scholarly journals SARS-CoV-2 Antigen Tests Predict Infectivity Based on Viral Culture: Comparison of Antigen, PCR Viral Load, and Viral Culture Testing on a Large Sample Cohort

2021 ◽  
Author(s):  
James E Kirby ◽  
Stefan Riedel ◽  
Sanjucta Dutta ◽  
Ramy Arnaout ◽  
Annie Cheng ◽  
...  
Keyword(s):  
Viral Load ◽  
Diagnostic Testing ◽  
Lateral Flow ◽  
Nasopharyngeal Swab ◽  
Viral Culture ◽  
Culture Positivity ◽  
Antigen Tests ◽  
Relationship Of ◽  
The Relationship ◽  
Antigen Testing

The relationship of SARS-CoV-2 antigen testing results, viral load, and viral culture detection remains to be fully defined. Presumptively, viral culture can provide a surrogate measure for infectivity of sampled individuals, and thereby inform how and where to most appropriately deploy available diagnostic testing modalities. We therefore determined the relationship of antigen testing results from three lateral flow and one microfluidics assay to viral culture performed in parallel in 181 nasopharyngeal swab samples positive for SARS-CoV-2. Sample viral loads, determined by RT-qPCR, were distributed across the range of viral load values observed in our testing population. We found that antigen tests were predictive of viral culture positivity, with the LumiraDx method showing enhanced sensitivity (90%; 95% confidence interval (95% CI) 83-94%) compared with the BD Veritor (74%, 95% CI 65-81%), CareStart (74%, 95% CI 65-81%) and Oscar Corona (74%, 95% CI 65-82%) lateral flow antigen tests. Antigen and viral culture positivity were also highly correlated with sample viral load, with areas under the receiver?operator characteristic curves (ROCs) of 0.94-0.97 and 0.92, respectively. In particular, a viral load threshold of 100,000 copies/mL was 95% sensitive (95% CI, 90-98%) and 72% specific (95% CI, 60-81%) for predicting viral culture positivity. Taken together, the detection of SARS-CoV-2 antigen identified highly infectious individuals, some of whom may harbor 10,000-fold more virus in their samples than those with any detectable infectious virus. As such, our data support use of antigen testing in defining infectivity status at the time of sampling.

scholarly journals Association between viral load and positivization time of a SARS-CoV-2 rapid antigen test in routine nasopharyngeal specimens

2021 ◽  
Author(s):  
Gian Luca Salvagno ◽  
Brandon Michael Henry ◽  
Simone De Nitto ◽  
Laura Pighi ◽  
Giuseppe Lippi
Keyword(s):  
Viral Load ◽  
Diagnostic Testing ◽  
Area Under The Curve ◽  
High Viral Load ◽  
Antigen Test ◽  
Potential Association ◽  
Antigen Tests ◽  
Antigen Testing ◽  
Spearman’S Correlation ◽  
Positive Results

Abstract Background: Rapid SARS-CoV-2 antigen tests are potentially useful tools for screening carriers with high viral load. This study was aimed to assess the potential association between viral load and positivization time of a manual SARS-CoV-2 commercial antigen test in routine nasopharyngeal specimens. Methods: In a sample of subjects undergoing routine diagnostic testing, SARS-CoV-2 positivity of nasopharyngeal samples was assayed with both molecular (Altona Diagnostics RealStar SARS-CoV-2 RT-PCR Kit) and antigenic (Roche SARS-CoV-2 Rapid Antigen Test) tests. Positivization time of rapid antigen test was correlated and compared with viral load expressed as mean of SARS-CoV-2 E/S genes cycle threshold (Ct) values.Results: The study sample consisted of 106 patients (median age 48 years, 55 women) with positive results of rapid SARS-CoV-2 antigen testing. A highly significant Spearman’s correlation was found between mean SARS-CoV-2 E/S genes Ct values and positivization time of manual antigen test (r= 0.70; p<0.001). The positivization time of rapid SARS-CoV-2 antigen test displayed an area under the curve of 0.82 (95%CI, 0.74-0.89) for predicting nasopharyngeal samples with high viral load (i.e., mean Ct <20). A positivization time cut-off of 32 sec had 94.9% sensitivity and 58.2% specificity for detecting specimens with high viral load. The overall agreement between mean Ct value <20 and positivization time <32 sec was 70.8%.Conclusions: Positivization time of rapid SARS-CoV-2 antigen tests may provide easy and rapid information on viral load, thus making this type of manual assay potentially suitable for quick and reliable detection and isolation of super-carries.

scholarly journals Performance of antigen testing for diagnosis of COVID-19: a direct comparison of a lateral flow device to nucleic acid amplification based tests

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Maria Kahn ◽  
Lukas Schuierer ◽  
Christina Bartenschlager ◽  
Stephan Zellmer ◽  
Ramona Frey ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Real Life ◽  
Lateral Flow ◽  
Nucleic Acid Amplification ◽  
University Hospital ◽  
Nasopharyngeal Swab ◽  
Screening Programs ◽  
Asymptomatic Patients ◽  
Antigen Tests ◽  
Antigen Testing

Abstract Objectives The gold standard for diagnosing an infection with SARS-CoV-2 is detection of viral RNA by nucleic acid amplification techniques. Test capacities, however, are limited. Therefore, numerous easy-to-use rapid antigen tests based on lateral flow technology have been developed. Manufacturer-reported performance data seem convincing, but real-world data are missing. Methods We retrospectively analysed all prospectively collected antigen tests results performed between 23.06.2020 and 26.11.2020, generated by non-laboratory personnel at the point-of-care from oro- or nasopharyngeal swab samples at the University Hospital Augsburg and compared them to concomitantly (within 24 h.) generated results from molecular tests. Results For a total of 3630 antigen tests, 3110 NAAT results were available. Overall, sensitivity, specificity, NPV and PPV of antigen testing were 59.4%, 99.0%, 98.7% and 64.8%, respectively. Sensitivity and PPV were lower in asymptomatic patients (47.6% and 44.4%, respectively) and only slightly higher in patients with clinical symptoms (66.7% and 85.0%, respectively). Some samples with very low Ct-values (minimum Ct 13) were not detected by antigen testing. 31 false positive results occurred. ROC curve analysis showed that reducing the COI cut-off from 1, as suggested by the manufacturer, to 0.9 is optimal, albeit with an AUC of only 0.66. Conclusion In real life, performance of lateral-flow-based antigen tests are well below the manufacturer's specifications, irrespective of patient’s symptoms. Their use for detection of individual patients infected with SARS-CoV2 should be discouraged. This does not preclude their usefulness in large-scale screening programs to reduce transmission events on a population-wide scale.

scholarly journals Favorable outcome on viral load and culture viability using Ivermectin in early treatment of non-hospitalized patients with mild COVID-19, A double-blind, randomized placebo-controlled trial.

2021 ◽  
Author(s):  
Asaf Biber ◽  
Michal Mandelboim ◽  
Geva Harmelin ◽  
Dana Lev ◽  
Li Ram ◽  
...  
Keyword(s):  
Viral Load ◽  
Early Stage ◽  
Controlled Trial ◽  
Nasopharyngeal Swab ◽  
Multivariable Logistic Regression Model ◽  
Double Blind ◽  
Viral Shedding ◽  
Viral Culture ◽  
Culture Viability ◽  
Double Blinded

Background: Ivermectin, an antiparasitic agent, also has antiviral properties. Our aim was to assess whether ivermectin can shorten the viral shedding in patients at an early stage of COVID19 infection. Methods: The double blinded trial compared patients receiving ivermectin 0.2 mg/kg for 3 days vs. placebo in non-hospitalized COVID19 patients. RT-PCR from a nasopharyngeal swab was obtained at recruitment and then every two days. Primary endpoint was reduction of viral-load on the 6th day (third day after termination of treatment) as reflected by Ct level>30 (non-infectious level). The primary outcome was supported by determination of viral culture viability. Results: Eighty nine patients were eligible (47 in ivermectin and 42 in placebo arm). Their median age was 35 years. Females accounted for 21.6%, and 16.8% were asymptomatic at recruitment. Median time from symptom onset was 4 days. There were no statistical differences in these parameters between the two groups. On day 6, 34 out of 47 (72%) patients in the ivermectin arm reached the endpoint, compared to 21/ 42 (50%) in the placebo arm (OR 2.62; 95% CI: 1.09 to 6.31). In a multivariable logistic regression model, the odds of a negative test at day 6 was 2.62 time higher in the ivermectin group (95% CI: 1.06 to 6.45). Cultures at days 2 to 6 were positive in 3/23 (13.0%) of ivermectin samples vs. 14/29 (48.2%) in the placebo group (p=0.008). Conclusions: There were significantly lower viral loads and viable cultures in the ivermectin group, which could lead to shortening isolation time in these patients.

scholarly journals Viral Culture in Hospitalized Congregate Care Patients With Prolonged SARS-CoV-2 Viral RNA Detection

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. 734-735
Author(s):  
Thilaka Arunachalam ◽  
Amit Singh ◽  
Kathleen Stellrecht ◽  
Sarah Elmendorf ◽  
Tarani K Barman ◽  
...  
Keyword(s):  
Viral Load ◽  
Symptom Onset ◽  
Clinical Symptoms ◽  
Academic Medical Center ◽  
Clinical Signs ◽  
Viral Rna ◽  
Nasopharyngeal Swab ◽  
Active Virus ◽  
Viral Culture ◽  
Congregate Care

Abstract Prolonged detection of SARS-CoV-2 viral RNA has been observed in hospitalized congregate care patients following resolution of clinical symptoms. It is unknown whether patients with persistent PCR positivity pose a risk for COVID-19 transmission. The purpose of this study was to examine the results of serial PCR testing, viral load, and viral culture in patients awaiting discharge prior to a negative PCR test. We sampled 14 patients who were admitted from skilled nursing and/or rehabilitation facilities to a large academic medical center, had clinical signs and symptoms of COVID-19, and had multiple PCR-positive tests separated by at least 14 days. PCR-positive nasopharyngeal swabs were obtained from each patient for viral load quantification and viral culture. The mean age of patients was 72.5 years (55 – 92), with a mean peak SOFA score of 5.6 (1 – 11). Patients were hospitalized for a mean of 37.0 days (25 – 60). RNA was detected by PCR for a mean of 32.9 days (19 – 47). Mean viral load for the first PCR-positive nasopharyngeal swab collected at our hospital was 5.81 genomic copies/mL (2.12 – 9.72). Viral load decreased significantly with days from clinical symptom onset (R = -0.69, 95% CI, -0.80 – -0.55). Four out of 28 samples grew active virus via culture, with no active virus isolates after 2 days of symptom onset. Our viral culture data suggests that persistent PCR positivity may not correlate with infectivity, which has important implications for COVID-19 infection control precautions among older congregate care patients.

Study on the Width of Turbulent Area around Pier with Ship Impact

2011 ◽  
Vol 137 ◽  
pp. 186-191
Author(s):  
Xiao Ping Liu ◽  
Dong Yue Qian ◽  
Sen Song Fang ◽  
Yang Zhang
Keyword(s):  
Turbulent Flow ◽  
Hydrodynamic Model ◽  
Lateral Flow ◽  
Bridge Pier ◽  
Two Dimensional ◽  
Hydraulic Conditions ◽  
Relationship Of ◽  
The Relationship ◽  
Over Time

Most papers focused on the hydraulic conditions and seldom took the factor of ships into consideration when they studied the impacts of navigation-turbulence around bridge pier upon clear width. This paper establishes a two-dimensional hydrodynamic model by using dynamic meshes of the software Fluent. How the ship affects the turbulence pattern of pier is analyzed, and the relationship of span wise distance between ship and pier as well as the change of force on ship over time is studied when the ship passing through the bridge. The results show that both the lateral flow in front of pier and the turbulent flow behind it could result in a force upon ship. The magnitude of the force is related to the distance between ship and bridge. The motion of ship can increase the weaving amplitude of pier wake and the width of turbulent area after it passes through the bridge.

scholarly journals Validation of Snort-spit Saliva in Detecting COVID-19 Using RT-PCR and Rapid Antigen Detection Test

2021 ◽  
Vol 55 (2) ◽  
Author(s):  
RYNER JOSE CARRILLO ◽  
Abigail D. Sarmiento ◽  
Mark Anthony C. Ang ◽  
Michelle H. Diwa ◽  
Cecille C. Dungog ◽  
...  
Keyword(s):  
Likelihood Ratio ◽  
Predictive Value ◽  
Positive Likelihood Ratio ◽  
Negative Likelihood Ratio ◽  
Lateral Flow ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Cohen’S Kappa ◽  
Cohen's Kappa ◽  
Antigen Testing

Objective. To determine the diagnostic accuracy of self-collected snorted and spit saliva in detecting COVID-19 using RT-PCR (ssRT-PCR) and lateral flow antigen test (ssLFA) versus nasopharyngeal swab RT-PCR (npRT-PCR). Methods. One hundred ninety-seven symptomatic subjects for COVID-19 testing in a tertiary hospital underwent snort-spit saliva self-collection for RT-PCR and antigen testing and nasopharyngeal swab for RT-PCR as reference. Positivity rates, agreement, sensitivity, specificity, and likelihood ratios were estimated. Results. Estimated prevalence of COVID-19 using npRT-PCR was 9% (exact 95% CI of 5.5% - 14.1%). A higher positivity rate of 13% in the ssRT-PCR assay suggested possible higher viral RNA in the snort-spit samples. There was 92.9% agreement between ssRT-PCR and npRT-PCR (exact 95% CI of 88.4% to 96.1%; Cohen’s Kappa of 0.6435). If npRT-PCR will be assumed as reference standard, the estimated Sensitivity was 83.3% (exact 95% CI of 60.8% to 94.2%), Specificity 93.9% (exact 95% CI of 89.3% to 96.5%), Positive predictive value of 57.7% (exact 95% CI of 38.9% to 74.5%), Negative predictive value of 98.2% (exact 95% CI of 95% to 99.4%), positive likelihood ratio of 3.65 (95% CI of 7.37 to 24.9), negative likelihood ratio of 0.178 (95% CI of 0.063 to 0.499). There was 84.84% agreement (95% exact CI of 79.1% to 89.5%; Cohen’s Kappa of 0.2356) between ssLFAvs npRT-PCR, sensitivity of 38.9% (exact 95% CI of 20.3% to 61.4%), specificity of 89.4% (exact 95% CI of 84.1% to 93.1%), PPV of 26.9% (95% CI of 13.7% to 46.1%), NPV of 93.6% (exact 95% CI of 88.8% to 96.4%), LR+ of 3.67 (95% CI of 1.79 - 7.51), LR – of 0.68 (95% CI of 0.47 - 0.99). Conclusion. Our data showed that snort-spit saliva RT-PCR testing had acceptable diagnostic performance characteristics and can potentially be used as an alternative to the standard nasopharyngeal/oropharyngeal swab RT-PCR test for COVID-19 in certain situations. However, our data also showed that snort-spit saliva antigen testing using lateral flow assay did not offer acceptable performance.

Lessons Learned and Recent Advances in Dengue Research

2020 ◽  
Author(s):  
Juan Samuel Sulca Herencia
Keyword(s):  
Climate Change ◽  
Viral Load ◽  
Antiviral Activity ◽  
Prevention And Control ◽  
Lessons Learned ◽  
New Drugs ◽  
Diagnostic Assays ◽  
And Control ◽  
Relationship Of ◽  
The Relationship

Dengue is the most important arbovirus, many research have contributed to the diagnosis, management, prevention and control of this disease, which will be described in this chapter, for example: the importance of serotypes and genotypes for the development of the disease, the relationship of the viral load between symptomatic and asymptomatic people, the influence of antibodies on the development of the disease, co-infections with microorganisms and chronic diseases, possible reservoirs, the diagnostic assays, cross-reactions in the diagnosis, the influence of climate change on the disease and the vector, mechanisms of transmission of the disease, new drugs and plant extracts with antiviral activity, the dengue vaccine, the results of immunizations, etc. This information gives a concrete idea of the advances and challenges against this disease.

scholarly journals Infection and infectivity: Utility of rapid antigen tests for the diagnosis of COVID-19

2021 ◽  
Vol 34 (Suppl 1) ◽  
pp. 46-48
Author(s):  
Pablo Barreiro ◽  
Jesús San-Román ◽  
María del Mar Carretero ◽  
Francisco Javier Candel ◽  
Keyword(s):  
Viral Load ◽  
Point Of Care ◽  
Viral Transmission ◽  
Lateral Flow ◽  
Pretest Probability ◽  
Antigen Test ◽  
Diagnostic Strategies ◽  
Antigen Tests ◽  
Asymptomatic Individuals

Detection of SARS-CoV-2 proteins is commercially available in the form of lateral-flow rapid antigen test for the point-of-care diagnosis of COVID-19. This platform has been validated for symptomatic and asymptomatic individuals, for diagnosis or screening, and as part of single or sequential diagnostic strategies. Although in general less sensitive than amplification techniques, antigen tests may be particularly valid during the first days of symptoms and to detect individuals with greater viral load, thereby with enhanced chances of viral transmission. The simplicity of antigen tests make them very suitable to discard infection in settings with low pretest probability, and to detect infection in case of higher chances of having COVID-19.

scholarly journals Duration of viral shedding and culture positivity with post-vaccination breakthrough delta variant infections

2021 ◽  
Author(s):  
Mark J. Siedner ◽  
Julie Boucau ◽  
Rebecca Gilbert ◽  
Rockib Uddin ◽  
Jonathan Luu ◽  
...  
Keyword(s):  
Viral Load ◽  
Additional Data ◽  
Post Vaccination ◽  
Replication Competent Virus ◽  
Viral Shedding ◽  
Viral Culture ◽  
Culture Positivity ◽  
Nasal Swabs ◽  
Ambulatory Patients ◽  
Viral Load Quantification

Isolation guidelines for SARS-CoV-2 are largely derived from data collected prior to emergence of the delta variant. We followed a cohort of ambulatory patients with post-vaccination breakthrough SARS-CoV-2 infections with longitudinal collection of nasal swabs for SARS-CoV-2 viral load quantification, whole genome sequencing, and viral culture. All delta variant infections (8/8, 100%) in our cohort were symptomatic, compared with 64% (9/14) of non-delta variant infections. Delta variant breakthrough infections were characterized by higher initial viral load, longer duration of virologic shedding by PCR (median 13.5 vs 4 days, hazard ratio [HR] 0.45, 95%CI 0.17-1.17), greater likelihood of replication competent virus at early stages of infection (6/8 [75%] vs 3/14 [23%], P=0.03), and longer duration of culturable virus (median 7 vs 3 days, HR 0.38, 95%CI 0.14-1.02) compared to non-delta variants. Nonetheless, no individuals with delta variant infections had replication competent virus by day 10 after symptom onset or 24 hours after resolution of symptoms. These data support current US Center for Disease Control isolation guidelines and reinforce the importance of prompt testing and isolation among symptomatic individuals with delta variant breakthrough infections. Additional data are needed to evaluate these relationships among asymptomatic and more severe delta variant breakthrough infections.

scholarly journals Real-world clinical performance of commercial SARS-CoV-2 rapid antigen tests in suspected COVID-19: A systematic meta-analysis of available data as per November 20, 2020

2020 ◽  
Author(s):  
Johannes Hayer ◽  
Dusanka Kasapic ◽  
Claudia Zemmrich
Keyword(s):  
Viral Load ◽  
Real World ◽  
Clinical Performance ◽  
Meta Analysis ◽  
High Viral Load ◽  
Lateral Flow ◽  
Performance Data ◽  
Rt Pcr ◽  
Symptom Status ◽  
Antigen Tests

AbstractBackgroundImmunochromatographic rapid antigen tests (RATs) emerged onto the COVID-19 pandemic testing landscape to aid in the rapid diagnosis of people with suspected SARS-CoV-2 infection. RATs are particularly useful where RT-PCR is not immediately available and symptoms suggestive of a high viral load and infectiousness are assumed. Several lateral flow immunoassays have been authorized for use under EUA and/or the CE mark, presenting varying overall clinical performance data generated by the manufacturer or by independent investigators. To compare the real-world clinical performance of commercially available rapid chromatographic immunoassays intended for the qualitative detection of SARS-CoV-2, we performed a systematic meta-analysis of published data.MethodsWe searched the MEDLINE®, Embase, BIOSIS and Derwent Drug File (ProQuest)for manufacturer-independent prospective clinical performance studies comparing SARS-CoV-2 RATs and RT-PCR assays. Only studies on lateral flow assays not needing a separate reader for retrieving the result were included, if data were available on viral load, patients’ symptom status, sample type, and PCR assay used. For better data comparability, recalculation of the studies’ single performance data confidence intervals using the exact Clopper–Pearson method was applied.ResultsWe could include 19 studies (ten peer-reviewed) presenting detailed clinical performance data on 11,209 samples with 2449 RT-PCR-positives out of study prevalence rates between 1.9–100 % and between 50– 100% symptomatic samples. Four studies directly compared two to three different RATs and 15 studies compared one RAT to RT-PCR. Overall specificity ranged, with one test outlier, between 92.4% (87.4– 95.9) and 100% (99.7–100), and overall clinical sensitivity varied between 28.9% (16.4–44.3) and 98.3% (91.1–99.7), depending on assay, population characteristics, viral load, and symptom status. Sensitivity in high-viral-load samples (cycle threshold ≤25) showed a considerable heterogeneity among the assays ranging from 66.7% to 100%.ConclusionOnly two RATs offered sufficient manufacturer-independent, real-world performance data supporting use for the detection of current SARS-CoV-2 infection in symptomatic or high-viral-load patient populations. Reliable positive predictive values require testing of symptomatic patients or asymptomatic individuals only in case of a high pre-test probability. If RATs are used for screening of asymptomatic cases in low-prevalence scenarios, a lower positive predictive value of the result has to be considered.

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