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 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 On Pilot Massive COVID-19 Testing by Antigen Tests in Europe. Case Study: Slovakia

2021 ◽  
Vol 13 (1) ◽  
pp. 45-57
Author(s):  
Jaroslav Frnda ◽  
Marek Durica
Keyword(s):  
Mathematical Models ◽  
National Health ◽  
Health Authority ◽  
False Positive ◽  
Infection Rates ◽  
Rt Pcr ◽  
Sick People ◽  
Antigen Tests ◽  
Antigen Testing

This paper provides a summary of mass COVID-19 testing of almost the entire population in Slovakia by antigen tests. We focused on the results delivered by two testing rounds and analyzed the benefits and weaknesses of such type of testing. We prepared mathematical models to critically examine the effectiveness of the testing, and we also estimated the number of potentially sick people that would become infected by those marked as positives by antigen tests. Our calculations have proven that antigen testing in hotspots can flatten the curve of daily newly reported cases significantly, but in regions with low-risk of COVID-19, the benefit of such testing is questionable. As for the regions with low infection rates, we could only estimate the proportion of true and false-positive cases because the national health authority had not validated the results by RT–PCR tests. Therefore, this work can serve as an introductory study on the first nationwide testing by antigen tests in Europe.

scholarly journals The Performance of Two Rapid Antigen Tests During Population-Level Screening for SARS-CoV-2 Infection

2021 ◽  
Vol 8 ◽  
Author(s):  
Mohammad Alghounaim ◽  
Hamad Bastaki ◽  
Farah Bin Essa ◽  
Hoda Motlagh ◽  
Salman Al-Sabah
Keyword(s):  
Positive Predictive Value ◽  
Prospective Study ◽  
Predictive Value ◽  
Point Of Care ◽  
Population Level ◽  
Lower Sensitivity ◽  
Rt Pcr ◽  
Antigen Tests ◽  
A Prospective Study ◽  
Antigen Testing

Background: SARS-CoV-2 antigen assays offer a rapid mean to diagnose and isolate infected individuals. However, their utility in population-level screening is unknown.Objectives: The performance of two antigen tests in detecting SARS-CoV-2 was assessed among individuals randomly selected in the community.Study Design: A prospective study that performed head-to-head comparison of two SARS-CoV-2 antigen assays. Individuals were recruited during community SARS-CoV-2 screening over 10 working days. Demographic and clinical data were collected. Standard Q COVID-19 Ag test, a point-of-care chromatographic assay, was conducted immediately, and then the sample was transported to the virology laboratory to perform PCR and the LIAISON SARS-CoV-2 Ag chemiluminesence immunoassay.Results: respiratory samples from 991 individuals were collected, and 62 were positive by PCR. Inconclusive PCR results were observed in 19 samples and were excluded. The median age of participants was 40.2 years (IQR 32.3–47.8), and 932 (94%) were males. Most (77.4%) of infections were asymptomatic. The sensitivity and the specificity of the LIAISON assay were 43.3% (95%CI 30.6–56.8) and 99.9% (95%CI 99.3–100). The Standard Q assay had lower sensitivity (30.6%, 95%CI 19.6–43.7) but similar specificity (98.8%, 95%CI, 97.8–99.4). Similarly, the LIAISON assay had higher positive predictive value (96.3%, 95%CI 81–99.9% vs. 63.3%, 95%CI, 43.9–80.1%). Both assays performed better in symptomatic patients and among samples with a low-cycle threshold (Ct < 25).Conclusion: In our setting of random community surveillance, rapid antigen testing of nasopharyngeal swabs by either LIAISON SARS-CoV-2 Ag (DiaSorin) or Standard Q COVID-19 Ag (SD Biosensor) was less sensitive to detecting SARS-CoV-2 than the TaqPath COVID-19 RT-PCR.

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 Fast Detection of SARS-CoV-2 RNA Directly from Respiratory Samples Using a Loop-Mediated Isothermal Amplification (LAMP) Test

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 801
Author(s):  
Olympia E. Anastasiou ◽  
Caroline Holtkamp ◽  
Miriam Schäfer ◽  
Frieda Schön ◽  
Anna Maria Eis-Hübinger ◽  
...  
Keyword(s):  
Predictive Value ◽  
Lamp Assay ◽  
Detection Methods ◽  
Analytical Sensitivity ◽  
Rt Pcr ◽  
Viral Transport Medium ◽  
Rapid Tests ◽  
Sous Vide ◽  
Antigen Tests ◽  
Isothermal Assay

The availability of simple SARS-CoV-2 detection methods is crucial to contain the COVID-19 pandemic. This study examined whether a commercial LAMP assay can reliably detect SARS-CoV-2 genomes directly in respiratory samples without having to extract nucleic acids (NA) beforehand. Nasopharyngeal swabs (NPS, n = 220) were tested by real-time reverse transcription (RT)-PCR and with the LAMP assay. For RT-PCR, NA were investigated. For LAMP, NA from 26 NPS in viral transport medium (VTM) were tested. The other 194 NPS were analyzed directly without prior NA extraction (140 samples in VTM; 54 dry swab samples stirred in phosphate buffered saline). Ten NPS were tested directly by LAMP using a sous-vide cooking unit. The isothermal assay demonstrated excellent specificity (100%) but moderate sensitivity (68.8%), with a positive predictive value of 1 and a negative predictive value of 0.65 for direct testing of NPS in VTM. The use of dry swabs, even without NA extraction, improved the analytical sensitivity; up to 6% of samples showed signs of inhibition. LAMP could be performed successfully with a sous-vide cooking unit. This technique is very fast, requires little laboratory resources, and can replace rapid antigen tests or verify reactive rapid tests on-site.

scholarly journals Five Antigen Tests for SARS-CoV-2: Virus Viability Matters

Viruses ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 684
Author(s):  
Miroslav Homza ◽  
Hana Zelena ◽  
Jaroslav Janosek ◽  
Hana Tomaskova ◽  
Eduard Jezo ◽  
...  
Keyword(s):  
False Negative ◽  
Antigen Test ◽  
Rt Pcr ◽  
False Negatives ◽  
Predictive Values ◽  
Asymptomatic Patients ◽  
High Prevalence ◽  
Antigen Tests ◽  
Antigen Testing ◽  
Excellent Tool

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

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 Development and Clinical Evaluation of an Immunochromatography-Based Rapid Antigen Test (GenBody™ COVAG025) for COVID-19 Diagnosis

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 796
Author(s):  
Doyeong Kim ◽  
Jihoo Lee ◽  
Jyotiranjan Bal ◽  
Seul Ki Seo ◽  
Chom-Kyu Chong ◽  
...  
Keyword(s):  
Real Time ◽  
Sensitivity And Specificity ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Clinical Sensitivity ◽  
Viral Transport ◽  
Global Pandemic ◽  
Viral Transport Medium ◽  
Antigen Tests ◽  
Higher Sensitivity

Antigen tests for SARS-CoV-2 diagnosis are simpler and faster than their molecular counterparts. Clinical validation of such tests is a prerequisite before their field applications. We developed and clinically evaluated an immunochromatographic immunoassay, GenBody™ COVAG025, for the rapid detection of SARS-CoV-2 nucleocapsid (NP) antigen in two different clinical studies. Retrospectively, 130 residual nasopharyngeal swabs transferred in viral transport medium (VTM), pre-examined for COVID-19 through emergency use authorization (EUA)-approved real-time RT-PCR assay and tested with GenBody™ COVAG025, revealed a sensitivity and specificity of 90.00% (27/30; 95% CI: 73.47% to 97.89%) and 98.00% (98/100; 95% CI: 92.96% to 99.76%), respectively, fulfilling WHO guidelines. Subsequently, the prospective examination of 200 symptomatic and asymptomatic nasopharyngeal swabs, collected on site and tested with GenBody™ COVAG025 and EUA-approved real-time RT-PCR assay simultaneously, revealed a significantly higher sensitivity and specificity of 94.00% (94/100; 95% CI: 87.40% to 97.77%) and 100.00% (100/100; 95% CI: 96.38% to 100.00%), respectively. Clinical sensitivity and specificity were significantly high for samples with Ct values ≤ 30 as well as within 3 days of symptom onset, justifying its dependency on the viral load. Thus, it is assumed this can help with the accurate diagnosis and timely isolation and treatment of patients with COVID-19, contributing to better control of the global pandemic.

scholarly journals The dark side of SARS-CoV-2 rapid antigen testing: screening asymptomatic patients

2021 ◽  
Author(s):  
Giorgia Caruana ◽  
Laure-Line Lebrun ◽  
Oriane Aebischer ◽  
Onya Opota ◽  
Luis Urbano ◽  
...  
Keyword(s):  
Hospital Admissions ◽  
Screening Method ◽  
Dark Side ◽  
Pcr Analysis ◽  
Rt Pcr ◽  
Asymptomatic Patients ◽  
Antigen Tests ◽  
Outpatient Settings ◽  
Antigen Testing

AbstractMost of the reports describing SARS-CoV-2 rapid antigen tests (RATs) performances derive from COVID-19 symptomatic subjects in outpatient settings during periods of highest incidence of infections and high rates of hospital admissions. Here we investigated the role of RATs in an Emergency Department, as a screening tool before admission for COVID-19 asymptomatic patients. Each patient was screened with two simultaneous nasopharyngeal swabs: one immediately analyzed at the bedside using RAT and the other sent to the laboratory for RT-PCR analysis. A total of 116 patients were screened at hospital admission in a 250-bed community hospital in Morges (EHC), Switzerland. With a disease prevalence of 6% based on RT-PCR results, RAT detected only two out of seven RT-PCR positive patients (sensitivity 28.6%) and delivered two false positive results (specificity 98.2%), thus resulting not fiable enough to be used as a screening method in this clinical scenario.

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.

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