Antigen-detecting Rapid Diagnostic Tests Research Articles

SARS-CoV-2 rapid antigen test sensitivity and viral load in newly symptomatic hospital employees in Berlin, Germany, December, 2020 to February, 2022: an observational study

Evolving SARS-CoV-2 variants and changing levels of pre-existing immunity require re-evaluation of antigen-detecting rapid diagnostic test (Ag-RDT) performance. We investigated possible associations between Ag-RDT sensitivity and various potential influencing factors, such as immunisation status and viral variant, in symptomatic hospital employees. In this observational study, RT-PCR, Ag-RDT, and symptom-specific data were collected at three SARS-CoV-2 test centres for employees of the Charité-Universitätsmedizin Berlin hospital (Berlin, Germany). Employees reporting SARS-CoV-2-like symptoms, those at an increased risk of infection (eg, due to contact with an infected person), those testing positive in a previous self-administered Ag-RDT, or those seeking release-testing to return to work at least 7 days after a positive RT-PCR test were eligible for combined testing by RT-PCR and Ag-RDT. Only data from individuals with an ongoing SARS-CoV-2 infection as assessed by RT-PCR were used for further analysis. Bayesian regression analyses were done to evaluate possible differences in viral load and Ag-RDT sensitivity according to viral variant and immunisation status (previous vaccination or recovery from infection), using data from first RT-PCR positive samples in an infection. A comprehensive logistic regression analysis was used to investigate potential concomitant associations between Ag-RDT sensitivity and level of pre-existing immunity, time post symptom onset, viral load, gender, age, and Ag-RDT device. Ag-RDT performance was also compared between supernatants from cell cultures infected with the omicron variant of concern (VOC) or the wild-type strain (pre-VOC). Between Nov 30, 2020 and Feb 11, 2022, a total of 14 773 samples from 7675 employees were tested for SARS-CoV-2 by both RT-PCR and Ag-RDT. We found a negative association between immunisation status and Ag-RDT sensitivity in symptomatic employees, with an observed sensitivity of 82% (94% highest posterior density interval [HPDI] 78-86) in immunologically naive participants compared with 73% (68-78) in multiply immunised individuals (ie, those with at least two vaccinations or recoveries from infection) and median log10 viral loads of 7·02 (IQR 5·83-8·07) and 8·08 (6·80-8·89), respectively. The dominant viral variant changed several times during the study period, from the pre-VOC period (sensitivity 80% [94% HPDI 75-85] in symptomatic participants) through the alpha variant (82% [70-94]), delta variant (75% [69-82]), and omicron variant (72% [65-79]) waves, concomitantly with a steep increase in vaccination coverage in our dataset. In a comparison of Ag-RDT performance on cell culture supernatants, we found no difference between the wild-type and omicron viral variants. On the basis of our findings and data from other studies, we hypothesise that the observed reduction in clinical Ag-RDT sensitivity, despite higher SARS-CoV-2 RNA loads, is due to shorter incubation times later in our study period resulting from increased population immunity or changes in immune response dynamics caused by later SARS-CoV-2 VOCs. Berlin University Alliance, German Ministry of Education and Research, the EU (Projects EU4Health and ReCoVer), and the Berlin Institute of Health.

Temporal Trend of the SARS-CoV-2 Omicron Variant and RSV in the Nasal Cavity and Accuracy of the Newly Developed Antigen-Detecting Rapid Diagnostic Test.

The aim of this work is to analyze the viral titers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and respiratory syncytial virus (RSV) at the anterior nasal site (ANS) and nasopharyngeal site (NS), evaluate their virological dynamics, and validate the usefulness of a newly developed two-antigen-detecting rapid antigen diagnostic test (Ag-RDT) that simultaneously detects SARS-CoV-2 and RSV using clinical specimens. This study included 195 asymptomatic to severely ill patients. Overall, 668 specimens were collected simultaneously from the ANS and NS. The cycle threshold (Ct) values calculated from real-time polymerase chain reaction were used to analyze temporal changes in viral load and evaluate the sensitivity and specificity of the Ag-RDT. The mean Ct values for SARS-CoV-2-positive, ANS, and NS specimens were 28.8, 28.9, and 28.7, respectively. The mean Ct values for RSV-positive, ANS, and NS specimens were 28.7, 28.8, and 28.6, respectively. SARS-CoV-2 and RSV showed the same trend in viral load, although the viral load of NS was higher than that of ANS. The sensitivity and specificity of the newly developed Ag-RDT were excellent in specimens collected up to 10 days after the onset of SARS-CoV-2 infection and up to 6 days after the onset of RSV infection.

Performance of two rapid antigen tests against SARS-CoV-2 in neighborhoods of socioeconomic vulnerability from a middle-income country.

As new and improved antigen-detecting rapid diagnostic tests for SARS-CoV-2 infection (Ag-RDT) continue to be developed, assessing their diagnostic performance is necessary to increase test options with accurate and rapid diagnostic capacity especially in resource-constrained settings. This study aimed to assess the performance of two Ag-RDTs in a population-based study. We conducted a diagnostic accuracy study in neighborhoods with high socioeconomic vulnerability in Salvador-Brazil, including individuals aged ≥12 years old who attended primary health services, between July and December 2022, with COVID-19 symptoms or who had been in contact with a confirmed case. Two Ag-RDTs were compared in parallel using reverse transcription polymerase chain reaction (RT-PCR) as reference standard, the PanbioTM COVID-19 Ag test (Abbott®) and Immuno-Rapid COVID-19 Ag (WAMA Diagnostic®). Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated. For the Abbott test the sensitivity was 52.7% (95% CI: 44.3% - 61.0%), specificity 100% (95% CI: 98.7% - 100%), PPV 100% (95% CI: 95.4% - 100%) and NPV 80.4% (95% CI: 75.9% - 84.4%). For the WAMA test, the sensitivity was 53.4% (95% CI: 45.0% - 61.6%), specificity 100% (95% CI: 98.7% - 100%), PPV 100% (95% CI: 95.4% - 100%) and NPV 80.7% (95% CI: 76.2% - 84.6%). Sensitivity for the group with Cycle Threshold (CT) <24 was 82.3% (95%CI: 72.1-90.0, n = 83) for PanbioTM COVID-19 Ag test and 87.3% (95%CI: 77.9-93.8, n = 83) for Immuno-Rapid COVID-19 Ag test. Sensitivity for both Ag-RDT was lower than reported by manufacturers. In the stratified analysis, sensitivity was higher among those with lower CT values <24. Specificity was high for both rapid antigen tests. Both Ag-RDT showed to be useful for rapid diagnostic of potential cases of COVID-19. Negative results must be assessed carefully according to clinical and epidemiological information.

Feasibility and acceptability of COVID-19 self-testing in the Philippines

Self-testing for COVID-19 using antigen-detecting rapid diagnostic tests (Ag-RDTs) shows high promise in the Philippines. Self-testing has the potential to provide broader access to testing, empowering individuals by bringing healthcare services closer to them. We conducted 15 semi-structured interviews with health officers and decision-makers in the Philippines. These interviews explored the experiences and perspectives on the acceptability and feasibility of self-test use and implementation. We found that self-testing is easy-to-use, provides rapid results and can facilitate early detection. However, ­regulatory policies, linkages to care and effective health ­education plans must be in place for successful implementation.

The development of a highly sensitive and quantitative SARS-CoV-2 rapid antigen test applying newly developed monoclonal antibodies to an automated chemiluminescent flow-through membrane immunoassay device

BackgroundRapid and accurate diagnosis of individuals with SARS-CoV-2 infection is an effective way to prevent and control the spread of COVID-19. Although the detection of SARS‐CoV‐2 viral RNA by RT‐qPCR is the gold standard for COVID-19 testing, the use of antigen-detecting rapid diagnostic tests (Ag-RDTs) is emerging as a complementary surveillance tool as Omicron case numbers skyrocket worldwide. However, the results from Ag-RDTs are less accurate in individuals with low viral loads.ResultsTo develop a highly sensitive and accurate Ag-RDT, 90 monoclonal antibodies were raised from guinea pigs immunized with SARS CoV-2 nucleocapsid protein (CoV-2-NP). By applying a capture antibody recognizing the structural epitope of the N-terminal domain of CoV-2-NP and a detection antibody recognizing the C-terminal tail of CoV-2-NP to an automated chemiluminescence flow-through membrane immunoassay device, we developed a novel Ag-RDT, CoV-2-POCube. The CoV-2-POCube exclusively recognizes CoV-2-NP variants but not the nucleocapsid proteins of other human coronaviruses. The CoV-2-POCube achieved a limit of detection sensitivity of 0.20 ~ 0.66 pg/mL of CoV-2-NPs, demonstrating more than 100 times greater sensitivity than commercially available SARS-CoV-2 Ag-RDTs.ConclusionsCoV-2-POCube has high analytical sensitivity and can detect SARS-CoV-2 variants in 15 min without observing the high-dose hook effect, thus meeting the need for early SARS-CoV-2 diagnosis with lower viral load. CoV-2-POCube is a promising alternative to currently available diagnostic devices for faster clinical decision making in individuals with suspected COVID-19 in resource-limited settings.

Comparison of the Rapid Antigen Test to RT-qPCR in Diagnosis of SARS-CoV-2: A University Experience in Northern Cyprus

Objective: As an alternative to RT-qPCR assays used in the diagnosis SARS-CoV-2, antigen-detecting rapid diagnostic tests (Ag-RDTs) are available for the qualitative detection of SARS-CoV-2 in nasopharyngeal swab samples. The aim of this study was to assess the accuracy and reliability of Ag-RDTs as a diagnostic method of detecting SARS-CoV-2 positive cases within a given population.&#x0D; Methods: In first phase of this investigation, 357 nasopharyngeal swab samples were screened for SARS-CoV-2 using Ag-RDTs. For the purposes of this study RT-qPCR was then applied to the same 357 nasopharyngeal swab samples in order to compare the reliability of the two detection methods. In the second phase of this investigation, Ag-RDTs were applied to an additional 75 nasopharyngeal swab samples that were already known to be RT-qPCR positive. &#x0D; Results: In the first phase of this investigation, of the 357 samples screened using Ag-RDTs 14 samples were positive for SARS-CoV-2, in contrast, when RT-qPCR analysis was applied to the same 357 samples no SARS-CoV-2 samples were detected. Therefore, the false antigen positivity was determined to be at 3.9%. In the second phase of this investigation 75 RT-qPCR positive samples were re-evaluated with a rapid antigen test. Twenty-four of the 75 RT-qPCR positive sample were undetected.&#x0D; Conclusion: Solely relying on rapid antigen tests to detect SARS-CoV-2 infections in the community could consequently result in infectious individuals remaining in the population. The impact of false negative rapid test results can be reduced by implementing confirmatory RT-qPCR analysis particularly in symptomatic patients.

Organic Electrochemical Transistor Immuno-Sensors for Spike Protein Early Detection.

The global COVID-19 pandemic has had severe consequences from the social and economic perspectives, compelling the scientific community to focus on the development of effective diagnostics that can combine a fast response and accurate sensitivity/specificity performance. Presently available commercial antigen-detecting rapid diagnostic tests (Ag-RDTs) are very fast, but still face significant criticisms, mainly related to their inability to amplify the protein signal. This translates to a limited sensitive outcome and, hence, a reduced ability to hamper the spread of SARS-CoV-2 infection. To answer the urgent need for novel platforms for the early, specific and highly sensitive detection of the virus, this paper deals with the use of organic electrochemical transistors (OECTs) as very efficient ion-electron converters and amplifiers for the detection of spike proteins and their femtomolar concentration. The electrical response of the investigated OECTs was carefully analyzed, and the changes in the parameters associated with the transconductance (i.e., the slope of the transfer curves) in the gate voltage range between 0 and 0.3 V were found to be more clearly correlated with the spike protein concentration. Moreover, the functionalization of OECT-based biosensors with anti-spike and anti-nucleocapside proteins, the major proteins involved in the disease, demonstrated the specificity of these devices, whose potentialities should also be considered in light of the recent upsurge of the so-called "long COVID" syndrome.

Simultaneous screening for COVID-19 and tuberculosis, India.

To evaluate the implementation of new operational workflows for simultaneous screening of coronavirus disease 2019 (COVID-19) and tuberculosis at four high-volume COVID-19 testing centres located in tertiary hospitals in Mumbai, India. Each centre already offering antigen-detecting rapid diagnostic tests were equipped with a rapid molecular testing platform for COVID-19 and tuberculosis, sufficient laboratory staff, and reagents and consumables for screening. Using a verbal tuberculosis questionnaire, a patient follow-up agent screened individuals visiting the COVID-19 testing centres. Presumptive tuberculosis patients were asked to provide sputum samples for rapid molecular testing. Subsequently, we reversed our operational workflow to also screen patients visiting tuberculosis outpatient departments for COVID-19, using rapid diagnostic tests. From March to December 2021, we screened 14 588 presumptive COVID-19 patients for tuberculosis, of whom 475 (3.3%) were identified as having presumptive tuberculosis. Of these, 288 (60.6%) were tested and 32 individuals (11.1%) were identified as tuberculosis positive (219 cases per 100 000 individuals screened). Of the tuberculosis-positive individuals, three had rifampicin-resistant tuberculosis. Among the remaining 187 presumptive tuberculosis cases not tested, 174 reported no symptoms at follow-up and 13 individuals either refused testing or could not be traced. Of the 671 presumptive tuberculosis cases screened for COVID-19, 17 (2.5%) were positive by antigen rapid diagnostic tests, and five (0.7%) who tested negative, later tested positive on the molecular testing platform (2483 COVID-19 cases per 100 000 individuals screened). Simultaneous screening for COVID-19 and tuberculosis in India is operationally feasible and can improve real-time on-site detection of COVID-19 and tuberculosis.

Community-based COVID-19 active case finding and rapid response in the Democratic Republic of the Congo: Improving case detection and response.

A community-based coronavirus disease (COVID-19) active case-finding strategy using an antigen-detecting rapid diagnostic test (Ag-RDT) was implemented in the Democratic Republic of Congo (DRC) to enhance COVID-19 case detection. With this pilot community-based active case finding and response program that was designed as a clinical, prospective testing performance, and implementation study, we aimed to identify insights to improve community diagnosis and rapid response to COVID-19. This pilot study was modeled on the DRC's National COVID-19 Response Plan and the COVID-19 Ag-RDT screening algorithm defined by the World Health Organization (WHO), with case findings implemented in 259 health areas, 39 health zones, and 9 provinces. In each health area, a 7-member interdisciplinary field team tested the close contacts (ring strategy) and applied preventive and control measures to each confirmed case. The COVID-19 testing capacity increased from 0.3 tests per 10,000 inhabitants per week in the first wave to 0.4, 1.6, and 2.2 in the second, third, and fourth waves, respectively. From January to November 2021, this capacity increase contributed to an average of 10.5% of COVID-19 tests in the DRC, with 7,110 positive Ag-RDT results for 40,226 suspected cases and close contacts who were tested (53.6% female, median age: 37 years [interquartile range: 26.0-50.0)]. Overall, 79.7% (n = 32,071) of the participants were symptomatic and 7.6% (n = 3,073) had comorbidities. The Ag-RDT sensitivity and specificity were 55.5% and 99.0%, respectively, based on reverse transcription polymerase chain reaction analysis, and there was substantial agreement between the tests (k = 0.63). Despite its limited sensitivity, the Ag-RDT has improved COVID-19 testing capacity, enabling earlier detection, isolation, and treatment of COVID-19 cases. Our findings support the community testing of suspected cases and asymptomatic close contacts of confirmed cases to reduce disease spread and virus transmission.

Diagnostic Accuracy of a Rapid SARS-CoV-2 Antigen Test Among People Experiencing Homelessness: A Prospective Cohort and Implementation Study.

Detection strategies in vulnerable populations such as people experiencing homelessness (PEH) need to be explored to promptly recognize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreaks. This study investigated the diagnostic accuracy of a rapid SARS-CoV-2 Ag test in PEH during two pandemic waves compared with gold standard real-time multiplex reverse transcription polymerase chain reaction (rtRT-PCR). All PEH ≥ 18years requesting residence at the available shelters in Verona, Italy, across two cold-weather emergency periods (November 2020-May 2021 and December 2021-April 2022) were prospectively screened for SARS-CoV-2 infection by means of a naso-pharyingeal swab. A lateral flow immunochromatographic assay (Biocredit® COVID-19 Ag) was used as antigen-detecting rapid diagnostic test (Ag-RDT). The rtRT-PCR was performed with Allplex™ SARS-CoV-2 assay kit (Seegene). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated as measures for diagnostic accuracy. Overall, 503 participants were enrolled during the two intervention periods for a total of 732 paired swabs collected: 541 swabs in the first period and 191 in the second. No significant differences in demographic and infection-related characteristics were observed in tested subjects in the study periods, except for the rate of previous infection (0.8% versus 8%; p < 0.001) and vaccination (6% versus 73%; p < 0.001). The prevalence of SARS-CoV-2 in the cohort was 8% (58/732 swabs positive with rtRT-PCR). Seventeen swabs were collected from symptomatic patients (7%). Among them, the concordance between rtRT-PCR and Ag-RDT was 100%, 7 (41.2%) positive and 10 negative pairs. The overall sensitivity of Ag-RDT was 63.8% (95% CI 60.3-67.3) and specificity was 99.8% (95% CI 99.6-100). PPV and NPV were 97.5% and 96.8%, respectively. Sensitivity and specificity did not change substantially across the two periods (65.1% and 99.8% in 2020-2021 vs. 60% and 100% in 2021-2022). A periodic Ag-RDT-based screening approach for PEH at point of care could guide preventive measures, including prompt isolation, without referral to hospital-based laboratories for molecular test confirmation in case of positive detection even in individuals asymptomatic for COVID-19. This could help reduce the risk of outbreaks in shelter facilities.

The Use of Rapid COVID-19 Antigen Test in the Emergency Department as a Decision-Support Tool

The emergency department (ED) is the initial point of contact between hospital staff and patients potentially infected with SARS-CoV-2, thus, prevention of inadvertent exposure to other patients is a top priority. We aimed to assess whether the introduction of antigen-detecting rapid diagnostic tests (Ag-RDTs) to the ED affected the likelihood of unwanted SARS-CoV-2 exposures. In this retrospective single-center study, we compared the rate of unwarranted exposure of uninfected adult ED patients to SARS-CoV-2 during two separate research periods; one before Ag-RDTs were introduced, and one with Ag-RDT used as a decision-support tool. The introduction of Ag-RDTs to the ED significantly decreased the relative risk of SARS-CoV-2-negative patients being incorrectly assigned to the COVID-19 designated site ("red ED"), by 97%. There was no increase in the risk of SARS-CoV-2-positive patients incorrectly assigned to the COVID-19-free site ("green ED"). In addition, duration of ED admission was reduced in both the red and the green ED. Therefore, implementing the Ag-RDT-based triage protocol proved beneficial in preventing potential COVID-19 nosocomial transmission.

Feasibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen self-testing in school and summer camp attendees.

SARS-CoV-2 screening is one of the pillars of non-pharmaceutical preventive strategies to early identify and isolate infected individuals and therefore decrease community incidence. We assessed the feasibility of severe acute respiratory syndrome coronavirus 2 self-testing with antigen-detecting rapid diagnostic tests in attendees of educational settings. A total of 305 students (88.15%) and 41 staff (11.85%) from 9 to 56 years old participated in the self-testing procedure and answered the survey at the end of the study. 91.3% (n = 313) did not need help, 96.1% of participants reported the same outcome as the healthcare workers. 94.5% strongly or slightly agree with the statement "I would repeat the experience". The study demonstrates that self-testing is acceptable and usable in children, adolescents and adults when the epidemiological situation may require a systematic screening of these populations, although supervision by health care or previously trained personnel is recommended for younger age groups.

Rapid antigen test as a tool for the identification of SARS-CoV-2 infection and its potential as a self-testing device

SARS-CoV-2 virus originated in Wuhan (China) in December (2019) and quickly spread worldwide. Antigen tests are rapid diagnostic tests (RDT) that produce results in 15-30 min and are an important tool for the scale-up of COVID-19 testing. COVID-19 diagnostic tests are authorized for self-testing at home in some countries, including Brazil. Widespread COVID-19 diagnostic testing is required to guide public health policies and control the speed of transmission and economic recovery. Patients with suspected COVID-19 were recruited at the Hospital da Baleia (Belo Horizonte, Brazil). The SARS-CoV-2 antigen-detecting rapid diagnostic tests were evaluated from June 2020 to June 2021 using saliva, nasal, and nasopharyngeal swab samples from 609 patients. Patient samples were simultaneously tested using a molecular assay (RT-qPCR). Sensitivity, specificity, accuracy, and positive and negative predictive values were determined using the statistical program, MedCalc, and GraphPad Prism 8.0. The antigen-detecting rapid diagnostic tests displayed 98% specificity, 60% sensitivity, 96% positive predictive value, and moderate concordance with RT-qPCR. Substantial agreement was found between the two methods for patients tested < 7 days of symptom onset. Our findings support the use of Ag-RDT as a valuable and safe diagnostic method. Ag-RDT was also demonstrated to be an important triage tool for suspected COVID-19 patients in emergencies. Overall, Ag-RDT is an effective strategy for reducing the spread of SARS-CoV-2 and contributing to COVID-19 control.

Production of a Monoclonal Antibody to the Nucleocapsid Protein of SARS-CoV-2 and Its Application to ELISA-Based Detection Methods with Broad Specificity by Combined Use of Detector Antibodies.

The coronavirus disease 2019 pandemic, elicited by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is ongoing. Currently accessible antigen-detecting rapid diagnostic tests are limited by their low sensitivity and detection efficacy due to evolution of SARS-CoV-2 variants. Here, we produced and characterized an anti-SARS-CoV-2 nucleocapsid (N) protein-specific monoclonal antibody (mAb), 2A7H9. Monoclonal antibody 2A7H9 and a previously developed mAb, 1G10C4, have different specificities. The 2A7H9 mAb detected the N protein of S clade, delta, iota, and mu but not omicron, whereas the 1G10C4 antibody recognized the N protein of all variants under study. In a sandwich enzyme-linked immunosorbent assay, recombinant N protein bound to the 1G10C4 mAb could be detected by both 1G10C4 and 2A7H9 mAbs. Similarly, N protein bound to the 2A7H9 mAb was detected by both mAbs, confirming the existence of dimeric N protein. While the 1G10C4 mAb detected omicron and mu with higher efficiency than S clade, delta, and iota, the 2A7H9 mAb efficiently detected all the strains except omicron, with higher affinity to S clade and mu than others. Combined use of 1G10C4 and 2A7H9 mAb resulted in the detection of all the strains with considerable sensitivity, suggesting that antibody combinations can improve the simultaneous detection of virus variants. Therefore, our findings provide insights into the development and improvement of diagnostic tools with broader specificity and higher sensitivity to detect rapidly evolving SARS-CoV-2 variants.

317. Use cases for rapid antigen-detecting tests for COVID-19 screening and surveillance: a systematic review

Abstract Background Testing remains critical to controlling the COVID-19 pandemic. Antigen-detecting rapid diagnostic tests (Ag-RDTs), which can be used at the point of care, have the potential to increase access to COVID-19 testing, particularly in settings with limited laboratory capacity. This systematic review synthesized literature on specific use cases and performance of Ag-RDTs for detecting SARS-CoV-2, for the first comprehensive assessment of Ag-RDT use in real-world settings. Methods We searched three databases (PubMed, EMBASE and medRxiv) up to 12 April 2021 for publications on Ag-RDT use for large-scale screening and surveillance of COVID-19, excluding studies of only presumptive COVID-19 patients. We tabulated data on the study setting, populations, type of test, diagnostic performance, and operational findings. We assessed risk of bias using QUADAS-2 and an adapted tool for prevalence studies. Results From 4313 citations, 39 studies conducted in asymptomatic and symptomatic individuals were included. Of 39 studies, 37 (94.9%) investigated lateral flow Ag-RDTs and 2 (5.1%) investigated multiplex sandwich chemiluminescent enzyme immunoassay Ag-RDTs. Six categories of testing initiatives were identified: mass screening (n=13), targeted screening (n=11), healthcare entry testing (n=6), at-home testing (n=4), surveillance (n=4) and prevalence survey (n=1). Sensitivity and specificity values by testing category are shown in the table. Ag-RDTs were noted as convenient, easy-to-use, and low cost, with a rapid turnaround time and high user acceptability. Risk of bias was generally low or unclear across studies. Conclusion During the first year of the COVID-19 pandemic, Ag-RDTs were used across a wide range of real-world settings for screening and surveillance of COVID-19 in both symptomatic and asymptomatic individuals. Ag-RDTs were fast and simple to run, but due to their often low sensitivity, careful consideration must be given to their implementation and interpretation. Ag-RDTs have subsequently been rolled out more broadly and recommended for COVID-19 self-testing. Disclosures Talya Underwood, MPhil, Oncotherapeutics: Medical writing.

Evaluation of the Access Bio CareStart rapid SARS-CoV-2 antigen test in asymptomatic individuals tested at a community mass-testing program in Western Massachusetts

Point-of-care antigen-detecting rapid diagnostic tests (RDTs) to detect Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) represent a scalable tool for surveillance of active SARS-CoV-2 infections in the population. Data on the performance of these tests in real-world community settings are paramount to guide their implementation to combat the COVID-19 pandemic. We evaluated the performance characteristics of the CareStart COVID-19 Antigen test (CareStart) in a community testing site in Holyoke, Massachusetts. We compared CareStart to a SARS-CoV-2 reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) reference, both using anterior nasal swab samples. We calculated the sensitivity, specificity, and the expected positive and negative predictive values at different SARS-CoV-2 prevalence estimates. We performed 666 total tests on 591 unique individuals. 573 (86%) were asymptomatic. There were 52 positive tests by RT-qPCR. The sensitivity of CareStart was 49.0% (95% Confidence Interval (CI) 34.8-63.4) and specificity was 99.5% (95% CI 98.5-99.9). Among positive RT-qPCR tests, the median cycle threshold (Ct) was significantly lower in samples that tested positive on CareStart. Using a Ct ≤ 30 as a benchmark for positivity increased the sensitivity of the test to 64.9% (95% CI 47.5-79.8). Our study shows that CareStart has a high specificity and moderate sensitivity. The utility of RDTs, such as CareStart, in mass implementation should prioritize use cases in which a higher specificity is more important, such as triage tests to rule-in active infections in community surveillance programs.

The Performance of Antigen-detecting Rapid Diagnostic Test Among COVID-19 Outbreaks in North-Eastern Peninsular Malaysia

Background and aims: Accurate and timely diagnosis is crucial for coronavirus disease 2019 (COVID-19) outbreaks. Antigen-detecting rapid diagnostic tests (Ag-RDTs) are easily accessible and affordable, producing rapid results. They are an alternative to the limited gold-standard real-time reverse-transcription polymerase chain reaction (rRT-PCR) tests. This study assessed the performance of Ag-RDTs for COVID-19 outbreaks in institutional settings with high disease prevalence in Kelantan State, Malaysia. Methods: This study analyzed a total of 303 individuals from five institutional outbreaks with paired nasopharyngeal specimens tested for COVID-19 by Ag-RDTs and rRT-PCR. The diagnostic performance of Ag-RDTs was evaluated through rRT-PCR as the gold standard based on cycle threshold (Ct) value, disease prevalence, and manufacturers. Results: There was a moderate agreement between Ag-RDTs and RT-PCR (κ=0.603; 95% CI: 0.520- 0.686; P&lt;0.001). The overall specificity was 97.9% (95% CI: 94.1%-99.6%), sensitivity was 63.3% (95% CI: 55.3%-70.8%), accuracy Ag-RDTs was 81.2% (95% CI: 76.4%-85.5%), while positive and negative predictive value was 96.6% (95% CI: 90.2%-98.9%) and 74.1% (95% CI: 70.0%-77.9%), respectively. Further, lower median Ct was reported in 100 (33.0%) true-positive cases compared to 58 (19.1%) false-negative cases (20.3 vs 31.4, P&lt;0.001). The sensitivity was higher (P&lt;0.001) in those with high viral load (Ct value≤25.0) with better performance and a prevalence&gt;10%. In addition, no significant difference was observed between the studied manufacturers. Conclusion: The Ag-RDTs performed well in diagnosing COVID-19 among outbreaks with higher viral load and disease prevalence. High-risk cases tested negative by Ag-RDTs may have low viral load and require confirmation by rRT-PCR.

The Assessment of the Diagnostic Accuracy of Antigen-Detecting Rapid Diagnostic Test using Nasopharyngeal Swab Specimen in Detecting SARS-CoV-2 among Patients in a Private Hospital in Bulacan, Philippines

Abstract Introduction/Objective Continuous progression of the COVID-19 outbreak prompted an expensive, limited, and slow-moving laboratory-based molecular testing capacity of the gold standard, Real-time Reverse Transcription- Polymerase Chain Reaction (rRT-PCR), in detecting SARS-CoV-2. The vital step in mitigation is utilizing an accurate diagnostic detection assay to deploy various preventive measures. Therefore, there is a need to evaluate an accessible, fast, and inexpensive point-of-care immunoassay, such as Antigen-detecting Rapid Diagnostic Tests (Ag- RDTs). Thus, the study aimed to assess the diagnostic accuracy of Ag-RDT in detecting SARS-CoV-2. Methods/Case Report A non-experimental, quantitative, and cross-sectional cohort study utilized 272 SARS-CoV-2 Ag-RDT with rRT-PCR confirmation collected from April 2021 to February 2022 in a private primary hospital laboratory database in Bulacan, Philippines. Diagnostic accuracy parameters of Ag-RDT included in the study are sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Results (if a Case Study enter NA) The overall sensitivity and specificity of Ag-RDT were 69.6% and 98.8%, respectively. Additionally, it exhibited a PPV of 84.2% and an NPV of 97.2%. With a hypothetical 1% prevalence, PPV and NPV were 36.8% and 99.7%. Meanwhile, PPV and NPV were 86.5% and 96.7% at 10% prevalence. High specificity denotes that positive Ag-RDT test results can be confidently considered in true SARS-CoV-2 infection, while low sensitivity entails that a negative result must be subjected to confirmatory tests. Furthermore, when prevalence increases, PPV increases while NPV decreases. Conclusion The study primarily encapsulated that the Ag-RDT cannot replace rRT-PCR in detecting SARS-CoV-2 infections. Despite its shortcomings, Ag-RDT is still valuable in areas with moderate-to-high disease prevalence and with limited access to confirmatory test due to its high predictive values and advantages. A larger number of positive results of rRT-PCR, evaluation of factors correlating to low sensitivity, and a prospective study are recommended for future studies.

Performance of Two Rapid Antigen Detection Tests for Detecting COVID-19 Compared to RT-PCR in Indonesia

Antigen tests to screen coronavirus disease 2019 (COVID-19) is effective in symptomatic patients, leading to its wide usage in informing whether the person is COVID-19 positive or negative. Our current work had an objective to investigate the diagnostic performance of two antigen-detecting rapid diagnostic tests (Ag-RDTs) which are commonly used in Indonesia. A cross-sectional study was carried out to compare specificity, sensitivity, as well as expected predictive values of Anhui Ag-RDT and Lungene Ag-RDT by comparing the results with that obtained from real-time reverse transcription-polymerase chain reaction (RT-PCR) assay. A total of 98samples were tested for both Ag-RDTs and RT-PCR. The median value of the patients age obtained to be 41.78 years old (interquartile range: 1 to 91 years old). The proportion between female and males was: 52.53% vs 47.47%. The sensitivities of Anhui Ag-RDT and Lungene Ag-RDT were 55.56% and 51.58%, where both Ag-RDTs had specificity of 100%. In conclusion, sensitivity values of Lungene Ag-RDT and Anhui Ag-RDT are similar, where both possess 100% specificity with zero false-positive results. Both of the investigated Ag-RDTs are useful since positive results are likely to be COVID-19 positive.

Comparative Evaluation of Different SARS-CoV-2 Rapid Point-of-Care Antigen Tests with SARS-CoV-2 PCR for Diagnosis of COVID-19

BACKGROUND: Detection of positive 2019-nCoV nucleic acids by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR)-based assays performed on the upper and lower respiratory samples remains the gold standard for the diagnosis of COVID-19. However, antigen-detecting rapid diagnostic tests can offer a faster (15–30 min) and less expensive way to diagnose active severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than nucleic acid amplification tests. AIM: Hence, the present study aimed to compare and evaluate the results of different SARS-CoV-2 rapid point-of-care antigen tests with SARS-CoV-2 PCR as a reference method. METHODS: Sixty-five nasopharyngeal swab specimens were collected from attendees of the Reference Laboratory of Egyptian university hospitals. The samples were placed in viral transport medium for RNA extraction. The remaining part of the suspension was stored at −70°C until use for COVID-19 antigen testing. All samples were processed for the COVID-19 Ag rapid test and RT-PCR simultaneously. RESULTS: RT-PCR assay revealed 46 (70.8%) positive samples and 19 (29.2%) negative samples for COVID-19. All eight rapid antigen assays indicated specificity and positive predictive value of 100% each. As for the other parameters, the sensitivity, negative predictive value (NPV), and accuracy ranged from 43.8 to 93.8, 33.3 to 90, and 60 to 96, respectively. Biozak exhibited the best performance with the highest sensitivities 91.3, 81.8, and 93.75, respectively, while Viro and Standard Q were the worst among the tested kits with sensitivity, NPV, and accuracy of 50, 33.3, and 60 each. Regarding the relationship between the viral load of COVID-19 detected by RT-PCR and the results of the eight rapid antigen tests (RAT), we deduced that the higher the viral load, the better the sensitivity observed. CONCLUSION: The RATs used, in our study, exhibited heterogeneous diagnostic performance, where some of them showed very promising results in comparison to the reference RT-PCR assay.