Evaluation of a rapid antigen test (Panbio™ COVID-19 Ag rapid test device) for SARS-CoV-2 detection in asymptomatic close contacts of COVID-19 patients
Objectives: There is limited information on the performance of rapid antigen detection (RAD) tests to identify SARS-CoV-2-infected asymptomatic individuals. In this field study, we evaluated the Panbio™ COVID-19 Ag Rapid Test Device (Abbott Diagnostics, Jena, Germany) for this purpose.
Methods: A total of 634 individuals (355 female; median age, 37 years; range, 9-87) were enrolled. Two nasopharyngeal swabs were collected from household (n=338) and non-household contacts (n=296) of COVID-19 cases. RAD testing was carried out at the point of care. The RT-PCR test used was the TaqPath COVID-19 Combo Kit (Thermo Fisher Scientific, Massachusetts, USA).
Results: Household contacts were tested at a median of 2 days (range, 1-7) after diagnosis of the index case, whereas non-household contacts (n=296) were tested at a median of 6 days (range, 1-7) after exposure. In total, 79 individuals (12.4%) tested positive by RT-PCR, of whom 38 (48.1%) yielded positive RAD results. The overall sensitivity and specificity of the RAD test was 48.1% (95% CI: 37.4-58.9) and 100% (95% CI: 99.3-100), respectively. Sensitivity was higher in household (50.8%; 95% CI: 38.9-62.5) than in non-household (35.7%; 95% CI:16.3-61.2%) contacts. Individuals testing positive by RAD test were more likely (P<0.001) to become symptomatic than their negative counterparts.
Conclusion: The Panbio test displays low sensitivity in asymptomatic close contacts of COVID-19 patients, particularly in non-household contacts. Nonetheless, establishing the optimal timing for upper respiratory tract collection in this group seems imperative to pinpoint test sensitivity.
Evaluation of two rapid antigen tests to detect SARS-CoV-2 in a hospital setting
Successful containment strategies for the SARS-CoV-2 pandemic will depend on reliable diagnostic assays. Point-of-care antigen tests (POCT) may provide an alternative to time-consuming PCR tests to rapidly screen for acute infections on site. Here, we evaluated two SARS-CoV-2 antigen tests: the STANDARD™ F COVID-19 Ag FIA (FIA) and the SARS-CoV-2 Rapid Antigen Test (RAT). For diagnostic assessment, we used a large set of PCR-positive and PCR-negative respiratory swabs from asymptomatic and symptomatic patients and health care workers in the setting of two University Hospitals in Munich, Germany, i.e. emergency rooms, patient care units or employee test centers.
For FIA, overall clinical sensitivity and specificity were 45.4% (n = 381) and 97.8% (n = 360), respectively, and for RAT, 50.3% (n = 445) and 97.7% (n = 386), respectively. For primary diagnosis of asymptomatic and symptomatic individuals, diagnostic sensitivities were 60.9% (FIA) (n = 189) and 64.5% (RAT) (n = 256). This questions these tests’ utility for the reliable detection of acute SARS-CoV-2-infected individuals, in particular in high-risk settings. We support the proposal that convincing high-quality outcome data on the impact of false-negative and false-positive antigen test results need to be obtained in a POCT setting. Moreover, the efficacy of alternative testing strategies to complement PCR assays must be evaluated by independent laboratories, prior to widespread implementation in national and international test strategies.
Head-to-Head Comparison of Rapid and Automated Antigen Detection Tests for the Diagnosis of SARS-CoV-2 Infection
(1) Background: The detection of SARS-CoV-2 RNA in nasopharyngeal samples through real-time reverse transcription-polymerase chain reaction (RT-PCR) is considered the standard gold method for the diagnosis of SARS-CoV-2 infection. Antigen detection (AD) tests are more rapid, less laborious, and less expensive alternatives but still require clinical validation.
(2) Methods: This study compared the clinical performance of five AD tests, including four rapid AD (RAD) tests (biotical, Panbio, Healgen, and Roche) and one automated AD test (VITROS). For that purpose, 118 (62.8%) symptomatic patients and 70 (37.2%) asymptomatic subjects were tested, and results were compared to RT-PCR.
(3) Results: The performance of the RAD tests was modest and allowed us to identify RT-PCR positive patients with higher viral loads. For Ct values ≤25, the sensitivity ranged from 93.1% (95% CI: 83.3-98.1%) to 96.6% (95% CI: 88.1-99.6%), meaning that some samples with high viral loads were missed. Considering the Ct value proposed by the CDC for contagiousness (i.e., Ct values ≤33) sensitivities ranged from 76.2% (95% CI: 65.4-85.1%) to 88.8% (95% CI: 79.7-94.7%) while the specificity ranged from 96.3% (95% CI: 90.8-99.0%) to 99.1% (95% CI: 95.0-100%). The VITROS automated assay showed a 100% (95% CI: 95.5-100%) sensitivity for Ct values ≤33, and had a specificity of 100% (95% CI: 96.6-100%);
(4) Conclusions: Compared to RAD tests, the VITROS assay fully aligned with RT-PCR for Ct values up to 33, which might allow a faster, easier and cheaper identification of SARS-CoV-2 contagious patients.
An Aggregation-Induced Emission Material Labeling Antigen-Based Lateral Flow Immunoassay Strip for Rapid Detection of Escherichia coli O157:H7
Escherichia coli O157:H7 (E. coli O157:H7) is a dangerous foodborne pathogen, mainly found in beef, milk, fruits, and their products, causing harm to human health or even death. Therefore, the detection of E. coli O157:H7 in food is particularly important. In this paper, we report a lateral flow immunoassay strip (LFIS) based on aggregation-induced emission (AIE) material labeling antigen as a fluorescent probe for the rapid detection of E. coli O157:H7. The detection sensitivity of the strip is 105 CFU/mL, which is 10 times higher than that of the colloidal gold test strip. This method has good specificity and stability and can be used to detect about 250 CFU of E. coli O157:H7 successfully in 25 g or 25 mL of beef, jelly, and milk. AIE-LFIS might be valuable in monitoring food pathogens for rapid detection
Comparative Analysis of Rapid Test and Enzyme Linked Immunosorbent Assay for Screening of Blood Donors for Hepatitis B Surface Antigen Seropositivity
Background: The Hepatitis B surface Antigen (HBsAg) is the most utilized indicator marker of hepatitis B infection. This study assesses the accuracy of the two most common screening assays used to detect HBsAg among blood donors.
Materials and methods: A total of 350 eligible blood donors were screened for HBsAg using both Bio-Check HBsAg Rapid screening kit (BioCheck Inc, South San Francisco, USA) and a fourth-generation Enzyme-Linked Immunoassays (ELISA) kit, MonolisaTM HBs Ag Ultra (Bio-Rad Laboratories, Marnes-la-Coquette-France). Questionnaires were used to inquire about risk factors for HBV infection among blood donors. The calculation of sensitivity, specificity, negative predictive and positive predictive values were carried out by comparing the performance of the rapid kit with ELISA test as the reference standard.
Results: The prevalence of HBV infection using Rapid Diagnostic Test (RDT) was 5.7% but was 14.6% by ELISA. Using ELISA as a reference, the sensitivity and specificity of RDT were 31.4% and 98.7% respectively. The positive predictive value and negative predictive value for RDT were 80.0% and 89.4% respectively. Overall non-compliance with transfusion-transmitted infection (TTI) risk-related deferral criteria was 38%.
Conclusion: The low sensitivity of RDT kits precludes its continuous use in high HBV endemic regions where many donors fail to disclose full and truthful information about their risk for TTI. It is suggested that blood banks should complement the use of RDT with a more sensitive assay such as ELISA.
Performance characteristics of a rapid SARS-CoV-2 antigen detection assay at a public plaza testing site in San Francisco
We evaluated the performance of the Abbott BinaxNOW TM Covid-19 rapid antigen test (Binax-CoV2) to detect virus among persons, regardless of symptoms, at a public plaza site of ongoing community transmission. Titration with cultured SARS-CoV-2 yielded a human observable threshold between 1.6×10 4-4.3×10 4 viral RNA copies (cycle threshold (Ct) of 30.3-28.8).
Among 878 subjects tested, 3% (26/878) were positive by RT-PCR, of which 15/26 had Ct<30, indicating high viral load. 40% (6/15) of Ct<30 were asymptomatic. Using this Ct<30 threshold for Binax-CoV2 evaluation, the sensitivity of Binax-CoV2 was 93.3% (14/15), 95% CI: 68.1-99.8%, and the specificity was 99.9% (855/856), 95% CI: 99.4-99.9%.