Covid-19 antigen testing: better than we know? A test accuracy study.
Ontology highlight
ABSTRACT: Background
Antigen testing for SARS-CoV-2 is considered to be less sensitive than the standard reference method - real-time PCR (RT-PCR). It has been suggested that many patients with positive RT-PCR 'missed' by antigen testing might be non-infectious.Methods
In a real-world high-throughput setting for asymptomatic or mildly symptomatic patients, 494 patients were tested using RT-PCR as well as a single lateral flow antigen test (Ecotest, AssureTech, China). Where the results differed, virus viability was evaluated by cell culture. The test parameters were calculated with RT-PCR and RT-PCR adjusted on viability as reference standards.Results
The overall sensitivity of the used antigen test related to the RT-PCR only was 76.2%, specificity was 97.3%. However, 36 out of 39 patients 'missed' by the antigen test contained no viable virus. After adjusting on that, the sensitivity grew to 97.7% and, more importantly for disease control purposes, the negative predictive value reached 99.2%.Conclusions
We propose that viability testing should be always performed when evaluating a new antigen test. A well-chosen and validated antigen test provides excellent results in identifying patients who are shedding viable virus (although some caveats still remain) in the real-world high-throughput setting of asymptomatic or mildly symptomatic individuals.
SUBMITTER: Homza M
PROVIDER: S-EPMC8127166 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:We test the predictive accuracy of forecasts of the number of COVID-19 fatalities produced by several forecasting teams and collected by the United States Centers for Disease Control and Prevention for the epidemic in the United States. We find three main results. First, at the short horizon (1-week ahead) no forecasting team outperforms a simple time-series benchmark. Second, at longer horizons (3- and 4-week ahead) forecasters are more successful and sometimes outperform the benchmark. Third, one of the best performing forecasts is the Ensemble forecast, that combines all available predictions using uniform weights. In view of these results, collecting a wide range of forecasts and combining them in an ensemble forecast may be a superior approach for health authorities, rather than relying on a small number of forecasts.
| S-EPMC8801780 | biostudies-literature
Project description:AimsMass antigen testing programs have been challenged because of an alleged insufficient specificity, leading to a large number of false positives. The objective of this study is to derive a lower bound of the specificity of the SD Biosensor Standard Q Ag-Test in large scale practical use.MethodsBased on county data from the nationwide tests for SARS-CoV-2 in Slovakia between 31.10.-1.11. 2020 we calculate a lower confidence bound for the specificity. As positive test results were not systematically verified by PCR tests, we base the lower bound on a worst case assumption, assuming all positives to be false positives.Results3,625,332 persons from 79 counties were tested. The lowest positivity rate was observed in the county of Rožňava where 100 out of 34307 (0.29%) tests were positive. This implies a test specificity of at least 99.6% (97.5% one-sided lower confidence bound, adjusted for multiplicity).ConclusionThe obtained lower bound suggests a higher specificity compared to earlier studies in spite of the underlying worst case assumption and the application in a mass testing setting. The actual specificity is expected to exceed 99.6% if the prevalence in the respective regions was non-negligible at the time of testing. To our knowledge, this estimate constitutes the first bound obtained from large scale practical use of an antigen test.
| S-EPMC8320988 | biostudies-literature
Project description:Testing is viewed as a critical aspect of any strategy to tackle epidemics. Much of the dialogue around testing has concentrated on how countries can scale up capacity, but the uncertainty in testing has not received nearly as much attention beyond asking if a test is accurate enough to be used. Even for highly accurate tests, false positives and false negatives will accumulate as mass testing strategies are employed under pressure, and these misdiagnoses could have major implications on the ability of governments to suppress the virus. The present analysis uses a modified SIR model to understand the implication and magnitude of misdiagnosis in the context of ending lockdown measures. The results indicate that increased testing capacity alone will not provide a solution to lockdown measures. The progression of the epidemic and peak infections is shown to depend heavily on test characteristics, test targeting, and prevalence of the infection. Antibody based immunity passports are rejected as a solution to ending lockdown, as they can put the population at risk if poorly targeted. Similarly, mass screening for active viral infection may only be beneficial if it can be sufficiently well targeted, otherwise reliance on this approach for protection of the population can again put them at risk. A well targeted active viral test combined with a slow release rate is a viable strategy for continuous suppression of the virus.
| S-EPMC7577497 | biostudies-literature
Project description:AimsTo validate the diagnostic accuracy of the Augurix SARS-CoV-2 IgM/IgG rapid immunoassay diagnostic test (RDT) for COVID-19.MethodsIn this unmatched 1:1 case-control study, blood samples from 46 real-time RT-PCR-confirmed SARS-CoV-2 hospitalized cases and 45 healthy donors (negative controls) were studied. Diagnostic accuracy of the IgG RDT was assessed against both an in-house recombinant spike-expressing immunofluorescence assay (rIFA), as an established reference method (primary endpoint), and the Euroimmun SARS-CoV-2 IgG enzyme-linked immunosorbent assays (ELISA) (secondary endpoint).ResultsCOVID-19 patients were more likely to be male (61% vs 20%; P = .0001) and older (median 66 vs 47 years old; P < .001) than controls. Whole blood IgG-RDT results showed 86% and 93% overall Kendall concordance with rIFA and IgG ELISA, respectively. IgG RDT performances were similar between plasma and whole blood. Overall, RDT sensitivity was 88% (95% confidence interval [95%CI]: 70-96), specificity 98% (95%CI: 90-100), PPV 97% (95%CI: 80-100) and NPV 94% (95%CI: 84-98). The IgG-RDT carried out from 0 to 6 days, 7 to 14 days and > 14 days after the SARS-CoV-2 RT-PCR test displayed 30%, 73% and 100% positivity rates in the COVID-19 group, respectively. When considering samples taken >14 days after RT-PCR diagnosis, NPV was 100% (95%CI:90-100), and PPV was 100% (95%CI:72-100).ConclusionsThe Augurix IgG-RDT done in whole blood displays a high diagnostic accuracy for SARS-CoV-2 IgG in high COVID-19 prevalence settings, where its use could be considered in the absence of routine diagnostic serology facilities.
| S-EPMC7404380 | biostudies-literature
Project description:ImportanceAdequate sampling of the nasopharynx is crucial to performing accurate SARS-CoV-2 (COVID) testing. Formalized education of nasal anatomy may improve provider testing technique and reduce false-negative test results.ObjectiveTo assess the effect of nasal anatomy education on medical providers' comfort level and knowledge base in performing accurate SARS-CoV-2 (COVID) testing.Study designPre-post survey.SettingsTertiary care academic hospital.Participants17 nurses performing COVID testing were enrolled.InterventionAn educational session on COVID nasopharyngeal testing technique and nasal anatomy was presented by an otolaryngologist.Main outcomes and measuresA pre-session survey assessed providers' prior nasal testing training and COVID testing challenges. Provider comfort level with COVID testing was surveyed pre-and post-session. A 6-question nasal anatomy test was administered pre- and post-session.Results16 out of 17 nurses performed fewer than 10 COVID tests prior to the educational session (94%). Reported challenges with COVID testing included patient discomfort (79.6%), inability to pass the test swab (23.5%) and nasal bleeding (11.8%). The number of providers comfortable with independently performing COVID testing increased from pre- to post-session (5 and 14, p = 0.013). The average number of correct responses to the 6-question nasal anatomy test increased following the session (3.2 ± 1.2 to 5.1 ± 1.1, p = 0.003). Specifically, the number of providers able to localize the nasopharynx increased from 8 providers pre-session to 14 providers post-session (p = 0.04).ConclusionEarly implementation of nasal anatomy and nasopharyngeal swab technique education can help improve provider comfort and knowledge in performing accurate COVID testing.
| S-EPMC7581395 | biostudies-literature
Project description:Restrictions adopted by many countries in 2020 due to Covid-19 pandemic had severe consequences on the management of sensory and consumer testing that strengthened the tendency to move data collection out of the laboratory. Remote sensory testing, organized at the assessor's home or workplace and carried out under the live online supervision of the panel leader, represents a trade-off between adequate control and the convenience of conducting testing out of the lab. The Italian Sensory Science Society developed the "Remote sensory testing" research project aimed at testing the effectiveness and validity of the sensory tests conducted remotely through a comparison with evaluations in a classical laboratory setting. Guidelines were developed to assist panel leaders in setting up and controlling the evaluation sessions in remote testing conditions. Different methods were considered: triangle and tetrad tests, Descriptive Analysis and Temporal Dominance of Sensations tests, all of which involved trained panels, and Check-All-That-Apply and hedonic tests with consumers. Remote sensory testing provided similar results to the lab testing in all the cases, with the exception of the tetrad test run at work. Findings suggest that remote sensory testing, if conducted in strict compliance with specifically developed sensory protocols, is a promising alternative to laboratory tests that can be applied with both trained assessors and consumers even beyond the global pandemic.
| S-EPMC8548442 | biostudies-literature
Project description:BackgroundEgypt was among the first 10 countries in Africa that experienced COVID-19 cases. The sudden surge in the number of cases is overwhelming the capacity of the national healthcare system, particularly in developing countries. Central to the containment of the ongoing pandemic is the availability of rapid and accurate diagnostic tests that could pinpoint patients at early disease stages. In the current study, we aimed to (1) Evaluate the diagnostic performance of the rapid antigen test (RAT) "Standard™ Q COVID-19 Ag" against reverse transcriptase quantitative real-time PCR (RT-qPCR) in eighty-three swabs collected from COVID-19 suspected individuals showing various demographic features, clinical and radiological findings. (2) Test whether measuring laboratory parameters in participant's blood would enhance the predictive accuracy of RAT. (3) Identify the most important features that determine the results of both RAT and RT-qPCR.MethodsDiagnostic measurements (e.g. sensitivity, specificity, etc.) and receiver operating characteristic curve were used to assess the clinical performance of "Standard™ Q COVID-19 Ag". We used the support vector machine (SVM) model to investigate whether measuring laboratory indices would enhance the accuracy of RAT. Moreover, a random forest classification model was used to determine the most important determinants of the results of RAT and RT-qPCR for COVID-19 diagnosis.ResultsThe sensitivity, specificity, and accuracy of RAT were 78.2, 64.2, and 75.9%, respectively. Samples with high viral load and those that were collected within one-week post-symptoms showed the highest sensitivity and accuracy. The SVM modeling showed that measuring laboratory indices did not enhance the predictive accuracy of RAT.Conclusion"Standard™ Q COVID-19 Ag" should not be used alone for COVID-19 diagnosis due to its low diagnostic performance relative to the RT-qPCR. RAT is best used at the early disease stage and in patients with high viral load.
| S-EPMC8192262 | biostudies-literature
Project description:BackgroundConsidering the possibility of nasal self-sampling and the ease of use in performing SARS-CoV-2 antigen-detecting rapid diagnostic tests (Ag-RDTs), self-testing is a feasible option.ObjectiveThe goal of this study was a head-to-head comparison of diagnostic accuracy of patient self-testing with professional testing using a SARS-CoV-2 Ag-RDT.Study designWe performed a manufacturer-independent, prospective diagnostic accuracy study of nasal mid-turbinate self-sampling and self-testing with symptomatic adults using a WHO-listed SARS-CoV-2 Ag-RDT. Procedures were observed without intervention. For comparison, Ag-RDTs with nasopharyngeal sampling were professionally performed. Estimates of agreement, sensitivity, and specificity relative to RT-PCR on a combined oro-/nasopharyngeal sample were calculated. Feasibility was evaluated by observer and participant questionnaires.ResultsAmong 146 symptomatic adults, 40 (27.4%) were RT-PCR-positive for SARS-CoV-2. Sensitivity with self-testing was 82.5% (33/40; 95% CI 68.1-91.3), and 85.0% (34/40; 95% CI 70.9-92.9) with professional testing. At high viral load (≥7.0 log10 SARS-CoV-2 RNA copies/ml), sensitivity was 96.6% (28/29; 95% CI 82.8-99.8) for both self- and professional testing. Deviations in sampling and testing were observed in 25 out of the 40 PCR-positives. Most participants (80.9%) considered the Ag-RDT as easy to perform.ConclusionLaypersons suspected for SARS-CoV-2 infection were able to reliably perform the Ag-RDT and test themselves. Procedural errors might be reduced by refinement of the instructions for use or the product design/procedures. Self-testing allows more wide-spread and frequent testing. Paired with the appropriate information of the public about the benefits and risks, self-testing may have significant impact on the pandemic.
| S-EPMC8163726 | biostudies-literature
Project description:BackgroundManagement of large numbers of reverse transcriptase-polymerase chain reactions (RT-PCR) for diagnosis of coronavirus 2019 disease (COVID-19) requires robust infrastructures, located in dedicated premises with a high standard of biosafety procedures, and well-trained personnel. The handling of a "run-of-river sample" to obtain rapid reporting of results is challenging.MethodsWe studied the clinical performance of the Idylla™ SARS-CoV-2 Test (index test) on a platform capable of fully automated nucleic acid testing including extraction, amplification, and detection in a single-use cartridge to establish the diagnosis of COVID-19. The study was conducted on a prospective cohort of 112 volunteers with recent symptoms and an unknown SARS-CoV-2 status who came to free screening centers of the Nice metropolitan area. All subjects underwent bilateral nasopharyngeal sampling. One sample was processed using the index test, the other using the standard of care RT-PCR. Samples were treated blind.ResultsMost of the participants (70%) were sampled within 4 days of symptom onset. Forty-five (40.2%) were positive for COVID-19. No clinical symptoms were distinguished between SARS-CoV-2 RT-PCR positive and negative subjects except anosmia and dysgeusia. Positive and negative agreement between the index and the standard of care test was 100%.ConclusionsThe Idylla™ SARS-CoV-2 Test is very sensitive, specific, rapid and easy to use in a near-patient RT-PCR approach to distinguish between symptomatic SARS-CoV-2 positive and negative patients in selected settings.
| S-EPMC8263856 | biostudies-literature