scholarly journals Reduced Relative Sensitivity of the Elecsys SARS-CoV-2 Antigen Assay in Saliva Compared to Nasopharyngeal Swabs

2021 ◽  
Vol 9 (8) ◽  
pp. 1700
Author(s):  
Annette Audigé ◽  
Jürg Böni ◽  
Peter W. Schreiber ◽  
Thomas Scheier ◽  
Roberto Buonomano ◽  
...  
Keyword(s):  
Relative Sensitivity ◽  
Test System ◽  
Screening Tests ◽  
Rt Pcr ◽  
Entire Cohort ◽  
Viral Loads ◽  
Non Invasive ◽  
Sensitivity Loss ◽  
Antigen Assay ◽  
Antigen Tests

Early identification and isolation of SARS-CoV-2-infected individuals is central to contain the COVID-19 pandemic. Nasopharyngeal swabs (NPS) serve as a specimen for detection by RT-PCR and rapid antigen screening tests. Saliva has been confirmed as a reliable alternative specimen for RT-PCR and has been shown to be valuable for diagnosing children and in repetitive mass testing due to its non-invasive collection. Combining the advantages of saliva with those of antigen tests would be highly attractive to further increase test capacities. Here, we evaluated the performance of the Elecsys SARS-CoV-2 Antigen assay (Roche) in RT-PCR-positive paired NPS and saliva samples (N = 87) and unpaired NPS (N = 100) with confirmed SARS-CoV-2 infection (Roche cobas SARS-CoV-2 IVD test). We observed a high positive percent agreement (PPA) of the antigen assay with RT-PCR in NPS, reaching 87.2% across the entire cohort, whereas the overall PPA for saliva was insufficient (40.2%). At Ct values ≤ 28, PPA were 100% and 91.2% for NPS and saliva, respectively. At lower viral loads, the sensitivity loss of the antigen assay in saliva was striking. At Ct values ≤ 35, the PPA for NPS remained satisfactory (91.5%), whereas the PPA for saliva dropped to 46.6%. In conclusion, saliva cannot be recommended as a reliable alternative to NPS for testing with the Elecsys Anti-SARS-CoV-2 Antigen assay. As saliva is successfully used broadly in combination with RT-PCR testing, it is critical to create awareness that suitability for RT-PCR cannot be translated to implementation in antigen assays without thorough evaluation of each individual test system.

scholarly journals Sensitivity of rapid antigen testing and RT-PCR performed on nasopharyngeal swabs versus saliva samples in COVID-19 hospitalized patients: results of a prospective comparative trial (RESTART)

2021 ◽  
Author(s):  
Antonios Kritikos ◽  
Giorgia Caruana ◽  
René Brouillet ◽  
John-Paul Miroz ◽  
Abed-Maillard Samia ◽  
...  
Keyword(s):  
Comparative Trial ◽  
Hospitalized Patients ◽  
Rt Pcr ◽  
Duration Of Symptoms ◽  
Non Invasive ◽  
Viral Transport Medium ◽  
One Step ◽  
Antigen Tests ◽  
Low Sensitivity ◽  
Antigen Testing

AbstractObjectivesSaliva sampling could serve as an alternative non-invasive sample for SARS-CoV-2 diagnosis while rapid antigen testing (RAT) might help to mitigate the shortage of reagents sporadically encountered with RT-PCR. Thus, in the RESTART study we compared antigen and RT-PCR testing methods on nasopharyngeal (NP) swabs and salivary samples.MethodsWe conducted a prospective observational study among COVID-19 hospitalized patients between 10th December 2020 and 1st February 2021. Paired saliva and NP samples were investigated by RT-PCR (Cobas 6800, Roche-Switzerland) and by two rapid antigen tests: One Step Immunoassay Exdia® COVID-19 Ag (Precision Biosensor, Korea) and Standard Q® COVID-19 Rapid Antigen Test (Roche-Switzerland).ResultsA total of 58 paired NP-saliva specimens were collected. Thirty-two of 58 (55%) patients were hospitalized in the intensive care unit and the median duration of symptoms was 11 days (IQR 5-19). NP and salivary RT-PCR exhibited sensitivity of 98% and 69% respectively whereas the specificity of these RT-PCRs assays were of 100%. NP RAT exhibited much lower diagnostic performances with sensitivities of 35% and 41% for the Standard Q® and Exdia® assays respectively, when a wet-swab approach was used (i.e. when the swab was diluted in the viral transport medium (VTM) before testing). The sensitivity of the dry-swab approach was slightly better (47%). These antigen tests exhibited very low sensitivity (4 and 8%) when applied to salivary swabs.ConclusionsNasopharyngeal RT-PCR is the most accurate test for COVID-19 diagnosis in hospitalized patients. RT-PCR on salivary samples may be used when nasopharyngeal swabs are contraindicated. RAT are not appropriate for hospitalized patients.

scholarly journals Evaluation of Rapid Antigen Tests Using Nasal Samples to Diagnose SARS-CoV-2 in Symptomatic Patients

2022 ◽  
Vol 9 ◽  
Author(s):  
Manaf Alqahtani ◽  
Abdulkarim Abdulrahman ◽  
Fathi Mustafa ◽  
Abdulla I. Alawadhi ◽  
Batool Alalawi ◽  
...  
Keyword(s):  
Early Detection ◽  
Nasal Swab ◽  
Cost Effective ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Rapid Antigen Detection Test ◽  
Viral Loads ◽  
Antigen Tests ◽  
Stratified Analysis ◽  
Potential Use

IntroductionThe best way to mitigate an outbreak besides mass vaccination is via early detection and isolation of infected cases. As such, a rapid, cost-effective test for the early detection of COVID-19 is required.MethodsThe study included 4,183 mildly symptomatic patients. A nasal and nasopharyngeal sample obtained from each patient was analyzed to determine the diagnostic ability of the rapid antigen detection test (RADT, nasal swab) in comparison with the current gold-standard (RT-PCR, nasopharyngeal swab).ResultsThe calculated sensitivity and specificity of the RADT was 82.1 and 99.1%, respectively. Kappa's coefficient of agreement between the RADT and RT-PCR was 0.859 (p < 0.001). Stratified analysis showed that the sensitivity of the RADT improved significantly when lowering the cut-off RT-PCR Ct value to 24.ConclusionOur study's results support the potential use of nasal swab RADT as a screening tool in mildly symptomatic patients, especially in patients with higher viral loads.

scholarly journals ImplemeNting SARS-CoV-2 Rapid antigen testing in the Emergency wArd of a Swiss univErsity hospital: the INCREASE study

2021 ◽  
Author(s):  
Giorgia Caruana ◽  
Antony Croxatto ◽  
Eleftheria Kampouri ◽  
Antonios Kritikos ◽  
Onya Opota ◽  
...  
Keyword(s):  
University Hospital ◽  
Lower Sensitivity ◽  
Clinical Settings ◽  
Rt Pcr ◽  
Emergency Ward ◽  
Viral Loads ◽  
Molecular Tests ◽  
One Step ◽  
Antigen Tests ◽  
Second Wave

BackgroundWhile facing a second wave in SARS-CoV-2 pandemic, in November 2020 the Swiss Federal Office of Public Health (FOPH) authorized the use of rapid antigen tests (RATs) in addition to the gold-standard reverse transcription-polymerase chain reaction (RT-PCR).MethodsWe implemented the use of RAT in the emergency ward of our university hospital for rapid patients’ triaging and compared performances of four different antigen tests. All results were compared to SARS-CoV-2 specific RT-PCR (reference standard).ResultsTriaging patients using RAT in association with RT-PCR allowed us to isolate promptly positive patients and to save resources, in a context of rapid RT-PCR reagents shortage. Among 532 patients with valid results, overall sensitivities were 48.3% for One Step Exdia and 41.2% for Standard Q®, Panbio−and BD Veritor. All four antigen tests exhibited specificity above 99%. Sensitivity increased up to 74.6%, 66.2%, 66.2% and 64.8% for One Step Exdia, Standard Q, Panbio, and BD Veritor respectively, when considering viral loads above 105copies/ml, up to 100%, 97.8%, 96.6% and 95.6% for viral loads above 106 copies/ml and 100% (for all tests) when considering viral loads above 107 copies/ml. Sensitivity was significantly higher for patients presenting with symptoms onset within 4 days (74.3%, 69.2%, 69.2% and 64%, respectively) versus patients with evolution of symptoms for more than 4 days (36.8%, 21.1%, 21.1% and 23.7%, respectively). Sensitivities of all RAT assays were of only 33% among hospitalized patients without COVID-19 symptoms.ConclusionRAT might represent a useful epidemiological resource in selected clinical settings as a complementary tool to the molecular tests for rapid patients triaging, but the lower sensitivity compared to RT-PCR, especially in late presenters and subjects without COVID-19 symptoms, must be taken into account in order to correctly use RAT for triaging.

scholarly journals Evaluation and modelling of the performance of an automated SARS-CoV-2 antigen assay according to sample type, target population and epidemic trends

2022 ◽  
Author(s):  
Nicolas Yin ◽  
Cyril Debuysschere ◽  
Valery Daubie ◽  
Marc Hildebrand ◽  
Charlotte Martin ◽  
...  
Keyword(s):  
Viral Load ◽  
Target Population ◽  
Daily Routine ◽  
Sample Type ◽  
Rt Pcr ◽  
Viral Loads ◽  
Detection Assay ◽  
Assay Performance ◽  
Antigen Assay ◽  
Risk Patients

The Lumipulse® G SARS-CoV-2 Ag assay performance was evaluated on prospectively collected saliva and nasopharyngeal swabs (NPS) of recently ill in- and outpatients and according to the estimated viral load. Performances were calculated using RT-PCR positive NPS from patients with symptoms ≤ 7 days and RT-PCR negative NPS as gold standard. In addition, non-selected positive NPS were analyzed to assess the performances on various viral loads. This assay yielded a sensitivity of 93.1% on NPS and 71.4% on saliva for recently ill patients. For NPS with a viral load > 103 RNA copies/mL, sensitivity was 96.4%. A model established on our daily routine showed fluctuations of the performances depending on the epidemic trends but an overall good negative predictive value. Lumipulse® G SARS-CoV-2 assay yielded good performance for an automated antigen detection assay on NPS. Using it for the detection of recently ill patient or to screen high-risk patients could be an interesting alternative to the more expensive RT-PCR.

scholarly journals Multicenter evaluation of a fully automated high-throughput SARS-CoV-2 antigen immunoassay

2021 ◽  
Author(s):  
Dominik Noerz ◽  
Flaminia Olearo ◽  
Stojan Perisic ◽  
Matthais Bauer ◽  
Elena Riester ◽  
...  
Keyword(s):  
High Throughput ◽  
Large Scale ◽  
Molecular Testing ◽  
Viral Loads ◽  
Critical Areas ◽  
Large Scale Testing ◽  
Antigen Assay ◽  
Antigen Tests ◽  
Lateral Flow Tests ◽  
Rna Concentration

Background: Molecular testing for SARS-CoV-2 continues to suffer from delays and shortages. Antigen tests have recently emerged as a viable alternative to detect patients with high viral loads, associated with elevated risk of transmission. While rapid lateral flow tests greatly improved accessibility of SARS-CoV-2 detection in critical areas, their manual nature limits scalability and suitability for large-scale testing schemes. The Elecsys® SARS-CoV-2 Antigen assay allows antigen immunoassays to be carried out on fully automated high-throughput serology platforms. Methods: A total of 3139 nasopharyngeal and oropharyngeal swabs were collected at 3 different testing sites in Germany. Swab samples were pre-characterized by RT-qPCR and consecutively subjected to the antigen immunoassay on either the cobas e411 or cobas e801 analyzers. Results: Of the tested respiratory samples, 392 were PCR positive for SARS-CoV-2 RNA. Median concentration was 2.95×104 (interquartile range [IQR] 5.1×102–3.5×106) copies/mL. Overall sensitivity and specificity of the antigen immunoassay were 60.5% (95% confidence interval [CI] 55.5–65.4) and 99.9% (95% CI 99.6–100), respectively. A 93.7% (95% CI 89.7–96.5) sensitivity was achieved at a viral RNA concentration ≥104 copies/mL (cycle threshold (Ct) value <29.9). Conclusion: The Elecsys SARS-CoV-2 Antigen assay reliably detected patient samples with viral loads of 10,000 copies/mL and higher. It thus represents a viable high-throughput alternative for pre-screening of patients, or in situations where PCR testing is not readily available.

scholarly journals Performance of the LIAISON® SARS-CoV-2 Antigen Assay vs. SARS-CoV-2-RT-PCR

Pathogens ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 658
Author(s):  
Melanie Fiedler ◽  
Caroline Holtkamp ◽  
Ulf Dittmer ◽  
Olympia E. Anastasiou
Keyword(s):  
Reference Method ◽  
Respiratory Viruses ◽  
Cross Reactivity ◽  
Clinical Samples ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Chain Reaction ◽  
Viral Loads ◽  
Antigen Assay ◽  
Polymerase Chain

We aimed to evaluate the LIAISON® SARS-CoV-2 antigen assay (DiaSorin), comparing its performance to real-time polymerase chain reaction (RT-PCR) for the detection of SARS-CoV-2 RNA. 182 (110 PCR-positive and 72 PCR-negative) nasopharyngeal swab samples were taken for the detection of SARS-CoV-2. RT-PCR and antigen assay were performed using the same material. The sensitivity and specificity of the antigen assay were calculated for different cut-offs, with RT-PCR serving as the reference method. Stored clinical samples that were positive for other respiratory viruses were tested to evaluate cross-reactivity. One third (33/110, 30%) were falsely classified as negative, while no false positives were found using the 200 TCID50/mL cut-off for the SARS-CoV-2 antigen as proposed by the manufacturer. This corresponded to a sensitivity of 70% (60–78%) and a specificity of 100% (94–100%). Lowering the cut-off for positivity of the antigen assay to 22.79 or 57.68 TCID50/mL increased the sensitivity of the method, reaching a sensitivity of 92% (85–96%) vs. 79% (70–86%) and a specificity of 81% (69–89%) vs. 99% (91–100%), respectively. The antigen assay reliably detected samples with high SARS-CoV-2 viral loads (≥106 copies SARS-CoV-2/mL), while it cannot differentiate between negative and low positive samples. Cross-reactivity toward other respiratory viruses was not detected.

scholarly journals Sensitivity of Rapid Antigen Testing and RT-PCR Performed on Nasopharyngeal Swabs versus Saliva Samples in COVID-19 Hospitalized Patients: Results of a Prospective Comparative Trial (RESTART)

2021 ◽  
Vol 9 (9) ◽  
pp. 1910
Author(s):  
Antonios Kritikos ◽  
Giorgia Caruana ◽  
René Brouillet ◽  
John-Paul Miroz ◽  
Samia Abed-Maillard ◽  
...  
Keyword(s):  
Comparative Trial ◽  
Hospitalized Patients ◽  
Rt Pcr ◽  
Duration Of Symptoms ◽  
Non Invasive ◽  
Viral Transport Medium ◽  
One Step ◽  
Antigen Tests ◽  
Low Sensitivity ◽  
Antigen Testing

Saliva sampling could serve as an alternative non-invasive sample for SARS-CoV-2 diagnosis while rapid antigen tests (RATs) might help to mitigate the shortage of reagents sporadically encountered with RT-PCR. Thus, in the RESTART study we compared antigen and RT-PCR testing methods on nasopharyngeal (NP) swabs and salivary samples. We conducted a prospective observational study among COVID-19 hospitalized patients between 10 December 2020 and 1 February 2021. Paired saliva and NP samples were investigated by RT-PCR (Cobas 6800, Roche-Switzerland, Basel, Switzerland) and by two rapid antigen tests: One Step Immunoassay Exdia® COVID-19 Ag (Precision Biosensor, Daejeon, Korea) and Standard Q® COVID-19 Rapid Antigen Test (Roche-Switzerland). A total of 58 paired NP-saliva specimens were collected. A total of 32 of 58 (55%) patients were hospitalized in the intensive care unit, and the median duration of symptoms was 11 days (IQR 5-19). NP and salivary RT-PCR exhibited sensitivity of 98% and 69% respectively, whereas the specificity of these RT-PCRs assays was 100%. The NP RATs exhibited much lower diagnostic performance, with sensitivities of 35% and 41% for the Standard Q® and Exdia® assays, respectively, when a wet-swab approach was used (i.e., when the swab was diluted in the viral transport medium (VTM) before testing). The sensitivity of the dry-swab approach was slightly better (47%). These antigen tests exhibited very low sensitivity (4% and 8%) when applied to salivary swabs. Nasopharyngeal RT-PCR is the most accurate test for COVID-19 diagnosis in hospitalized patients. RT-PCR on salivary samples may be used when nasopharyngeal swabs are contraindicated. RATs are not appropriate for hospitalized patients.

scholarly journals Large parallel screen of saliva and nasopharyngeal swabs in a test center setting proofs utility of saliva as alternate specimen for SARS-CoV-2 detection by RT-PCR

2020 ◽  
Author(s):  
Michael Huber ◽  
Peter W. Schreiber ◽  
Thomas Scheier ◽  
Annette Audigé ◽  
Roberto Buonomano ◽  
...  
Keyword(s):  
High Volume ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Viral Loads ◽  
Non Invasive ◽  
Test Strategies ◽  
Percent Agreement ◽  
Home Testing ◽  
Attractive Option ◽  
Adults And Children

AbstractBackgroundA high volume of testing followed by rapid isolation and quarantine measures is critical to the containment of SARS-CoV-2. RT-PCR of nasopharyngeal swabs (NPS) has been established as sensitive gold standard for the detection of SARS-CoV-2 infection. Yet, additional test strategies are in demand to increase and broaden testing opportunities. As one attractive option, saliva has been discussed as an alternative to NPS as its collection is simple, non-invasive, suited for children and amenable for mass- and home-testing.MethodsHere, we report on the outcome of a head-to-head comparison of SARS-CoV-2 detection by RT-PCR in saliva and nasopharyngeal swab (NPS) of 1187 adults and children reporting to outpatient test centers and an emergency unit for an initial SARS-CoV-2 screen.ResultsIn total, 252 individuals were tested SARS-CoV-2 positive in either NPS or saliva. SARS-CoV-2 RT-PCR results in the two specimens showed a high agreement (Overall Percent Agreement = 98.0%). Despite lower viral loads in saliva, we observed sensitive detection of SARS-CoV-2 in saliva up to a threshold of Ct 33 in the corresponding NPS (Positive Percent Agreement = 97.7%). In patients with Ct above 33 in NPS, agreement rate dropped but still reaches notable 55.9%.ConclusionThe comprehensive parallel analysis of NPS and saliva reported here establishes saliva as a reliable specimen for the detection of SARS-CoV-2 that can be readily added to the diagnostic portfolio to increase and facilitate testing.Key pointsComparison with nasopharyngeal swabs in a large test center-based study shows that saliva is a reliable and convenient material for the detection of SARS-CoV-2 by RT-PCR in adults and children.

scholarly journals Surveillance testing for SARS-COV-2 infection in an asymptomatic athlete population: a prospective cohort study with 123 362 tests and 23 463 paired RT-PCR/antigen samples

2021 ◽  
Vol 7 (2) ◽  
pp. e001137
Author(s):  
Kimberly Harmon ◽  
Anabelle M de St Maurice ◽  
Adam C Brady ◽  
Sankar Swaminathan ◽  
Doug F Aukerman ◽  
...  
Keyword(s):  
Screening Programme ◽  
Sports Participation ◽  
High Specificity ◽  
Turnaround Time ◽  
Screening Tests ◽  
Rt Pcr ◽  
Pcr Screening ◽  
Testing Approach ◽  
Antigen Tests ◽  
Antigen Testing

ObjectiveTo assess the diagnostic accuracy of antigen compared with reverse transcriptase (RT)-PCR testing in an asymptomatic athlete screening programme and to monitor infection in college athletes.MethodsQuidel Sofia-2 SARS-CoV-2 Antigen Tests were performed daily before sports participation for football, basketball, wrestling and water polo from 29 September 2020 to 28 February 2021. Paired RT-PCR and antigen tests were performed at least once a week. Positive antigen tests were confirmed with RT-PCR.Results81 175 antigen and 42 187 RT-PCR tests were performed, including 23 462 weekly paired antigen/RT-PCR screening tests in 1931 athletes. One hundred and seventy-two athletes had a positive screening RT-PCR (0.4%), of which 83 (48%) occurred on paired testing days. The sensitivity of antigen tests varied with the frequency of RT-PCR testing and prevalence of COVID-19. The sensitivity of antigen testing was 35.7% (95% CI: 17% to 60%) and specificity 99.8% (95% CI: 99.7% to 99.9%) with once-a-week RT-PCR testing after adjusting for school prevalence. Daily antigen testing was similar to RT-PCR testing two to three times a week in identifying infection. Antigen testing identified infection before the next scheduled PCR on 89 occasions and resulted in 234 days where potentially infectious athletes were isolated before they would have been isolated with RT-PCR testing alone. Two athletic-related outbreaks occurred; 86% of total infections were community acquired.ConclusionAntigen testing has high specificity with a short turnaround time but is not as sensitive as RT-PCR. Daily antigen testing or RT-PCR testing two to three times a week is similar. There are benefits and drawbacks to each testing approach.

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

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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