scholarly journals SARS-CoV-2 y RT-PCR en pacientes asintomáticos: resultados de una cohorte de trabajadores del Aeropuerto Internacional El Dorado de Bogotá, 2020

Biomédica ◽  
2020 ◽  
Vol 40 (Supl. 2) ◽  
pp. 166-172 ◽  
Author(s):  
Jeadran Malagón-Rojas ◽  
Claudia Gómez-Rendón ◽  
Eliana L. Parra ◽  
Julia Almentero ◽  
Ruth Palma ◽  
...  
Keyword(s):  
Rt Pcr ◽  
Cycle Threshold ◽  
El Dorado

Introducción. La pandemia de COVID-19 ha ocasionado cerca de 25 millones de casos en el mundo. Se ha descrito que los pacientes asintomáticos pueden ser fuentes de transmisión. Sin embargo, es difícil detectarlos y no es claro su papel en la dinámica de transmisión del virus, lo que obstaculiza la implementación de estrategias para la prevención.Objetivo. Describir el comportamiento de la infección asintomática por SARS-CoV-2 en una cohorte de trabajadores del Aeropuerto Internacional El Dorado “Luis Carlos Galán Sarmiento” de Bogotá, Colombia.Materiales y métodos. Se diseñó una cohorte prospectiva de trabajadores del Aeropuerto El Dorado. El seguimiento se inició en junio de 2020 con una encuesta a cada trabajador para caracterizar sus condiciones de salud y trabajo. Cada 21 días se tomó una muestra de hisopado nasofaríngeo para detectar la presencia del SARS-CoV-2 mediante reacción en cadena de la polimerasa con transcriptasa inversa (RT-PCR). Se analizó el comportamiento del umbral del ciclo (cycle threshold) de los genes ORF1ab y N según el día de seguimiento. Resultados. En los primeros tres seguimientos de la cohorte se encontró una incidencia de la infección por SARS-CoV-2 del 16,51 %. La proporción de contactos positivos fue del 14,08 %. La mediana del umbral del ciclo fue de 33,53.Conclusión. Se determinaron las características de la infección asintomática por el SARSCoV-2 en una cohorte de trabajadores. La detección de infectados asintomáticos sigue siendo un reto para los sistemas de vigilancia epidemiológica.

scholarly journals Preanalytical Issues and Cycle Threshold Values in SARS-CoV-2 Real-Time RT-PCR Testing: Should Test Results Include These?

ACS Omega ◽  
2021 ◽  
Author(s):  
Ilka Engelmann ◽  
Enagnon Kazali Alidjinou ◽  
Judith Ogiez ◽  
Quentin Pagneux ◽  
Sana Miloudi ◽  
...  
Keyword(s):  
Real Time ◽  
Test Results ◽  
Threshold Values ◽  
Rt Pcr ◽  
Cycle Threshold

scholarly journals Cycle Threshold Values in the Context of Multiple RT-PCR Testing for SARS-CoV-2

2021 ◽  
Vol Volume 14 ◽  
pp. 1311-1317
Author(s):  
Daniel Romero-Alvarez ◽  
Daniel Garzon-Chavez ◽  
Franklin Espinosa ◽  
Edison Ligña ◽  
Enrique Teran ◽  
...  
Keyword(s):  
Threshold Values ◽  
Rt Pcr ◽  
Cycle Threshold

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

2020 ◽  
Vol 154 (4) ◽  
pp. 479-485 ◽  
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.

scholarly journals Assessment of Specimen Pooling to Conserve SARS CoV-2 Testing Resources

2020 ◽  
Vol 153 (6) ◽  
pp. 715-718 ◽  
Author(s):  
Baha Abdalhamid ◽  
Christopher R Bilder ◽  
Emily L McCutchen ◽  
Steven H Hinrichs ◽  
Scott A Koepsell ◽  
...  
Keyword(s):  
Incidence Rate ◽  
Group Testing ◽  
Viral Rna ◽  
Optimal Parameters ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Web Based ◽  
Negative Patient ◽  
Cycle Threshold ◽  
Unselected Group

Abstract Objectives To establish the optimal parameters for group testing of pooled specimens for the detection of SARS-CoV-2. Methods The most efficient pool size was determined to be five specimens using a web-based application. From this analysis, 25 experimental pools were created using 50 µL from one SARS-CoV-2 positive nasopharyngeal specimen mixed with 4 negative patient specimens (50 µL each) for a total volume of 250 µL. Viral RNA was subsequently extracted from each pool and tested using the CDC SARS-CoV-2 RT-PCR assay. Positive pools were consequently split into individual specimens and tested by extraction and PCR. This method was also tested on an unselected group of 60 nasopharyngeal specimens grouped into 12 pools. Results All 25 pools were positive with cycle threshold (Ct) values within 0 and 5.03 Ct of the original individual specimens. The analysis of 60 specimens determined that 2 pools were positive followed by identification of 2 individual specimens among the 60 tested. This testing was accomplished while using 22 extractions/PCR tests, a savings of 38 reactions. Conclusions When the incidence rate of SARS-CoV-2 infection is 10% or less, group testing will result in the saving of reagents and personnel time with an overall increase in testing capability of at least 69%.

scholarly journals SARS-CoV-2 variants of concern are associated with lower RT-PCR amplification cycles between January and March 2021 in France

2021 ◽  
Author(s):  
Benedicte Roquebert ◽  
Stephanie Haim-Boukobza ◽  
Sabine Trombert-Paolantoni ◽  
Emmanuel Lecorche ◽  
Laura Verdurme ◽  
...  
Keyword(s):  
Pcr Amplification ◽  
Wild Type ◽  
Rt Pcr ◽  
Cycle Threshold ◽  
Type Strains

SARS-CoV-2 variants raise concern regarding the mortality caused by COVID-19 epidemics. We analyse 88,375 cycle amplification (Ct) values from variant-specific RT-PCR tests performed between January 26 and March 13, 2021. We estimate that on March 12, nearly 85% of the infections were caused by the V1 variant and that its transmission advantage over wild type strains was between 38 and 44%. We also find that tests positive for V1 and V2/V3 variants exhibit significantly lower cycle threshold (Ct) values.

scholarly journals Predictors of illness severity in COVID-19 cases

2020 ◽  
Author(s):  
Reem A. AlDossary ◽  
Amani Alnimr ◽  
Reem Aljindan ◽  
Khaled Alkharsah ◽  
Ahmed Al-Qurayn ◽  
...  
Keyword(s):  
Case Fatality ◽  
Severity Of Illness ◽  
P Value ◽  
Rt Pcr ◽  
Asian Ethnicity ◽  
Cycle Threshold ◽  
Viral Shedding ◽  
Epidemiological Features ◽  
First Case ◽  
Clinical Presentations

Abstract Background Multiple studies worldwide reported the clinical and epidemiological features of coronavirus disease 2019 (COVID-19) with limited reports form the Middle East area. Methods This is an observational study to describe the clinical and epidemiological features of 341 COVID-19 cases in the Eastern Province of Saudi Arabia over the first three months from reporting the first case in the country and identify factors associated with severity of the illness. Results The median age was 45 years and males were twice as affected as females (p value < 0.0001). The duration of viral shedding ranged from 9 to 36 days. The most common clinical presentations include fever, shortness of breath, cough, myalgia, sore throat, vomiting, and headache. Severe and critical cases were significantly higher in males compared to females (23% vs 8.7%), senior adults (> 65 years), Bengali ethnicity, and in patient with com-morbidities including diabetes, hypertension, and dyslipidemia (p-value = 0.001). Furthermore, case fatality rate was found to be 10% and was significantly higher in male gender compared to female (13.8%vs 2.6%), and in Asian ethnicity (17.9%) compared to Arabs (6%) and African counterparts (0) (p-value = 0.002). No association was found between viral load represented by the RT-PCR cycle threshold (Ct) values and severity of illness. Conclusion Age, gender and ethnicity are important predictors of COVID-19 severity while Cycle threshold (Ct) of SARS-CoV-2 RT-PCR test cannot be used as a predictor of criticality of illness.

scholarly journals #27: Comparison of RT-PCR Cycle Threshold Values from Respiratory Specimens in Symptomatic and Asymptomatic Children with SARS CoV-2 Infection

2021 ◽  
Vol 10 (Supplement_2) ◽  
pp. S10-S11
Author(s):  
John Strutner ◽  
Nanda Ramchandar ◽  
Shruti Dubey ◽  
Mary Gamboa ◽  
Michelle K Vanderpool ◽  
...  
Keyword(s):  
Medical Record ◽  
Electronic Medical Record ◽  
Tertiary Care ◽  
Severe Illness ◽  
Rt Pcr ◽  
Respiratory Specimen ◽  
Cycle Threshold ◽  
Ct Value ◽  
Asymptomatic Children ◽  
The Mean

Abstract Background Understanding viral kinetics of SARS-CoV-2 is important to assess risk of transmission, manage treatment, and determine the need for isolation and protective equipment. Children have been noted to have less severe illness than adults and may have less transmission potential. We sought to determine whether children deemed to be asymptomatic had a difference in the PCR cycle threshold (Ct) value of respiratory samples from symptomatic children with SARS CoV-2 infection. Methods This was a retrospective cross-sectional study to compare PCR Ct values of 728 children who tested positive for SARS-CoV-2 by respiratory samples collected over a 4-month period. The study was a single center review of patients who tested positive for SARS-CoV-2 by RT-PCR from a respiratory specimen at a large tertiary care children’s hospital. Inclusion criteria included children 0–18 years of age who tested positive for SARS-CoV-2 by RT-PCR from a respiratory specimen for whom clinical information was available in the electronic medical record. Results We analyzed 728 children who tested positive for SARS-CoV-2 by RT-PCR from a respiratory sample over a 4-month period and for whom data was available in the electronic medical record. Overall, 71.2% of infected children were symptomatic. The mean Ct value for symptomatic patients (Ct mean 19.9, SD 6.3) was significantly lower than asymptomatic patients (Ct mean 23.5, SD 6.5) (P value &lt; 0.001, CI95th 2.6 - 4.6). The mean PCR Ct value was lowest in children less than 5 years of age. Conclusions and Relevance In this retrospective review of children who tested positive by RT-PCR for SARS CoV-2, the mean Ct was significantly lower in symptomatic children and was lowest in children under 5 years of age.

scholarly journals The 501Y.V2 SARS-CoV-2 variant has an intermediate viral load between the 501Y.V1 and the historical variants in nasopharyngeal samples from newly diagnosed COVID-19 patients

2021 ◽  
Author(s):  
Elisa Teyssou ◽  
Cathia Soulie ◽  
Benoit Visseaux ◽  
Sidonie Lambert-Niclot ◽  
Valentine Ferre ◽  
...  
Keyword(s):  
Viral Load ◽  
Newly Diagnosed ◽  
Threshold Values ◽  
Rt Pcr ◽  
Cycle Threshold ◽  
The World

The 501Y.V2 and the 501Y.V1 SARS-CoV-2 variants emerged and spread rapidly into the world. We analysed the RT-PCR cycle threshold values of 643 nasopharyngeal samples of COVID-19 patients at diagnosis and found that the 501Y.V2 variant presented an intermediate viral load between the 501Y.V1 and the historical variants.

A CYCLE THRESHOLD VALUE-BASED EPIDEMIC PROGNOSTICATION TO MONITOR LONG-TERM EPIDEMIOLOGIC TRENDS OF SARS-COV-2 VIRUS

2021 ◽  
pp. 24-30
Author(s):  
Aditi Munmun Sengupta ◽  
Diptendu Chatterjee ◽  
Bibhuti Saha
Keyword(s):  
Meta Analysis ◽  
Threshold Value ◽  
High Viral Load ◽  
World Health ◽  
Rt Pcr ◽  
Cycle Threshold ◽  
Ct Value ◽  
Health Organization ◽  
The Impact

The real-time reverse transcription-polymerase chain reaction (RT-PCR) is considered as the sensitive proof for detecting the viral infection of the SARS-CoV-2 virus obtained from respiratory samples. The quantitative values for the analysis are benecial for estimating the transmissibility of people who test positive for SARS-CoV-2. This can be further achieved by analyzing the samples by semiquantitative means through the interpretation of the cycle threshold (Ct) values of RT-PCR that represent the rst cycle of PCR at which a detectable signal appears during the assays. The Ct value shows a correlation between high viral load and disease infectiousness, which is observed with other respiratory viruses, including the inuenza B infection and rhinovirus infection. Hence, the present study aims to analyze the surveillance of COVID-19 to monitor longer-term epidemiologic trends and trends in deaths due to COVID-19. In order to achieve this aim, the present review was reported to the preferred reporting items for systematic reviews and meta-analysis statements (PRISMA) for analyzing the Ct value-based epidemic predictions and to monitor long-term epidemiologic trends of SARS-CoV-2 virus. Total 33 studies have been nalized for nding out the results of the study. The epidemiologic parameter and a representative of the surveillance data for reporting to the World Health Organization were fullled by analyzing the systematic review and metaanalysis of the selected study. Moreover, the evaluation of the impact of the pandemic on the health care system and society was achieved by analyzing the studies mentioned here.

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