, we demonstrate that the addition of a preamplification step enhances the LoD of the Fluidigm method by 1,000-fold, enabling detection below 1 copy/μl. We applied this method to analyze 182 clinical NP swab samples previously diagnosed using a standard RT-qPCR protocol (91 positive, 91 negative) and demonstrate reproducible detection of SARS-CoV-2 over five orders of magnitude (< 1 to 106 viral copies/μl). Crucially, we detect SARS-CoV-2 with relatively low viral load estimates (<1 to 40 viral copies/μl) in 17 samples with negative clinical diagnosis, indicating a potential false negative rate of 18.7% by clinical diagnostic procedures. Conclusion: The three-step nano-scale RT-qPCR method can robustly detect SARS-CoV-2 in samples with relatively low viral loads (< 1 viral copy/μl) and has the potential to reduce the false negative rate of standard RT-PCR-based diagnostic tests for SARS-CoV-2 and other viral infections.

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149. Extraction-free RT-PCR to Detect SARS-CoV-2 Variants of Concern

Open Forum Infectious Diseases ◽

10.1093/ofid/ofab466.149 ◽

2021 ◽

Vol 8 (Supplement_1) ◽

pp. S89-S91

Author(s):

Brian L Harry ◽

Yue Qiu ◽

Ling Lu ◽

Mara Couto-Rodriguez ◽

Dorottya Nagy-Szakal ◽

...

Keyword(s):

Viral Load ◽

Real Time ◽

Limit Of Detection ◽

Turnaround Time ◽

Clinical Samples ◽

Rt Pcr ◽

Research Support ◽

Pcr Assay ◽

Synthetic Controls ◽

Novel Coronavirus

Abstract Background SARS-CoV-2 variants of concern (VOC) have challenged real-time reverse transcriptase polymerase chain reaction (RT-PCR) methods for the diagnosis of COVID-19. Methods The CDC 2019-Novel Coronavirus real-time RT-PCR panel was modified to create a single-plex extraction-free proxy RT-PCR assay, VOCFast™. This assay uses the nucleocapsid N1 as well as novel primer/probe pairs to target VOC mutations in the Orf1a and spike (S) genes. For analytical validation of VOCFast, synthetic controls for the Wuhan, alpha/B.1.1.7, beta/B.1.351, and gamma/P.1 strains were tested at various concentrations. Clinical validation was performed using patient anterior nares swab and saliva specimens collected in the Denver, CO area between Nov 2020 and Feb 2021 or in March 2021. Orthogonal next-generation sequencing (NGS) was also performed. Results Similar N1 quantification cycle (Cq) values corresponding to viral load were observed for all strains, suggesting that VOC mutations do not affect performance of the N1 primer/probe. Orf1a-mut and S1-mut primer/probes generated a stable high Cq value for the Wuhan strain. Conversely, Orf1a-mut Cq values were inversely correlated with viral load for all VOC. The S1-mut Cq was inversely correlated with viral load of the alpha strain, but did not reliably amplify beta/gamma VOC. The limit of detection was 8 copies/uL. The first set of COVID-19 patient specimens revealed no amplification using Orf1a-mut whereas 53% of specimens collected in Mar 2021 demonstrated amplification by Orf-1a. Orthogonal testing by the SARS-CoV-2 NGS Assay and COVID-DX software demonstrated that 12/12 alpha strains, 2/2 beta/gamma strains, and 33/33 Wuhan strains were correctly identified by VOCFast. Detection of VOC in clinical specimens and validation by NGS Conclusion The combination of the N1, Orf1a-mut, and S1-mut primers/probes in VOCFast can distinguish the Wuhan, alpha, and beta/gamma strains and it consistent with NGS results. Testing of clinical samples revealed that VOC emerged in Denver, CO in March 2021. Future work to discriminate beta, gamma, and emerging VOC is ongoing. In summary, VOCFast is an extraction-free RT-PCR assay for nasal swab and saliva specimens that can identify VOC with a turnaround time suitable for clinical testing. Disclosures Brian L. Harry, MD PhD, Summit Biolabs Inc. (Grant/Research Support, Shareholder) Mara Couto-Rodriguez, MS, Biotia (Employee) Dorottya Nagy-Szakal, MD PhD, Biotia Inc (Employee, Shareholder) Niamh B. O’Hara, PhD, Biotia (Board Member, Employee, Shareholder) Shi-Long Lu, MD PhD, Summit Biolabs Inc. (Grant/Research Support, Shareholder)

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Development and Evaluation of AccuPower® COVID-19 Multiplex Real-Time RT-PCR Kit and AccuPower® SARS-CoV-2 Multiplex Real-Time RT-PCR Kit for SARS-CoV-2 Detection in Sputum, NPS/OPS, Saliva and Pooled Samples

10.1101/2021.11.21.21264927 ◽

2021 ◽

Author(s):

In Bum Suh ◽

Jaegyun Lim ◽

Hyo Seon Kim ◽

Guil Rhim ◽

Heebum Kim ◽

...

Keyword(s):

Real Time ◽

Limit Of Detection ◽

Clinical Performance ◽

Rna Extraction ◽

Kappa Coefficient ◽

N Gene ◽

Clinical Samples ◽

Rt Pcr ◽

Current Standard ◽

Pooled Samples

Rapid and accurate detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential for the successful control of the current global COVID-19 pandemic. The real-time reverse transcription polymerase chain reaction (Real-time RT-PCR) is the most widely used detection technique. This research describes the development of two novel multiplex real-time RT-PCR kits, AccuPower ® COVID-19 Multiplex Real-Time RT-PCR Kit (NCVM) specifically designed for use with the ExiStation ™48 system (comprised of ExiPrep ™48 Dx and Exicycler ™96 by BIONEER, Korea) for sample RNA extraction and PCR detection, and AccuPower ® SARS-CoV-2 Multiplex Real-Time RT-PCR Kit (SCVM) designed to be compatible with manufacturers` on-market PCR instruments. The limit of detection (LoD) of SCVM was 2 copies/µ L and the LoD of the NCVM was 120 copies/mL for both the gene and the SARS-CoV-2 gene (N gene and RdRp gene). The AccuPower ® kits demonstrated high precision with no cross reactivity to other respiratory-related microorganisms. The clinical performance of AccuPower ® kits was evaluated using the following clinical samples: sputum and nasopharyngeal/oropharyngeal swab (NPS/OPS) samples. Overall agreement of the AccuPower ® kits with a Food and Drug Administration (FDA) approved emergency use authorized commercial kit (STANDARD ™ M nCoV Real-Time Detection kit, SD BIOSENSOR, Korea) was above 95% (Cohen`s kappa coefficient ≥ 0.95), with a sensitivity of over 95%. The NPS/OPS specimen pooling experiment was conducted to verify the usability of AccuPower ® kits on pooled samples and the results showed greater than 90% agreement with individual NPS/OPS samples. The clinical performance of AccuPower ® kits with saliva samples was also compared with NPS/OPS samples and demonstrated over 95% agreement (Cohen`s kappa coefficient > 0.95). This study shows the BIONEER NCVM and SCVM assays are comparable with the current standard confirmation assay and are suitable for effective clinical management and control of SARS-CoV-2.

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Highly accurate and sensitive diagnostic detection of SARS-CoV-2 by digital PCR

10.1101/2020.03.14.20036129 ◽

2020 ◽

Cited By ~ 12

Author(s):

Lianhua Dong ◽

Junbo Zhou ◽

Chunyan Niu ◽

Quanyi Wang ◽

Yang Pan ◽

...

Keyword(s):

Viral Load ◽

Reverse Transcription ◽

Clinical Symptoms ◽

Limit Of Detection ◽

Digital Pcr ◽

Pharyngeal Swab ◽

Positive Rate ◽

Novel Coronavirus ◽

Sensitivity Specificity ◽

Close Contacts

BACKGROUNDThe outbreak of COVID-19 caused by a novel Coronavirus (termed SARS-CoV-2) has spread to over 140 countries around the world. Currently, reverse transcription quantitative qPCR (RT-qPCR) is used as the gold standard for diagnostics of SARS-CoV-2. However, the positive rate of RT-qPCR assay of pharyngeal swab samples are reported to vary from 30∼60%. More accurate and sensitive methods are urgently needed to support the quality assurance of the RT-qPCR or as an alternative diagnostic approach.METHODSWe established a reverse transcription digital PCR (RT-dPCR) protocol to detect SARS-CoV-2 on 194 clinical pharyngeal swab samples, including 103 suspected patients, 75 close contacts and 16 supposed convalescents.RESULTSThe limit of blanks (LoBs) of the RT-dPCR assays were ∼1.6, ∼1.6 and ∼0.8 copies/reaction for ORF 1ab, N and E genes, respectively. The limit of detection (LoD) was 2 copies/reaction. For the 103 fever suspected patients, the sensitivity of SARS-CoV-2 detection was significantly improved from 28.2% by RT-qPCR to 87.4% by RT-dPCR. For close contacts, the suspect rate was greatly decreased from 21% down to 1%. The overall sensitivity, specificity and diagnostic accuracy of RT-dPCR were 90%, 100% and 93 %, respectively. In addition, quantification of the viral load for convalescents by RT-dPCR showed that a longer observation period was needed in the hospital for elderly patients.CONCLUSIONRT-dPCR could be a confirmatory method for suspected patients diagnosed by RT-qPCR. Furthermore, RT-dPCR was more sensitive and suitable for low viral load specimens from the both patients under isolation and those under observation who may not be exhibiting clinical symptoms.

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Lumipulse G SARS-CoV-2 Ag assay evaluation using clinical samples from different testing groups

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm-2021-0182 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Giulia Menchinelli ◽

Licia Bordi ◽

Flora Marzia Liotti ◽

Ivana Palucci ◽

Maria Rosaria Capobianchi ◽

...

Keyword(s):

Positive Result ◽

Limit Of Detection ◽

False Negative ◽

Clinical Samples ◽

Nasopharyngeal Swab ◽

Repeated Testing ◽

Rt Pcr ◽

Subgenomic Rna ◽

Negative Results ◽

Percent Agreement

Abstract Objectives Compared to RT-PCR, lower performance of antigen detection assays, including the Lumipulse G SARS-CoV-2 Ag assay, may depend on specific testing scenarios. Methods We tested 594 nasopharyngeal swab samples from individuals with COVID-19 (RT-PCR cycle threshold [Ct] values ≤ 40) or non-COVID-19 (Ct values > 40) diagnoses. RT-PCR positive samples were assigned to diagnostic, screening, or monitoring groups of testing. Results With a limit of detection of 1.2 × 104 SARS-CoV-2 RNA copies/ml, Lumipulse showed positive percent agreement (PPA) of 79.9% (155/194) and negative percent agreement of 99.3% (397/400), whereas PPAs were 100% for samples with Ct values of <18 or 18–<25 and 92.5% for samples with Ct values of 25–<30. By three groups, Lumipulse showed PPA of 87.0% (60/69), 81.1% (43/53), or 72.2% (52/72), respectively, whereas PPA was 100% for samples with Ct values of <18 or 18–<25, and was 94.4, 80.0, or 100% for samples with Ct values of 25–<30, respectively. Additional testing of RT-PCR positive samples for SARS-CoV-2 subgenomic RNA showed that, by three groups, PPA was 63.8% (44/69), 62.3% (33/53), or 33.3% (24/72), respectively. PPAs dropped to 55.6, 20.0, or 41.7% for samples with Ct values of 25–<30, respectively. All 101 samples with a subgenomic RNA positive result had a Lumipulse assay’s antigen positive result, whereas only 54 (58.1%) of remaining 93 samples had a Lumipulse assay’s antigen positive result. Conclusions Lumipulse assay was highly sensitive in samples with low RT-PCR Ct values, implying repeated testing to reduce consequences of false-negative results.

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Sensitivity evaluation of 2019 novel coronavirus (SARS-CoV-2) RT-PCR detection kits and strategy to reduce false negative

10.1101/2020.04.28.20083956 ◽

2020 ◽

Cited By ~ 1

Author(s):

Yunying Zhou ◽

Fengyan Pei ◽

Li Wang ◽

Huailong Zhao ◽

Huanjie Li ◽

...

Keyword(s):

Viral Load ◽

Nucleic Acid ◽

Prevention And Control ◽

False Negative ◽

Infection Prevention And Control ◽

Nucleic Acid Detection ◽

Rt Pcr ◽

Current Standard ◽

Asymptomatic Patients ◽

And Control

ABSTRACTAn ongoing outbreak of pneumonia associated with SARS-CoV-2 has now been confirmed globally. In absence of effective vaccines, infection prevention and control through diagnostic testing and quarantine is critical. Early detection and differential diagnosis of respiratory infections increases the chances for successful control of COVID-19 disease. The nucleic acid RT-PCR test is regarded as the current standard for molecular diagnosis with high sensitivity. However, the highest specificity confirmation target ORF1ab gene is considered to be less sensitive than other targets in clinical application. In addition, a large amount of recent evidence indicates that the initial missed diagnosis of asymptomatic patients with SARS-CoV-2 and discharged patients with “re-examination positive” may be due to low viral load, and the ability of rapid mutation of coronavirus also increases the rate of false negative results. We aimed to evaluate the sensitivity of different nucleic acid detection kits so as to make recommendations for the selection of validation kit, and amplify the suspicious result to be reportable positive by means of simple continuous amplification, which is of great significance for the prevention and control of the current epidemic and the discharge criteria of low viral load patients.

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