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3.
Protein Eng Des Sel ; 342021 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-33991088

RESUMO

To combat the enduring and dangerous spread of COVID-19, many innovations to rapid diagnostics have been developed based on proteinprotein interactions of the SARS-CoV-2 spike and nucleocapsid proteins to increase testing accessibility. These antigen tests have most prominently been developed using the lateral flow assay (LFA) test platform which has the benefit of administration at point-of-care, delivering quick results, lower cost, and does not require skilled personnel. However, they have gained criticism for an inferior sensitivity. In the last year, much attention has been given to creating a rapid LFA test for detection of COVID-19 antigens that can address its high limit of detection while retaining the advantages of rapid antibodyantigen interaction. In this review, a summary of these proteinprotein interactions as well as the challenges, benefits, and recent improvements to protein based LFA for detection of COVID-19 are discussed.


Assuntos
Teste Sorológico para COVID-19/métodos , COVID-19/diagnóstico , Testes Imediatos , SARS-CoV-2/isolamento & purificação , Animais , Anticorpos Antivirais/análise , Anticorpos Antivirais/imunologia , Antígenos Virais/análise , Antígenos Virais/imunologia , COVID-19/imunologia , Teste Sorológico para COVID-19/instrumentação , Proteínas do Nucleocapsídeo de Coronavírus/análise , Proteínas do Nucleocapsídeo de Coronavírus/imunologia , Desenho de Equipamento , Humanos , Fosfoproteínas/análise , Fosfoproteínas/imunologia , SARS-CoV-2/imunologia , Glicoproteína da Espícula de Coronavírus/análise , Glicoproteína da Espícula de Coronavírus/imunologia
4.
Sci Rep ; 11(1): 10519, 2021 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-34006975

RESUMO

The clinical utility of antigen test using anterior nasal samples has not been well evaluated. We conducted a prospective study in a drive-through testing site located at a PCR center to evaluate the diagnostic performance of the antigen test QuickNavi-COVID19 Ag using anterior nasal samples and to compare the degrees of coughs or sneezes induction and the severity of pain between anterior nasal collection and nasopharyngeal collection. The study included a total of 862 participants, of which 91.6% were symptomatic. The median duration from symptom onset to sample collection was 2.0 days. Fifty-one participants tested positive for severe acute respiratory syndrome coronavirus 2 on reverse transcription PCR (RT-PCR) with nasopharyngeal samples, and all of them were symptomatic. In comparison to the findings of RT-PCR, the antigen test using anterior nasal samples showed 72.5% sensitivity (95% confidence interval [CI] 58.3-84.1%) and 100% specificity (95% CI 99.3-100%). Anterior nasal collection was associated with a significantly lower degree of coughs or sneezes induction and the severity of pain in comparison to nasopharyngeal collection (p < 0.001). The antigen test using anterior nasal samples showed moderate sensitivity in symptomatic patients who were at the early stages of the disease course but was less painful and induced fewer coughs or sneezes.


Assuntos
Antígenos Virais/análise , /isolamento & purificação , Adolescente , Adulto , Idoso , /virologia , Feminino , Humanos , Imunoensaio , Masculino , Pessoa de Meia-Idade , Cavidade Nasal/virologia , Nasofaringe/virologia , Estudos Prospectivos , RNA Viral/análise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , /metabolismo , Índice de Gravidade de Doença , Carga Viral , Adulto Jovem
5.
mBio ; 12(3)2021 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-34006662

RESUMO

The ongoing coronavirus disease 2019 (COVID-19) pandemic has seen an unprecedented increase in the demand for rapid and reliable diagnostic tools, leaving many laboratories scrambling for resources. We present a fast and simple assay principle for antigen detection and demonstrate its functionality by detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in nasopharyngeal swabs. The method is based on the detection of SARS-CoV-2 nucleoprotein (NP) and S protein (SP) via time-resolved Förster resonance energy transfer (TR-FRET) with donor- and acceptor-labeled polyclonal anti-NP and -SP antibodies. Using recombinant proteins and cell culture-grown SARS-CoV-2, the limits of detection were established as 25 pg of NP or 20 infectious units (IU) and 875 pg of SP or 625 IU. Testing reverse transcription-PCR (RT-PCR)-positive (n = 48, with cycle threshold [CT ] values from 11 to 30) or -negative (n = 96) nasopharyngeal swabs demonstrated that the assay yielded positive results for all samples with CT values of <25 and for a single RT-PCR-negative sample. Virus isolation from the RT-PCR-positive nasopharyngeal swabs showed a strong association between the presence of infectious virus and a positive antigen test result. The NP-based assay showed 97.4% (37/38) sensitivity and 100% (10/10) specificity in comparison with virus isolation and 77.1% (37/48) sensitivity and 99.0% (95/96) specificity in comparison with SARS-CoV-2 RT-PCR. The assay is performed in a buffer that neutralizes SARS-CoV-2 infectivity, and the assay is relatively simple to set up as an "in-house" test. Here, SARS-CoV-2 served as the model pathogen, but the assay principle is applicable to other viral infections, and the test format could easily be adapted to high-throughput testing.IMPORTANCE PCR is currently the gold standard for the diagnosis of many acute infections. While PCR and its variants are highly sensitive and specific, the time from sampling to results is measured in hours at best. Antigen tests directly detect parts of the infectious agent, which may enable faster diagnosis but often at lower sensitivity and specificity. Here, we describe a technique for rapid antigen detection and demonstrate the test format's potential using SARS-CoV-2 as the model pathogen. The 10-min test, performed in a buffer that readily inactivates SARS-CoV-2, from nasopharyngeal samples identified 97.4% (37/38) of the samples from which we could isolate the virus. This suggests that the test performs well in identifying patients potentially shedding the virus. Although SARS-CoV-2 served as the model pathogen to demonstrate proof of concept, the test principle itself would be applicable to a wide variety of infectious and perhaps also noninfectious diseases.


Assuntos
Antígenos Virais/análise , Transferência Ressonante de Energia de Fluorescência , /isolamento & purificação , Antígenos Virais/imunologia , /virologia , /imunologia , Humanos , Limite de Detecção , Nasofaringe/virologia , Fosfoproteínas/análise , Fosfoproteínas/imunologia , Estudo de Prova de Conceito , Proteínas Recombinantes/imunologia , Sensibilidade e Especificidade , Glicoproteína da Espícula de Coronavírus/análise , Glicoproteína da Espícula de Coronavírus/imunologia , Fatores de Tempo
6.
MMWR Morb Mortal Wkly Rep ; 70(19): 702-706, 2021 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-33983916

RESUMO

Prompt and accurate detection of SARS-CoV-2, the virus that causes COVID-19, has been important during public health responses for containing the spread of COVID-19, including in hospital settings (1-3). In vitro diagnostic nucleic acid amplification tests (NAAT), such as real-time reverse transcription-polymerase chain reaction (RT-PCR) can be expensive, have relatively long turnaround times, and require experienced laboratory personnel.* Antigen detection tests can be rapidly and more easily performed and are less expensive. The performance† of antigen detection tests, compared with that of NAATs, is an area of interest for the rapid diagnosis of SARS-CoV-2 infection. The Quidel Sofia 2 SARS Antigen Fluorescent Immunoassay (FIA) (Quidel Corporation) received Food and Drug Administration Emergency Use Authorization for use in symptomatic patients within 5 days of symptom onset (4). The reported test positive percentage agreement§ between this test and an RT-PCR test result is 96.7% (95% confidence interval [CI] = 83.3%-99.4%), and the negative percentage agreement is 100.0% (95% CI = 97.9%-100.0%) in symptomatic patients.¶ However, performance in asymptomatic persons in a university setting has shown lower sensitivity (5); assessment of performance in a clinical setting is ongoing. Data collected during June 30-August 31, 2020, were analyzed to compare antigen test performance with that of RT-PCR in a hospital setting. Among 1,732 paired samples from asymptomatic patients, the antigen test sensitivity was 60.5%, and specificity was 99.5% when compared with RT-PCR. Among 307 symptomatic persons, sensitivity and specificity were 72.1% and 98.7%, respectively. Health care providers must remain aware of the lower sensitivity of this test among asymptomatic and symptomatic persons and consider confirmatory NAAT testing in high-prevalence settings because a false-negative result might lead to failures in infection control and prevention practices and cause delays in diagnosis, isolation, and treatment.


Assuntos
Antígenos Virais/análise , /diagnóstico , /isolamento & purificação , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , /prevenção & controle , Infecção Hospitalar/prevenção & controle , Feminino , Hospitais , Humanos , Los Angeles/epidemiologia , Masculino , Pessoa de Meia-Idade , Sensibilidade e Especificidade , Adulto Jovem
7.
Ann Biol Clin (Paris) ; 79(2): 168-175, 2021 Apr 01.
Artigo em Francês | MEDLINE | ID: mdl-33985935

RESUMO

BACKGROUND: Discovered in 2019 in the region of Wuhan, China, the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) rapidly established itself as a major pathogenic agent of morbidity and mortality. France has implemented a strategy to fight this virus which relies essentially on widespread RT-PCR virological testing in order to isolate positive patients. Antigenic tests have recently been made available to help the diagnostics. We have conducted a retrospective study to determine the sensitivity of these antigenic tests, comparing them to the reference RT-PCR method. METHOD: Between December 7, 2020 and January 31, 2021, each patient we received in our laboratories for an RT-PCR test was enrolled. Out of 271,649 patients, 4,881 had been submitted to an antigenic test (TDR) in the preceding 24 hours. Comparing the data resulting from both tests, we established the sensitivity and the specificity of the antigenic tests. For our analysis we included the parameter of symptom and/or the value of Cycles threshold (Ct) in our parameters. RESULTS: The sensitivity of the TDRs compared to all the positive RT-PCR tests is 56%. We further demonstrate the correlation between the symptom duration and the reduction of the nasopharyngeal viral load. Based on this data, we have established that the sensitivity of the TDRs decreases very rapidly after symptom onset, contrary to the estimated viral load in the RT-PCR. Indeed, less the 24 hours after clinical symptom onset, the sensitivity of the TDRs decreases from 74% to 60%. By including the Ct value in our parameters, we have established that, despite a high viral load and clinical symptoms since 7 days or less, the sensitivity of the TDRs is 66%. Although, a high number of asymptomatic patients among carriers of SARS-CoV-2, we have estimated a specificity of 93% for our test. CONCLUSIONS: Performance in terms of sensitivity and specificity of the TDR, as assessed in practice, are inferior to those given by the manufacturer, which raises several questions. What is the impact of falsely negative results for patients carrying a high viral load? Are the implemented measures sufficient to prevent the epidemic?


Assuntos
/métodos , /diagnóstico , Antígenos Virais/análise , Humanos , Pessoa de Meia-Idade , Estudos Retrospectivos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sensibilidade e Especificidade
8.
J Clin Virol ; 139: 104838, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33946040

RESUMO

BACKGROUND: An accurate diagnosis is essential to identify and manage SARS-CoV-2 infected patients and implement infection control measures. Although real-time reverse transcription polymerase chain reaction (RT-PCR) is the current recommended laboratory method, several rapid antigen point-of-care tests (POCTs) were developed as frontline testing for SARS-CoV-2 infection diagnosis. OBJECTIVES: The aim of this study was to assess a recently CE-approved POCT, SARS-CoV-2 Ag Test on the LumiraDx™ Platform (LumiraDx GmbH, Cologne, Germany) for the identification of SARS-COV-2 infected subjects at hospital setting. METHODS: LumiraDx POCT was implemented in three hospital settings: adult and pediatric emergency departments and occupational medicine department along two-month period during the second peak of Italian SARS-CoV-2 pandemic. Rapid antigen testing was performed on direct nasal swabs and results were compared with those obtained by Xpert Xpress SARS-CoV-2 assay. RESULTS: Overall sensitivity, specificity, NPV and PPV were 90.3%, 92.1%, 95.1%, and 84.9%, respectively, compared to reference method. Sensitivity, specificity, PPV and NPV for symptomatic group were 89.3% [95% IC 84.2-93.3], 88.2% [95% IC 72.5-96.7], 97.8% [95% IC 94.6-99.1], and 58.8% [95% IC 48.4-68.5], respectively. Sensitivity, specificity, PPV and NPV for asymptomatic group were 92.1% [95% IC 85-96.5], 92.3% [95% IC 89.9-94.4], 67.9% [95% IC 61.3-73.8], and 98.5% [95% IC 97.1-99.2], respectively. False positive and negative antigen testing results in both symptomatic and asymptomatic group were observed. CONCLUSION: SARS-CoV-2 Ag POCT may represent an interesting tool to rapidly identify symptomatic or asymptomatic infected subjects. However, in hospital setting in which false negative or false positive results may have relevant implications, confirmatory NAAT always remains necessary for the appropriate management of patients.


Assuntos
Antígenos Virais/análise , Testes Imediatos , /imunologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Erros de Diagnóstico , Feminino , Imunofluorescência , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Sensibilidade e Especificidade , Adulto Jovem
9.
Biosensors (Basel) ; 11(4)2021 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-33917183

RESUMO

This review summarizes the state of the art of paper-based biosensors (PBBs) for coronavirus disease 2019 (COVID-19) detection. Three categories of PBB are currently being been used for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostics, namely for viral gene, viral antigen and antibody detection. The characteristics, the analytical performance, the advantages and drawbacks of each type of biosensor are highlighted and compared with traditional methods. It is hoped that this review will be useful for scientists for the development of novel PBB platforms with enhanced performance for helping to contain the COVID-19 outbreak, by allowing early diagnosis at the point of care (POC).


Assuntos
Técnicas Biossensoriais/métodos , Papel , Antígenos Virais/análise , Técnicas Biossensoriais/instrumentação , Sistemas CRISPR-Cas/genética , Humanos , Imunoensaio , Sistemas Automatizados de Assistência Junto ao Leito , RNA Viral/análise , /isolamento & purificação , /metabolismo
10.
PLoS One ; 16(4): e0249710, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33819311

RESUMO

BACKGROUND: Rapid antigen tests hold much promise for use in the school environment. However, the performance of these tests in non-clinical settings and among one of the main target populations in schools-asymptomatic children-is unclear. To address this gap, we examined the positive and negative concordance between the BinaxNOW™ rapid SARS-CoV-2 antigen assay and an RT-PCR test among children at a community-based Covid-19 testing site. METHODS: We conducted rapid antigen (BinaxNOW™) and oral fluid RT-PCR (Curative Labs) tests on children presenting at a walk-up testing site in Los Angeles County from November 25, 2020 to December 9, 2020. Positive concordance was determined as the fraction of RT-PCR positive participants that were also antigen positive. Negative concordance was determined as the fraction of RT-PCR negative participants that were also antigen negative. Multivariate logistic regression models were used to examine the association between positive or negative concordance and participant age, race-ethnicity, sex at birth, symptoms and Ct values. RESULTS: 226 children tested positive on RT-PCR; 127 children or 56.2% (95% CI: 49.5% to 62.8%) of these also tested positive on the rapid antigen test. Positive concordance was higher among symptomatic children (64.4%; 95% CI: 53.4% to 74.4%) compared to asymptomatic children (51.1%; 95% CI: 42.5% to 59.7%). Positive concordance was negatively associated with Ct values and was 93.8% (95% CI: 69.8% to 99.8%) for children with Ct values less than or equal to 25. 548 children tested negative on RT-PCR; 539 or 98.4% (95% CI: 96.9% to 99.2%) of these also tested negative on the rapid antigen test. Negative concordance was higher among asymptomatic children. CONCLUSIONS: Rapid antigen testing can successfully identify most COVID infections in children with viral load levels likely to be infectious. Serial rapid testing may help compensate for limited sensitivity in early infection.


Assuntos
Antígenos Virais/análise , /diagnóstico , Programas de Rastreamento/métodos , Adolescente , /métodos , Criança , Pré-Escolar , Feminino , Humanos , Los Angeles/epidemiologia , Masculino , Instituições Acadêmicas , Sensibilidade e Especificidade , Carga Viral/métodos
11.
Med Microbiol Immunol ; 210(2-3): 165-171, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33856557

RESUMO

Several rapid antigen tests (RATs) for the detection of SARS-CoV-2 were evaluated recently. However, reliable performance data for laboratory-based, high-throughput antigen tests are lacking. Therefore and in response to a short-term shortage of PCR reagents, we evaluated DiaSorin's LIAISON SARS-CoV-2 antigen test in comparison to RT-qPCR, and concerning the application of screening non-COVID-19 patients on hospital admission. Applying the manufacturer-recommended cut-off of 200 arbitrary units (AU/mL) the specificity of the LIAISON Test was 100%, the overall analytical sensitivity 40.2%. Lowering the cut-off to 100 AU/mL increased the sensitivity to 49.7% and decreased the specificity to 98.3%. Confining the analysis to samples with an RT-qPCR result < 25 Ct resulted in a sensitivity of 91.2%. The quality of the LIAISON test is very similar to that of good RATs described in the literature with the advantage of high throughput and the disadvantage of relatively long analysis time. It passes the WHO quality criteria for rapid antigen tests and is characterized by particularly high specificity. The LIAISON test can therefore be used for the same applications as recommended for RATs by the WHO. Due to limited sensitivity, the LIAISON test should only be used for screening, if PCR-based assays are not available.


Assuntos
/normas , /diagnóstico , Antígenos Virais/análise , Infecções Assintomáticas , Alemanha , Hospitais , Humanos , Programas de Rastreamento , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sensibilidade e Especificidade
12.
Ann Biol Clin (Paris) ; 79(2): 123-142, 2021 Apr 01.
Artigo em Francês | MEDLINE | ID: mdl-33881398

RESUMO

The SARS-CoV-2 has emerged in China at the end of 2019. In order to meet the growing demand in laboratories for RT-PCR testing for viral genome detection, rapid tests detecting a SARS-CoV-2 protein (antigenic rapid test) have been developed. In this review, we present for different SARS-CoV-2 antigenic rapid tests authorized in France: legislation, technological principle, and analytical and clinical performances. Data bellow are those provided by the manufacturer/distributor. From the list of tests authorized by the French Ministry of Health, we have selected 25 for which the distributors/manufacturers have provided the technical data essential to their comparative analysis. The kits use immunochromatography technology, with detection of the nucleocapsid protein (n = 24) or the spike protein (n = 1). The matrix used is a nasopharyngeal (n = 23), oropharyngeal (n = 9) or nasal (n = 3) swab. According to the test, the reading of the result is done from 15 to 30 minutes after it is performed. The clinical sensitivity, for the more performant tests is conversely linked to the Ct of RT-PCR, ranging from 80.2% to 98.4%, according to the quantity of virus present in the sample. This percentage is inversely proportional to the Ct obtained using RT-PCR. The limit of detection ranges from 31.55 to 7200 TCID50/mL. The clinical specificity, compared to a negative result of RT-PCR, is between 99.2% and 100%. Analytical specificity evaluated on other microorganisms is 100%, except for 3 kits that show cross-reactivities with SARS-CoV-1 (n = 3) and MERS-CoV (n = 1). Positive and negative predictive values range from 96.3% to 100% and 95% to 99.4%, respectively.


Assuntos
/diagnóstico , Antígenos Virais/análise , Cromatografia de Afinidade , França , Humanos , Legislação Médica , Valor Preditivo dos Testes , Sensibilidade e Especificidade , Glicoproteína da Espícula de Coronavírus/isolamento & purificação
13.
Viruses ; 13(4)2021 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-33921164

RESUMO

Antigen testing for SARS-CoV-2 (AGT) is generally considered inferior to RT-PCR testing in terms of sensitivity. However, little is known about the infectiousness of RT-PCR positive patients who pass undetected by AGT. In a screening setting for mildly symptomatic or asymptomatic patients with high COVID-19 prevalence (30-40%), 1141 patients were tested using one of five AGTs and RT-PCR. Where the results differed, virus viability in the samples was tested on cell culture (CV-1 cells). The test battery included AGTs by JOYSBIO, Assure Tech, SD Biosensor, VivaChek Biotech and NDFOS. Sensitivities of the ATGs compared to RT-PCR ranged from 42% to 76%. The best test yielded a 76% sensitivity, 97% specificity, 92% positive, and 89% negative predictive values, respectively. However, in the best performing ATG tests, almost 90% of samples with "false negative" AGT results contained no viable virus. Corrected on the virus viability, sensitivities grew to 81-97% and, with one exception, the tests yielded high specificities >96%. Performance characteristics of the best test after adjustment were 96% sensitivity, 97% specificity, 92% positive, and 99% negative predictive values (high prevalence population). We, therefore, believe that virus viability should be considered when assessing the AGT performance. Also, our results indicate that a well-performing antigen test could in a high-prevalence setting serve as an excellent tool for identifying patients shedding viable virus. We also propose that the high proportion of RT-PCR-positive samples containing no viable virus in the group of "false negatives" of the antigen test should be further investigated with the aim of possibly preventing needless isolation of such patients.


Assuntos
Antígenos Virais/análise , /imunologia , Viabilidade Microbiana , Testes Sorológicos/métodos , Adulto , Reações Falso-Negativas , Feminino , Humanos , Masculino , Programas de Rastreamento , Pessoa de Meia-Idade , Sensibilidade e Especificidade
14.
J Virol Methods ; 293: 114165, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33872650

RESUMO

Seeing the global emergence and the lack of a definitive cure for COVID-19, it is essential to find the most sensitive and specific detection method to identify infected patients in a timely manner. Our paper aims to compare the clinical sensitivity of different commercial RT-qPCR (Genesig, 1copy, DNA-Techonolgy and Charité primer-probe sets), isothermal PCR (Ustar Isothermal Amplification-Real Time Fluorescent Assay) and immunochromatographic antigen detection (BIOCREDIT COVID-19 Ag) assays developed to use in laboratory diagnosis of COVID-19. A total of 119 nasopharyngeal swab specimens were collected from symptomatic patients. A subset of samples, positive with two RT-qPCR assays were then tested with isothermal PCR and rapid antigen tests. Of the 119 specimens, 65 were positive by at least two PCR assays. All PCR assays showed substantial or perfect match, although some variations in the clinical performance was observed. Of the 37 and 32 remnant nasopharyngeal samples positive by RT-qPCR, respectively, three were positive by the BIOCREDIT COVID-19 Ag and 14 were detected by the isothermal amplification assay. In conclusion, in the clinical settings we recorded that each of the RT-qPCR assays was superior to other test formats, in particular, the routine use of the DNA-technology assay is recommended. Although alternative recommendations exist, we belive that the use of isothermal amplifiaction assays and antigen rapid tests for COVID-19 diagnosis can only serve as adjuncts while awaiting the PCR result because of their high false-negative rate.


Assuntos
/métodos , Testes Imediatos , /genética , Antígenos Virais/análise , Humanos , Kit de Reagentes para Diagnóstico , Fluxo de Trabalho
15.
BMC Med ; 19(1): 75, 2021 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-33685466

RESUMO

BACKGROUND: Testing plays a critical role in treatment and prevention responses to the COVID-19 pandemic. Compared to nucleic acid tests (NATs), antigen-detection rapid diagnostic tests (Ag-RDTs) can be more accessible, but typically have lower sensitivity and specificity. By quantifying these trade-offs, we aimed to inform decisions about when an Ag-RDT would offer greater public health value than reliance on NAT. METHODS: Following an expert consultation, we selected two use cases for analysis: rapid identification of people with COVID-19 amongst patients admitted with respiratory symptoms in a 'hospital' setting and early identification and isolation of people with mildly symptomatic COVID-19 in a 'community' setting. Using decision analysis, we evaluated the health system cost and health impact (deaths averted and infectious days isolated) of an Ag-RDT-led strategy, compared to a strategy based on NAT and clinical judgement. We adopted a broad range of values for 'contextual' parameters relevant to a range of settings, including the availability of NAT and the performance of clinical judgement. We performed a multivariate sensitivity analysis to all of these parameters. RESULTS: In a hospital setting, an Ag-RDT-led strategy would avert more deaths than a NAT-based strategy, and at lower cost per death averted, when the sensitivity of clinical judgement is less than 90%, and when NAT results are available in time to inform clinical decision-making for less than 85% of patients. The use of an Ag-RDT is robustly supported in community settings, where it would avert more transmission at lower cost than relying on NAT alone, under a wide range of assumptions. CONCLUSIONS: Despite their imperfect sensitivity and specificity, Ag-RDTs have the potential to be simultaneously more impactful, and have a lower cost per death and infectious person-days averted, than current approaches to COVID-19 diagnostic testing.


Assuntos
/métodos , /imunologia , Antígenos Virais/análise , Antígenos Virais/imunologia , /virologia , Testes Diagnósticos de Rotina/métodos , Humanos , Pandemias , Sensibilidade e Especificidade
16.
Cochrane Database Syst Rev ; 3: CD013705, 2021 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-33760236

RESUMO

BACKGROUND: Accurate rapid diagnostic tests for SARS-CoV-2 infection could contribute to clinical and public health strategies to manage the COVID-19 pandemic. Point-of-care antigen and molecular tests to detect current infection could increase access to testing and early confirmation of cases, and expediate clinical and public health management decisions that may reduce transmission. OBJECTIVES: To assess the diagnostic accuracy of point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection. We consider accuracy separately in symptomatic and asymptomatic population groups. SEARCH METHODS: Electronic searches of the Cochrane COVID-19 Study Register and the COVID-19 Living Evidence Database from the University of Bern (which includes daily updates from PubMed and Embase and preprints from medRxiv and bioRxiv) were undertaken on 30 Sept 2020. We checked repositories of COVID-19 publications and included independent evaluations from national reference laboratories, the Foundation for Innovative New Diagnostics and the Diagnostics Global Health website to 16 Nov 2020. We did not apply language restrictions. SELECTION CRITERIA: We included studies of people with either suspected SARS-CoV-2 infection, known SARS-CoV-2 infection or known absence of infection, or those who were being screened for infection. We included test accuracy studies of any design that evaluated commercially produced, rapid antigen or molecular tests suitable for a point-of-care setting (minimal equipment, sample preparation, and biosafety requirements, with results within two hours of sample collection). We included all reference standards that define the presence or absence of SARS-CoV-2 (including reverse transcription polymerase chain reaction (RT-PCR) tests and established diagnostic criteria). DATA COLLECTION AND ANALYSIS: Studies were screened independently in duplicate with disagreements resolved by discussion with a third author. Study characteristics were extracted by one author and checked by a second; extraction of study results and assessments of risk of bias and applicability (made using the QUADAS-2 tool) were undertaken independently in duplicate. We present sensitivity and specificity with 95% confidence intervals (CIs) for each test and pooled data using the bivariate model separately for antigen and molecular-based tests. We tabulated results by test manufacturer and compliance with manufacturer instructions for use and according to symptom status. MAIN RESULTS: Seventy-eight study cohorts were included (described in 64 study reports, including 20 pre-prints), reporting results for 24,087 samples (7,415 with confirmed SARS-CoV-2). Studies were mainly from Europe (n = 39) or North America (n = 20), and evaluated 16 antigen and five molecular assays. We considered risk of bias to be high in 29 (50%) studies because of participant selection; in 66 (85%) because of weaknesses in the reference standard for absence of infection; and in 29 (45%) for participant flow and timing. Studies of antigen tests were of a higher methodological quality compared to studies of molecular tests, particularly regarding the risk of bias for participant selection and the index test. Characteristics of participants in 35 (45%) studies differed from those in whom the test was intended to be used and the delivery of the index test in 39 (50%) studies differed from the way in which the test was intended to be used. Nearly all studies (97%) defined the presence or absence of SARS-CoV-2 based on a single RT-PCR result, and none included participants meeting case definitions for probable COVID-19. Antigen tests Forty-eight studies reported 58 evaluations of antigen tests. Estimates of sensitivity varied considerably between studies. There were differences between symptomatic (72.0%, 95% CI 63.7% to 79.0%; 37 evaluations; 15530 samples, 4410 cases) and asymptomatic participants (58.1%, 95% CI 40.2% to 74.1%; 12 evaluations; 1581 samples, 295 cases). Average sensitivity was higher in the first week after symptom onset (78.3%, 95% CI 71.1% to 84.1%; 26 evaluations; 5769 samples, 2320 cases) than in the second week of symptoms (51.0%, 95% CI 40.8% to 61.0%; 22 evaluations; 935 samples, 692 cases). Sensitivity was high in those with cycle threshold (Ct) values on PCR ≤25 (94.5%, 95% CI 91.0% to 96.7%; 36 evaluations; 2613 cases) compared to those with Ct values >25 (40.7%, 95% CI 31.8% to 50.3%; 36 evaluations; 2632 cases). Sensitivity varied between brands. Using data from instructions for use (IFU) compliant evaluations in symptomatic participants, summary sensitivities ranged from 34.1% (95% CI 29.7% to 38.8%; Coris Bioconcept) to 88.1% (95% CI 84.2% to 91.1%; SD Biosensor STANDARD Q). Average specificities were high in symptomatic and asymptomatic participants, and for most brands (overall summary specificity 99.6%, 95% CI 99.0% to 99.8%). At 5% prevalence using data for the most sensitive assays in symptomatic people (SD Biosensor STANDARD Q and Abbott Panbio), positive predictive values (PPVs) of 84% to 90% mean that between 1 in 10 and 1 in 6 positive results will be a false positive, and between 1 in 4 and 1 in 8 cases will be missed. At 0.5% prevalence applying the same tests in asymptomatic people would result in PPVs of 11% to 28% meaning that between 7 in 10 and 9 in 10 positive results will be false positives, and between 1 in 2 and 1 in 3 cases will be missed. No studies assessed the accuracy of repeated lateral flow testing or self-testing. Rapid molecular assays Thirty studies reported 33 evaluations of five different rapid molecular tests. Sensitivities varied according to test brand. Most of the data relate to the ID NOW and Xpert Xpress assays. Using data from evaluations following the manufacturer's instructions for use, the average sensitivity of ID NOW was 73.0% (95% CI 66.8% to 78.4%) and average specificity 99.7% (95% CI 98.7% to 99.9%; 4 evaluations; 812 samples, 222 cases). For Xpert Xpress, the average sensitivity was 100% (95% CI 88.1% to 100%) and average specificity 97.2% (95% CI 89.4% to 99.3%; 2 evaluations; 100 samples, 29 cases). Insufficient data were available to investigate the effect of symptom status or time after symptom onset. AUTHORS' CONCLUSIONS: Antigen tests vary in sensitivity. In people with signs and symptoms of COVID-19, sensitivities are highest in the first week of illness when viral loads are higher. The assays shown to meet appropriate criteria, such as WHO's priority target product profiles for COVID-19 diagnostics ('acceptable' sensitivity ≥ 80% and specificity ≥ 97%), can be considered as a replacement for laboratory-based RT-PCR when immediate decisions about patient care must be made, or where RT-PCR cannot be delivered in a timely manner. Positive predictive values suggest that confirmatory testing of those with positive results may be considered in low prevalence settings. Due to the variable sensitivity of antigen tests, people who test negative may still be infected. Evidence for testing in asymptomatic cohorts was limited. Test accuracy studies cannot adequately assess the ability of antigen tests to differentiate those who are infectious and require isolation from those who pose no risk, as there is no reference standard for infectiousness. A small number of molecular tests showed high accuracy and may be suitable alternatives to RT-PCR. However, further evaluations of the tests in settings as they are intended to be used are required to fully establish performance in practice. Several important studies in asymptomatic individuals have been reported since the close of our search and will be incorporated at the next update of this review. Comparative studies of antigen tests in their intended use settings and according to test operator (including self-testing) are required.


Assuntos
Antígenos Virais/análise , /diagnóstico , Técnicas de Diagnóstico Molecular/métodos , Sistemas Automatizados de Assistência Junto ao Leito , /imunologia , Adulto , Infecções Assintomáticas , Viés , Criança , Estudos de Coortes , Reações Falso-Negativas , Reações Falso-Positivas , Humanos , Técnicas de Diagnóstico Molecular/normas , Valor Preditivo dos Testes , Padrões de Referência , Sensibilidade e Especificidade
17.
Int J Mol Sci ; 22(5)2021 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-33673426

RESUMO

During persistent human beta-herpesvirus (HHV) infection, clinical manifestations may not appear. However, the lifelong influence of HHV is often associated with pathological changes in the central nervous system. Herein, we evaluated possible associations between immunoexpression of HHV-6, -7, and cellular immune response across different brain regions. The study aimed to explore HHV-6, -7 infection within the cortical lobes in cases of unspecified encephalopathy (UEP) and nonpathological conditions. We confirmed the presence of viral DNA by nPCR and viral antigens by immunohistochemistry. Overall, we have shown a significant increase (p < 0.001) of HHV antigen expression, especially HHV-7 in the temporal gray matter. Although HHV-infected neurons were found notably in the case of HHV-7, our observations suggest that higher (p < 0.001) cell tropism is associated with glial and endothelial cells in both UEP group and controls. HHV-6, predominantly detected in oligodendrocytes (p < 0.001), and HHV-7, predominantly detected in both astrocytes and oligodendrocytes (p < 0.001), exhibit varying effects on neural homeostasis. This indicates a high number (p < 0.001) of activated microglia observed in the temporal lobe in the UEP group. The question remains of whether human HHV contributes to neurological diseases or are markers for some aspect of the disease process.


Assuntos
Encefalopatias/imunologia , Herpesvirus Humano 6 , Herpesvirus Humano 7 , Imunidade Celular , Neuroglia/virologia , Infecções por Roseolovirus/imunologia , Adulto , Idoso , Antígenos Virais/análise , Astrócitos/virologia , Encéfalo/imunologia , Encéfalo/virologia , Encefalopatias/virologia , Células Endoteliais/virologia , Feminino , Humanos , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Oligodendroglia/virologia
19.
Biosens Bioelectron ; 180: 113111, 2021 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-33743492

RESUMO

Significant barriers to the diagnosis of latent and acute SARS-CoV-2 infection continue to hamper population-based screening efforts required to contain the COVID-19 pandemic in the absence of widely available antiviral therapeutics or vaccines. We report an aptamer-based SARS-CoV-2 salivary antigen assay employing only low-cost reagents ($3.20/test) and an off-the-shelf glucometer. The test was engineered around a glucometer as it is quantitative, easy to use, and the most prevalent piece of diagnostic equipment globally, making the test highly scalable with an infrastructure that is already in place. Furthermore, many glucometers connect to smartphones, providing an opportunity to integrate with contact tracing apps, medical providers, and electronic health records. In clinical testing, the developed assay detected SARS-CoV-2 infection in patient saliva across a range of viral loads - as benchmarked by RT-qPCR - within 1 h, with 100% sensitivity (positive percent agreement) and distinguished infected specimens from off-target antigens in uninfected controls with 100% specificity (negative percent agreement). We propose that this approach provides an inexpensive, rapid, and accurate diagnostic for distributed screening of SARS-CoV-2 infection at scale.


Assuntos
Antígenos Virais/análise , Técnicas Biossensoriais/métodos , /diagnóstico , Testes Imediatos , Saliva/virologia , Adulto , Feminino , Humanos , Masculino , Fosfoproteínas/análise , Técnica de Seleção de Aptâmeros , Sensibilidade e Especificidade , Glicoproteína da Espícula de Coronavírus/análise
20.
J Clin Virol ; 137: 104782, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33711691

RESUMO

BACKGROUND: SARS-CoV-2 molecular diagnostics is facing material shortages and long turnaround times due to exponential increase of testing demand. OBJECTIVE: We evaluated the analytic performance and handling of four rapid Antigen Point of Care Tests (AgPOCTs) I-IV (Distributors: (I) Roche, (II) Abbott, (III) MEDsan and (IV) Siemens). METHODS: 100 RT-PCR negative and 84 RT-PCR positive oropharyngeal swabs were prospectively collected and used to determine performance and accuracy of these AgPOCTs. Handling was evaluated by 10 healthcare workers/users through a questionnaire. RESULTS: The median duration from symptom onset to sampling was 6 days (IQR 2-12 days). The overall respective sensitivity were 49.4 % (CI95 %: 38.9-59.9), 44.6 % (CI95 %: 34.3-55.3), 45.8 % (CI95 %: 35.5-56.5) and 54.9 % (CI95 %: 43.4-65.9) for tests I, II, III and IV, respectively. In the high viral load subgroup (containing >106 copies of SARS-CoV-2 /swab, n = 26), AgPOCTs reached sensitivities of 92.3 % or more (range 92.3 %-100 %). Specificity was 100 % for tests I, II (CI95 %: 96.3-100 for both tests) and IV (CI95 %: 96.3-100) and 97 % (CI95 %: 91.5-98.9) for test III. Regarding handling, test I obtained the overall highest scores, while test II was considered to have the most convenient components. Of note, users considered all assays, with the exception of test I, to pose a significant risk for contamination by drips or spills. DISCUSSION: Besides some differences in sensitivity and handling, all four AgPOCTs showed acceptable performance in high viral load samples. However, due to the significantly lower sensitivity compared to RT-qPCR, a careful consideration of pro and cons of AgPOCT has to be taken into account before clinical implementation.


Assuntos
Antígenos Virais/análise , /métodos , /isolamento & purificação , /imunologia , Humanos , Nasofaringe/virologia , Orofaringe/virologia , Testes Imediatos , /imunologia , Sensibilidade e Especificidade , Testes Sorológicos/métodos , Manejo de Espécimes/métodos , Carga Viral
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