scholarly journals Characterising the persistence of RT-PCR positivity and incidence in a community survey of SARS-CoV-2

Author(s):  
Oliver Eales ◽  
Caroline E. Walters ◽  
Haowei Wang ◽  
David Haw ◽  
Kylie E. C. Ainslie ◽  
...  

Background Community surveys of SARS-CoV-2 RT-PCR swab-positivity provide prevalence estimates largely unaffected by biases from who presents for routine case testing. The REal-time Assessment of Community Transmission-1(REACT-1) has estimated swab-positivity approximately monthly since May 2020 in England from RT-PCR testing of self-administered throat and nose swabs in random non-overlapping cross-sectional community samples. Estimating infection incidence from swab-positivity requires an understanding of the persistence of RT-PCR swab positivity in the community. Methods During round 8 of REACT-1 from 6 January to 22 January 2021, of the 2,282 participants who tested RT-PCR positive, we recruited 896 (39%) from whom we collected up to two additional swabs for RT-PCR approximately 6 and 9 days after the initial swab. We estimated sensitivity and duration of positivity using an exponential model of positivity decay, for all participants and for subsets by initial N-gene cycle threshold (Ct) value, symptom status, lineage and age. Estimates of infection incidence were obtained for the entire duration of the REACT-1 study using P-splines. Results We estimated the overall sensitivity of REACT-1 to detect virus on a single swab as 0.79 (0.77, 0.81) and median duration of positivity following a positive test as 9.7 (8.9, 10.6) days. We found greater median duration of positivity where there was a low N-gene Ct value, in those exhibiting symptoms, or for infection with the Alpha variant. The estimated proportion of positive individuals detected on first swab, P0, was found to be higher for those with an initially low N-gene Ct value and those who were pre-symptomatic. When compared to swab-positivity, estimates of infection incidence over the duration of REACT-1 included sharper features with evident transient increases around the time of key changes in social distancing measures. Discussion Home self-swabbing for RT-PCR based on a single swab, as implemented in REACT-1, has high overall sensitivity. However, participants' time-since-infection, symptom status and viral lineage affect the probability of detection and the duration of positivity. These results validate previous efforts to estimate incidence of SARS-CoV-2 from swab-positivity data, and provide a reliable means to obtain community infection estimates to inform policy response.

2021 ◽  
Vol 68 (3) ◽  
pp. 399-405
Author(s):  
Cokorda Agung Wahyu Purnamasidhi ◽  
◽  
Richard Christian Suteja ◽  
I Komang Hotra Adiputra ◽  
Giovanca Verentzia Purnama ◽  
...  

Background. Medical screening and diagnostic cost and equipment availability has been a major obstacle to supposed-to-be extensive tracing, and overall, to the end of COVID-19 pandemic. Even though RT-PCR is the gold diagnostic standard, it is costly, lengthy, and may be unavailable in remote areas. Therefore, antigen-based COVID-19 rapid tests may be a solution to quickly detect and screen communities suspected of contracting COVID-19. Objective. This paper aims to observe how reliable antigen-based COVID-19 rapid tests are compared to RT-PCR testing. Material and methods. An observational cross-sectional study was performed on 101 samples to find the specificity, sensitivity, and accuracy of antigen-based rapid testing compared to RT-PCR testing performed on every individual. Then, a pattern between CT values and duration between onset of symptoms and testing to antigen-based rapid test result was observed to find a cut-off value such that the person may be deemed safe to exit isolation. Outcomes. A cut-off CT value of above 30.04 (p < 0.01) with a sensitivity of 66.7% and specificity of 77.8% (moderate accuracy) obtained from ROC analysis showed negative results on antigen-based rapid tests. The tests showed an overall accuracy of 67.3%, where results between the two tests were consistent. Conclusion. Therefore, an estimated CT value of 30 was moderately proved to be used as a criterion to end isolation and presume the person no longer sheds SARS-CoV-2.


Author(s):  
Susane Giti ◽  
Md Monirul Hoque ◽  
Arif Ahmed Khan ◽  
Md Mehedhi Hasan Shourov

Introduction: The recent outbreak of COVID-19 is a serious global concern. The emergence of SARS-CoV-2 led to a current pandemic of unprecedented levels. Early detection of the infection and prompt isolation of the cases are fundamental for containment of such outbreak. By this time, healthcare systems are facing shortages of reagents for diagnosing this disease. In this context, sample pooling can be an effective strategy to overcome this situation. This study aimed to evaluate the effectiveness of sample pooling strategy for RT-PCR tests for diagnosing and screening of COVID- 19 in mass population. Methods: A cross-sectional study was performed at the COVID-19 laboratory of Armed Forces Institute of Pathology of Bangladesh to evaluate the efficacy of sample pooling technique for detecting SARS-CoV-2 infection. In this laboratory, nasopharyngeal and oropharyngeal swabs were taken for the RT-PCR test to diagnose COVID-19. For each patient, both nasopharyngeal and oropharyngeal samples were taken and then mixed to make a single sample. Pooling was performed from the samples collected from 1 April 2020 to 30 April 2020. Total 350 samples were distributed randomly in 70 pools, so that each pool contains 5 samples. Positive pools were deconvulated and each sample was tested separately. Screening was performed by using RT-PCR targeting the ORF-1ab Region and N-gene. Results: Out of 70 pools 16 (22.85%) were found positive. Eighty samples of these 16 pools were tested individually and 21 (21/80, 26.25%) samples were found positive. All the positive pools were reproducible with testing of the individual samples of that pool (100%). Conclusion: Strategies of using pooled samples for screening may facilitate detection of early community transmission of SARS-CoV-2 and enable timely implementation of appropriate infection control measures to reduce spread. J Bangladesh Coll Phys Surg 2020; 38(0): 16-20


2021 ◽  
Author(s):  
Belete Woldesemayat Hailemariam ◽  
Gebremedihin Gebremicael ◽  
Kidist Zealias ◽  
Amelework Yilma ◽  
Sisay Adane ◽  
...  

Abstract Background: Coronavirus disease 2019 (COVID-19) specimen handling needs a major concern due to the virus has a potential of easily transmittable to health care workers and laboratory personnel. Heat inactivation before nucleic acid isolation might permit safe testing, even though, the effect of heat inactivation on SARS-CoV-2 RT-PCR detection results needs to be determined. Methods: An experimental study was conducted in Ethiopian Public Health Institute (EPHI) from September 25 to October 15, 2020. A total of 188 Oro-pharyngeal swabs were collected from COVID-19 suspected cases, referred to EPHI for SARS COV-2 testing during the study period. One group of the sample was inactivated at 56 °C heat for 30 min, and the other group was stored at 4°C for a similar period of time. RNA extraction and detection were done by DAAN Gene extraction and detection kit. Abbott m2000 RT-PCR was used for amplification and detection. Data analysis was done by using SPSS version 23.0; Chi-square and Pearson correlation test for qualitative and semi-quantitative analysis were used. P-value < 0.05 was considered as statistically significant.Results: Out of 188 total samples, 117 (62.2 %) and 118 (62.8%) were positive for ORF1a/b and N gene respectively before inactivation. Whereas after inactivation, 111 (59 %) was ORF1a/b and 116 (61.7 %) was N gene positive. Rate of positivity between groups was not statistically significant (p>0.05). The mean CT value difference between the two groups of ORF1a/b gene and N gene was 0.042 (95 % CI, -0.247- 0.331; t= 0.28; p = 0.774) and 0.38 (95% CI, 0.097 - 0.682; t =2.638; p = 0.010) respectively.Conclusion: Heat inactivation at 56 ℃ for 30 min has not statistically significant effect for the qualitative rRT-PCR detection of SARS-CoV-2. However, the finding also showed that there was statistically significant CT value increment after heat inactivation compared to untreated samples. Therefore, false-negative results with high CT value results (CT > 35) were found to be the challenge of this protocol. Hence alternative inactivation methods should be investigated and further studies should be considered.


Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1091
Author(s):  
Ali A. Rabaan ◽  
Raghavendra Tirupathi ◽  
Anupam A Sule ◽  
Jehad Aldali ◽  
Abbas Al Mutair ◽  
...  

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.


2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Umar Saeed ◽  
Sara Rizwan Uppal ◽  
Zahra Zahid Piracha ◽  
Azhar Rasheed ◽  
Zubair Aftab ◽  
...  

AbstractRapid diagnosis of SARS-CoV-2 during pandemic enables timely treatment and prevention of COVID-19. Evaluating the accuracy and reliability of rapid diagnostic testing kits is crucial for surveillance and diagnosis of SARS-CoV-2 infections in general population, injection drug users, multi-transfused populations, healthcare workers, prisoners, barbers and other high risk populations. The aim of this study was to evaluate performance and effectiveness of nasopharyngeal swab (NSP) and saliva based rapid antigen detection testing kits in comparison with USFDA approved triple target gold standard real-time polymerase chain reaction. A cross-sectional study was conducted on 33,000 COVID-19 suspected patients. From RT-PCR positive patients, nasopharyngeal swab (NSP) and saliva samples were obtained for evaluation of rapid COVID-19 testing kits (RDT). 100/33,000 (0.3%) of specimens were RT-PCR positive for SARS-CoV-2. Among RT-PCR positive, 62% were males, 34% were females, and 4% were children. The NSP-RDT (Lepu Medical China) analysis revealed 53% reactivity among males, 58% reactivity among females, and 25% reactivity among children. However saliva based RDT (Lepu Medical China) analysis showed 21% reactivity among males and 23% among females, and no reactivity in children. False negative results were significantly more pronounced in saliva based RDT as compared to NSP-RDT. The sensitivity of these NSP-RDT and saliva based RDT were 52% and 21% respectively. The RDTs evaluated in this study showed limited sensitivities in comparison to gold standard RT-PCR, indicating that there is a dire need in Pakistan for development of suitable testing to improve accurate COVID-19 diagnosis in line with national demands.


Author(s):  
Oladele Vincent Adeniyi ◽  
David Stead ◽  
Mandisa Singata-Madliki ◽  
Joanne Batting ◽  
Leo Hyera ◽  
...  

Healthcare workers (HCWs) are at increased risk of infection by the virulent severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Though data exist on the positivity rate of the SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) test as well as COVID-19-related deaths amongst HCWs in South Africa, the overall infection rate remains underestimated by these indicators. It is also unclear whether the humoral immune response after SARS-CoV-2 infection offers durable protection against reinfection. This study will assess the SARS-CoV-2 seroprevalence amongst HCWs in the Eastern Cape (EC) and examine the longitudinal changes (rate of decay) in the antibody levels after infection in this cohort. Using a multi-stage cluster sampling of healthcare workers in selected health facilities in the EC, a cross-sectional study of 2250 participants will be recruited. In order to assess the community infection rate, 750 antenatal women in the same settings will be recruited. Relevant demographic and clinical characteristics will be obtained by a self-administered questionnaire. A chemiluminescent microparticle immunoassay (CMIA) will be used for the qualitative detection of IgG antibodies against SARS-CoV-2 nucleocapsid protein. A nested cohort study will be conducted by performing eight-weekly antibody assays (X2) from 201 participants who tested positive for both SARS-CoV-2 RT-PCR and serology. Logistic regression models will be fitted to identify the independent risk factors for SARS-CoV-2 infection. The cumulative SARS-CoV-2 infection rate and infection fatality rate among the frontline HCWs will be estimated. In addition, the study will highlight the overall effectiveness of infection prevention and control measures (IPC) per exposure sites/wards at the selected health facilities. Findings will inform the South African Department of Health’s policies on how to protect HCWs better as the country prepares for the second wave of the SARS-CoV pandemic.


Author(s):  
Sebastián Videla ◽  
Aurema Otero ◽  
Sara Martí ◽  
M. Ángeles Domínguez ◽  
Nuria Fabrellas ◽  
...  

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic started in December 2019 and still is a major global health challenge. Lockdown measures and social distancing sparked a global shift towards online learning, which deeply impacted universities’ daily life, and the University of Barcelona (UB) was not an exception. Accordingly, we aimed to determine the impact of the SARS-CoV-2 pandemic at the UB. To that end, we performed a cross-sectional study on a sample of 2784 UB members (n = 52,529). Participants answered a brief, ad hoc, online epidemiological questionnaire and provided a nasal swab for reverse transcription polymerase chain reaction (RT-PCR) SARS-CoV-2 analysis and a venous blood sample for SARS-CoV-2 IgG antibody assay. Total prevalence of SARS-CoV-2 infection (positive RT-PCR or positive IgG) was 14.9% (95%CI 13.3 to 17.0%). Forty-four participants (1.6%, 95%CI: 1.2–2.1%) were positive for SARS-CoV-2 RT-PCR. IgG against SARS-CoV-2 was observed in 12.8% (95%CI: 11.6–14.1%) of participants. Overall, while waiting for population vaccination and/or increased herd immunity, we should concentrate on identifying and isolating new cases and their contacts.


Author(s):  
Ron M Kagan ◽  
Amy A Rogers ◽  
Gwynngelle A Borillo ◽  
Nigel J Clarke ◽  
Elizabeth M Marlowe

Abstract Background The use of a remote specimen collection strategy employing a kit designed for unobserved self-collection for SARS-CoV-2 RT-PCR can decrease the use of PPE and exposure risk. To assess the impact of unobserved specimen self-collection on test performance, we examined results from a SARS-CoV-2 qualitative RT-PCR test for self-collected specimens from participants in a return-to-work screening program and assessed the impact of a pooled testing strategy in this cohort. Methods Self-collected anterior nasal swabs from employee return to work programs were tested using the Quest Diagnostics SARS-CoV-2 RT-PCR EUA. The Ct values for the N1 and N3 N-gene targets and a human RNase P (RP) gene control target were tabulated. For comparison, we utilized Ct values from a cohort of HCP-collected specimens from patients with and without COVID-19 symptoms. Results Among 47,923 participants, 1.8% were positive. RP failed to amplify for 13/115,435 (0.011%) specimens. The median (IQR) Cts were 32.7 (25.0-35.7) for N1 and 31.3 (23.8-34.2) for N3. Median Ct values in the self-collected cohort were significantly higher than those of symptomatic, but not asymptomatic patients. Based on Ct values, pooled testing with 4 specimens would have yielded inconclusive results in 67/1,268 (5.2%) specimens but only a single false-negative result. Conclusions Unobserved self-collection of nasal swabs provides adequate sampling for SARS-CoV-2 RT-PCR testing. These findings alleviate concerns of increased false negatives in this context. Specimen pooling could be used for this population as the likelihood of false negative results is very low due when using a sensitive, dual-target methodology.


2016 ◽  
Vol 144 (16) ◽  
pp. 3422-3425 ◽  
Author(s):  
P. SINGH ◽  
M. CHHABRA ◽  
P. SHARMA ◽  
R. JAISWAL ◽  
G. SINGH ◽  
...  

SUMMARYCrimean-Congo haemorrhagic fever (CCHF) is an emerging zoonotic disease in India which is prevalent in neighbouring countries. CCHF virus (CCHFV) is a widespread tick-borne virus which is endemic in Africa, Asia, Eastern Europe and the Middle East. In the present study, samples of clinically suspected human cases from different areas of northern-western India were tested for the presence of CCHFV by RT–PCR through amplification of nucleocapsid (N) gene of CCHFV. Positive samples were sequenced to reveal the prevailing CCHFV genotype(s) and phylogenetic relatedness. A phylogenetic tree revealed the emergence of diverse strains in the study region showing maximum identity with the Pakistan, Afghanistan and Iran strains, which was different from earlier reported Indian strains. Our findings reveal for the first time the emergence of the Asia 1 group in India; while earlier reported CCHFV strains belong to the Asia 2 group.


Author(s):  
Thanh Xuan Nguyen

TÓM TẮT Đặt vấn đề: Bệnh COVID-19 đa dạng từ không có triệu chứng đến có các triệu chứng nhẹ cho đến viêm phổi nặng, hội chứng suy hô hấp cấp tiến triển (ARDS), nhiễm khuẩn huyết suy đa tạng và tử vong. Người cao tuổi, người có bệnh mạn tính sẽ có nguy cơ diễn biến nặng nhiều hơn. Nghiên cứu này nhằm xác định nồng độ lactate và PCT ở những bệnh nhân Covid-19 và xét mối liên quan giữa lactate và PCT trên bệnh nhân Covid-19. Đối tượng và phương pháp: Nghiên cứu mô tả cắt ngang trên 126 bệnh nhân được chẩn đoán nhiễm Sars-Cov-2 bằng xét nghiệm RT PCR. Kết quả: Tuổi trung bình 55,98 ± 17,1 tuổi (4 - 98 tuổi). Bệnh nhân > 60 tuổi chiếm tỉ lệ cao nhất (42,8%). Trung vị PCT: 3,6 (95%CI:3,21 - 3,75) ng/ml; trung vị lactate 1,5 (95%CI:1,21 - 1,91) mmol/L; lactate có tương quan thuận và yếu với procalcitonin với r = 0,241; p < 0,001. Nồng độ procalcitonin > 0,1 ng/ml; lactate > 2 mmol/l ở bệnh nhân Covid-19 chiếm tỷ lệ cao với 89,7% và 39,7%. Kết luận: Chỉ điểm procalcitonin, lactate tăng cao ở bệnh nhân Covid-19. ABSTRACT ASSESSMENT OF SERUM LEVEL OF LACTATE AND PROCALCITONIN IN COVID-19 PATIENTS Background: Sars-CoV-2 has been identified as the cause of acute respiratory infections in Wuhan city, Hubei province, China, and has since spread worldwide. Sars-CoV-2 is capable of aerosol transmission in enclosed, crowded, and poorly ventilated spaces. COVID-19 illness ranges from asymptomatic to mild symptoms to severe pneumonia, acute respiratory distress syndrome (ARDS), sepsis, multiple organ failure, and death. This study aims to determine lactate and PCT levels in Covid-19 patients and examine the relationship between lactate and PCT in Covid-19 patients. Methods: A cross-sectional study was performed on 126 patients diagnosed with Sars-Cov-2 infection by RT-PCR. Results: Mean age was 55.98 ± 17.1 years (range: 4-98 years). Patients more than 60 years old were accounted for the highest rate (42.8%). Median PCT: 3.6 (95%CI:3.21 - 3.75) ng/ml; median lactate 1.5 (95%CI:1.21 - 1,91) mmol/L; lactate has a positive and weak correlation with procalcitonin with r = 0.241; p < 0.001. Procalcitonin concentration > 0.1 ng/ml; lactate > 2 mmol/l in patients with Covid-19 accounted for a high rate with 89.7% and 39.7%. Conclusion: Serum level of procalcitonin and lactate raise highly in Covid-19 patients. Keywords: Covid-19, procalcitonin, lactate.


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