scholarly journals Head-to-head comparison of nasal and nasopharyngeal sampling using SARS-CoV-2 rapid antigen testing in Lesotho

2022 ◽  
Author(s):  
Niklaus Daniel Labhardt ◽  
Lucia Gonzalez Fernandez ◽  
Bulemba Katende ◽  
Josephine Muhairwe ◽  
Moniek Bresser ◽  
...  
Keyword(s):  
Point Of Care ◽  
High Specificity ◽  
Good Alternative ◽  
Nasopharyngeal Swab ◽  
Symptom Duration ◽  
High Agreement ◽  
Minimum Requirement ◽  
History Of ◽  
Antigen Testing ◽  
Or History

Objectives To assess the real-world diagnostic performance of nasal and nasopharyngeal swabs for SD Biosensor STANDARD Q COVID-19 Antigen Rapid Diagnostic Test (Ag-RDT). Methods Individuals ≥5 years with COVID-19 compatible symptoms or history of exposure to SARS-CoV-2 presenting at hospitals in Lesotho received two nasopharyngeal and one nasal swab. Ag-RDT from nasal and nasopharyngeal swabs were performed as point-of-care on site, the second nasopharyngeal swab used for polymerase chain reaction (PCR) as the reference standard. Results Out of 2198 participants enrolled, 2131 had a valid PCR result (61% female, median age 41 years, 8% children), 84.5% were symptomatic. Overall PCR positivity rate was 5.8%. The sensitivity for nasopharyngeal, nasal, and combined nasal and nasopharyngeal Ag-RDT result was 70.2% (95%CI: 61.3-78.0), 67.3% (57.3-76.3) and 74.4% (65.5-82.0), respectively. The respective specificity was 97.9% (97.1-98.4), 97.9% (97.2-98.5) and 97.5% (96.7-98.2). For both sampling modalities, sensitivity was higher in participants with symptom duration ≤ 3days versus ≤ 7days. Agreement between nasal and nasopharyngeal Ag-RDT was 99.4%. Conclusions The STANDARD Q Ag-RDT showed high specificity. Sensitivity was, however, below the WHO recommended minimum requirement of ≥ 80%. The high agreement between nasal and nasopharyngeal sampling suggests that for Ag-RDT nasal sampling is a good alternative to nasopharyngeal sampling.

scholarly journals A nanobody-functionalized organic electrochemical transistor for the rapid detection of SARS-CoV-2 and MERS antigens at the physical limit

2020 ◽  
Author(s):  
Keying Guo ◽  
Shofarul Wustoni ◽  
Anil Koklu ◽  
Escarlet Díaz-Galicia ◽  
Maximilian Moser ◽  
...  
Keyword(s):  
Single Molecule ◽  
Fluorescent Protein ◽  
Point Of Care ◽  
Protein Detection ◽  
High Specificity ◽  
Human Saliva ◽  
Nasopharyngeal Swab ◽  
Transistor Channel ◽  
Electrochemical Transistor ◽  
Detection And Quantification

AbstractThe COVID-19 pandemic highlights the need for rapid protein detection and quantification at the single-molecule level in a format that is simple and robust enough for widespread point-of-care applications. We here introduce a modular nanobody-organic electrochemical transistor architecture that enables the fast and specific detection and quantification of single-molecule to nanomolar protein antigen concentrations in complex bodily fluids. The sensor combines a new solution-processable organic semiconductor material in the transistor channel with the high-density and orientation-controlled bioconjugation of nanobody fusion proteins on disposable gate electrodes. It provides results after a 10 minutes exposure to 5 µL of unprocessed samples, maintains high specificity and single-molecule sensitivity in human saliva or serum, and is rapidly reprogrammed towards any protein target for which nanobodies exist. We demonstrate the use of this highly modular platform for the detection of green fluorescent protein, SARS-CoV-1/2, and MERS-CoV spike proteins and validate the sensor for COVID-19 screening in unprocessed clinical nasopharyngeal swab and saliva samples.

scholarly journals Performance of SARS-CoV-2 antigen testing in symptomatic and asymptomatic adults: a single-center evaluation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Stephanie L. Mitchell ◽  
Steven Orris ◽  
Tanner Freeman ◽  
Megan C. Freeman ◽  
Michelle Adam ◽  
...  
Keyword(s):  
Symptom Onset ◽  
Point Of Care ◽  
False Negative ◽  
Poor Performance ◽  
Nasopharyngeal Swab ◽  
Lower Sensitivity ◽  
Negative Results ◽  
Asymptomatic Patients ◽  
False Negative Results ◽  
Antigen Testing

Abstract Background Antigen testing offers rapid and inexpensive testing for SARS-CoV-2 but concerns regarding performance, especially sensitivity, remain. Limited data exists for use of antigen testing in asymptomatic patients; thus, performance and reliability of antigen testing remains unclear. Methods 148 symptomatic and 144 asymptomatic adults were included. A nasal swab was collected for testing by Quidel Sofia SARS IFA (Sofia) as point of care. A nasopharyngeal swab was also collected and transported to the laboratory for testing by Cepheid Xpert Xpress SARS-CoV-2/Flu/RSV RT-PCR (Cepheid). Results Overall, Sofia had good agreement with Cepheid (> 95%) in adults, however was less sensitive. Sofia had a sensitivity of 87.8% and 33.3% for symptomatic and asymptomatic patients, respectively. Among symptomatic patients, testing > 5 days post symptom onset resulted in lower sensitivity (82%) when compared with testing within 5 days of symptom onset (90%). Of the four Sofia false-negative results in the asymptomatic cohort, 50% went on to develop COVID-19 disease within 5 days of testing. Specificity in both symptomatic and asymptomatic cohorts was 100%. Conclusions Sofia has acceptable performance in symptomatic adults when tested < 5 days of symptom onset. Caution should be taken when testing patients with ≥ 5 days of symptoms. The combination of low prevalence and reduced sensitivity results in relatively poor performance of in asymptomatic patients. NAAT-based diagnostic assays should be considered in when antigen testing is unreliable, particularly in symptomatic patients with > 5 days of symptom onset and asymptomatic patients.

scholarly journals Evaluation of saliva molecular point of care for detection of SARS-CoV-2 in ambulatory care

2021 ◽  
Author(s):  
Jerome Le Goff ◽  
Solen Kerneis ◽  
Caroline Elie ◽  
Severine Mercier Delarue ◽  
Nabil Gastli ◽  
...  
Keyword(s):  
Point Of Care ◽  
False Negative ◽  
Lamp Assay ◽  
Rapid Identification ◽  
Ambulatory Setting ◽  
Nasopharyngeal Swab ◽  
Lower Sensitivity ◽  
Rt Pcr ◽  
A Prospective Study ◽  
Antigen Testing

Background: The rapid identification of SARS-CoV-2 infected individuals is a cornerstone in strategies for the control of virus spread. The sensitivity of SARS-CoV-2 RNA detection by RT-PCR is similar in saliva and nasopharyngeal swab. Rapid molecular point-of-care tests in saliva could facilitate, broaden and speed up the diagnosis. Objectives and methods: We conducted a prospective study in two community COVID-19 screening centers to evaluate the performances of a CE-marked RT-LAMP assay (EasyCoV) specifically designed for the detection of SARS-CoV-2 RNA from fresh saliva samples, compared to nasopharyngeal RT-PCR as reference test, saliva RT-PCR and nasopharyngeal antigen testing. Results: Overall, 117 of the 1718 participants (7%) were tested positive with nasopharyngeal RT-PCR. Sensitivities of saliva RT-PCR and nasopharyngeal antigen test were 93% (95% Confidence Interval (95%CI): 86-97) and 85% (95%CI: 77-91), respectively. The sensitivity and specificity of the RT-LAMP assay in saliva were 34% (95%CI: 26-44) and 97% (95%CI: 96-98). The performance was similar in symptomatic and asymptomatic participants and whatever the reference standard considered. Ct values of nasopharyngeal RT-PCR were significantly lower in the 40 true positive subjects with saliva RT-LAMP (Ct 25.9) than in the 48 false negative subjects with saliva RT-LAMP (Ct 28.4) (p=0.028). Conclusion: In the ambulatory setting, the detection of SARS-CoV-2 from crude saliva samples with the RT-LAMP assay had a lower sensitivity than nasopharyngeal RT-PCR, saliva RT-PCR and nasopharyngeal antigen testing.

scholarly journals Spike vs nucleocapsid SARS-CoV-2 antigen detection: application in nasopharyngeal swab specimens

2021 ◽  
Author(s):  
Moria Barlev-Gross ◽  
Shay Weiss ◽  
Amir Ben-Shmuel ◽  
Assa Sittner ◽  
Keren Eden ◽  
...  
Keyword(s):  
Point Of Care ◽  
High Specificity ◽  
Antigen Detection ◽  
Screening Tools ◽  
Nasopharyngeal Swab ◽  
Lower Sensitivity ◽  
Sample Collection ◽  
Time Resolved ◽  
Qrt Pcr ◽  
Optimal Target

AbstractPublic health experts emphasize the need for quick, point-of-care SARS-CoV-2 detection as an effective strategy for controlling virus spread. To this end, many “antigen” detection devices were developed and commercialized. These devices are mostly based on detecting SARS-CoV-2’s nucleocapsid protein. Recently, alerts issued by both the FDA and the CDC raised concerns regarding the devices’ tendency to exhibit false positive results. In this work we developed a novel alternative spike-based antigen assay, comprised of four high-affinity, specific monoclonal antibodies, directed against different epitopes on the spike’s S1 subunit. The assay’s performance was evaluated for COVID-19 detection from nasopharyngeal swabs, compared to an in-house nucleocapsid-based assay, composed of antibodies directed against the nucleocapsid. Detection of COVID-19 was carried out in a cohort of 284 qRT-PCR positive and negative nasopharyngeal swab samples. The time resolved fluorescence (TRF) ELISA spike-assay displayed very high specificity (99%) accompanied with a somewhat lower sensitivity (66% for Ct<25), compared to the nucleocapsid ELISA assay which was more sensitive (85% for Ct<25) while less specific (87% specificity). Despite being out-performed by qRT-PCR, we suggest that there is room for such tests in the clinical setting, as cheap and rapid pre-screening tools. Our results further suggest that when applying antigen detection, one must consider its intended application (sensitivity vs specificity), taking into consideration that the nucleocapsid might not be the optimal target. In this regard, we propose that a combination of both antigens might contribute to the validity of the results.Abstract FigureGraphic abstractSchematic representation of sample collection and analysis. The figure was created using BioRender.com

scholarly journals Evaluation of saliva molecular point of care for detection of SARS-CoV-2 in ambulatory care

2021 ◽  
Author(s):  
Jérôme LeGoff ◽  
Solen Kernéis ◽  
Caroline Elie ◽  
Séverine Mercier Delarue ◽  
Nabil Gastli ◽  
...  
Keyword(s):  
Point Of Care ◽  
False Negative ◽  
Lamp Assay ◽  
Rapid Identification ◽  
Nasopharyngeal Swab ◽  
Lower Sensitivity ◽  
Rt Pcr ◽  
Registration Number ◽  
A Prospective Study ◽  
Antigen Testing

Abstract Background Rapid identification of SARS-Cov-2 infected individuals is a cornerstone for the control of virus spread. The sensitivity of SARS-CoV-2 RNA detection by RT-PCR is similar in saliva and nasopharyngeal swab. Rapid molecular point-of-care tests in saliva could facilitate, broaden and speed up the diagnosis. Methods We conducted a prospective study in two community COVID-19 screening centers to evaluate the performances of a CE-marked RT-LAMP assay (EasyCoV™) designed for the detection of SARS-CoV2 RNA from fresh saliva samples, compared to nasopharyngeal RT-PCR, to saliva RT-PCR and to nasopharyngeal antigen testing. Results Overall, 117 of the 1718 participants (7%) were tested positive with nasopharyngeal RT-PCR. Compared to nasopharyngeal RT-PCR, the sensitivity and specificity of the RT-LAMP assay in saliva were 34% and 97% respectively. The Ct values of nasopharyngeal RT-PCR were significantly lower in the 40 true positive subjects with saliva RT-LAMP (Ct 25.9) than in the 48 false negative subjects with saliva RT-LAMP (Ct 28.4) (p = 0.028). Considering six alternate criteria for reference test, including saliva RT-PCR and nasopharyngeal antigen, the sensitivity of saliva RT-LAMP ranged between 27 and 44%. Conclusion The detection of SARS-CoV-2 from crude saliva samples with a RT-LAMP assay had a lower sensitivity than nasopharyngeal RT-PCR, saliva RT-PCR and nasopharyngeal antigen testing. Registration number : NCT04578509

Thanato-Laboratorien. Theorien von Tod und Sterben und Elias Canettis Buch gegen den Tod

2020 ◽  
Vol 4 (1) ◽  
pp. 67-86
Author(s):  
Elisabeth Heyne
Keyword(s):  
Human Life ◽  
Death And Dying ◽  
Point Of View ◽  
Visual Images ◽  
Elias Canetti ◽  
History Of ◽  
Series Of Experiments ◽  
First Time ◽  
Textual Form ◽  
Or History

AbstractAlthough visual culture of the 21th century increasingly focuses on representation of death and dying, contemporary discourses still lack a language of death adequate to the event shown by pictures and visual images from an outside point of view. Following this observation, this article suggests a re-reading of 20th century author Elias Canetti. His lifelong notes have been edited and published posthumously for the first time in 2014. Thanks to this edition Canetti's short texts and aphorisms can be focused as a textual laboratory in which he tries to model a language of death on experimental practices of natural sciences. The miniature series of experiments address the problem of death, not representable in discourses of cultural studies, system theory or history of knowledge, and in doing so, Canetti creates liminal texts at the margins of western concepts of (human) life, science and established textual form.

scholarly journals Making sense of rapid antigen testing in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostics

Diagnosis ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Camilla Mattiuzzi ◽  
Brandon M. Henry ◽  
Giuseppe Lippi
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Point Of Care ◽  
Turnaround Time ◽  
Molecular Testing ◽  
Upper Respiratory Tract ◽  
Making Sense ◽  
Skilled Personnel ◽  
Potential Benefits ◽  
Antigen Testing ◽  
Care Availability

AbstractAlthough the most effective strategy for preventing or containing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreaks relies on early diagnosis, the paramount and unprecedented number of tests needed to fully achieve this target is overwhelming worldwide testing supply and capacity. Molecular detection of SARS-CoV-2 RNA in nasopharyngeal swabs is still considered the reference diagnostic approach. Nonetheless, identification of SARS-CoV-2 proteins in upper respiratory tract specimens and/or saliva by means of rapid (antigen) immunoassays is emerging as a promising screening approach. These tests have some advantages compared to molecular analysis, such as point of care availability, no need of skilled personnel and dedicated instrumentation, lower costs and short turnaround time. However, these advantages are counterbalanced by lower diagnostic sensitivity compared to molecular testing, which would only enable to identifying patients with higher SARS-CoV-2 viral load. The evidence accumulated to-date has hence persuaded us to develop a tentative algorithm, which would magnify the potential benefits of rapid antigen testing in SARS-CoV-2 diagnostics.

scholarly journals No evidence of false-negative Plasmodium falciparum rapid diagnostic results in Monrovia, Liberia

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Mandella King ◽  
Alexander E. George ◽  
Pau Cisteró ◽  
Christine K. Tarr-Attia ◽  
Beatriz Arregui ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
False Negative ◽  
Malaria Diagnosis ◽  
Rapid Diagnostic Tests ◽  
Molecular Testing ◽  
False Negatives ◽  
Gene Deletions ◽  
History Of ◽  
Catholic Hospital ◽  
Or History

Abstract Background Malaria diagnosis in many malaria-endemic countries relies mainly on the use of rapid diagnostic tests (RDTs). The majority of commercial RDTs used in Africa detect the Plasmodium falciparum histidine-rich protein 2 (PfHRP2). pfhrp2/3 gene deletions can therefore lead to false-negative RDT results. This study aimed to evaluate the frequency of PCR-confirmed, false-negative P. falciparum RDT results in Monrovia, Liberia. Methods PfHRP2-based RDT (Paracheck Pf®) and microscopy results from 1038 individuals with fever or history of fever (n = 951) and pregnant women at first antenatal care (ANC) visit (n = 87) enrolled in the Saint Joseph’s Catholic Hospital (Monrovia) from March to July 2019 were used to assess the frequency of false-negative RDT results. True–false negatives were confirmed by detecting the presence of P. falciparum DNA by quantitative PCR in samples from individuals with discrepant RDT and microscopy results. Samples that were positive by 18S rRNA qPCR but negative by PfHRP2-RDT were subjected to multiplex qPCR assay for detection of pfhrp2 and pfhrp3. Results One-hundred and eighty-six (19.6%) and 200 (21.0%) of the 951 febrile participants had a P. falciparum-positive result by RDT and microscopy, respectively. Positivity rate increased with age and the reporting of joint pain, chills and shivers, vomiting and weakness, and decreased with the presence of coughs and nausea. The positivity rate at first ANC visit was 5.7% (n = 5) and 8% (n = 7) by RDT and microscopy, respectively. Out of 207 Plasmodium infections detected by microscopy, 22 (11%) were negative by RDT. qPCR confirmed absence of P. falciparum DNA in the 16 RDT-negative but microscopy-positive samples which were available for molecular testing. Among the 14 samples that were positive by qPCR but negative by RDT and microscopy, 3 only amplified pfldh, and among these 3 all were positive for pfhrp2 and pfhrp3. Conclusion There is no qPCR-confirmed evidence of false-negative RDT results due to pfhrp2/pfhrp3 deletions in this study conducted in Monrovia (Liberia). This indicates that these deletions are not expected to affect the performance of PfHRP2-based RDTs for the diagnosis of malaria in Liberia. Nevertheless, active surveillance for the emergence of PfHRP2 deletions is required.

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