Efficacy comparison of three rapid antigen tests for SARS‐CoV‐2 and how viral load impact their performance

Abstract Background: While the COVID-19 pandemic is a worldwide crisis, tests with high sensitivity and specificity are essential for identifying and managing COVID-19 patients. Globally, several rapid antigen tests RATs for COVID-19 have been developed, but their clinical efficacy has not been well established. This study aimed to evaluate the performance of several rapid antigen tests (RATs) to diagnose SARS-CoV-2 infection.Methods: This prospective observational study was conducted at Shaheed Suhrawardy Medical College hospital from February 2021 to April 2021 in Dhaka, Bangladesh. This study included the patients admitted in this hospital at the COVID-19 isolation unit or referred from the triage facility of the outdoor department of this hospital suspected as COVID-19 case. Two nasopharyngeal samples were collected simultaneously. one sample was used on the spot for the RAT. The other was sent to the adjacent Shaheed Suhrawardy Medical College COVID-19 RT-PCR laboratory for real-time reverse transcription-polymerase chain reaction (qRT-PCR). The performance of the RAT was evaluated using the results of qRT-PCR as a reference.Results: A total of 223 patients were included in this study, and the real-time RT-PCR detected SARS-CoV-2 in 84 (37.7%) patients. Of these 84 patients, 9 (10.7%) were asymptomatic. The overall sensitivity and specificity of RATs were 78.6% and 99.3%, respectively. The sensitivity was 81.3% in symptomatic cases and 55.6% in asymptomatic cases. False-negatives were observed in 18 patients, 3 of whom were asymptomatic and had a low viral load (cycle threshold (Ct) > 30). The detection rate of RATs was 100% when the Ct value was up to 24. The detection rate was 42.3% when the Ct was >29. The detection rate of RATs was 92.3% when the onset of symptoms was within three days. The detection rate was 33.3% when the onset of symptoms was >7 days.Conclusions: RATs for COVID-19 used in this study delivered an acceptable performance in patients with high viral load and within the first week of the onset of symptoms. They can be used as a supplementary method to RT-PCR for the diagnosis of COVID-19 patients.

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SARS-CoV-2 Antigen Tests Predict Infectivity Based on Viral Culture: Comparison of Antigen, PCR Viral Load, and Viral Culture Testing on a Large Sample Cohort

10.1101/2021.12.22.21268274 ◽

2021 ◽

Author(s):

James E Kirby ◽

Stefan Riedel ◽

Sanjucta Dutta ◽

Ramy Arnaout ◽

Annie Cheng ◽

...

Keyword(s):

Viral Load ◽

Diagnostic Testing ◽

Lateral Flow ◽

Nasopharyngeal Swab ◽

Viral Culture ◽

Culture Positivity ◽

Antigen Tests ◽

Relationship Of ◽

The Relationship ◽

Antigen Testing

The relationship of SARS-CoV-2 antigen testing results, viral load, and viral culture detection remains to be fully defined. Presumptively, viral culture can provide a surrogate measure for infectivity of sampled individuals, and thereby inform how and where to most appropriately deploy available diagnostic testing modalities. We therefore determined the relationship of antigen testing results from three lateral flow and one microfluidics assay to viral culture performed in parallel in 181 nasopharyngeal swab samples positive for SARS-CoV-2. Sample viral loads, determined by RT-qPCR, were distributed across the range of viral load values observed in our testing population. We found that antigen tests were predictive of viral culture positivity, with the LumiraDx method showing enhanced sensitivity (90%; 95% confidence interval (95% CI) 83-94%) compared with the BD Veritor (74%, 95% CI 65-81%), CareStart (74%, 95% CI 65-81%) and Oscar Corona (74%, 95% CI 65-82%) lateral flow antigen tests. Antigen and viral culture positivity were also highly correlated with sample viral load, with areas under the receiver?operator characteristic curves (ROCs) of 0.94-0.97 and 0.92, respectively. In particular, a viral load threshold of 100,000 copies/mL was 95% sensitive (95% CI, 90-98%) and 72% specific (95% CI, 60-81%) for predicting viral culture positivity. Taken together, the detection of SARS-CoV-2 antigen identified highly infectious individuals, some of whom may harbor 10,000-fold more virus in their samples than those with any detectable infectious virus. As such, our data support use of antigen testing in defining infectivity status at the time of sampling.

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Diagnostic accuracy of rapid antigen tests in asymptomatic and presymptomatic close contacts of individuals with confirmed SARS-CoV-2 infection: cross sectional study

BMJ ◽

10.1136/bmj.n1676 ◽

2021 ◽

pp. n1676

Author(s):

Ewoud Schuit ◽

Irene K Veldhuijzen ◽

Roderick P Venekamp ◽

Wouter van den Bijllaardt ◽

Suzan D Pas ◽

...

Keyword(s):

Viral Load ◽

Cross Sectional Study ◽

Antigen Test ◽

Sectional Study ◽

Rt Pcr ◽

Cross Sectional ◽

Predictive Values ◽

Test Sensitivity ◽

Antigen Tests ◽

Close Contacts

Abstract Objective To assess the diagnostic test accuracy of two rapid antigen tests in asymptomatic and presymptomatic close contacts of people with SARS-CoV-2 infection on day 5 after exposure. Design Prospective cross sectional study. Setting Four public health service covid-19 test sites in the Netherlands. Participants 4274 consecutively included close contacts (identified through test-and-trace programme or contact tracing app) aged 16 years or older and asymptomatic for covid-19 when requesting a test. Main outcome measures Sensitivity, specificity, and positive and negative predictive values of Veritor System (Beckton Dickinson) and Biosensor (Roche Diagnostics) rapid antigen tests, with reverse-transcriptase polymerase chain reaction (RT-PCR) testing as reference standard. The viral load cut-off above which 95% of people with a positive RT-PCR test result were virus culture positive was used as a proxy of infectiousness. Results Of 2678 participants tested with Veritor, 233 (8.7%) had a RT-PCR confirmed SARS-CoV-2 infection of whom 149 were also detected by the rapid antigen test (sensitivity 63.9%, 95% confidence interval 57.4% to 70.1%). Of 1596 participants tested with Biosensor, 132 (8.3%) had a RT-PCR confirmed SARS-CoV-2 infection of whom 83 were detected by the rapid antigen test (sensitivity 62.9%, 54.0% to 71.1%). In those who were still asymptomatic at the time of sampling, sensitivity was 58.7% (51.1% to 66.0%) for Veritor (n=2317) and 59.4% (49.2% to 69.1%) for Biosensor (n=1414), and in those who developed symptoms were 84.2% (68.7% to 94.0%; n=219) for Veritor and 73.3% (54.1% to 87.7%; n=158) for Biosensor. When a viral load cut-off was applied for infectiouness (≥5.2 log10 SARS-CoV-2 E gene copies/mL), the overall sensitivity was 90.1% (84.2% to 94.4%) for Veritor and 86.8% (78.1% to 93.0%) for Biosensor, and 88.1% (80.5% to 93.5%) for Veritor and 85.1% (74.3% to 92.6%) for Biosensor, among those who remained asymptomatic throughout. Specificities were >99%, and positive and negative predictive values were >90% and >95%, for both rapid antigen tests in all analyses. Conclusions The sensitivities of both rapid antigen tests in asymptomatic and presymptomatic close contacts tested on day 5 onwards after close contact with an index case were more than 60%, increasing to more than 85% after a viral load cut-off was applied as a proxy for infectiousness.

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Association between viral load and positivization time of a SARS-CoV-2 rapid antigen test in routine nasopharyngeal specimens

10.21203/rs.3.rs-1191771/v1 ◽

2021 ◽

Author(s):

Gian Luca Salvagno ◽

Brandon Michael Henry ◽

Simone De Nitto ◽

Laura Pighi ◽

Giuseppe Lippi

Keyword(s):

Viral Load ◽

Diagnostic Testing ◽

Area Under The Curve ◽

High Viral Load ◽

Antigen Test ◽

Potential Association ◽

Antigen Tests ◽

Antigen Testing ◽

Spearman’S Correlation ◽

Positive Results

Abstract Background: Rapid SARS-CoV-2 antigen tests are potentially useful tools for screening carriers with high viral load. This study was aimed to assess the potential association between viral load and positivization time of a manual SARS-CoV-2 commercial antigen test in routine nasopharyngeal specimens. Methods: In a sample of subjects undergoing routine diagnostic testing, SARS-CoV-2 positivity of nasopharyngeal samples was assayed with both molecular (Altona Diagnostics RealStar SARS-CoV-2 RT-PCR Kit) and antigenic (Roche SARS-CoV-2 Rapid Antigen Test) tests. Positivization time of rapid antigen test was correlated and compared with viral load expressed as mean of SARS-CoV-2 E/S genes cycle threshold (Ct) values.Results: The study sample consisted of 106 patients (median age 48 years, 55 women) with positive results of rapid SARS-CoV-2 antigen testing. A highly significant Spearman’s correlation was found between mean SARS-CoV-2 E/S genes Ct values and positivization time of manual antigen test (r= 0.70; p<0.001). The positivization time of rapid SARS-CoV-2 antigen test displayed an area under the curve of 0.82 (95%CI, 0.74-0.89) for predicting nasopharyngeal samples with high viral load (i.e., mean Ct <20). A positivization time cut-off of 32 sec had 94.9% sensitivity and 58.2% specificity for detecting specimens with high viral load. The overall agreement between mean Ct value <20 and positivization time <32 sec was 70.8%.Conclusions: Positivization time of rapid SARS-CoV-2 antigen tests may provide easy and rapid information on viral load, thus making this type of manual assay potentially suitable for quick and reliable detection and isolation of super-carries.

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Diagnostic accuracy of three prevailing rapid antigen tests for detection of SARS-CoV-2 infection in the general population: cross sectional study

10.1101/2021.11.19.21266579 ◽

2021 ◽

Author(s):

Roderick P Venekamp ◽

Irene K Veldhuijzen ◽

Karel GM Moons ◽

Wouter van den Bijllaardt ◽

Suzan D Pas ◽

...

Keyword(s):

Viral Load ◽

Diagnostic Accuracy ◽

False Negative ◽

Cross Sectional Study ◽

Sectional Study ◽

Cross Sectional ◽

Predictive Values ◽

Routine Sampling ◽

Antigen Tests

Objective To assess the diagnostic accuracy of three rapid antigen tests (Ag-RDTs) for detecting SARS-CoV-2 infection in the general population. Design Cross-sectional study with follow-up using pseudonymised record linkage. Setting Three Dutch public health service COVID-19 test sites. Participants Consecutively included individuals aged 16 years and older presenting for SARS-CoV-2 testing. Main outcome measures Sensitivity, specificity, positive and negative predictive values of BD-Veritortm System (Becton Dickinson), PanBio (Abbott), and SD-Biosensor (Roche Diagnostics), applying routinely used sampling methods (combined oropharyngeal and nasal [OP-N] or nasopharyngeal [NP] swab), with molecular testing as reference standard. For SDBiosensor, the diagnostic accuracy with OP-N sampling was also assessed. A viral load cutoff (≥5.2 log10 SARS-CoV-2 E-gene copies/mL) served as a proxy of infectiousness. Results SARS-CoV-2 prevalence and overall sensitivities with 95% confidence intervals were 188/1441 (13.0%) and 129/188 (68.6% [61.5%-75.2%]) for BD-Veritor, 173/2056 (8.4%) and 119/173 (68.8% [61.3%-75.6%]) for PanBio, and 215/1769 (12.2%) and 160/215 (74.4% [68.0%-80.1%]) for SD-Biosensor with routine sampling, and 164/1689 (9.7%) and 123/164 (75.0% [67.7%-81.4%]) for SD-Biosensor with OP-N sampling. In those symptomatic or asymptomatic at sampling, sensitivities were 72.2%-83.4% and 54.0%-55.9%, respectively. With a viral load cut-off, sensitivities were 125/146 (85.6% [78.9%-90.9%]) for BD-Veritor, 108/121 (89.3% [82.3%-94.2%]) for PanBio, 160/182 (87.9% [82.3%-92.3%]) for SD-Biosensor with routine sampling, and 118/141 (83.7% [76.5%-89.4%]) with OP-N sampling. Specificities were >99%, and positive and negative predictive values >95%, for all tests in most analyses. 61.3% of false negative Ag-RDT participants returned for testing within 14 days (median of 3 days, interquartile range 3) of whom 90.3% tested positive. Conclusions The overall sensitivities of the three Ag-RDTs were 68.6%-75.0%, increasing to at least 85.6% after the viral load cut-off was applied. For SD-Biosensor, the diagnostic accuracy with OP-N and NP sampling was comparable. Over 55% of false negative Ag-RDT participants tested positive during follow-up.

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Analytical sensitivity and effectiveness of different SARS-CoV-2 testing options

10.1101/2021.11.26.21265946 ◽

2021 ◽

Author(s):

Nico Lelie ◽

Marco Koppelman ◽

Harry Van Drimmelen ◽

Sylvia Bruisten

Keyword(s):

Viral Load ◽

Probit Analysis ◽

Nucleic Acid Amplification ◽

Analytical Sensitivity ◽

Working Standard ◽

Infectious Dose ◽

Clinical Sensitivity ◽

Nucleic Acid Amplification Technology ◽

Sensitivity Data ◽

Antigen Tests

We prepared severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) working standards and reference panels from a pool of swab fluid samples before and after inactivation by beta-propiolactone and quantified viral load in nucleic acid amplification technology (NAT) detectable RNA copies/mL using limiting dilution analysis. The following 50% lower limits of detection (LOD) were estimated by probit analysis as compared to detection limits of rapid antigen tests on 1.5 fold dilutions of the native material: Roche cobas PCR 1.8 (1.0-3.3), Hologic Aptima TMA 6.6 (4.4-9.9), DRW SAMBA 15 (7-30), Molgen LAMP 23 (13-42), Fluorecare antigen 50,000, Abbott Panbio antigen 75,000 and Roche antigen 100,000 copies/mL. One 50% Tissue Culture Infectious Dose (TCID50)/mL of culture fluid was estimated to be equivalent to approximately 1000 RNA copies/mL (2700- 4300 International Units) in our working standard. When assuming this level as start of contagiousness in a log-linear ramp up viremia model with 10-fold rise of viral load per day for the B.1 (Wuhan) type we estimated relative time points of first detectability of early infection by the different SARS-CoV-2 assays from the LODs mentioned above. The four NAT assays would be able to detect early viremia 40-66 hours earlier than the 1000 copies/mL infectivity threshold, whereas the three antigen tests would become positive 41-48 hours later. Our modeling of analytical sensitivity data was found to be compatible with clinical sensitivity data of rapid antigen tests and confirms that NAT assays are more reliable than antigen assays for identifying early infected asymptomatic individuals who are potentially infectious.

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Infection and infectivity: Utility of rapid antigen tests for the diagnosis of COVID-19

Revista Española de Quimioterapia ◽

10.37201/req/s01.14.2021 ◽

2021 ◽

Vol 34 (Suppl 1) ◽

pp. 46-48

Author(s):

Pablo Barreiro ◽

Jesús San-Román ◽

María del Mar Carretero ◽

Francisco Javier Candel ◽

Keyword(s):

Viral Load ◽

Point Of Care ◽

Viral Transmission ◽

Lateral Flow ◽

Pretest Probability ◽

Antigen Test ◽

Diagnostic Strategies ◽

Antigen Tests ◽

Asymptomatic Individuals

Detection of SARS-CoV-2 proteins is commercially available in the form of lateral-flow rapid antigen test for the point-of-care diagnosis of COVID-19. This platform has been validated for symptomatic and asymptomatic individuals, for diagnosis or screening, and as part of single or sequential diagnostic strategies. Although in general less sensitive than amplification techniques, antigen tests may be particularly valid during the first days of symptoms and to detect individuals with greater viral load, thereby with enhanced chances of viral transmission. The simplicity of antigen tests make them very suitable to discard infection in settings with low pretest probability, and to detect infection in case of higher chances of having COVID-19.

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Real-world clinical performance of commercial SARS-CoV-2 rapid antigen tests in suspected COVID-19: A systematic meta-analysis of available data as per November 20, 2020

10.1101/2020.12.22.20248614 ◽

2020 ◽

Author(s):

Johannes Hayer ◽

Dusanka Kasapic ◽

Claudia Zemmrich

Keyword(s):

Viral Load ◽

Real World ◽

Clinical Performance ◽

Meta Analysis ◽

High Viral Load ◽

Lateral Flow ◽

Performance Data ◽

Rt Pcr ◽

Symptom Status ◽

Antigen Tests

AbstractBackgroundImmunochromatographic rapid antigen tests (RATs) emerged onto the COVID-19 pandemic testing landscape to aid in the rapid diagnosis of people with suspected SARS-CoV-2 infection. RATs are particularly useful where RT-PCR is not immediately available and symptoms suggestive of a high viral load and infectiousness are assumed. Several lateral flow immunoassays have been authorized for use under EUA and/or the CE mark, presenting varying overall clinical performance data generated by the manufacturer or by independent investigators. To compare the real-world clinical performance of commercially available rapid chromatographic immunoassays intended for the qualitative detection of SARS-CoV-2, we performed a systematic meta-analysis of published data.MethodsWe searched the MEDLINE®, Embase, BIOSIS and Derwent Drug File (ProQuest)for manufacturer-independent prospective clinical performance studies comparing SARS-CoV-2 RATs and RT-PCR assays. Only studies on lateral flow assays not needing a separate reader for retrieving the result were included, if data were available on viral load, patients’ symptom status, sample type, and PCR assay used. For better data comparability, recalculation of the studies’ single performance data confidence intervals using the exact Clopper–Pearson method was applied.ResultsWe could include 19 studies (ten peer-reviewed) presenting detailed clinical performance data on 11,209 samples with 2449 RT-PCR-positives out of study prevalence rates between 1.9–100 % and between 50– 100% symptomatic samples. Four studies directly compared two to three different RATs and 15 studies compared one RAT to RT-PCR. Overall specificity ranged, with one test outlier, between 92.4% (87.4– 95.9) and 100% (99.7–100), and overall clinical sensitivity varied between 28.9% (16.4–44.3) and 98.3% (91.1–99.7), depending on assay, population characteristics, viral load, and symptom status. Sensitivity in high-viral-load samples (cycle threshold ≤25) showed a considerable heterogeneity among the assays ranging from 66.7% to 100%.ConclusionOnly two RATs offered sufficient manufacturer-independent, real-world performance data supporting use for the detection of current SARS-CoV-2 infection in symptomatic or high-viral-load patient populations. Reliable positive predictive values require testing of symptomatic patients or asymptomatic individuals only in case of a high pre-test probability. If RATs are used for screening of asymptomatic cases in low-prevalence scenarios, a lower positive predictive value of the result has to be considered.

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Handling and accuracy of four rapid antigen tests for the diagnosis of SARS-CoV-2 compared to RT-qPCR

10.1101/2020.12.05.20244673 ◽

2020 ◽

Author(s):

Flaminia Olearo ◽

Dominik Nörz ◽

Fabian Heinrich ◽

Jan Peter Sutter ◽

Kevin Rödel ◽

...

Keyword(s):

Viral Load ◽

Point Of Care ◽

Significant Risk ◽

Relative Sensitivity ◽

High Viral Load ◽

Careful Consideration ◽

Lower Sensitivity ◽

Clinical Implementation ◽

Rt Pcr ◽

Antigen Tests

AbstractBackgroundSARS-CoV-2 molecular diagnostics is facing material shortages and long turnaround times due to exponential increase of testing demand.ObjectiveWe 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).Methods100 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.ResultsThe median duration from symptom onset to sampling was 6 days (IQR 2-12 days). The overall relative sensitivity was 49.4%, 44.6%, 45.8% and 54.9 % 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 and IV and 97% 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.DiscussionBesides 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.

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