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Rapid and accurate detection of respiratory virus aerosols is highlighted for virus surveillance and infection control. Here, we report a wireless immunoassay technology for fast (within 10 min), on-site (wireless and battery-free), and sensitive (limit of detection down to fg/L) detection of virus antigens in aerosols. The wireless immunoassay leverages the immuno-responsive hydrogel-modulated radio frequency resonant sensor to capture and amplify the recognition of virus antigen, and flexible readout network to transduce the immuno bindings into electrical signals. The wireless immunoassay achieves simultaneous detection of respiratory viruses such as severe acute respiratory syndrome coronavirus 2, influenza A H1N1 virus, and respiratory syncytial virus for community infection surveillance. Direct detection of unpretreated clinical samples further demonstrates high accuracy for diagnosis of respiratory virus infection. This work provides a sensitive and accurate immunoassay technology for on-site virus detection and disease diagnosis compatible with wearable integration., (© 2024. The Author(s).)

High-precision viral detection at point of need with clinical samples plays a pivotal role in the diagnosis of infectious diseases and the control of a global pandemic. However, the complexity of clinical samples that often contain very low viral concentrations makes it a huge challenge to develop simple diagnostic devices that do not require any sample processing and yet are capable of meeting performance metrics such as very high sensitivity and specificity. Herein we describe a new single-pot and single-step electrochemical method that uses real-time kinetic profiling of the interaction between a high-affinity aptamer and an antigen on a viral surface. This method generates many data points per sample, which when combined with machine learning, can deliver highly accurate test results in a short testing time. We demonstrate this concept using both SARS-CoV-2 and Influenza A viruses as model viruses with specifically engineered high-affinity aptamers. Utilizing this technique to diagnose COVID-19 with 37 real human saliva samples results in a sensitivity and specificity of both 100 % (27 true negatives and 10 true positives, with 0 false negative and 0 false positive), which showcases the superb diagnostic precision of this method., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Objectives: Rapid management of patients with respiratory tract infections in hospital emergency departments is one of the main objectives since the concurrent circulation of respiratory viruses following the SARS-CoV-2 pandemic. The use of new combined point-of-care antigen tests for detecting influenza A/B and SARS-CoV-2 represents an advantage in response time over the molecular tests. The objective was to evaluate the suitability of the CLINITEST® Rapid Covid-19 + Influenza Antigen test (Siemens Healthineers, Germany) (RCIA test) by measuring the sensitivity, specificity, Cohen's kappa, and cut-off values., Methods: Nasopharyngeal samples were collected from a randomised group of symptomatic patients of all ages at emergency department during January-February 2023. In parallel, these patients were screened for influenza A/B, and SARS-CoV-2 using RT-PCR. The Ct (cycle threshold) values were collected for positive [RT-PCR (+) /RCIA test (+)] and false negative [(RT-PCR (+) /RCIA test (-)] samples. A subanalysis was performed in the paediatric population (< 16 years-old)., Results: We included 545 patients (55.8% females) with a median age of 7 years-old (IQR: 1-66.5). The RCIA test showed a sensitivity of 59.7% [95%CI: 46.9-67.33] for influenza A, 65.6% [95%CI: 49.5-80.3] for influenza B, and 76.9% [95%CI: 45.8-84.8] for SARS-CoV-2. The specificity was between 90.7%-99.7% with a moderate/high level of agreement with RT-PCR (kappa score: 0.6-0.8) for the three respiratory viruses included in the RCIA test., Conclusions: The sensitivity of the RCIA test is insufficient for screening of patients, including patients with low Ct values (Ct > 20). Despite its good specificity and Cohen's kappa value, its use as a screening test is not comparable to RT-PCR systems in the ED environment with a high number of false negative results., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

An epidemic of highly pathogenic avian influenza (HPAI) began in North America in the winter of 2021. The introduced Eurasian H5N1 clade 2.3.4.4b virus subsequently reassorted with North American avian influenza strains. This postmortem study describes the lesions and influenza A virus antigen distribution in 3 species of raptors, including bald eagles ( Haliaeetus leucocephalus , n = 6), red-tailed hawks ( Buteo jamaicensis , n = 9), and great horned owls ( Bubo virginianus , n = 8), naturally infected with this virus strain based on positive reverse transcriptase polymerase chain reaction and sequencing results from oropharyngeal swabs. The birds presented with severe neurologic signs and either died or were euthanized because of the severity of their clinical signs and suspected influenza virus infection. Gross lesions were uncommon and included forebrain hemorrhages in 2 eagles, myocarditis in 1 hawk, and multifocal pancreatic necrosis in 3 owls. Histological lesions were common and included encephalitis, myocarditis, multifocal pancreas necrosis, multifocal adrenal necrosis, histiocytic splenitis, and anterior uveitis in decreasing frequency. Influenza A viral antigen was detected in brain, heart, pancreas, adrenal gland, kidney, spleen, liver, and eye. In conclusion, bald eagles, red-tailed hawks, and great horned owls infected with the HPAI clade 2.3.4.4b virus strain and showing neurological signs of illness may develop severe or fatal disease with histologically detectable lesions in the brain that are frequently positive for viral antigen., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Avian leukemia is an infectious tumorous disease of chickens caused by subgroup A of the avian leukemia virus (ALV-A), which mainly causes long-term viremia, slow growth, immune suppression, decreased production performance, multi-tissue tumors, and even death. The infection rate of this disease is very high in chicken herds in China, causing huge economic losses to the poultry industry every year. We successfully expressed the specific antigen protein of ALV (P27) through recombinant protein technology and screened a pair of highly sensitive monoclonal antibodies (mAbs) through mouse immunity, cell fusion, and antibody pairing. Based on this pair of antibodies, we established a dual antibody sandwich ELISA and gold nanoparticle immunochromatographic strip (AuNP-ICS) detection method. In addition, the parameters of the dual antibody sandwich ELISA and AuNP-ICS were optimized under different reaction conditions, which resulted in the minimum detection limits of 0.2 ng mL -1 and 1.53 ng ml -1 , respectively. Commonly available ELISA and AuNP-ICS products on the market were compared, and we found that our established immune rapid chromatography had higher sensitivity. This established AuNP-ICS had no cross-reactivity with Influenza A (H1N1), Influenza A (H9N2), respiratory syncytial virus (RSV), varicella-zoster virus (VZV), Listeria monocytogenes listeriolysin (LLO), and Staphylococcal enterotoxin SED or SEC. Finally, the established AuNP-ICS was used to analyze 35 egg samples, and the results showed 5 positive samples and 30 negative samples. The AuNP-ICS rapid detection method established by our group had good specificity, high sensitivity, and convenience, and could be applied to the clinical sample detection of ALV-A.

Background: During the COVID-19 pandemic, antigen diagnostic tests were frequently used for screening, triage, and diagnosis. Novel instrument-based antigen tests (iAg tests) hold the promise of outperforming their instrument-free, visually-read counterparts. Here, we provide a systematic review and meta-analysis of the SARS-CoV-2 iAg tests' clinical accuracy., Methods: We systematically searched MEDLINE (via PubMed), Web of Science, medRxiv, and bioRxiv for articles published before November 7th, 2022, evaluating the accuracy of iAg tests for SARS-CoV-2 detection. We performed a random effects meta-analysis to estimate sensitivity and specificity and used the QUADAS-2 tool to assess study quality and risk of bias. Sub-group analysis was conducted based on Ct value range, IFU-conformity, age, symptom presence and duration, and the variant of concern., Results: We screened the titles and abstracts of 20,431 articles and included 114 publications that fulfilled the inclusion criteria. Additionally, we incorporated three articles sourced from the FIND website, totaling 117 studies encompassing 95,181 individuals, which evaluated the clinical accuracy of 24 commercial COVID-19 iAg tests. The studies varied in risk of bias but showed high applicability. Of 24 iAg tests from 99 studies assessed in the meta-analysis, the pooled sensitivity and specificity compared to molecular testing of a paired NP swab sample were 76.7% (95% CI 73.5 to 79.7) and 98.4% (95% CI 98.0 to 98.7), respectively. Higher sensitivity was noted in individuals with high viral load (99.6% [95% CI 96.8 to 100] at Ct-level ≤ 20) and within the first week of symptom onset (84.6% [95% CI 78.2 to 89.3]), but did not differ between tests conducted as per manufacturer's instructions and those conducted differently, or between point-of-care and lab-based testing., Conclusion: Overall, iAg tests have a high pooled specificity but a moderate pooled sensitivity, according to our analysis. The pooled sensitivity increases with lower Ct-values (a proxy for viral load), or within the first week of symptom onset, enabling reliable identification of most COVID-19 cases and highlighting the importance of context in test selection. The study underscores the need for careful evaluation considering performance variations and operational features of iAg tests., (© 2024. The Author(s).)

Outbreaks of viral diseases seriously jeopardize people's health and cause huge economic losses. At the same time, virology provides a new perspective for biology, molecular biology and cancer research, and it is important to study the discovered viruses with potential applications. Therefore, the development of immediate and rapid viral detection methods for the prevention and treatment of viral diseases as well as the study of viruses has attracted extensive attention from scientists. With the continuous progress of science and technology, especially in the field of bioanalysis, a series of new detection techniques have been applied to the on-site rapid detection of viruses, which has become a powerful approach for human beings to fight against viruses. In this paper, the latest research progress of rapid point-of-care detection of viral nucleic acids, antigens and antibodies is presented. In addition, the advantages and disadvantages of these technologies are discussed from the perspective of practical application requirements. Finally, the problems and challenges faced by rapid viral detection methods and their development prospects are discussed.

As population immunity to SARS-CoV-2 evolves and new variants emerge, the role and accuracy of antigen tests remain active questions. To describe recent test performance, the detection of SARS-CoV-2 by antigen testing was compared with that by reverse transcription-polymerase chain reaction (RT-PCR) and viral culture testing during November 2022-May 2023. Participants who were enrolled in a household transmission study completed daily symptom diaries and collected two nasal swabs (tested for SARS-CoV-2 via RT-PCR, culture, and antigen tests) each day for 10 days after enrollment. Among participants with SARS-CoV-2 infection, the percentages of positive antigen, RT-PCR, and culture results were calculated each day from the onset of symptoms or, in asymptomatic persons, from the date of the first positive test result. Antigen test sensitivity was calculated using RT-PCR and viral culture as references. The peak percentage of positive antigen (59.0%) and RT-PCR (83.0%) results occurred 3 days after onset, and the peak percentage of positive culture results (52%) occurred 2 days after onset. The sensitivity of antigen tests was 47% (95% CI = 44%-50%) and 80% (95% CI = 76%-85%) using RT-PCR and culture, respectively, as references. Clinicians should be aware of the lower sensitivity of antigen testing compared with RT-PCR, which might lead to false-negative results. This finding has implications for timely initiation of SARS-CoV-2 antiviral treatment, when early diagnosis is essential; clinicians should consider RT-PCR for persons for whom antiviral treatment is recommended. Persons in the community who are at high risk for severe COVID-19 illness and eligible for antiviral treatment should seek testing from health care providers with the goal of obtaining a more sensitive diagnostic test than antigen tests (i.e., an RT-PCR test)., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Edwin J. Asturias reports grant support from Pfizer, consulting fees from Hillevax and Moderna, and payment from Merck for a lecture delivered at the Latin American Vaccine Summit. Carlos G. Grijalva reports support from the Food and Drug Administration and grants from the National Institutes of Health (NIH) and Syneos Health. Son H. McLaren reports institutional support from the Respiratory Virus Transmission Network, receipt of the Ken Graff Young Investigator Award from the American Academy of Pediatrics, Section on Emergency Medicine, institutional support from the National Center for Advancing Translational Science, the National Heart, Lung, and Blood Institute, and the Doris Duke Charitable Foundation COVID-19 Fund to Retain Clinician-Scientists. Suchitra Rao reports grant support from Biofire. Melissa S. Stockwell reports institutional support from the University of Washington, Boston Children’s Hospital, Westat, and New York University, and service as the Associate Director of the American Academy of Pediatrics Pediatric Research in Office Settings Research Network (payment to the trustees of Columbia University). Huong Q. Nguyen reports research support from CSL Seqirus, GSK, and ModernaTX, and an honorarium from ModernaTX for participating in a consultancy group, outside the submitted work. No other potential conflicts of interest were disclosed.

The emergence and rapid spread of Mpox (formerly monkeypox) have caused significant societal challenges. Adequate and appropriate diagnostics procedures are an urgent necessity. Herein, we discover a pair of aptamers through the systematic evolution of ligands by exponential enrichment (SELEX) that exhibit high affinity and bind to different sites towards the A29 protein of the Mpox virus. Subsequently, we propose a facile, sensitive, convenient CRISPR/Cas12a-mediated aptasensor for detecting the A29 antigen. The procedure employs the bivalent aptamers recognition, which induces the formation of a proximity switch probe and initiates subsequent cascade strand displacement reactions, then triggers CRISPR/Cas12a DNA trans-cleavage to achieve the sensitive detection of Mpox. Our method enables selective and ultrasensitive evaluation of the A29 protein within the range of 1 ng mL -1 to 1 μg mL -1 , with a limit of detection (LOD) at 0.28 ng mL -1 . Moreover, spiked A29 protein recovery exceeds 96.9%, while the detection activity remains above 91.9% after six months of storage at 4 °C. This aptasensor provides a novel avenue for exploring clinical diagnosis in cases involving Mpox as facilitating development in various analyte sensors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Real-time surveillance of COVID-19 in large-scale community outbreaks presents challenges. Simple counts of the daily confirmed cases can be misleading due to constraints from bottlenecks in access to care or laboratory testing. This study aimed to investigate the role of the SARS-CoV-2 antigen rapid diagnostic test (Ag-RDT) in addressing these challenges for real-time COVID-19 surveillance., Methods: This study included the results of 86,933 SARS-CoV-2 Ag-RDT and real-time reverse transcription polymerase chain reaction (RT-PCR) tests. These were conducted at four community testing stations within the Taipei metropolitan area during a community COVID-19 outbreak spanning from May 17, 2021, to August 9, 2021. We examined the correlation between the positive rates of Ag-RDT tests and the epidemic curve of laboratory-confirmed COVID-19 cases by onset date to examine its role in real-time surveillance., Results: During the 85-day study period, the trend of Ag-RDT test positive rates paralleled that of the epidemic curve. The correlation between the Ag-RDT positive rate and the number of cases (Pearson correlation coefficient: 0.968) is comparable to that of the RT-PCR positive rate (Pearson correlation coefficient: 0.964). The Ag-RDT positive rate exhibited a more advanced leading trend, with Ag-RDT leading by 3 days in comparison to the 2-day lead for RT-PCR., Conclusion: The positive rate of SARS-CoV-2 Ag-RDT tests at community testing stations serves as a good surrogate for assessing virus activity within the community and a useful tool for real-time COVID-19 surveillance. It is a robust indicator of the outbreak trend and near-term numbers of cases. This finding may facilitate the management of subsequent outbreaks of emerging infectious diseases., Competing Interests: Conflict of interest disclosure All authors have no competing interest to disclose., (Copyright © 2023 Formosan Medical Association. Published by Elsevier B.V. All rights reserved.)

Objective: This study aims to analyze the onset of otitis media secretory, the peak period of infection with the Omicron strain of SARS-CoV-2 virus, and the time of transmigration during a pandemic of the Omicron strain. Additionally, the study aims to investigate to study the presence of SARS-CoV-2 virus in the middle ear cavity of patients with otitis media secretory and the survival time through a new method for detecting SARS-CoV-2 virus antigen in middle ear effusion., Methods: Retrospective comparison of the incidence of otitis media secretory during infection with SARS-CoV-2 virus Omicron strain from December 15, 2022, to January 15, 2023, versus the noninfection period from December 15, 2021, to January 15, 2022. We used a questionnaire star application to investigate the demographic and epidemiological characteristics of the 40 patients with otitis media secretory who participated in this study were investigated. A novel coronavirus (2019-nCoV) antigen detection kit (colloidal gold method) was used to detect middle ear effusion in patients with otitis media secretory. The data were statistically analyzed using SPSS 29.0 software. The measurement data are expressed as x ± s , the count data are expressed as the number of cases (%), and the data were compared using the χ 2 test. p < 0.05 indicated a statistically significant difference., Results: During the SARS-CoV-2 virus Omicron strain pandemic, the incidence of otitis media secretory increased by 15% compared with the noninfection period. The peak infection period for the SARS-CoV-2 virus Omicron strain was December 25, 2022, and December 15, 2022, and the peak time of conversion was 7 to 9 days after the infection. Middle ear effusion SARS-CoV-2 virus antigen testing was performed in patients with otitis media secretory after conversion; 5 patients (12%) were positive, and 35 patients (88%) were negative. The disease duration in patients with negative results was more than 3 weeks., Conclusions: Otitis media secretory is one of the most common ear complications after infection with the Omicron strain of SARS-CoV-2 virus, and the significantly higher incidence is associated with middle ear viral infection. Middle ear effusion SARS-CoV-2 virus antigen test detected the virus, which survived longer in the middle ear effusion than in the nasal cavity. The middle ear effusion test can detect SARS-CoV-2 virus antigen and determine whether the organism contains virus residue., Competing Interests: Conflict of interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of Otology & Neurotology, Inc.)

African swine fever (ASF) is a lethal disease caused by ASF virus (ASFV), severely impacting the global swine industry. Though nuclear acid-based detection methods are reliable, they are laboratory-dependent. In this study, we developed a device-independent, user friendly and cost-effective quantum dots based immunochromatographic strip (QDs-ICS) with high specificity and sensitivity for the rapid and on-site detection of ASFV antigen. For the preparation of the QDs-ICS, we generated a monoclonal antibody (mAb) mAb-8G8 and polyclonal antibody (pAb) against ASFV-p72 protein. The pAb was labelled with QDs to be used as the detection probe and the mAb-8G8 was coated on the nitrocellulose membrane as the test line. Our results proved that the strip displayed no cross-reactivity with other swine viruses and detection limit of the QDs-ICS was down to 1 ng/mL for the ASFV-p72 protein with great reproducibility. The strip also exhibited high stability with a storage period up to 12 months under room temperature. Twenty blind samples and one hundred clinical samples were examined by the QDs-ICS, conventional PCR and real-time PCR method, respectively. Results showed that the agreement rate between the QDs-ICS and PCR method was 100%, and the agreement rate between the strip and real-time PCR was 94%. The novel QDs-ICS developed here would be an effective tool for on-site detection of ASFV., Competing Interests: Declaration of competing interest The authors declared no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objectives: Many reverse transcription polymerase chain reaction (RT-PCR) methods exist that can detect SARS-CoV-2 RNA in different matrices. RT-PCR is highly sensitive, although viral RNA may be detected long after active infection has taken place. SARS-CoV-2 proteins have shorter detection windows hence their detection might be more meaningful. Given salivary droplets represent a main source of transmission, we explored the detection of viral RNA and protein using four different detection platforms including SISCAPA peptide immunoaffinity liquid chromatography-mass spectrometry (SISCAPA-LC-MS) using polyclonal capture antibodies., Methods: The SISCAPA-LC MS method was compared to RT-PCR, RT-loop-mediated isothermal amplification (RT-LAMP), and a lateral flow rapid antigen test (RAT) for the detection of virus material in the drool saliva of 102 patients hospitalised after infection with SARS-CoV-2. Cycle thresholds (Ct) of RT-PCR ( E gene) were compared to RT-LAMP time-to-positive (TTP) ( NE and Orf1a genes), RAT optical densitometry measurements (test line/control line ratio) and to SISCAPA-LC-MS for measurements of viral protein., Results: SISCAPA-LC-MS showed low sensitivity (37.7 %) but high specificity (89.8 %). RAT showed lower sensitivity (24.5 %) and high specificity (100 %). RT-LAMP had high sensitivity (83.0 %) and specificity (100.0 %). At high initial viral RNA loads (<20 Ct), results obtained using SISCAPA-LC-MS correlated with RT-PCR (R 2 0.57, p-value 0.002)., Conclusions: Detection of SARS-CoV-2 nucleoprotein in saliva was less frequent than the detection of viral RNA. The SISCAPA-LC-MS method allowed processing of multiple samples in <150 min and was scalable, enabling high throughput., (© 2023 Walter de Gruyter GmbH, Berlin/Boston.)

Background: Transmission of SARS-CoV-2 from donor to recipient is a clinically relevant risk for developing severe COVID-19 after lung transplantation (LTx). This risk of iatrogenic transmission can be reduced by timely detection of viral RNA or antigen in samples of bronchoalveolar lavage (BAL) fluid obtained at the time of lung procurement. We aimed to retrospectively evaluate the detection of SARS-CoV-2 RNA or antigen in BAL fluid samples using three point-of-care tests (POCTs)., Methods: BAL fluid samples came from patients hospitalized in an intensive care unit during the COVID-19 pandemic. These pandemic samples were scored as positive or negative for SARS-CoV-2 by a RT-qPCR comparator assay for orf1ab. Three commercially available POCTs were then evaluated: cobas SARS-CoV-2 & Influenza A/B assay with the cobas Liat RT-qPCR system (Roche Diagnostics), ID NOW COVID-19 and COVID-19 2.0 (Abbott), and SARS-CoV-2 Rapid Antigen Test (RAT) (Roche Diagnostics). Samples from the pre-pandemic era served as negative controls., Results: We analyzed a total of 98 BAL fluid samples, each from a different patient: 58 positive pandemic samples (orf1ab Ct<38), 20 putatively negative pandemic samples (orf1ab Ct≥38), and 20 pre-pandemic samples. Univariate logistic regression shows that the probability of detection was highest for cobas Liat, followed by ID NOW, and then RAT. Of clinical relevance, cobas Liat detected SARS-CoV-2 RNA in 30 of the 31 positive pandemic samples that were collected within 10 days after RT-qPCR diagnosis of SARS-CoV-2 infection. None of the 20 pre-pandemic samples had a false-positive result for any POCT., Conclusions: POCTs enable the detection of SARS-CoV-2 RNA or antigen in BAL fluid samples and may provide additional information to decide if donor lungs are suitable for transplantation. Detection of respiratory pathogens with POCTs at the time of donor lung procurement is a potential strategy to increase safety in LTx by preventing iatrogenic transmission and severe postoperative infections., Competing Interests: Declaration of Competing Interest The authors declare they have no competing interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Development of specific signal reporters with signal amplification effect are highly needed for sensitive and accurate detection of pathogen. Herein, we design a colorimetric immunosensing nanosystem based on liposome encapsulated quantum dots-sized MnO 2 nanozyme (MnO 2 QDs@Lip) as a signal reporter for ultrasensitive and fast detection of SARS-CoV-2 antigen. The pathogenic antigens captured and separated by antibody-conjugated magnetic beads (MBs) are further connected with antibody-modified MnO 2 QDs@Lip to form a sandwich-like immunocomplex structure. After triggered release, MnO 2 QDs efficiently catalyze colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB, which can be qualitatively observed by naked eyes and quantitatively analyzed by UV-Vis spectra or smartphone platforms. By taking advantages of immuno-magnetic separation, excellent peroxidase-like catalytic activity of MnO 2 QDs, and high encapsulation efficiency of MnO 2 QDs@Lip, ultrasensitive detection of SARS-CoV-2 antigen ranging from 0.1 pg/mL to 100 ng/mL is achieved within 20 min. The limit of detection (LOD) is calculated to be 65 fg/mL in PBS buffer. Furthermore, real clinical samples of SARS-CoV-2 antigens can be effectively identified by this immunosensing nanosystem with excellent accuracy. This proposed detection nanosystem provides a strategy for simple, rapid and ultrasensitive detection of pathogens and may shed light on the development of new POCT detection platforms for early diagnosis of pathogens and surveillance in public health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The gold standard test available for detecting COVID-19 patients is Real Time RT-PCR. However, this method is expensive, needing special equipment and skilled laboratory staff. Recently, less expensive antigen tests have become available, that could easily and rapidly identify new COVID-19 cases. Our objective was to evaluate the Boson Rapid Antigen Test Card versus the RT-rtPCR, using samples taken both by laymen (self-testing) and professionals. The sensitivity, specificity and accuracy rates were, 98.18%, 100.00%, and 99.28%, respectively. The positive and negative predictive values were 100.00% and 98.82%, respectively. The detection rate for asymptomatic patients was 90.48%, and detection rate for Ct values ≥30 was 91.67%. Our results indicate a high coincidence rate between the Boson and the referencing RT-rtPCR method, meeting the performance standards recommended by the WHO. Therefore, this test could facilitate a fast self-testing screening method, for the detection of infected individuals., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The gold standard for COVID-19 diagnosis-reverse-transcriptase polymerase chain reaction (RT-PCR)- is expensive and often slow to yield results whereas lateral flow tests can lack sensitivity., Methods: We tested a rapid, lateral flow antigen (LFA) assay with artificial intelligence read (LFAIR) in subjects from COVID-19 treatment trials (N = 37; daily tests for 5 days) and from a population-based study (N = 88; single test). LFAIR was compared to RT-PCR from same-day samples., Results: Using each participant's first sample, LFAIR showed 86.2% sensitivity (95% CI 73.6%-98.8) and 94.3% specificity (88.8%-99.7%) compared to RT-PCR. Adjusting for days since symptom onset and repeat testing, sensitivity was 97.8% (89.9%-99.5%) on the first symptomatic day and decreased with each additional day. Sensitivity improved with artificial intelligence (AI) read (86.2%) compared to the human eye (71.4%)., Conclusion: LFAIR showed improved accuracy compared to LFA alone. particularly early in infection., Competing Interests: Declaration of competing interest The authors report no conflicts of interest relevant to this article, (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Rapid diagnostics are vital for curving the transmission and control of the COVID-19 pandemic. Although many commercially available antigen-based rapid diagnostic tests (Ag-RDTs) for the detection of SARS-CoV-2 are recommended by the WHO, their diagnostic performance has not yet been assessed in Ethiopia. So far, the vast majority of studies assessing diagnostic accuracies of rapid antigen tests considered RT-PCR as a reference standard, which inevitably leads to bias when RT-PCR is not 100% sensitive and specific. Thus, this study aimed to evaluate the diagnostic performance of Panbio™ jointly with the RT-PCR for the detection of SARS-CoV-2., Methods: A prospective cross-sectional study was done from July to September 2021 in Addis Ababa, Ethiopia, during the third wave of the pandemic involving two health centers and two hospitals. Diagnostic sensitivity and specificity of Panbio™ and RT-PCR were obtained using Bayesian Latent-Class Models (BLCM)., Results: 438 COVID-19 presumptive clients were enrolled, 239 (54.6%) were females, of whom 196 (44.7%) had a positive RT-PCR and 158 (36.1%) were Panbio™ positive. The Panbio™ and RT-PCR had a sensitivity (95% CrI) of 99.6 (98.4-100) %, 89.3 (83.2-97.6) % and specificity (95% CrI) of 93.4 (82.3-100) %, and 99.1 (97.5-100) %, respectively. Most of the study participants, 318 (72.6%) exhibited COVID-19 symptoms; the most reported was cough 191 (43.6%)., Conclusion: As expected the RT-PCR performed very well with a near-perfect specificity and a high, but not perfect sensitivity. The diagnostic performance of Panbio™ is coherent with the WHO established criteria of having a sensitivity ≥80% for Ag-RDTs. Both tests displayed high diagnostic accuracies in patients with and without symptoms. Hence, we recommend the use of the Panbio™ for both symptomatic and asymptomatic individuals in clinical settings for screening purposes., Competing Interests: We, the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper

Hantaan virus is the causative agent of hemorrhagic fever with renal syndrome (HFRS). The Hantaan virus strain, Korean hemorrhagic fever virus clone-5 (KHF5), causes weight loss and renal hemorrhage in laboratory mice. Clone-4 (KHF4), which has a single E417K amino acid change in its glycoprotein, is an avirulent variant. In this study, KHF4 and KHF5 were compared to evaluate pathological differences in mice in vitro and in vivo. The characteristics of the two glycoproteins were not significantly different in vitro. However, the virulent KHF5 strain targeted the lungs and caused pneumonia and edema in vivo. Both strains induced high infectivity levels in the liver and caused hepatitis; however, petechial hemorrhage and glycogen storage reduction were observed in KHF5-infected mice alone. Renal hemorrhage was observed using viral antigens in the tubular region of KHF5-infected mice. In addition, an increase in white blood cell levels and neutrophilia were found in KHF5-infected mice. Microarray analysis of liver cells showed that CD8+ T cell activation, acute-phase protein production, and neutrophil activation was induced by KHF5 infection. KHF5 infectivity was significantly increased in vivo and the histological and clinicopathological findings were similar to those in patients with HFRS.

The impact of the COVID-19 pandemic has reinforced the need for rapid, cost-effective, and reliable point-of-care testing (POCT) devices for massive population screening. The co-circulation of SARS-CoV-2 with several seasonal respiratory viruses highlights the need for multiplexed biosensing approaches. Herein, we present a fast and robust all-in-one POCT device for parallel viral antigen and serological analysis. The biosensing approach consists of a functionalized polycarbonate disc-shaped surface with microfluidic structures, where specific bioreagents are immobilized in microarray format, and a portable optoelectronic analyzer. The biosensor quantifies the concentration of viral antigens and specific immunoglobulins G and M for SARS-CoV-2, influenza A/B, adenovirus, and respiratory syncytial virus, using 30 μL of a sample. The semi-automated analysis of 6 samples is performed in 30 min. Validation studies performed with 135 serum samples and 147 nasopharyngeal specimens reveal high diagnostic sensitivity (98-100%) and specificity (84-98%), achieving an excellent agreement (κ = 0.937) with commercial immunoassays, which complies with the World Health Organization criteria for POC COVID-19 diagnostic tests. The versatility of the POCT device paves the way for the detection of other pathogens and analytes in the incoming post-pandemic world, integrating specific bioreagents against different variants of concerns and interests., (Copyright © 2022. Published by Elsevier B.V.)

Background: As new SARS-CoV-2 variants of concern emerge, there is a need to scale up testing to minimize transmission of the Coronavirus disease 2019 (COVID-19). Many countries especially those in the developing world continue to struggle with scaling up reverse transcriptase polymerase reaction (RT-PCR) to detect SARS-CoV-2 due to scarcity of resources. Alternatives such as antigen rapid diagnostics tests (Ag-RDTs) may provide a solution to enable countries scale up testing., Methods: In this study, we evaluated the Panbio™ and STANDARD Q Ag-RDTs in the laboratory using 80 COVID-19 RT-PCR confirmed and 80 negative nasopharyngeal swabs. The STANDARD Q was further evaluated in the field on 112 symptomatic and 61 asymptomatic participants., Results: For the laboratory evaluation, both tests had a sensitivity above 80% (Panbio™ = 86% vs STANDARD Q = 88%). The specificity of the Panbio™ was 100%, while that of the STANDARD Q was 99%. When evaluated in the field, the STANDARD Q maintained a high specificity of 99%, however the sensitivity was reduced to 56%., Conclusion: Using Ag-RDTs in low resource settings will be helpful in scaling-up SARS-CoV-2 testing, however, negative results should be confirmed by RT-PCR where possible to rule out COVID-19 infection., Competing Interests: The authors have declared that no competing interests exist.

Background: Rapid and accurate detection of SARS-CoV-2 infection is the cornerstone of prompt patient care. However, the reliability of the antigen rapid diagnostic test (Ag-RDT) in the diagnosis of SARS-CoV-2 infection remains inconclusive., Methods: We conducted a field evaluation of Ag-RDT performance during the Shanghai Coronavirus disease 2019 (COVID-19) quarantine and screened 7225 individuals visiting our Emergency Department. 83 asymptomatic SARS-CoV-2 (+) individuals were enrolled in the current study. Simultaneously, Ag-RDT was performed to evaluate its testing performance., Results: For the Ag-RDT(-) cases, the average cycle threshold (Ct) values of the N gene were 27.26 ± 4.59, which were significantly higher than the Ct value (21.9 ± 4.73) of the Ag-RDT(+) individuals (p < 0.0001). The overall sensitivity of Ag-RDT versus that of RT-PCR was 43.37%. The Ag-RDT(+) individuals regarding the N gene's Ct value were 16 cases in the < 20 range, 12 in 20-25, 5 in 25-30, and 3 in 30-35. The corresponding sensitivity was 84.21%, 52.17%, 21.74% and 16.67%, respectively. Meanwhile, sampling had a straight specificity of 100% regardless of the Ct value., Conclusions: The Ag-RDT were extremely sensitive in asymptomatic COVID-19 individuals with a Ct value < 20., (© 2022. The Author(s).)

SARS-CoV-2 continues to develop new, increasingly infectious variants including delta and omicron. We evaluated the efficacy of the Abbott BinaxNOW Rapid Antigen Test against Reverse Transcription PCR (RT-PCR) in 1,054 pediatric participants presenting to a high-volume Coronavirus Disease 2019 (COVID-19) testing site while the delta variant was predominant. Both tests utilized anterior nares swabs. Participants were grouped by COVID-19 exposure and symptom status. 5.2% of samples tested positive by RT-PCR for SARS-CoV-2. For all participants, sensitivity of the BinaxNOW was 92.7% (95% CI 82.4%-98.0%), and specificity was 98.0% (95% CI 97.0%-98.8%). For symptomatic participants, positive predictive value (PPV) was 72.7% (95% CI 54.5%-86.7%) and negative predictive value (NPV) was 99.2% (95% CI 98.2%-100%). Among asymptomatic participants, PPV was 71.4% (95% CI 53.7%-85.4%) and NPV was 99.7% (95% CI 99.0%-100%). Our reported sensitivity and NPV are higher than other pediatric studies, potentially because of higher viral load from the delta variant, but specificity and PPV are lower. IMPORTANCE The BinaxNOW rapid antigen COVID-19 test had a sensitivity of nearly 92% in both symptomatic and asymptomatic children when performed at a high-throughput setting during the more transmissible delta variant dominant period. The test may play an invaluable role in asymptomatic screening and keeping children safe in school.

Anti-retroviral therapy (ART) generally suppresses HIV replication to undetectable levels in peripheral blood, but immune activation associated with increased morbidity and mortality is sustained during ART, and infection rebounds when treatment is interrupted. To identify drivers of immune activation and potential sources of viral rebound, we modified RNAscope in situ hybridization to visualize HIV-producing cells as a standard against which to compare the following assays of potential sources of immune activation and virus rebound following treatment interruption: (i) envelope detection by induced transcription-based sequencing (EDITS) assay; (ii) HIV-Flow; (iii) Flow-FISH assays that can scan tissues and cell suspensions to detect rare cells expressing env mRNA, gag mRNA/Gag protein and p24; and (iv) an ultrasensitive immunoassay that detects p24 in cell/tissue lysates at subfemtomolar levels. We show that the sensitivities of these assays are sufficient to detect one rare HIV-producing/env mRNA + /p24 + cell in one million uninfected cells. These high-throughput technologies provide contemporary tools to detect and characterize rare cells producing virus and viral antigens as potential sources of immune activation and viral rebound. IMPORTANCE Anti-retroviral therapy (ART) has greatly improved the quality and length of life for people living with HIV, but immune activation does not normalize during ART, and persistent immune activation has been linked to increased morbidity and mortality. We report a comparison of assays of two potential sources of immune activation during ART: rare cells producing HIV and the virus' major viral protein, p24, benchmarked on a cell model of active and latent infections and a method to visualize HIV-producing cells. We show that assays of HIV envelope mRNA (EDITS assay), gag mRNA, and p24 (Flow-FISH, HIV-Flow. and ultrasensitive p24 immunoassay) detect HIV-producing cells and p24 at sensitivities of one infected cell in a million uninfected cells, thereby providing validated tools to explore sources of immune activation during ART in the lymphoid and other tissue reservoirs.

Members of the enterovirus genus are promising oncolytic agents. Their morphogenesis involves the generation of both genome-packed infectious capsids and empty capsids. The latter are typically considered as an impurity in need of removal from the final product. The separation of empty and full capsids can take place with centrifugation methods, which are of low throughput and poorly scalable, or scalable chromatographic processes, which typically require peak cutting and a significant trade-off between purity and yield. Here we demonstrate the application of packed bed cation exchange (CEX) column chromatography for the separation of empty capsids from infectious virions for a prototype strain of Coxsackievirus A21. This separation was developed using high throughput chromatography techniques and scaled up as a bind and elute polishing step. The separation was robust over a wide range of operating conditions and returned highly resolved empty and full capsids. The CEX step could be operated in bind and elute or flowthrough mode with similar selectivity and returned yields greater than 70% for full mature virus particles. Similar performance was also achieved using a selection of other bead based CEX chromatography media, demonstrating general applicability of this type of chromatography for Coxsackievirus A21 purification. These results highlight the wide applicability and excellent performance of CEX chromatography for the purification of enteroviruses, such as Coxsackievirus A21., Competing Interests: Declaration of Competing Interest Spyridon Konstantinidis reports a relationship with Merck & Co Inc that includes: employment and equity or stocks. Murphy R Poplyk reports a relationship with Merck & Co Inc that includes: employment and equity or stocks. Andrew R Swartz reports a relationship with Merck & Co Inc that includes: employment and equity or stocks. Richard R Rustandi reports a relationship with Merck & Co Inc that includes: employment and equity or stocks. Rachel Thompson reports a relationship with Merck & Co Inc that includes: employment and equity or stocks. Sheng-Ching Wang reports a relationship with Merck & Co Inc that includes: employment and equity or stocks. Spyridon Konstantinidis has patent #US20210187049A1 pending to Merck Sharp and Dohme Corp. Murphy R Poplyk has patent #US20210187049A1 pending to Merck Sharp and Dohme Corp. Andrew R Swartz has patent #US20210187049A1 pending to Merck Sharp and Dohme Corp., (Copyright © 2022. Published by Elsevier B.V.)

Background: Viral antigen detection test is the most common method used to detect viruses in the field rapidly. However, due to the low sensitivity, it can only be used as an auxiliary diagnosis method for virus infection. Improving sensitivity is crucial for developing more accurate viral antigen tests. Nano luciferase (Nluc) is a sensitive reporter that has not been used in virus detection., Results: In this study, we produced an intracellularly Nluc labeled detection antibody (Nluc-ch2C5) and evaluated its ability to improve the detection sensitivity of respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens. Compared with the traditional horse-radish peroxidase (HRP) labeled antibody (HRP-ch2C5), Nluc-ch2C5 was 41 times more sensitive for inactivated SARS-CoV-2 virus by sandwich chemiluminescence ELISA. Then we applied Nluc-ch2C5 to establish an automatic magnet chemiluminescence immune assay (AMCA) for the SARS-CoV-2 viral spike protein, the limit of detection was 68 pfu/reaction. The clinical sensitivity and specificity reached 75% (24/32) and 100% (48/48) using 32 PCR-positive and 48 PCR-negative swab samples for clinical evaluation, which is more sensitive than the commercial ELSA kit and colloid gold strip kit., Conclusions: Here, monoclonal antibody ch2C5 served as a model antibody and the SARS-CoV-2 served as a model pathogen. The Nluc labeled detecting antibody (Nluc-ch2C5) significantly improved the detection sensitivity of SARS-CoV-2 antigen. This labeling principle applies to other viral infections, so this labeling and test format could be expected to play an important role in detecting other virus antigens., (© 2022. The Author(s).)

A rapid and accurate diagnosis is a crucial strategy for containing the coronavirus disease (COVID-19) pandemic. Considering the obstacles to upscaling the use of RT-qPCR, rapid tests based on antigen detection (Ag-RDT) have become an alternative to enhance mass testing, reducing the time for a prompt diagnosis and virus spreading. However, the performances of several commercially available Ag-RDTs have not yet been evaluated in several countries. Here, we evaluate the performance of eight Ag-RDTs available in Brazil to diagnose COVID-19. Patients admitted to tertiary hospitals with moderate or mild COVID-19 symptoms and presenting risk factors for severe disease were included. The tests were performed using a masked protocol, strictly following the manufacturer's recommendations and were compared with RT-qPCR. The overall sensitivity of the tests ranged from 9.8 to 81.1%, and specificity greater than 83% was observed for all the evaluated tests. Overall, slight or fair agreement was observed between Ag-RDTs and RT-PCR, except for the Ag-RDT COVID-19 (Acro Biotech), in which moderate agreement was observed. Lower sensitivity of Ag-RDTs was observed for patients with cycle threshold > 25, indicating that the sensitivity was directly affected by viral load, whereas the effect of the disease duration was unclear. Despite the lower sensitivity of Ag-RDTs compared with RT-qPCR, its easy fulfillment and promptness still justify its use, even at hospital admission. However, the main advantage of Ag-RDTs seems to be the possibility of increasing access to the diagnosis of COVID-19 in patients with a high viral load, allowing immediate clinical management and reduction of infectivity and community transmission., Competing Interests: The authors have declared that no competing interests exist.

Objectives: PCR on nasopharyngeal exudates, the cornerstone of the detection of SARS-CoV-2, is time-consuming and commonly unavailable at primary health care centres. Detection of viral nucleocapsid antigens using lateral flow point-of-care tests is helpful for the early triage of patients who attend health care facilities., Methods: This was a prospective study carried out in clinically suspected cases and close asymptomatic contacts who attended a primary care centre (Madrid, Spain) for SARS-CoV-2 detection. Patients were divided into three 300-patient cohorts (n = 200 symptomatic cases and n = 100 close asymptomatic contacts per cohort). Three antigen detection tests (SGTI-Flex COVID-19 Ag, Panbio COVID-19 Ag Rapid Test Device, and GSD NovaGen SARS-CoV-2 Ag Rapid Test) were used and compared. Paired nasopharyngeal exudates were obtained, one swab for PCR and the other for antigen detection. Each antigen detection test was evaluated on one cohort., Results: All tests showed invariably 100% specificity. Sensitivity was 68.9% (95% CI: 55.7-80; SGTI-Flex), 71.1% (95% CI: 55.6-83.6; Panbio), and 84.6% (95% CI: 72-93.1; NovaGen) in clinically suspected patients and 84.6% (95% CI: 54.5-98.1), 33.3% (95% CI: 11.8-61.6), and 55.6% (95% CI: 30.7-78.4) in close asymptomatic contacts, respectively. Sensitivity was systematically higher in samples yielding positive PCR results with Ct ≤ 20., Discussion: We found considerable test-to-test antigen detection variations among patients with clinical suspicion of COVID-19 and close asymptomatic contacts. Negative antigen results, regardless of the test used, should be confirmed by PCR., (Copyright © 2022 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Introduction: Since respiratory sample collection is an uncomfortable experience, simultaneous detection of pathogens with a single swab is preferable. We prospectively evaluated the clinical performance of a newly developed antigen test QuickNavi-Flu+COVID19 Ag (Denka Co., Ltd., Tokyo, Japan) which can detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza viruses at the same time with a single testing device., Methods: We included those who were suspected of contracting coronavirus disease 2019 (COVID-19) and were referred to a PCR center at Ibaraki prefecture in Japan, between August 2, 2021 to September 13, 2021, when the variant carrying L452R spike mutation of SARS-CoV-2 were prevalent. Additional nasopharyngeal samples and anterior nasal samples were obtained for the antigen test and were compared with a reference real-time reverse transcription PCR (RT-PCR) using nasopharyngeal samples., Results: In total, 1510 nasopharyngeal samples and 862 anterior nasal samples were evaluated. During the study period, influenza viruses were not detected by QuickNavi-Flu+COVID19 Ag and reference real-time RT-PCR. For SARS-CoV-2 detection in nasopharyngeal samples, the sensitivity and specificity of the antigen test were 80.9% and 99.8%, respectively. The sensitivity and specificity using anterior nasal samples were 67.8% and 100%, respectively. In symptomatic cases, the sensitivities increased to 88.3% with nasopharyngeal samples and 73.7% with anterior nasal samples. There were three cases of discrepant results between the antigen test and the real-time RT-PCR. All of them were positive with the antigen test but negative with the real-time RT-PCR in SARS-CoV-2 detection., Conclusion: A combo kit, QuickNavi-Flu+COVID19 Ag, showed an acceptable sensitivity and sufficient specificity for SARS-CoV-2 detection, especially using nasopharyngeal sample collected from symptomatic patients., (Copyright © 2022 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Purpose: To assess whether one swab can be used to perform both the antigen-detection rapid diagnostic test (Ag-RDT) and reverse transcriptase polymerase chain reaction (RT-PCR) for COVID-19 detection during an outbreak in the nursing home (NH) setting., Methods: The single-swab method (SSM), where the Ag-RDT is performed with the transport medium used for RT-PCR, was evaluated in three Dutch NHs and compared to the laboratory setting. We collected Ag-RDT and RT-PCR results, NH resident characteristics and symptomatology. In addition, two focus groups were held with the involved care professionals to gain insight into the feasibility of the SMM in the NH setting., Results: In the NH setting, the SSM had a sensitivity of 51% and a specificity of 89% compared to RT-PCR. These were lower than in the laboratory setting (69% and 100% respectively). Yet, when stratified for cycle threshold values, the sensitivity became comparable between the settings. Symptoms occurred more frequent in the Ag-RDT+ group than Ag-RDT- group. Resident characteristics did not differ between these groups. Based on the focus groups, the SSM was feasible to perform if certain requirements, such as availability of staff, equipment and proper training, were met. However, the rapid availability of the test results were perceived as a dilemma., Conclusion: The advantages and disadvantages need to be considered before implementation of the SSM can be recommended in the NH setting. For the vulnerable NH residents, it is important to find the right balance between effective testing policy and the burden this imposes., (© 2021. The Author(s), under exclusive licence to European Geriatric Medicine Society.)

Background: Surveillance and control of SARS-CoV-2 outbreak through gold standard detection, that is, real-time polymerase chain reaction (RT-PCR), become a great obstacle, especially in overwhelming outbreaks. In this study, we aimed to analyze the performance of rapid antigen home test (RAHT) as an alternative detection method compared with RT-PCR., Methods: In total, 79 COVID-19-positive and 217 COVID-19-negative patients confirmed by RT-PCR were enrolled in this study. A duration from symptom onset to COVID-19 confirmation of <5 days was considered a recruiting criterion for COVID-19-positive cases. A nasal cavity specimen was collected for the RAHT, and a nasopharyngeal swab specimen was collected for RT-PCR., Results: Sensitivity of the STANDARD Q COVID-19 Ag Home Test (SD Biosensor, Korea), compared with RT-PCR, was 94.94% (75/79) (95% [confidence interval] CI, 87.54%-98.60%), and specificity was 100%. Sensitivity was significantly higher in symptomatic patients (98.00%) than in asymptomatic (89.66%) patients (p-value = 0.03). There was no difference in sensitivity according to the duration of symptom onset to confirmation (100% for 0-2 days and 96.97% for 3-5 days, respectively) (p-value = 1.00). The RAHT detected all 51 COVID-19 patients whose Ct values were ≤25 (100%), whereas sensitivity was 73.33% (11/15) among patients with Ct values >25 (p-value = 0.01)., Conclusion: The RAHT showed an excellent sensitivity for COVID-19-confirmed cases, especially for those with symptoms. There was a decrease in sensitivity when the Ct value is over 25, indicating that RAHT screening may be useful during the early phase of symptom onset, when the viral numbers are higher and it is more transmissible., (© 2022 The Authors. Journal of Clinical Laboratory Analysis published by Wiley Periodicals LLC.)

The purpose of this study was to assess the clinical performance of STANDARD F COVID-19 Ag FIA (SD Biosensor Inc., Gyeonggi-do, Republic of Korea), a rapid antigen detection test (RADT) for diagnosing SARS-CoV-2, in patients attended at the Emergency Department with signs or symptoms compatible with COVID-19 that had started in the last 5 days. The clinical performance of the antigen test was compared with RT-PCR, the reference standard. We included 663 specimens from non-repetitive patients. Clinical sensitivity and specificity were 84.0% (95% CI 76.1-89.7) and 99.6% (95% CI 98.5-99.9), respectively. The positive and negative predictive values were 98.1% (95% CI 92.7-99.7) and 96.4% (95% CI 94.4-97.7), respectively. The kappa index agreement between RT-PCR and the RADT was 0.89 (95% CI 0.84-0.93). We concluded that STANDARD F COVID-19 Ag FIA is an excellent first-line RADT method to diagnose symptomatic patients in the emergency department., Competing Interests: Declaration of competing interest The authors report no conflicts of interest relevant to this article, (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objective: The objective of this study was to evaluate the performance of seven antigen rapid diagnostic tests (Ag RDTs) in a clinical setting to identify those that could be recommended for use in the diagnosis of SARS-CoV-2 infection in Uganda., Methods: This was a cross-sectional prospective study. Nasopharyngeal swabs were collected consecutively from COVID-19 PCR positive and COVID-19 PCR negative participants at isolation centers and points of entry, and tested with the SARS-CoV-2 Ag RDTs. Test sensitivity and specificity were generated by comparing results against qRT-PCR results (Berlin Protocol) at a cycle threshold (Ct) cut-off of ≤39. Sensitivity was also calculated at Ct cut-offs ≤29 and ≤33., Results: None of the Ag RDTs had a sensitivity of ≥80% at Ct cut-off values ≤33 and ≤39. Two kits, Panbio™ COVID-19 Ag and VivaDiag™ SARS-CoV-2 Ag had a sensitivity of ≥80% at a Ct cut-off value of ≤29. Four kits: BIOCREDIT COVID -19 Ag, COVID-19 Ag Respi-Strip, MEDsan® SARS-CoV-2 Antigen Rapid Test and Panbio™ COVID-19 Ag Rapid Test had a specificity of ≥97%., Conclusions: This evaluation identified one Ag RDT, Panbio™ COVID-19 Ag with a performance at high viral load (Ct value ≤29) reaching that recommended by WHO. This kit was recommended for screening of patients with COVID -19-like symptoms presenting at health facilities., Competing Interests: RD is a consultant at Abbott. Therefore he did not participate in the investigation of Panbio™ COVID-19 Ag Rapid test performance. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Background: Point-of-care antigen tests (AgTs) for the detection of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) enable the rapid testing of infected individuals and are easy-to-use. However, there are few studies evaluating their clinical use., Objective: The present study aimed to evaluate and compare the clinical performance characteristics of various commercial SARS-CoV-2 AgTs., Design: The sensitivity of five AgTs, comprising four rapid antigen tests (RAT; AMP Rapid Test SARS-CoV-2 Ag, NADAL COVID-19 Antigen Rapid Test, CLINITEST Rapid COVID-19 Antigen Test, and Roche SARS-CoV-2 Rapid Antigen Test) and one sandwich chemiluminescence immunoassay (CLIA; LIAISON SARS-CoV-2 Assay), were evaluated in 300 nasopharyngeal (NP) swabs. Reverse transcriptase (RT) polymerase chain reaction (PCR) was used as a reference method., Participants: NP swabs were collected from patients admitted to hospital due to COVID-19., Key Results: Sensitivities of the AgTs ranged from 64.9 to 91.7% for samples with RT-PCR cycle threshold (Ct) values lower than 30 and were 100% for cycle threshold (Ct) values lower than 20. The highest sensitivity was observed for CLINITEST Rapid COVID-19 Antigen Test, and Roche SARS-CoV-2 rapid antigen test. Multivariate analysis using time from symptom onset and the Ct value for AgT sensitivity showed an inverse correlation. Further, the female sex was an independent factor of lower RAT sensitivity., Conclusions: Antigen tests from NP swab samples show high sensitivity in patients with a Ct value < 20. The best clinical sensitivity can be obtained using AgTs within the first 6 days after symptom onset., (© 2022. The Author(s) under exclusive licence to Society of General Internal Medicine.)

Objectives: To evaluate the performance of nasal mid-turbinate self-testing using rapid antigen detection tests (RDT) for persons with suspected coronavirus disease 2019 (COVID-19) in the community. Self-testing for COVID-19 infection with lateral flow assay severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RDT, provides rapid results and could enable frequent and extensive testing in the community, thereby improving the control of SARS-CoV-2., Methods: Participants visiting a municipal SARS-CoV-2 testing centre, received self-testing kits containing either the BD Veritor System (BD-RDT) or Roche SARS-CoV-2 antigen detection test (Roche-RDT). Oro-nasopharyngeal swabs were collected from the participants for quantitative RT-PCR (qRT-PCR) testing. As a proxy for contagiousness, viral culture was performed on a selection of qRT-PCR positive samples to determine the Ct-value at which the chance of a positive culture dropped below 0.5 (Ct-value cut-off). Sensitivity and specificity of self-testing were compared to qRT-PCR with a Ct-value below the Ct value cut-off. Determinants independently associated with a false-negative self-test result were determined., Results: A total of 3201 participants were included (BD-RDT n = 1595; Roche-RDT n = 1606). Sensitivity and specificity of self-testing compared with the qRT-PCR results with a Ct-value below the Ct-value cut-off were 78.4% (95% CI 73.2%-83.5%) and 99.4% (95% CI 99.1%-99.7%), respectively. A higher age was independently associated with a false-negative self-testing result with an odds ratio of 1.024 (95% CI 1.003-1.044)., Conclusions: Self-testing using currently available RDT has a high specificity and relatively high sensitivity to identify individuals with a high probability of contagiousness., (Copyright © 2021 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Background: SARS-CoV-2 rapid antigen tests are an important public health tool., Objective: To evaluate field performance of the BinaxNOW rapid antigen test (Abbott) compared with reverse transcriptase polymerase chain reaction (RT-PCR) for detecting infection with the Omicron variant of SARS-CoV-2., Design: Cross-sectional surveillance study., Setting: Free, walk-up, outdoor, urban community testing and vaccine site led by Unidos en Salud, serving a predominantly Latinx community highly impacted by COVID-19., Participants: Persons seeking COVID-19 testing in January 2022., Measurements: Simultaneous BinaxNOW and RT-PCR from nasal, cheek, and throat swabs, including cycle threshold (Ct) measures; a lower Ct value is a surrogate for higher amounts of virus., Results: Among 731 persons tested with nasal swabs, there were 296 (40.5%) positive results on RT-PCR; 98.9% were the Omicron variant. BinaxNOW detected 95.2% (95% CI, 91% to 98%) of persons who tested positive on RT-PCR with a Ct value below 30, 82.1% (CI, 77% to 87%) of those who tested positive on RT-PCR with a Ct value below 35, and 65.2% (CI, 60% to 71%) of all who were positive on RT-PCR. Among 75 persons with simultaneous nasal and cheek swabs, BinaxNOW using a cheek swab failed to detect 91% (20 of 22) of specimens that were positive on BinaxNOW with a nasal swab. Among persons with simultaneous nasal and throat swabs who were positive on RT-PCR with a Ct value below 30, 42 of 49 (85.7%) were detected by nasal BinaxNOW, 23 of 49 (46.9%) by throat BinaxNOW, and 44 of 49 (89.8%) by either., Limitation: Participants were a cross-sectional sample from a community-based sentinel surveillance site, precluding study of viral or symptom dynamics., Conclusion: BinaxNOW detected persons with high SARS-CoV-2 levels during the Omicron surge, enabling rapid responses to positive test results. Cheek or throat swabs should not replace nasal swabs. As currently recommended, high-risk persons with an initial negative BinaxNOW result should have repeated testing., Primary Funding Source: University of California, San Francisco.

Increasing the diagnostic capacity for COVID-19 (SARS-CoV-2 infection) is required to improve case detection, reduce COVID-19 expansion, and boost the world economy. Rapid antigen detection tests are less expensive and easier to implement, but their diagnostic performance has been questioned compared to reverse transcription-PCR (RT-PCR). Here, we evaluate the performance of the Standard Q COVID-19 antigen test for diagnosing SARS-CoV-2 infection and predicting contagiousness compared to RT-PCR and viral culture, respectively. The antigen test was 100.0% specific but only 40.9% sensitive for diagnosing infection compared to RT-PCR. Interestingly, SARS-CoV-2 contagiousness is highly unlikely with a negative antigen test since it exhibited a negative predictive value of 99.9% compared to viral culture. Furthermore, a cycle threshold ( C T ) value of 18.1 in RT-PCR was shown to be the one that best predicts contagiousness (area under the curve [AUC], 97.6%). Thus, screening people with antigen testing is a good approach to prevent SARS-CoV-2 contagion and allow returning to daily activities. IMPORTANCE The importance of our results is the excellent agreement between the Standard Q COVID-19 antigen test and the viral culture, indicating that it is important as a marker of contagiousness. Due to its high positive predictive value in situations of a high prevalence of infection, positive results do not require confirmation with another test. Likewise, its high negative predictive value for contagiousness makes possible to use this test as a criterion to discharge patients in isolation and screen people moving into environments that could facilitate the transmission of the virus. Screening people with antigen testing is a good approach to prevent SARS-CoV-2 contagion and allow returning to daily activities.

Microbiological diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a challenge. Although real-time reverse transcription PCR (RT-PCR) represents the gold standard method, strategies that allow rapid and simple diagnosis are necessary for the early identification of cases. In this study, we evaluated the diagnostic performance of six different commercial rapid antigen tests (Coronavirus antigen [Ag] rapid test cassette [Healgen Scientific, Houston, TX, USA], COVID-19 Ag FIA [Vircell, SD Biosensor Inc., Gyeonggi-do, Republic of Korea], Clinitest rapid COVID-19 antigen test [Siemens, Healthineers, Erlangen, Germany], SARS-CoV-2 rapid antigen test [SD Biosensor; Roche Diagnostics, Basel, Switzerland], Panbio COVID-19 Ag rapid test device [Abbott, Chicago, IL, USA], and SARS-CoV-2 test [MonLab, Barcelona, Spain]) in 130 nasopharyngeal swab samples tested previously by RT-PCR. The overall sensitivity of the rapid tests ranged from 65% to 79%, and the specificity was 100% for all of them. The sensitivity was higher for those samples with RT-PCR cycle threshold ( C T ) values below 25 and those from patients presenting within the first week of symptoms. The Siemens test showed the highest sensitivity for patients with high viral loads while the Vircell test performed better than the rest for C T values of ≥25. IMPORTANCE The rapid detection of people infected with SARS-CoV-2 is essential for a correct and effective control of the disease it causes. This process must be sensitive, fast, and simple, and it must be possible to carry out in any type of health center. Rapid antigen tests are the answer to this need. Knowing its ability to detect the virus in different stages of the disease is essential for a correct diagnosis, which is why this study has been carried out to evaluate the sensitivity and specificity of 6 different antigens tests in nasopharyngeal smear samples.

Successful control of emerging infectious diseases requires accelerated development of fast, affordable, and accessible assays for wide implementation at a high frequency. This paper presents a design for an in-solution assay pipeline, featuring nanobody-functionalized nanoparticles for rapid, electronic detection (Nano2RED) of Ebola and COVID-19 antigens. Synthetic nanobody binders with high affinity, specificity, and stability are selected from a combinatorial library and site-specifically conjugated to gold nanoparticles (AuNPs). Without requiring any fluorescent labelling, washing, or enzymatic amplification, these multivalent AuNP sensors reliably transduce antigen binding signals upon mixing into physical AuNP aggregation and sedimentation processes, displaying antigen-dependent optical extinction readily detectable by spectrometry or portable electronic circuitry. With Ebola virus secreted glycoprotein (sGP) and a SARS-CoV-2 spike protein receptor binding domain (RBD) as targets, Nano2RED showed a high sensitivity (the limit of detection of ∼10 pg /mL, or 0.13 pM for sGP and ∼40 pg/mL, or ∼1.3 pM for RBD in diluted human serum), a high specificity, a large dynamic range (∼7 logs),and fast readout within minutes. The rapid detection, low material cost (estimated <$0.01 per test), inexpensive and portable readout system (estimated <$5), and digital data output, make Nano2RED a particularly accessible assay in screening of patient samples towards successful control of infectious diseases., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Use of antigen tests for the diagnosis of COVID-19 has become widespread. The aim of this study was to evaluate the diagnostic accuracy of the nasopharyngeal rapid antigen diagnostic (RAD) immunoassay LumiraDx UK in an Emergency Department (ED). All patients admitted to our ED between November 11 and December 8, 2020, and had both a RAD test and a real-time-reverse-transcription-polymerase-chain-reaction (RT-PCR) test were enrolled. RAD was considered as the index test and RT-PCR test was used as the reference standard. Sensitivity, specificity, negative and positive predictive values, and likelihood ratios were calculated with the 95% confidence interval. The sensitivity and specificity of RAD were 34.2% and 92.3%. Positive and negative likelihood ratios were 4.4 and 0.71. Our results demonstrate that the diagnostic accuracy of the LumiraDx RAD test is too low for routine use as a diagnostic method in the ED., Competing Interests: Declaration of competing interest All authors declare no conflict of interest., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objectives: The LumiraDx SARS-CoV-2 Ag Test has previously been shown to accurately detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in individuals symptomatic for coronavirus disease 2019 (COVID-19). This evaluation investigated the LumiraDx SARS-CoV-2 Ag Test as an aid in the diagnosis of SARS-CoV-2 infection in asymptomatic adults and children., Methods: Asymptomatic individuals at high risk of COVID-19 infection were recruited in 5 point-of-care (POC) settings. Two paired anterior nasal swabs were collected from each participant, tested by using the LumiraDx SARS-CoV-2 Ag Test at the POC, and compared with results from reverse transcription-polymerase chain reaction (RT-PCR) assays (cobas 6800 [Roche Diagnostics] or TaqPath [Thermo Fisher Scientific]). We calculated positive percent agreement (PPA) and negative percent agreement (NPA), then stratified results on the basis of RT-PCR reference platform and cycle threshold., Results: Of the 222 included study participants confirmed to be symptom-free for at least 2 weeks before testing, the PPA was 82.1% (95% confidence interval [CI], 64.4%-92.1%). The LumiraDx SARS-CoV-2 Ag Test correctly identified 95.8% (95% CI, 79.8%-99.3%) of the samples confirmed positive in fewer than 33 RT-PCR cycles and 100% (95% CI, 85.1%-100%) in fewer than 30 RT-PCR cycles while maintaining 100% NPA., Conclusions: This rapid, high-sensitivity test can be used to screen asymptomatic patients for acute SARS-CoV-2 infection in clinic- and community-based settings., (© American Society for Clinical Pathology, 2021.)

Introduction: Rapid antigen tests to detect SARS-CoV-2 virus need to be validated. The purpose of clinical validation is to place the test into the everyday working process in health care institutions., Methodology: The clinical validation of Alltest Covid19 antigen test (Alltest, China) and Vivadiag Pro SARS- CoV-2 antigen tests (Vivacheck, China) started in four Slovenian health care institutions in December as a point-of-care test. Institutions compared the results of antigen tests to Seegene Allplex™ 2019-nCoV rt-PCR assay (SeeGene, South Korea) and Cobas 6800 SARS CoV-2 rt-PCR (Roche, USA)., Results: Sensitivity (90.6%, 95% CI = 84.94%-94.36%) and specificity (100%, 95% CI = 99.41%-100%) of Vivadiag Pro SARS CoV-2 Ag test were observed. While validating Alltest Covid19 Ag assay we got similar results (sensitivity 94.37%, 95% CI = 89.20% - 97.54%), specificity 100% (95% CI = 98.83% - 100%)., Conclusions: Vivadiag Pro SARS CoV-2 Ag test and Alltest Covid19 test proved to be a good screening tool to detect SARS-CoV-2. The accurate information about the patient's status was available almost immediately and there was no need to wait for rt-PCR results. We could prevent further spread of the SARS-CoV-2 in primary care and hospital settings., Competing Interests: No Conflict of Interest is declared, (Copyright (c) 2022 Miha Skvarc.)

Background: Real time reverse transcription polymerase chain reaction (real time RT-PCR) testing is the gold standard for the diagnosis of SARS-CoV-2 infections. However, to expand the testing capacity, new SARS-CoV-2 rapid antigen tests (Ag-RDTs) have been implemented. Ag-RDTs are more rapid, but less reliable in terms of sensitivity, and real-life data on their performance in comparison with the real time RT-PCR test are lacking. Methods: We aimed at assessing the diagnostic performance of the third-generation antigenic swab LumiraDx™ compared with real time RT-PCR in a retrospective cohort study at the Infectious Diseases Unit of Padua. All of the patients who were consecutively tested for SARS-CoV-2 in our centre (by both real time RT-PCR and Ag-RTD LumiraDxTM) from 19 January to 30 May 2021, were included. Cycle-threshold (Ct) values of positive real time RT-PCR were recorded as well as the number of days from symptoms’ onset to testing. Results: Among the 282 patients included, 80.9% (N = 228) tested positive to real time RT-PCR, and among these, 174 tested positive also to LumiraDx™. Compared with real time RT-PCR, which is considered as the gold standard for the assessment of the presence/absence of SARS-CoV-2 infection, LumiraDx™ showed an overall sensitivity of 76.3% and specificity of 94.4%. Sensitivity increased to 91% when testing was performed <10 days from symptoms’ onset, and to 95% when considering Ct < 25. Multivariable binomial logistic regression showed that false negative LumiraDx™ results were significantly associated with high Ct values, and with further testing from symptoms’ onset. Conclusions: The results of our study suggested that the LumiraDx™ SARS-CoV-2 antigen assay may be appropriate for the detection of SARS-CoV-2 infection, especially in its early phase when the test largely meets the performance requirements of the European Centre for Disease Prevention and Control (ECDC).

This review focuses on critical scientific barriers that the field of point-of-care (POC) testing of SARS-CoV-2 is facing and possible solutions to overcome these barriers using functional nucleic acid (FNA)-based technology. Beyond the summary of recent advances in FNA-based sensors for COVID-19 diagnostics, our goal is to outline how FNA might serve to overcome the scientific barriers that currently available diagnostic approaches are suffering. The first introductory section on the operationalization of the COVID-19 pandemic in historical view and its clinical features contextualizes essential SARS-CoV-2-specific biomarkers. The second part highlights three major scientific barriers for POC COVID-19 diagnosis, that is, the lack of a general method for (1) designing receptors of SARS-CoV-2 variants; (2) improving sensitivity to overcome false negatives; and (3) signal readout in resource-limited settings. The subsequent part provides fundamental insights into FNA and technical tricks to successfully achieve effective COVID-19 diagnosis by using in vitro selection of FNA to overcome receptor design barriers, combining FNA with multiple DNA signal amplification strategies to improve sensitivity, and interfacing FNA with portable analyzers to overcome signal readout barriers. This review concludes with an overview of further opportunities and emerging applications for FNA-based sensors against COVID-19., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The widespread and long-lasting effect of the COVID-19 pandemic has called attention to the significance of technological advances in the rapid diagnosis of SARS-CoV-2 virus. This study reports the use of a highly stable buffer-based zinc oxide/reduced graphene oxide (bbZnO/rGO) nanocomposite coated on carbon screen-printed electrodes for electrochemical immuno-biosensing of SARS-CoV-2 nuelocapsid (N-) protein antigens in spiked and clinical samples. The incorporation of a salt-based (ionic) matrix for uniform dispersion of the nanomixture eliminates multistep nanomaterial synthesis on the surface of the electrode and enables a stable single-step sensor nanocoating. The immuno-biosensor provides a limit of detection of 21 fg/mL over a linear range of 1-10 000 pg/mL and exhibits a sensitivity of 32.07 ohms·mL/pg·mm 2 for detection of N-protein in spiked samples. The N-protein biosensor is successful in discriminating positive and negative clinical samples within 15 min, demonstrating its proof of concept used as a COVID-19 rapid antigen test.

The coronavirus disease 2019 (COVID-19) pandemic has imposed an enormous disease burden worldwide, and the Delta variant now has become dominant in 53 countries. Recently published studies have shown that during periods of high viral load, rapid antigen tests (RAT) yield similar results to reverse transcriptase-polymerase chain reaction (RT-PCR) tests, and when used in serial screening (e.g., every three days), it has a high sensitivity. In this perspective, we recommend RT-PCR combined with RAT at points of entry: (i) RAT can be added to the detection phase at ports of entry to detect asymptomatic infections as early as possible; (ii) RAT can be added to post-entry quarantine every three days or less to reduce the rate of missed detection in later quarantine; (iii) Adding regular RAT to regular PCR testing for key airport personnel to prevent cross-infection and conduct closed-off management. In the face of sporadic Delta variant outbreaks, the combination of the two could help rapid triage and management of suspected populations at an early stage and thus contain the outbreak more quickly and effectively. We also discuss the issue whether the current antigen detection reagents can cope with various SARS-CoV-2 variants., (© 2021. The Author(s).)