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1.
J Infect Dev Ctries ; 16(3): 418-421, 2022 Mar 31.
Article in English | MEDLINE | ID: covidwho-1786131

ABSTRACT

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.


Subject(s)
COVID-19 , SARS-CoV-2 , Antigens, Viral/analysis , COVID-19/diagnosis , COVID-19 Serological Testing , Hospitals , Humans , SARS-CoV-2/genetics , Sensitivity and Specificity
2.
Mikrochim Acta ; 189(3): 128, 2022 03 02.
Article in English | MEDLINE | ID: covidwho-1718736

ABSTRACT

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.


Subject(s)
COVID-19 Testing/methods , Nucleic Acids/chemistry , SARS-CoV-2/metabolism , Antibodies, Viral/blood , Antigens, Viral/analysis , COVID-19/diagnosis , COVID-19/virology , Humans , Point-of-Care Systems , RNA, Viral/analysis , RNA, Viral/metabolism , SARS-CoV-2/genetics , SARS-CoV-2/isolation & purification
3.
Euro Surveill ; 27(8)2022 02.
Article in English | MEDLINE | ID: covidwho-1714940

ABSTRACT

BackgroundSARS-CoV-2 RT-PCR assays are more sensitive than rapid antigen detection assays (RDT) and can detect viral RNA even after an individual is no longer infectious. RDT can reduce the time to test and the results might better correlate with infectiousness.AimWe assessed the ability of five RDT to identify infectious COVID-19 cases and systematically recorded the turnaround time of RT-PCR testing.MethodsSensitivity of RDT was determined using a serially diluted SARS-CoV-2 stock with known viral RNA concentration. The probability of detecting infectious virus at a given viral load was calculated using logistic regression of viral RNA concentration and matched culture results of 78 specimens from randomly selected non-hospitalised cases. The probability of each RDT to detect infectious cases was calculated as the sum of the projected probabilities for viral isolation success for every viral RNA load found at the time of diagnosis in 1,739 confirmed non-hospitalised COVID-19 cases.ResultsThe distribution of quantification cycle values and estimated RNA loads for patients reporting to drive-through testing was skewed to high RNA loads. With the most sensitive RDT (Abbott and SD Biosensor), 97.30% (range: 88.65-99.77) of infectious individuals would be detected. This decreased to 92.73% (range: 60.30-99.77) for Coris BioConcept and GenBody, and 75.53% (range: 17.55-99.77) for RapiGEN. Only 32.9% of RT-PCR results were available on the same day as specimen collection.ConclusionThe most sensitive RDT detected infectious COVID-19 cases with high sensitivity and may considerably improve containment through more rapid isolation and contact tracing.


Subject(s)
COVID-19 , SARS-CoV-2 , Antigens, Viral/analysis , COVID-19/diagnosis , COVID-19/epidemiology , COVID-19 Testing , Humans , Netherlands/epidemiology , SARS-CoV-2/genetics , Sensitivity and Specificity
4.
BMC Med ; 20(1): 97, 2022 02 24.
Article in English | MEDLINE | ID: covidwho-1700066

ABSTRACT

BACKGROUND: Rapid antigen diagnostic tests (Ag-RDTs) are the most widely used point-of-care tests for detecting SARS-CoV-2 infection. Since the accuracy may have altered by changes in SARS-CoV-2 epidemiology, indications for testing, sampling and testing procedures, and roll-out of COVID-19 vaccination, we evaluated the performance of three prevailing SARS-CoV-2 Ag-RDTs. METHODS: In this cross-sectional study, we consecutively enrolled individuals aged >16 years presenting for SARS-CoV-2 testing at three Dutch public health service COVID-19 test sites. In the first phase, participants underwent either BD-Veritor System (Becton Dickinson), PanBio (Abbott), or SD-Biosensor (Roche Diagnostics) testing with routine sampling procedures. In a subsequent phase, participants underwent SD-Biosensor testing with a less invasive sampling method (combined oropharyngeal-nasal [OP-N] swab). Diagnostic accuracies were assessed against molecular testing. RESULTS: Six thousand nine hundred fifty-five of 7005 participants (99%) with results from both an Ag-RDT and a molecular reference test were analysed. SARS-CoV-2 prevalence and overall sensitivities were 13% (188/1441) and 69% (129/188, 95% CI 62-75) for BD-Veritor, 8% (173/2056) and 69% (119/173, 61-76) for PanBio, and 12% (215/1769) and 74% (160/215, 68-80) for SD-Biosensor with routine sampling and 10% (164/1689) and 75% (123/164, 68-81) for SD-Biosensor with OP-N sampling. In those symptomatic or asymptomatic at sampling, sensitivities were 72-83% and 54-56%, respectively. Above a viral load cut-off (≥5.2 log10 SARS-CoV-2 E-gene copies/mL), sensitivities were 86% (125/146, 79-91) for BD-Veritor, 89% (108/121, 82-94) for PanBio, and 88% (160/182, 82-92) for SD-Biosensor with routine sampling and 84% (118/141, 77-89) with OP-N sampling. Specificities were >99% for all tests in most analyses. Sixty-one per cent of false-negative Ag-RDT participants returned for testing within 14 days (median: 3 days, interquartile range 3) of whom 90% tested positive. CONCLUSIONS: Overall sensitivities of three SARS-CoV-2 Ag-RDTs were 69-75%, increasing to ≥86% above a viral load cut-off. The decreased sensitivity among asymptomatic participants and high positivity rate during follow-up in false-negative Ag-RDT participants emphasise the need for education of the public about the importance of re-testing after an initial negative Ag-RDT should symptoms develop. For SD-Biosensor, the diagnostic accuracy with OP-N and deep nasopharyngeal sampling was similar; adopting the more convenient sampling method might reduce the threshold for professional testing.


Subject(s)
COVID-19 , Adolescent , Antigens, Viral/analysis , COVID-19 Testing , COVID-19 Vaccines , Cross-Sectional Studies , Humans , SARS-CoV-2 , Sensitivity and Specificity
5.
J Chin Med Assoc ; 84(11): 1028-1037, 2021 11 01.
Article in English | MEDLINE | ID: covidwho-1699812

ABSTRACT

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic continues to affect countries worldwide. To inhibit the transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), testing of patients, contact tracing, and quarantine of their close contacts have been used as major nonpharmaceutical interventions. The advantages of antigen tests, such as low cost and rapid turnaround, may allow for the rapid identification of larger numbers of infectious persons. This meta-analysis aimed to evaluate the diagnostic accuracy of antigen tests for SARS-CoV-2. METHODS: We searched PubMed, Embase, Cochrane Library, and Biomed Central databases from inception to January 2, 2021. Studies evaluating the diagnostic accuracy of antigen testing for SARS-CoV-2 with reference standards were included. We included studies that provided sufficient data to construct a 2 × 2 table on a per-patient basis. Only articles in English were reviewed. Summary sensitivity and specificity for antigen tests were generated using a random-effects model. RESULTS: Fourteen studies with 8624 participants were included. The meta-analysis for antigen testing generated a pooled sensitivity of 79% (95% CI, 66%-88%; 14 studies, 8624 patients) and a pooled specificity of 100% (95% CI, 99%-100%; 14 studies, 8624 patients). The subgroup analysis of studies that reported specimen collection within 7 days after symptom onset showed a pooled sensitivity of 95% (95% CI, 78%-99%; four studies, 1342 patients) and pooled specificity of 100% (95% CI, 97%-100%; four studies, 1342 patients). Regarding the applicability, the patient selection, index tests, and reference standards of studies in our meta-analysis matched the review title. CONCLUSION: Antigen tests have moderate sensitivity and high specificity for the detection of SARS-CoV-2. Antigen tests might have a higher sensitivity in detecting SARS-CoV-2 within 7 days after symptom onset. Based on our findings, antigen testing might be an effective method for identifying contagious individuals to block SARS-CoV-2 transmission.


Subject(s)
Antigens, Viral/analysis , COVID-19 Serological Testing/methods , COVID-19/diagnosis , SARS-CoV-2/immunology , Humans , Sensitivity and Specificity
6.
ACS Appl Mater Interfaces ; 14(8): 10844-10855, 2022 Mar 02.
Article in English | MEDLINE | ID: covidwho-1692677

ABSTRACT

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·mm2 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.


Subject(s)
Antigens, Viral/analysis , COVID-19/diagnosis , Coronavirus Nucleocapsid Proteins/analysis , Graphite/chemistry , Nanocomposites/chemistry , Zinc Oxide/chemistry , Antibodies, Immobilized/immunology , Antigens, Viral/immunology , Biosensing Techniques/instrumentation , Biosensing Techniques/methods , Coronavirus Nucleocapsid Proteins/immunology , Electrochemical Techniques/instrumentation , Electrochemical Techniques/methods , Electrodes , Humans , Immunoassay/instrumentation , Immunoassay/methods , Limit of Detection , Phosphoproteins/analysis , Phosphoproteins/immunology , Proof of Concept Study , SARS-CoV-2/chemistry
7.
J Clin Virol ; 148: 105119, 2022 03.
Article in English | MEDLINE | ID: covidwho-1693295

ABSTRACT

BACKGROUND: Rapid antigen detection tests (RADT) are commonly used as SARS-CoV-2 diagnostic tests both by medical professionals and laypeople. However, the performance of RADT in vaccinated individuals has not been fully investigated. OBJECTIVES: RT-qPCR and rapid antigen detection testing were performed to evaluate the performance of the Standard Q COVID-19 Ag Test in detecting SARS-CoV-2 breakthrough infections in vaccinated individuals. STUDY DESIGN: Two swab specimens, one for RT-qPCR and one for RADT, were collected from vaccinated individuals in an outpatient clinic. For comparison of RADT performance in vaccinated and unvaccinated individuals, a dataset already published by this group was used as reference. RESULTS: During the delta wave, a total of 696 samples were tested with both RT-qPCR and RADT that included 692 (99.4%) samples from vaccinated individuals. Of these, 76 (11.0%) samples were detected SARS-CoV-2 positive by RT-qPCR and 45 (6.5%) samples by the Standard Q COVID-19 Ag test. Stratified by Ct values, sensitivity of the RADT was 100.0%, 94.4% and 81.1% for Ct ≤ 20 (n=18), Ct ≤ 25 (n=36) and Ct ≤ 30 (n=53), respectively. Samples with Ct values ≥ 30 (n=23) were not detected. Overall RADT specificity was 99.7% and symptom status did not affect RADT performance. Notably, RADT detected 4 out of 4 samples of probable Omicron variant infection based on single nucleotide polymorphism analysis. CONCLUSION: Our results show that RADT testing remains a valuable tool in detecting breakthrough infections with high viral RNA loads.


Subject(s)
Antigens, Viral/analysis , COVID-19 Serological Testing/standards , COVID-19 , Vaccination , COVID-19/diagnosis , Humans , Reproducibility of Results , SARS-CoV-2 , Sensitivity and Specificity
8.
Microbiol Spectr ; 10(1): e0245521, 2022 02 23.
Article in English | MEDLINE | ID: covidwho-1691400

ABSTRACT

Containment measures employed during the COVID-19 pandemic included prompt recognition of cases, isolation, and contact tracing. Bilateral nasal (NA) swabs applied to a commercial antigen-based rapid diagnostic test (Ag-RDT) offer a simpler and more comfortable alternative to nasopharyngeal (NP) collection; however, little is known about the sensitivity of this method in an asymptomatic population. Participants in community-based asymptomatic testing sites were screened for SARS-CoV-2 using an Ag-RDT with NP sampling. Positive individuals returned for confirmatory molecular testing and consented to repeating the Ag-RDT using a bilateral NA swab for comparison. Residual test buffer (RTB) from Ag-RDTs was subjected to real-time reverse transcription-PCR (RT-PCR). Of 123,617 asymptomatic individuals, 197 NP Ag-RDT-positive participants were included, with 175 confirmed positive by RT-PCR. Of these cases, 154 were identified from the NA swab collection with Ag-RDT, with a sensitivity of 88.0% compared to the NP swab collection. Stratifying results by RT-PCR cycle threshold demonstrated that sensitivity of the nasal collection method varied based on the cycle threshold (CT) value of the paired RT-PCR sample. RT-PCR testing on the RTB from the Ag-RDT using NP and NA swab collections resulted in 100.0% and 98.7% sensitivity, respectively. NA swabs provide an adequate alternative to NP swab collection for use with Ag-RDT, with the recognition that the test is most sensitive in specimens with high viral loads. With the high sensitivity of RT-PCR testing on RTB from Ag-RDT, a more streamlined approach to confirmatory testing is possible without recollection or use of paired collections strategies. IMPORTANCE Nasal swabbing for SARS-CoV-2 (COVID-19) comes with many benefits but is slightly less sensitive than traditional nasopharyngeal swabbing; however, confirmatory lab-based testing could be performed directly from the residual buffer from either sample type.


Subject(s)
Antigens, Viral/analysis , COVID-19/virology , Carrier State/virology , Nasopharynx/virology , Nose/virology , SARS-CoV-2/isolation & purification , Specimen Handling/methods , Antigens, Viral/genetics , Antigens, Viral/immunology , Asymptomatic Diseases , COVID-19/diagnosis , COVID-19 Serological Testing , Humans , Reverse Transcriptase Polymerase Chain Reaction , SARS-CoV-2/classification , SARS-CoV-2/genetics , SARS-CoV-2/immunology , Sensitivity and Specificity
9.
Microbiol Spectr ; 10(1): e0202921, 2022 02 23.
Article in English | MEDLINE | ID: covidwho-1673365

ABSTRACT

The objective of our study was to evaluate the sensitivity and specificity of rapid antigen detection tests versus those of reverse transcriptase PCR (RT-PCR) using oral, anterior nasal, and nasopharyngeal swabs. The underlying prospective, diagnostic case-control-type accuracy study included 87 hospitalized and nonhospitalized participants in a positive and a negative sample cohort between 16 March and 14 May 2021 in two hospitals in Vienna. SARS-CoV-2 infection status was confirmed by RT-PCR. Participants self-performed one oral and one anterior nasal swab for the rapid antigen test, immediately followed by two nasopharyngeal swabs for the rapid antigen test and RT-PCR by the investigator. Test results were read after 15 min, and participants completed a questionnaire in the meantime. Test parameters were calculated based on the evaluation of 87 participants. The overall sensitivity of rapid antigen detection tests versus that of RT-PCR with oral, anterior nasal, and nasopharyngeal samples was 18.18% (95% confidence interval [CI] 8.19% to 32.71%), 63.04% (95% CI 47.55% to 76.79%), and 73.33% (95% CI 58.06% to 85.4%), respectively. All sampling methods had a test specificity of 100% regardless of the cycle threshold (CT) value. Rapid antigen detection tests using self-collected anterior nasal swabs proved to be as sensitive as and more tolerable than professionally collected nasopharyngeal swabs for CT values up to 30 determined by RT-PCR. This finding illustrates the reliability of tests obtained by adequate self-collected anterior nasal specimen. Sensitivity was dependent upon the CT value for each sampling method. While the main advantage of rapid antigen detection tests is the immediate availability of results, PCR should be preferred in crucial settings wherever possible. IMPORTANCE Rapid antigen detection devices for SARS-CoV-2 represent a valuable tool for monitoring the spread of infection. However, the reliability of the tests depends largely on the test performance and the respective sampling method. Nasopharyngeal swabs mark the gold standard for sample collection in suspected respiratory tract infections but are unsuitable for widespread application, as they must be performed by medically trained personnel. With the underlying study, the head-to-head test performance and the usability of self-collected samples for SARS-CoV-2 detection using rapid antigen detection devices were evaluated. The results confirm similar sensitivity of self-collected anterior nasal swabs to that of professionally collected nasopharyngeal swabs for patients with a CT of < 30 determined by RT-PCR.


Subject(s)
COVID-19 Serological Testing/methods , COVID-19/diagnosis , Mouth/virology , Nasopharynx/virology , Nose/virology , SARS-CoV-2/isolation & purification , Adult , Aged , Aged, 80 and over , Antigens, Viral/analysis , COVID-19/virology , COVID-19 Nucleic Acid Testing , Female , Humans , Male , Middle Aged , Polymerase Chain Reaction , Prospective Studies , SARS-CoV-2/genetics , SARS-CoV-2/immunology , Sensitivity and Specificity , Young Adult
10.
Microbiol Spectr ; 10(1): e0122021, 2022 02 23.
Article in English | MEDLINE | ID: covidwho-1636464

ABSTRACT

Accurate tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been critical in efforts to control its spread. The accuracy of tests for SARS-CoV-2 has been assessed numerous times, usually in reference to a gold standard diagnosis. One major disadvantage of that approach is the possibility of error due to inaccuracy of the gold standard, which is especially problematic for evaluating testing in a real-world surveillance context. We used an alternative approach known as Bayesian latent class modeling (BLCM), which circumvents the need to designate a gold standard by simultaneously estimating the accuracy of multiple tests. We applied this technique to a collection of 1,716 tests of three types applied to 853 individuals on a university campus during a 1-week period in October 2020. We found that reverse transcriptase PCR (RT-PCR) testing of saliva samples performed at a campus facility had higher sensitivity (median, 92.3%; 95% credible interval [CrI], 73.2 to 99.6%) than RT-PCR testing of nasal samples performed at a commercial facility (median, 85.9%; 95% CrI, 54.7 to 99.4%). The reverse was true for specificity, although the specificity of saliva testing was still very high (median, 99.3%; 95% CrI, 98.3 to 99.9%). An antigen test was less sensitive and specific than both of the RT-PCR tests, although the sample sizes with this test were small and the statistical uncertainty was high. These results suggest that RT-PCR testing of saliva samples at a campus facility can be an effective basis for surveillance screening to prevent SARS-CoV-2 transmission in a university setting. IMPORTANCE Testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been vitally important during the COVID-19 pandemic. There are a variety of methods for testing for this virus, and it is important to understand their accuracy in choosing which one might be best suited for a given application. To estimate the accuracy of three different testing methods, we used a data set collected at a university that involved testing the same samples with multiple tests. Unlike most other estimates of test accuracy, we did not assume that one test was perfect but instead allowed for some degree of inaccuracy in all testing methods. We found that molecular tests performed on saliva samples at a university facility were similarly accurate as molecular tests performed on nasal samples at a commercial facility. An antigen test appeared somewhat less accurate than the molecular tests, but there was high uncertainty about that.


Subject(s)
Antigens, Viral/analysis , COVID-19/diagnosis , SARS Virus/immunology , SARS-CoV-2/isolation & purification , Saliva/virology , Antigens, Viral/blood , Bayes Theorem , COVID-19/epidemiology , COVID-19/virology , COVID-19 Nucleic Acid Testing , Humans , Predictive Value of Tests , Prevalence , Reproducibility of Results , SARS-CoV-2/immunology , Sensitivity and Specificity , Universities , Young Adult
11.
Diagn Microbiol Infect Dis ; 102(4): 115635, 2022 Apr.
Article in English | MEDLINE | ID: covidwho-1631995

ABSTRACT

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.


Subject(s)
COVID-19 , Antigens, Viral/analysis , COVID-19/diagnosis , Emergency Service, Hospital , Humans , SARS-CoV-2 , Sensitivity and Specificity
12.
Int J Infect Dis ; 116: 358-364, 2022 Mar.
Article in English | MEDLINE | ID: covidwho-1620728

ABSTRACT

BACKGROUND: One strategy for reducing spread of COVID-19 is to contain the infection with broad screening, isolating infected individuals, and tracing contacts. This strategy requires widely available, reliable SARS-CoV-2 testing. To increase testing, rapid antigen detection tests (RADTs) were developed for self-sampling, self-testing, and self-interpretation. This study examined diagnostic performance, user acceptability, and safety of nasal self-RADTs compared with polymerase chain reaction (PCR) testing. METHODS: Self-RADT kits were distributed at a public COVID-19 test center in Aarhus, Denmark or delivered to participants. Participants reported test results and test preferences. During enrollment, participants reported occurrence and duration of symptoms consistent with COVID-19. Sensitivity and specificity of self-RADT, relative to oropharyngeal PCR testing, were calculated. RESULTS: Among 827 participants, 102 showed positive PCR test results. Sensitivities of the self-RADTs were 65.7% (95% confidence interval [CI]: 49.2-79.2; DNA Diagnostic) and 62.1% (95% CI: 50.1-72.9; Hangzhou), and specificities were 100% (95% CI: 99.0-100; DNA Diagnostic) and 100% (95% CI: 98.9-100; Hangzhou). The sensitivities of both self-RADTs appeared higher in symptomatic participants than in asymptomatic participants. Two of every 3 participants preferred self-RADT over PCR test. CONCLUSION: Self-performed RADTs were reliable, user-acceptable, and safe among laypeople as a supplement to professionally collected oropharyngeal PCR testing.


Subject(s)
COVID-19 , SARS-CoV-2 , Antigens, Viral/analysis , COVID-19/diagnosis , COVID-19 Testing , Humans , Immunologic Tests , Sensitivity and Specificity
13.
Biosens Bioelectron ; 202: 113971, 2022 Apr 15.
Article in English | MEDLINE | ID: covidwho-1611632

ABSTRACT

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.


Subject(s)
Antigens, Viral/analysis , Biosensing Techniques , COVID-19 , Metal Nanoparticles , Biosensing Techniques/methods , Ebolavirus , Glycoproteins , Gold/chemistry , Humans , Metal Nanoparticles/chemistry , SARS-CoV-2 , Spike Glycoprotein, Coronavirus , Viral Proteins
14.
J Epidemiol Glob Health ; 12(1): 13-15, 2022 03.
Article in English | MEDLINE | ID: covidwho-1608872

ABSTRACT

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.


Subject(s)
COVID-19 Nucleic Acid Testing , COVID-19 Testing/methods , COVID-19 , Mass Screening , Antigens, Viral/analysis , COVID-19/diagnosis , COVID-19/prevention & control , Humans , Pandemics/prevention & control , SARS-CoV-2 , Sensitivity and Specificity
15.
Medicine (Baltimore) ; 100(51): e28398, 2021 Dec 23.
Article in English | MEDLINE | ID: covidwho-1598050

ABSTRACT

ABSTRACT: Hospital-wide screenings for coronavirus disease (COVID-19) are important to identify healthcare workers at risk of exposure. However, the currently available diagnostic tests are expensive or only identify past infection. Therefore, this single-center observational study aimed to assess the positivity rate of hospital-wide antigen screening tests for COVID-19 and evaluate clinical factors associated with antigen positivity during a COVID-19 institutional outbreak in Sapporo, Japan.We analyzed the data of 1615 employees who underwent salivary or nasal swab antigen tests on November 18, 2020, to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Laboratory confirmation using reverse transcriptase polymerase chain reaction was performed for those with positive viral serology. The demographic characteristics, job titles, and risk of contact with COVID-19 patients were compared between employees with and without COVID-19.A total of 19 employees (1.2%) tested positive for the SARS-CoV-2 antigen. The positivity rate was high among rehabilitation therapists (2.1%) and employees in the low-risk contact group (6.1%). Although there was no association between the job titles and the seropositivity rate, those in the low-risk contact group had an increased risk of testing positive for the viral antigen (odds ratio, 8.67; 95% confidence interval, 3.30-22.8).The antigen positivity rate was low during the hospital outbreak, suggesting that risk assessment of exposure to COVID-19 patients may provide more useful information than using job titles to identify infected health care providers.


Subject(s)
COVID-19 , Health Personnel , Antigens, Viral/analysis , COVID-19/diagnosis , COVID-19 Testing , Diagnostic Tests, Routine , Hospitals , Humans , Japan/epidemiology , SARS-CoV-2 , Tertiary Care Centers
16.
Diagn Microbiol Infect Dis ; 102(2): 115591, 2022 Feb.
Article in English | MEDLINE | ID: covidwho-1596631

ABSTRACT

Testing for SARS-CoV-2 in resource-poor settings remains a considerable challenge. Gold standard nucleic acid tests are expensive and depend on availability of expensive equipment and highly trained laboratory staff. More affordable and easier rapid antigen tests are an attractive alternative. This study assessed field performance of such a test in western Kenya. We conducted a prospective multi-facility field evaluation study of NowCheck COVID-19 Ag-RDT compared to gold standard PCR. Two pairs of oropharyngeal and nasopharyngeal swabs were collected for comparative analysis. With 997 enrolled participants the Ag-RDT had a sensitivity 71.5% (63.2-78.6) and specificity of 97.5% (96.2-98.5) at cycle threshold value <40. Highest sensitivity of 87.7% (77.2-94.5) was observed in samples with cycle threshold values ≤30. NowCheck COVID-19 Ag-RDT performed well at multiple healthcare facilities in an African field setting. Operational specificity and sensitivity were close to WHO-recommended thresholds.


Subject(s)
Antigens, Viral/analysis , COVID-19 Serological Testing/methods , COVID-19/diagnosis , Nasopharynx/virology , Oropharynx/virology , SARS-CoV-2/immunology , Adult , Child , Cross-Sectional Studies , Developing Countries , Diagnostic Tests, Routine , Female , Humans , Kenya , Male , Middle Aged , Point-of-Care Testing , Prospective Studies , Sensitivity and Specificity
17.
J Clin Lab Anal ; 36(2): e24203, 2022 Feb.
Article in English | MEDLINE | ID: covidwho-1589068

ABSTRACT

BACKGROUND: Globally, real-time reverse transcription-polymerase chain reaction (rRT-PCR) is the reference detection technique for SARS-CoV-2, which is expensive, time consuming, and requires trained laboratory personnel. Thus, a cost-effective, rapid antigen test is urgently needed. This study evaluated the performance of the rapid antigen tests (RATs) for SARS-CoV-2 compared with rRT-PCR, considering different influencing factors. METHODS: We enrolled a total of 214 symptomatic individuals with known COVID-19 status using rRT-PCR. We collected and tested paired nasopharyngeal (NP) and nasal swab (NS) specimens (collected from same individual) using rRT-PCR and RATs (InTec and SD Biosensor). We assessed the performance of RATs considering specimen types, viral load, the onset of symptoms, and presenting symptoms. RESULTS: We included 214 paired specimens (112 NP and 100 NS SARS-CoV-2 rRT-PCR positive) to the analysis. For NP specimens, the average sensitivity, specificity, and accuracy of the RATs were 87.5%, 98.6%, and 92.8%, respectively, when compared with rRT-PCR. While for NS, the overall kit performance was slightly lower than that of NP (sensitivity 79.0%, specificity 96.1%, and accuracy 88.3%). We observed a progressive decline in the performance of RATs with increased Ct values (decreased viral load). Moreover, the RAT sensitivity using NP specimens decreased over the time of the onset of symptoms. CONCLUSION: The RATs showed strong performance under field conditions and fulfilled the minimum performance limit for rapid antigen detection kits recommended by World Health Organization. The best performance of the RATs can be achieved within the first week of the onset of symptoms with high viral load.


Subject(s)
Antigens, Viral/analysis , COVID-19 Serological Testing , COVID-19/diagnosis , Adolescent , Adult , Aged , Aged, 80 and over , COVID-19 Serological Testing/methods , COVID-19 Serological Testing/standards , COVID-19 Serological Testing/statistics & numerical data , Child , Child, Preschool , Female , Humans , Infant , Male , Middle Aged , Nasopharynx/virology , Reagent Kits, Diagnostic/virology , SARS-CoV-2/isolation & purification , Sensitivity and Specificity , Time Factors , Viral Load , Young Adult
18.
Bioengineered ; 13(1): 876-883, 2022 01.
Article in English | MEDLINE | ID: covidwho-1585254

ABSTRACT

This research has developed a method for rapid detection of SARS-CoV-2 N protein on a paper-based microfluidic chip. The chitosan-glutaraldehyde cross-linking method is used to fix the coated antibody, and the sandwich enzyme-linked immunosorbent method is used to achieve the specific detection of the target antigen. The system studied the influence of coating antibody concentration and enzyme-labeled antibody concentration on target antigen detection. According to the average gray value measured under different N protein concentrations, the standard curve of the method was established and the sensitivity was tested, and its linear regression was obtained. The equation is y = 9.8286x+137.6, R2 = 0.9772 > 0.90, which shows a high degree of fit. When the concentration of coating antibody and enzyme-labeled antibody were 1 µg/mL and 2 µg/mL, P > 0.05, the difference was not statistically significant, so the lower concentration of 1 µg/mL was chosen as the coating antibody concentration. The results show that the minimum concentration of N protein that can be detected by this method is 8 µg/mL, and the minimum concentration of coating antibody and enzyme-labeled antibody is 1 µg/mL, which has the characteristics of high sensitivity and good repeatability.


Subject(s)
Antigens, Viral/analysis , COVID-19 Serological Testing/instrumentation , Coronavirus Nucleocapsid Proteins/analysis , Coronavirus Nucleocapsid Proteins/immunology , Lab-On-A-Chip Devices , SARS-CoV-2/chemistry , SARS-CoV-2/immunology , Antibodies, Viral/immunology , Biomedical Engineering , COVID-19/diagnosis , COVID-19/immunology , COVID-19/virology , COVID-19 Serological Testing/methods , COVID-19 Serological Testing/standards , Coronavirus Nucleocapsid Proteins/standards , Enzyme-Linked Immunosorbent Assay/instrumentation , Enzyme-Linked Immunosorbent Assay/methods , Enzyme-Linked Immunosorbent Assay/standards , Humans , Lab-On-A-Chip Devices/standards , Lab-On-A-Chip Devices/statistics & numerical data , Microchip Analytical Procedures/methods , Microchip Analytical Procedures/standards , Microchip Analytical Procedures/statistics & numerical data , Paper , Phosphoproteins/analysis , Phosphoproteins/immunology , Phosphoproteins/standards
19.
Clin Chem ; 67(11): 1545-1553, 2021 11 01.
Article in English | MEDLINE | ID: covidwho-1561050

ABSTRACT

BACKGROUND: We evaluated the analytical sensitivity and specificity of 4 rapid antigen diagnostic tests (Ag RDTs) for severe acute respiratory syndrome coronavirus 2, using reverse transcription quantitative PCR (RT-qPCR) as the reference method and further characterizing samples using droplet digital quantitative PCR (ddPCR) and a mass spectrometric antigen test. METHODS: Three hundred fifty (150 negative and 200 RT-qPCR positive) residual PBS samples were tested for antigen using the BD Veritor lateral flow (LF), ACON LF, ACON fluorescence immunoassay (FIA), and LumiraDx FIA. ddPCR was performed on RT-qPCR-positive samples to quantitate the viral load in copies/mL applied to each Ag RDT. Mass spectrometric antigen testing was performed on PBS samples to obtain a set of RT-qPCR-positive, antigen-positive samples for further analysis. RESULTS: All Ag RDTs had nearly 100% specificity compared to RT-qPCR. Overall analytical sensitivity varied from 66.5% to 88.3%. All methods detected antigen in samples with viral load >1 500 000 copies/mL RNA, and detected ≥75% of samples with viral load of 500 000 to 1 500 000 copies/mL. The BD Veritor LF detected only 25% of samples with viral load between 50 000 to 500 000 copies/mL, compared to 75% for the ACON LF device and >80% for LumiraDx and ACON FIA. The ACON FIA detected significantly more samples with viral load <50 000 copies/mL compared to the BD Veritor. Among samples with detectable antigen and viral load <50 000 copies/mL, sensitivity of the Ag RDT varied between 13.0% (BD Veritor) and 78.3% (ACON FIA). CONCLUSIONS: Ag RDTs differ significantly in analytical sensitivity, particularly at viral load <500 000 copies/mL.


Subject(s)
Antigens, Viral/analysis , COVID-19 Testing/methods , Point-of-Care Testing , Humans , Mass Spectrometry , Real-Time Polymerase Chain Reaction/methods , SARS-CoV-2/immunology , Sensitivity and Specificity , Viral Load
20.
Pan Afr Med J ; 39: 228, 2021.
Article in French | MEDLINE | ID: covidwho-1551883

ABSTRACT

INTRODUCTION: the COVID-19 pandemic causes biological diagnostic problems that remain relevant in low-income countries in general and in Cameroon in particular. Rapids tests that reliably detect SARS-CoV-2 virus antigen present themselves as an important alternative in several contexts. The objective of our study was to evaluate the diagnostic performance of two rapid diagnostic tests BIOSYNEX® COVID-19 Ag BSS and BIOSYNEX® COVID-19 Ag + BSS, compared to each other and to the AmpliQuick® SARS-CoV-2 PCR test. METHODS: a cross-sectional and comparative study was carried out from April 27 to May 29, 2021 in the city of Douala in Cameroon. The samples consisted of nasopharyngeal swabs received at the molecular biology laboratory of the Douala Gyneco-obstetric and pediatric hospital, whatever their origin. The socio-demographic parameters (age, profession, football players, travelers, others), marital status, nationality), comorbidity and known status of COVID-19, were recorded on the collection sites. The main collection sites were the Deïdo Health District and the Douala Gyneco-Obstetric and Pediatric Hospital. We performed the diagnosis of COVID-19 using the rapid diagnostic test (RDT) BIOSYNEX® COVID-19 Ag BSS and RDT BIOSYNEX® COVID-19 Ag + BSS compared to each other and to the AmpliQuick® SARS-CoV-2 polymerase chain reaction (PCR) test on each sample. Statistical analysis of the data was performed using Microsoft Excel and SPSS version 17 software. To determine the sensitivity of the two RDTs, the Bayesian latent class model was performed on the median with a 95% confidence interval with p<0.05 as the significant level. An ethical clearance was sought and obtained from the University of Douala Institutional Ethics Committee. RESULTS: a total of 1813 participants were included in our study, with a predominance of men (1226, 68.68 %) and the most represented age group was that of 31 to 40 years (568, 31.33 %). Most of the participants were married (888, 53.46%) and only a few had a known COVID-19 status (75, 5.47%). The two rapid tests on our study population show much closed COVID-19 prevalence values, respectively 2.03 for BIOSYNEX® COVID-19 Ag BSS and 2.17 for BIOSYNEX® COVID-19 Ag + BSS. RDT BIOSYNEX® COVID-19 Ag + BSS showed higher sensitivity 94.1% vs. 87.5% for RDT BIOSYNEX® COVID-19 Ag BSS with almost identical specificity 98.9% for RDT BIOSYNEX® COVID-19 Ag + BSS vs. 98.7% for RDT BIOSYNEX® COVID-19 Ag BSS compared to AmpliQuick® SARS-CoV-2. BIOSYNEX® COVID-19 Ag + BSS RDT showed a negative predictive value of 99.9% compared to BIOSYNEX® COVID-19 Ag BSS RDT. There is a 99.9% agreement between the RDT BIOSYNEX® COVID-19 Ag BSS and the RDT BIOSYNEX® COVID-19 Ag + BSS. Conclusion: the RDT BIOSYNEX®COVID-19 Ag + BSS and RDT BIOSYNEX® COVID-19 Ag BSS can be used for the diagnosis of SARS-CoV-2 and can have an important contribution in the context of mass screenings and screening in remote areas.


Subject(s)
Antigens, Viral/analysis , COVID-19 Testing/methods , COVID-19/diagnosis , Polymerase Chain Reaction/methods , Adolescent , Adult , Aged , Cameroon , Child , Child, Preschool , Cross-Sectional Studies , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Predictive Value of Tests , SARS-CoV-2 , Sensitivity and Specificity , Young Adult
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