scholarly journals Evaluation of the performance of the COVID-19 rapid antigen tests in a tertiary level hospital in Bangladesh.

2021 ◽  
Author(s):  
Mohammad Jahidur Rahman Khan ◽  
Md. Shahadat Hossain ◽  
Samshad Jahan Shumu ◽  
Md. Selim Reza ◽  
Farzana Mim ◽  
...  
Keyword(s):  
Viral Load ◽  
Real Time ◽  
Sensitivity And Specificity ◽  
Detection Rate ◽  
High Sensitivity ◽  
Rt Pcr ◽  
College Hospital ◽  
Medical College ◽  
Qrt Pcr ◽  
Antigen Tests

Abstract Background: While the COVID-19 pandemic is a worldwide crisis, tests with high sensitivity and specificity are essential for identifying and managing COVID-19 patients. Globally, several rapid antigen tests RATs for COVID-19 have been developed, but their clinical efficacy has not been well established. This study aimed to evaluate the performance of several rapid antigen tests (RATs) to diagnose SARS-CoV-2 infection.Methods: This prospective observational study was conducted at Shaheed Suhrawardy Medical College hospital from February 2021 to April 2021 in Dhaka, Bangladesh. This study included the patients admitted in this hospital at the COVID-19 isolation unit or referred from the triage facility of the outdoor department of this hospital suspected as COVID-19 case. Two nasopharyngeal samples were collected simultaneously. one sample was used on the spot for the RAT. The other was sent to the adjacent Shaheed Suhrawardy Medical College COVID-19 RT-PCR laboratory for real-time reverse transcription-polymerase chain reaction (qRT-PCR). The performance of the RAT was evaluated using the results of qRT-PCR as a reference.Results: A total of 223 patients were included in this study, and the real-time RT-PCR detected SARS-CoV-2 in 84 (37.7%) patients. Of these 84 patients, 9 (10.7%) were asymptomatic. The overall sensitivity and specificity of RATs were 78.6% and 99.3%, respectively. The sensitivity was 81.3% in symptomatic cases and 55.6% in asymptomatic cases. False-negatives were observed in 18 patients, 3 of whom were asymptomatic and had a low viral load (cycle threshold (Ct) > 30). The detection rate of RATs was 100% when the Ct value was up to 24. The detection rate was 42.3% when the Ct was >29. The detection rate of RATs was 92.3% when the onset of symptoms was within three days. The detection rate was 33.3% when the onset of symptoms was >7 days.Conclusions: RATs for COVID-19 used in this study delivered an acceptable performance in patients with high viral load and within the first week of the onset of symptoms. They can be used as a supplementary method to RT-PCR for the diagnosis of COVID-19 patients.

scholarly journals Real-time RT-PCR diagnostics of virus causing COVID-19

2020 ◽  
Vol 13 (1) ◽  
pp. 52-63 ◽  
Author(s):  
E. V. Goncharova ◽  
A. E. Donnikov ◽  
V. V. Kadochnikova ◽  
S. A. Morozova ◽  
M. N. Boldyreva ◽  
...  
Keyword(s):  
Real Time ◽  
Sensitivity And Specificity ◽  
High Sensitivity ◽  
Medical Product ◽  
World Health ◽  
Differential Diagnostics ◽  
Clinical Samples ◽  
Rt Pcr ◽  
Study Results ◽  
Pcr Diagnostics

Aim: the study was aimed to develop a reagent kit for the real-time RT-PCR diagnostics of virus causing COVID-19.Materials and Methods. Three target sites were chosen in the genome SARS-CoV-2. The testing included 220 samples, 48 artificially created positive samples (made from patients’ biomaterial) and 172 clinical samples (scrapes from nasal and pharyngeal cavities, bronchoalveolar lavage, expectoration, endotracheal/nasopharyngeal aspirate, feces, post-mortem material), obtained from two medical centers. Preliminary, the obtained biomaterial was analyzed with a reagent kit of comparison. The evaluation was performed with a confidential interval CI 95%. The calculation of CI for the sensitivity and specificity was made based on the distribution of χ2.Results. The authors developed a technology of novel coronavirus infection (COVID-19) real-time RT-PCR diagnostics for the application in practical healthcare and proposed the variants of testing at all the stages (preanalytical, analytical, and post-analytical, including automated results processing). The proposed reagent kit meets the requirements of the World Health Organization and the Ministry of Healthcare of the Russian Federation. The study results demonstrated high sensitivity and specificity. The sensitivity was 100% (95% CI) 95.6–100%; the specificity was 100% (95% CI) 96.7–100%.Conclusion. The proposed reagent kit was registered in the RF as a medical product; the registration certificate No. RZN 2020/9948 dated 01.04.2020. The application of the reagent kit in network laboratories will provide patients with access to testing for the virus causing COVID-19 and contribute to quick differential diagnostics, improvement of pandemic control, and accurate statistics on the spread of the virus. 

scholarly journals Development and Clinical Evaluation of an Immunochromatography-Based Rapid Antigen Test (GenBody™ COVAG025) for COVID-19 Diagnosis

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 796
Author(s):  
Doyeong Kim ◽  
Jihoo Lee ◽  
Jyotiranjan Bal ◽  
Seul Ki Seo ◽  
Chom-Kyu Chong ◽  
...  
Keyword(s):  
Real Time ◽  
Sensitivity And Specificity ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Clinical Sensitivity ◽  
Viral Transport ◽  
Global Pandemic ◽  
Viral Transport Medium ◽  
Antigen Tests ◽  
Higher Sensitivity

Antigen tests for SARS-CoV-2 diagnosis are simpler and faster than their molecular counterparts. Clinical validation of such tests is a prerequisite before their field applications. We developed and clinically evaluated an immunochromatographic immunoassay, GenBody™ COVAG025, for the rapid detection of SARS-CoV-2 nucleocapsid (NP) antigen in two different clinical studies. Retrospectively, 130 residual nasopharyngeal swabs transferred in viral transport medium (VTM), pre-examined for COVID-19 through emergency use authorization (EUA)-approved real-time RT-PCR assay and tested with GenBody™ COVAG025, revealed a sensitivity and specificity of 90.00% (27/30; 95% CI: 73.47% to 97.89%) and 98.00% (98/100; 95% CI: 92.96% to 99.76%), respectively, fulfilling WHO guidelines. Subsequently, the prospective examination of 200 symptomatic and asymptomatic nasopharyngeal swabs, collected on site and tested with GenBody™ COVAG025 and EUA-approved real-time RT-PCR assay simultaneously, revealed a significantly higher sensitivity and specificity of 94.00% (94/100; 95% CI: 87.40% to 97.77%) and 100.00% (100/100; 95% CI: 96.38% to 100.00%), respectively. Clinical sensitivity and specificity were significantly high for samples with Ct values ≤ 30 as well as within 3 days of symptom onset, justifying its dependency on the viral load. Thus, it is assumed this can help with the accurate diagnosis and timely isolation and treatment of patients with COVID-19, contributing to better control of the global pandemic.

scholarly journals Comparison of an in house and a commercial real-time polymerase chain reaction targeting Toxoplasma gondii RE gene using various samples collected from patients in Turkey

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Mert Döşkaya ◽  
Hüsnü Pullukçu ◽  
Muhammet Karakavuk ◽  
Esra Atalay Şahar ◽  
Mehmet Sezai Taşbakan ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Real Time ◽  
Sensitivity And Specificity ◽  
Clinical Manifestations ◽  
High Sensitivity ◽  
Buffy Coat ◽  
Rt Pcr ◽  
Chain Reactions ◽  
Polymerase Chain ◽  
Pcr Test

Abstract Background Toxoplasma gondii is an opportunistic protozoan parasite that can infect all warm-blooded animals including humans and cause serious clinical manifestations. Toxoplasmosis can be diagnosed using histological, serological, and molecular methods. In this study, we aimed to detect T. gondii RE gene in various human samples by in house and commercial real time polymerase chain reactions. Methods A total of 38 suspected cases of toxoplasmosis [peripheral blood (n:12), amnion fluid (n:11), tissue (n:9), cerebrospinal fluid (n:5), and intraocular fluid (n:1)] were included to the study. An in house and a commercial RT-PCR were applied to investigate the T. gondii RE gene in these samples. Results The compatibility rate of the two tests was 94.7% (37/38). When the commercial RT-PCR kit was taken as reference, the sensitivity and specificity of in house RT-PCR test was 87.5 and 100%. When the in house RT-PCR test was taken as reference, the commercial RT-PCR kit has 100% sensitivity and 96.8% specificity. Incompatibility was detected in only in a buffy coat sample with high protein content. Conclusions Both the commercial and in house RT-PCR tests can be used to investigate T. gondii RE gene in various clinical specimens with their high sensitivity and specificity. In house RT-PCR assay can be favorable due to cost savings compared to using the commercial test.

scholarly journals Viral Dynamics and Real-Time RT-PCR Ct Values Correlation with Disease Severity in COVID-19

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1091
Author(s):  
Ali A. Rabaan ◽  
Raghavendra Tirupathi ◽  
Anupam A Sule ◽  
Jehad Aldali ◽  
Abbas Al Mutair ◽  
...  
Keyword(s):  
Viral Load ◽  
Real Time ◽  
Disease Severity ◽  
False Negative ◽  
Influential Factors ◽  
Confirmatory Test ◽  
Acid Extraction ◽  
Rt Pcr ◽  
Viral Kinetics ◽  
Ct Value

Real-time RT-PCR is considered the gold standard confirmatory test for coronavirus disease 2019 (COVID-19). However, many scientists disagree, and it is essential to understand that several factors and variables can cause a false-negative test. In this context, cycle threshold (Ct) values are being utilized to diagnose or predict SARS-CoV-2 infection. This practice has a significant clinical utility as Ct values can be correlated with the viral load. In addition, Ct values have a strong correlation with multiple haematological and biochemical markers. However, it is essential to consider that Ct values might be affected by pre-analytic, analytic, and post-analytical variables such as collection technique, specimen type, sampling time, viral kinetics, transport and storage conditions, nucleic acid extraction, viral RNA load, primer designing, real-time PCR efficiency, and Ct value determination method. Therefore, understanding the interpretation of Ct values and other influential factors could play a crucial role in interpreting viral load and disease severity. In several clinical studies consisting of small or large sample sizes, several discrepancies exist regarding a significant positive correlation between the Ct value and disease severity in COVID-19. In this context, a revised review of the literature has been conducted to fill the knowledge gaps regarding the correlations between Ct values and severity/fatality rates of patients with COVID-19. Various databases such as PubMed, Science Direct, Medline, Scopus, and Google Scholar were searched up to April 2021 by using keywords including “RT-PCR or viral load”, “SARS-CoV-2 and RT-PCR”, “Ct value and viral load”, “Ct value or COVID-19”. Research articles were extracted and selected independently by the authors and included in the present review based on their relevance to the study. The current narrative review explores the correlation of Ct values with mortality, disease progression, severity, and infectivity. We also discuss the factors that can affect these values, such as collection technique, type of swab, sampling method, etc.

scholarly journals EVALUATION OF ELEVEN IMMUNOCHROMATOGRAPHIC ASSAYS FOR SARS-CoV-2 DETECTION: INVESTIGATING DENGUE CROSS-REACTION

2020 ◽  
Author(s):  
Beatriz Araujo Oliveira ◽  
Lea Campos de Oliveira ◽  
Franciane Mendes de Oliveira ◽  
Geovana Maria Pereira ◽  
Regina Maia de Souza ◽  
...  
Keyword(s):  
Sensitivity And Specificity ◽  
High Sensitivity ◽  
Diagnostic Techniques ◽  
Cross Reactivity ◽  
Cross Reaction ◽  
List Type ◽  
Rt Pcr ◽  
Serum Samples ◽  
Igm Antibodies ◽  
Good Agreement

AbstractBackgroundCOVID-19 disease (Coronavirus disease 2019) caused by SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) is widespread worldwide, affecting more than 11 million people globally (July 6th, 2020). Diagnostic techniques have been studied in order to contain the pandemic. Immunochromatographic (IC) assays are feasible and low cost alternative for monitoring the spread of COVID-19 in the population.MethodsHere we evaluate the sensitivity and specificity of eleven different immunochromatographic tests in 98 serum samples from confirmed cases of COVID-19 through RT-PCR and 100 negative serum samples from blood donors collected in February 2019. Considering the endemic situation of Dengue in Brazil, we also evaluated the cross-reactivity with Dengue using 20 serum samples from patients with confirmed diagnosis for Dengue collected in early 2019 through four different tests.ResultsOur results demonstrated agreement between immunochromatographic assays and RT-PCR, especially after 10 days since the onset of symptoms. The evaluation of IgG and IgM antibodies combined demonstrated a strong level of agreement (0.85) of IC assays and RT-PCR. It was observed cross-reactivity between Dengue and COVID-19 using four different IC assays for COVID-19 diagnosis. The specificity of IC assays to detected COVID-19 IgM antibodies using Dengue serum samples varied from 80% to 85%; the specificity of IgG detection was 100% and total antibody was 95%.ConclusionsWe found high sensitivity, specificity and good agreement of IC assays, especially after 10 days onset of symptoms. However, we detected cross-reactivity between Dengue and COVID-19 mainly with IgM antibodies demonstrating the need for better studies about diagnostic techniques for these diseases.HighlightsImmunochromatographic assays demonstrated high sensitivity and specificity and good agreement with the gold-standard RT-PCR;Increase in sensitivity and specificity of assays using samples collected after the 10th day of symptoms;Cross-reaction with Dengue serology in evaluation of IgM.

O-091 Semen microbiota in patients with astenozoospermia and healthy controls: cluster analysis of real-time PCR data

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
E Panacheva ◽  
D Pochernikov ◽  
E Voroshilina
Keyword(s):  
Cluster Analysis ◽  
Real Time ◽  
Real Time Pcr ◽  
Detection Rate ◽  
Bacterial Load ◽  
Rrna Gene ◽  
Rt Pcr ◽  
Silhouette Index ◽  
Enterococcus Spp ◽  
Lactobacillus Spp

Abstract Study question What are the differences in the semen microbiota composition of patients with asthenozoospermia and normospermia according to cluster analysis of PCR data? Summary answer The detection rate of 4 stable semen microbiota clusters and the dominant bacteria groups varied in patients with asthenozoospermia and normospermia. What is known already Most of the research dedicated to analyzing normal and pathological semen microbiota is based on 16S rRNA gene specific Next generation sequencing (NGS). It has shown that microbiota is represented by polymicrobial communities (clusters) that consist of microorganisms from different genera and bacteria phyla. Despite it being highly informative, NGS has several weaknesses: complex sample preparation, difficult sample intake control, long analysis process, complicated results interpretation, high cost of equipment and reagents. These factors make it virtually impossible to use this approach in routine medical practice. Quantitative real-time PCR (RT-PCR) is far more suitable for this. Study design, size, duration Patients included in the study (n = 301) came to the “Garmonia” Medical Center (Yekaterinburg, Russia) either seeking preconception care or for infertility treatment. Depending on the spermiogram results, they were divided into two groups. Group 1 (n = 171) — asthenozoospermia, Group 2 (n = 130) — normospermia. Participants/materials, setting, methods Semen microbiota was analyzed using RT-PCR kit Androflor (DNA-Technology, Russia). Cluster analysis was performed for 201 samples with the total bacterial load (TBL) of at least 103 GE/ml (asthenozoospermia = 96, normospermia = 105). Cluster analysis was conducted using the k-means ++ algorithm, scikit-learn. The Silhouette index and the Davies–Bouldin index (DBI) were used to confirm the stability of clusters. Main results and the role of chance Both in the samples with normospermia and asthenozoospermia, four stable microbiota clusters were distinguished. Cluster I was characterized by the prevalence of obligate anaerobes, Lactobacillus spp. were prevalent in Cluster II, Gram-positive facultative anaerobes were prevalent in Cluster III, Enterobacteriaceae/Enterococcus spp. were prevalent in Cluster IV. Cluster I was detected the most often in both groups. However, in normospermia it was represented by various obligate anaerobes without pronounced quantitative predominance of any bacteria group. In samples with asthenozoospermia one of the bacteria groups were prevalent in Cluster I: Bacteroides spp./Porphyromonas spp./Prevotella spp., Peptostreptococcus spp./Parvimonas spp. or Eubacterium spp. In samples with asthenozoospermia Cluster II was characterized by the prevalence of Lactobacillus spp., while in samples with normospermia other bacteria groups were present along with lactobacilli, mainly obligate anaerobes. In samples with normospermia Corynebacterium spp. and Streptococcus spp., typical of normal microbiota of male UGT, were prevalent in Cluster III. In samples with asthenozoospermia Cluster III were characterized by the prevalence of Staphylococcus spp. In samples with asthenozoospermia Lactobacillus spp was present in Cluster IV along with Enterobacteriaceae/Enterococcus spp., which was not typical of the samples with normospermia. Limitations, reasons for caution Cluster analysis was not conducted for the samples with TBL lower than 103 GE/ml, since their results were incompatible with the data received for the negative control samples. Wider implications of the findings Further research could determine the detection rate of the described bacterial clusters in semen with other pathologies. Establishing the relationship between the characteristics of semen microbiota and infertility in men might allow the development of new algorithms for treating patients with reproductive disorders, depending on the composition of semen microbiota. Trial registration number not applicable

scholarly journals Biochemical parameters of mild, moderate & severe COVID-19 patients

2021 ◽  
Vol 11 (2) ◽  
pp. 031-039
Author(s):  
Khushbun Nahar Layla ◽  
Shahanara Yeasmin ◽  
Sharif Ahmed Khan ◽  
Masba Uddin Chowdhury ◽  
Afrina Binte Azad ◽  
...  
Keyword(s):  
Serum Creatinine ◽  
Serum Albumin ◽  
Prothrombin Time ◽  
Serum Ferritin ◽  
Biochemical Parameters ◽  
Rt Pcr ◽  
College Hospital ◽  
Positive Correlation ◽  
Medical College ◽  
D Dimer

Background and objectives: Coronavirus disease 2019 (COVID-19) is affecting millions of people world-wide. It is caused by the severe acute respiratory syndrome corona virus 2(SARS-CoV-2). The laboratory findings are very important to assess the progress of the disease. The present study is aimed to discuss the biochemical parameters among mild, moderate and severe COVID-19 patients. Materials and methods: A cross sectional study were conducted in the Department of Physiology, Dhaka Medical College, Dhaka from January 2020 to December 2020. After obtaining ethical clearance, a total of 100 real time-polymerase chain reaction (RT-PCR) COVID-19 positive patients were selected from Dhaka Medical College Hospital. With all aseptic precautions, 10 ml of venous blood was collected from ante-cubital vein. D-dimer, prothrombin time, C-reactive protein (CRP), lactate dehydrogenase (LDH), serum ferritin, random blood glucose (RBG), serum creatinine, serum glutamic-pyruvic-transaminase (SGPT) and serum albumin measured in the Department of Laboratory Medicine, Dhaka Medical College Hospital, Dhaka. CRP was measured by Immunoturbidimetric method, serum ferritin was estimated by Chemiluminescent microparticle immunoassay. STA-neoplastine CI plus used with STA-R analyzer was used for determination of prothrombin time. D-dimer was estimated by Immunofluorescence Assay method. Serum LDH is measured by Dimention clinical chemistry system, serum albumin is measured by bromocresol purple dye binding method, serum creatinine is measured by Jaffe alkaline picrate method and serum SGPT is measured by colourmetric (IFCC 1980) method and RBG is measured by enzymatic colorimetric method (GOD-PAP). Data were recorded in a pre-designed structured data collection form. For statistical analysis, ANOVA followed by Bonferroni test, Chi square test, Spearman’s rho correlation coefficient test was performed as applicable using SPSS for windows version 25.0. Results: By analyzing biochemical parameters of mild, moderate and severe RT-PCR positive 100 COVID-19 patients revealed evaluation of biochemical parameters shows severity of the disease was significantly associated with CRP, SGPT, S. Creatinine, LDH, Ferritin, D-dimer & Prothrombin time. No significant association was found with RBG & S. Albumin. Bonferroni correction following ANOVA was performed to compare between each group. Spearman’s correlation reveals statistically significant strong positive correlation with CRP, Ferritin & D-dimer, moderate positive correlation with S. Creatinine, LDH and mild positive correlation with SGPT & Prothrombin time. Conclusion: This study showed D-dimer, prothrombin time, CRP, LDH, ferritin, serum creatinine and SGPT are significantly associated with the severity of the illness that is higher in severe group in comparison to mild and moderate groups. So, comprehensive analysis of the biochemical parameters will be very helpful for early identification & better management of severe disease.

scholarly journals Comparison of three TaqMan Real-Time Reverse Transcription-PCR assays in detecting SARS-CoV-2

2020 ◽  
Author(s):  
Yan Xiao ◽  
Zhen Li ◽  
Xinming Wang ◽  
Yingying Wang ◽  
Ying Wang ◽  
...  
Keyword(s):  
Real Time ◽  
Reverse Transcription ◽  
Detection Rate ◽  
N Gene ◽  
Detection Rates ◽  
Qrt Pcr ◽  
Reverse Transcription Pcr ◽  
Linear Detection ◽  
Gene Assay ◽  
Pcr Assays

AbstractQuick and accurate detection of SARS-CoV-2 is critical for COVID-19 control. Dozens of real-time reverse transcription PCR (qRT-PCR) assays have been developed to meet the urgent need of COVID-19 control. However, methodological comparisons among the developed qRT-PCR assays are limited. In the present study, we evaluated the sensitivity, specificity, amplification efficiency, and linear detection ranges of three qRT-PCR assays, including the assays developed by our group (IPBCAMS), and the assays recommended by WHO and China CDC (CCDC). The three qRT-PCR assays exhibited similar sensitivities, with the limit of detection (LOD) at about 10 copies per reaction (except the ORF 1b gene assay in CCDC assays with a LOD at about 100 copies per reaction). No cross reaction with other respiratory viruses were observed in all of the three qRT-PCR assays. Wide linear detection ranges from 106 to 101 copies per reaction and acceptable reproducibility were obtained. By using 25 clinical specimens, the N gene assay of IPBCAMS assays and CCDC assays performed better (with detection rates of 92% and 100%, respectively) than that of the WHO assays (with a detection rate of 60%), and the ORF 1b gene assay in IPBCAMS assays performed better (with a detection rate of 64%) than those of the WHO assays and the CCDC assays (with detection rates of 48% and 20%, respectively). In conclusion, the N gene assays of CCDC assays and IPBCAMS assays and the ORF 1b gene assay of IPBCAMS assays were recommended for qRT-PCR screening of SARS-CoV-2.

scholarly journals Comparison of diagnostics of bacterial vaginosis according to clinical signs with results of laboratory investigations

2016 ◽  
Vol 65 (4) ◽  
pp. 76-82
Author(s):  
Elena V. Shipitsina ◽  
Tatyana A. Khusnutdinova ◽  
Olga S. Ryzhkova ◽  
Anna A. Krysanova ◽  
Olga V. Budilovskaya ◽  
...  
Keyword(s):  
Bacterial Vaginosis ◽  
Real Time ◽  
Sensitivity And Specificity ◽  
Real Time Pcr ◽  
Vaginal Discharge ◽  
Clinical Signs ◽  
High Sensitivity ◽  
Clinical Diagnostics ◽  
Laboratory Diagnostics ◽  
Molecular Method

Introduction. Bacterial vaginosis (BV) is associated with a number of reproductive health disorders, therefore timely and accurate diagnosis of this condition is exceedingly important. Objective.Comparison of effectiveness of clinical and laboratory diagnostics of BV in women with vaginal discharge. Material and methods. In total, 318 patients addressing gynecological clinics with complaints about vaginal discharge participated in the study. Clinical diagnostics of BV was performed in the clinics participating in patient enrollment in accordance with their clinical practice. For laboratory diagnostics, microscopy of Gram stained smears according to the Nugent method and quantitative real-time PCR were used. Sensitivity and specificity of clinical diagnostics of BV and the molecular method were evaluated using the Nugent method as reference standard. Results. With the Nugent method, BV was diagnosed in 27% of women, with real-time PCR — in 37% of women. Using clinical signs of BV, the condition was diagnosed in 91% women. Sensitivity and specificity of the real-time PCR were 97% and 87%, respectively. Sensitivity of clinical diagnostics was 100%, but specificity was only 17%. Conclusions. Diagnostics of BV based only on the presence of vaginal discharge leads to false positive results and requires laboratory confirmation. The molecular method has a high sensitivity and satisfactory specificity for BV diagnosis and can be used as an alternative to the Nugent method.

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.

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