Rapid Detection of SARS-CoV-2 Antigens and Antibodies Using OFET Biosensors Based on a Soft and Stretchable Semiconducting Polymer.

In the midst of the COVID-19 pandemic, adaptive solutions are needed to allow us to make fast decisions and take effective sanitation measures, e.g., the fast screening of large groups (employees, passengers, pupils, etc.). Although being reliable, most of the existing SARS-CoV-2 detection methods cannot be integrated into garments to be used on demand. Here, we report an organic field-effect transistor (OFET)-based biosensing device detecting of both SARS-CoV-2 antigens and anti-SARS-CoV-2 antibodies in less than 20 min. The biosensor was produced by functionalizing an intrinsically stretchable and semiconducting triblock copolymer (TBC) film either with the anti-S1 protein antibodies (S1 Abs) or receptor-binding domain (RBD) of the S1 protein, targeting CoV-2-specific RBDs and anti-S1 Abs, respectively. The obtained sensing platform is easy to realize due to the straightforward fabrication of the TBC film and the utilization of the reliable physical adsorption technique for the molecular immobilization. The device demonstrates a high sensitivity of about 19%/dec and a limit of detection (LOD) of 0.36 fg/mL for anti-SARS-Cov-2 antibodies and, at the same time, a sensitivity of 32%/dec and a LOD of 76.61 pg/mL for the virus antigen detection. The TBC used as active layer is soft, has a low modulus of 24 MPa, and can be stretched up to 90% with no crack formation of the film. The TBC is compatible with roll-to-roll printing, potentially enabling the fabrication of low-cost wearable or on-skin diagnostic platforms aiming at point-of-care concepts.

Effect of storage temperatures simulating transport conditions of nasopharyngeal swabs on the results of a chemiluminescence immunoassay (CLIA) to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen.

PURPOSE: Chemiluminescence Immunoassay (CLIA) is high throughput, rapid diagnostic test which has recently come up for the detection of SARS-CoV-2 antigen. The present study evaluated performance of CLIA antigen test in nasopharyngeal swab samples stored at different temperatures for 7 days to simulate the transport conditions and transit time across the country from remote peripheral laboratories to central facilities. MATERIALS AND METHODS: Limit of detection (LOD), sensitivity and specificity of VITROS® SARS-CoV-2 antigen assay was determined using Real-time reverse transcriptase PCR (rRT-PCR) confirmed SARS-CoV-2 positive and negative samples. To detect the effect of storage temperatures on VITROS ®SARS-CoV-2 antigen results, samples were stored at 4 â€‹°C, 25 â€‹°C & 37 â€‹°C for 7 days followed by detection of SARS-CoV-2 nucleocapsid antigen and compared with N-gene rRT-PCR. RESULTS: The VITROS® SARS-CoV-2 antigen test was found to have a sensitivity and specificity of 78.9% and 100% respectively with high sensitivity of 88.1% for samples with Ct â€‹< â€‹30. The LOD of VITROS assay was equivalent to 3800 copies of RNA per reactions as compared to 72 copies per reaction for rRT-PCR. We observed that more than 80% of samples with <30 Ct values could be detected by VITROS SARS-CoV-2 antigen assay at day 7 even when stored at 37 â€‹°C. For samples with Ct values between 26 and 30, on day 7 the positivity rate of N-antigen at 4 â€‹°C was 90.9% and 37 â€‹°C was 63.6%. CONCLUSIONS: CLIA testing can be carried out for the detection of SARS-CoV-2 N-protein in NP-swab samples transported in cold chain even with 7 days transit time, particularly for Ct â€‹< â€‹30 samples which represents cases with higher transmissibility. As drop in positivity for VITROS assay was lower as compared to rRT-PCR on day 7 in cold chain-maintained samples, the assay can be useful to screen samples received from remote peripheral areas before performing rRT-PCR.

Factors affecting the sensitivity of quantitative severe acute respiratory syndrome coronavirus 2 antigen test.

INTRODUCTION: The accuracy of nucleic acid amplification tests (NAATs) is affected by various factors; however, studies examining the factors affecting the accuracy of quantitative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen test (QAT) are limited. METHODS: A total of 347 nasopharyngeal samples were collected from patients with coronavirus disease 2019 (COVID-19), and the date of onset was obtained from the electronic medical records. The SARS-CoV-2 antigen level was measured using Lumipulse Presto SARS-CoV-2 Ag (Presto), while NAAT was performed using the Ampdirect 2019-nCoV Detection Kit. RESULTS: Presto had a sensitivity rate of 95.1% (95% confidence interval: 92.8-97.4) in detecting the SARS-CoV-2 antigen in 347 samples. The number of days from symptom onset to sample collection was negatively correlated with the amount of antigen (r = -0.515) and sensitivity of Presto (r = -0.711). The patients' age was lower in the Presto-negative samples (median age, 39 years) compared with that in the Presto-positive samples (median age, 53 years; p < 0.01). A significant positive correlation was observed between age (excluding teenagers) and Presto sensitivity (r = 0.764). Meanwhile, no association was found between the mutant strain, sex, and Presto results. CONCLUSION: Presto is useful for the accurate diagnosis of COVID-19 owing to its high sensitivity when the number of days from symptom onset to sample collection is within 12 days. Furthermore, age may affect the results of Presto, and this tool has a relatively low sensitivity in younger patients.

Role of SARS-COV2 antigen as a diagnostic test for COVID-19

Background: Successive waves of SARS-CoV-2 infections with increasing transmission rates may burden the laboratories performing molecular diagnostic testing. Alternative diagnostic methods may provide additional diagnostic capacity. Chemiluminescent totally automated antigen detection test for SARS-CoV-2 (Ortho VITROS SARS-CoV-2 antigen test) could be satisfactory replacement for reverse-transcription quantitative polymerase chain reaction (RT-qPCR) for mass screening during outbreaks. Methods: RT-qPCR and the VITROS® SARS-CoV-2 antigen were compared. Antigen detection test was assessed using clinical samples (nasopharyngeal swabs in viral transport medium) withdrawn from 668 patients suspected to have SARS-CoV-2 infection. Results: From 668 samples, 303 showed SARS-CoV-2 antigens positive and 365 SARS-CoV-2 antigens negative in comparison with RT-qPCR, the sensitivity was 89.11% and the specificity was 100.0% (PPV 100.0 and NPV 91.7). Ct value of 16.0 was the limit of detection of the assay. Conclusion: The given results show that VITROS® assay was acceptable for the detection of patients having contagious COVID-19 in the clinical setting. This test showed high sensitivity and specificity in the SARS-CoV-2 detection in samples with a Ct value of 32 or less. Chemiluminescent full automated antigen detection test for SARS-CoV-2 is a feasible substitute to (RT-qPCR) for mass screening. © 2020 The author (s).

Maternal COVID-19 Infection: A Cause of Neonatal Stroke?

Perinatal arterial ischemic stroke (PAIS) is a rare cause of neonatal seizures, with an incidence of 1 in 2500 to 4000 live births, globally. This is a case of a neonate with PAIS due to transpla-cental passage of COVID-19 IgG antibodies from the mother. A term, male neonate, born to a primigravida with an unevent-ful antenatal history was presented on the second day of life with multiple episodes of focal clonic seizures involving the right upper and lower limbs. Magnetic resonance imaging revealed an acute infarct in the left frontal lobe, extending into the parietal region, anterior limb, and genu of internal capsule suggestive of arterial ischemic stroke. The known causes of PAIS were evaluated and ruled out. The result of reverse transcription polymerase chain reaction analysis for SARS-CoV-2 antigen was negative for both the mother and the neonate. COVID-19 IgG antibodies in the mother and neonate were elevated. Seizures were controlled with antiepileptics. The neonate had no further seizure episodes and was discharged on oral levetiracetam. The infant was developmentally and neurologically normal at 3 months of age. PAIS is a rare cause of neonatal seizures, and maternal COVID-19 infection may be associated with neonatal stroke.Copyright © 2022, Himalaya Wellness Company. All rights reserved.

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

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.

Recurrent Acute Disseminated Encephalomyelitis (ADEM) after COVID-19-vaccination and after subsequent COVID-19-infection: A case report (part II).

Acute disseminated encephalomyelitis (ADEM) is an autoimmune disorder of the central nervous system (CNS), which is commonly associated to previous viral infection or immunization. Cases of ADEM with a potential relationship to both severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination have been reported. We recently published a rare case of a 65-year-old patient who suffered from a corticosteroid- and immunoglobulin-refractory multiple autoimmune syndrome including ADEM following Pfizer-BioNTech coronavirus disease (COVID)-19 vaccination, and whose symptoms largely resolved after repeated plasma exchange (PE). Four months later, the patient was diagnosed with SARS-CoV-2 omicron variant infection after experiencing mild upper respiratory tract symptoms. Few days later, the patient developed severe tetraparesis with magnetic resonance imaging (MRI) showing multiple new inflammatory contrast-enhancing lesions in the left middle cerebellar peduncle, cervical spinal cord, and ventral conus medullaris. Repeated cerebrospinal fluid (CSF) analyses indicated blood-brain barrier damage (increased albumin ratio) without signs of SARS-CoV-2 invasion (mild pleocytosis, no intrathecal antibody production). SARS-CoV-2 specific immunoglobulin G (IgG) were detected in serum and to a much lower degree in CSF with close correlation between both concentrations over time, reflecting antibody dynamics of vaccine- and infection-induced immune response, and blood-brain barrier patency. Daily PE therapy was initiated. Given the patient's lack of improvement after seven PE, treatment with rituximab was considered. After a first dose, however, the patient suffered epididymo-orchitis leading to sepsis, and declined rituximab continuation. At 3-months follow-up, clinical symptoms had dramatically improved. The patient regained walking ability without assistance. This case of recurrent ADEM after COVID-19-vaccination and after subsequent COVID-19-infection strongly supports the hypotheses of neuroimmunological complications in these conditions being promoted by a systemic immune response and mediated by molecular mimicry of, both, viral and vaccine SARS-CoV-2 antigens and CNS self-antigens.

Analytical performance evaluation of Lumipulse® SARS-CoV-2 antigen assay in 392 asymptomatic patients.

INTRODUCTION: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is one of the current public health care challenges. The main strategy adopted to prevent the spread of infection is the rapid identification of COVID-19-positive subjects. The aim of this study was to compare the performance of Lumipulse® antigen immunoassay with the real-time RT-PCR, the gold standard for the diagnosis of SARS-CoV-2 infection, in a strictly selected asymptomatic population. MATERIALS AND METHODS: A total of 392 consecutive oro-nasopharyngeal swabs were collected from patients with no symptoms related to COVID-19 at the Emergency Department of AORN Sant'Anna e San Sebastiano, Caserta, Italy to evaluate the analytical performance of Lumipulse® SARS-CoV-2 antigen compared to qualitative real-time RT-PCR in asymptomatic patients. RESULTS: Lumipulse® SARS-CoV-2 antigen assay shows an overall agreement rate of 97% with a sensitivity of 96% and a specificity of 98%, with a PPV and NPV of 97%. The sensitivity varies according to the cycle threshold (Ct )-value reaching 100% and 86% with 15 < Ct < 25 and Ct ≥ 25, respectively. The ROC analysis yielded an AUC value of 0.98, suggesting that the antigen test may accurately detect SARS-CoV-2. CONCLUSION: Our data showed that Lumipulse® SARS-CoV-2 antigen assay might be an efficient tool in the identification and limitation of SARS-CoV-2 transmission in large asymptomatic populations.

Evaluation of a laboratory-based high-throughput SARS-CoV-2 antigen assay.

OBJECTIVES: Antigen tests are an essential part of SARS-CoV-2 testing strategies. Rapid antigen tests are easy to use but less sensitive compared to nucleic acid amplification tests (NAT) and less suitable for large-scale testing. In contrast, laboratory-based antigen tests are suitable for high-throughput immunoanalyzers. Here we evaluated the diagnostic performance of the laboratory-based Siemens Healthineers SARS-CoV-2 Antigen (CoV2Ag) assay. METHODS: In a public test center, from 447 individuals anterior nasal swab specimens as well as nasopharyngeal swab specimens were collected. The nasal swab specimens were collected in sample inactivation medium and measured using the CoV2Ag assay. The nasopharyngeal swab specimens were measured by RT-PCR. Additionally, 9,046 swab specimens obtained for screening purposes in a tertiary care hospital were analyzed and positive CoV2Ag results confirmed by NAT. RESULTS: In total, 234/447 (52.3%) participants of the public test center were positive for SARS-CoV-2-RNA. Viral lineage B1.1.529 was dominant during the study. Sensitivity and specificity of the CoV2Ag assay were 88.5% (95%CI: 83.7-91.9%) and 99.5% (97.4-99.9%), respectively. Sensitivity increased to 93.7% (97.4-99.9%) and 98.7% (97.4-99.9%) for swab specimens with cycle threshold values <30 and <25, respectively. Out of 9,046 CoV2Ag screening tests from hospitalized patients, 21 (0.2%) swab specimens were determined as false-positive by confirmatory NAT. CONCLUSIONS: Using sample tubes containing inactivation medium the laboratory-based high-throughput CoV2Ag assay is a very specific and highly sensitive assay for detection of SARS-CoV-2 antigen in nasal swab specimens including the B1.1.529 variant. In low prevalence settings confirmation of positive CoV2Ag results by SARS-CoV-2-RNA testing is recommended.

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

Background: 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. Methods: We assessed the feasibility of severe acute respiratory syndrome coronavirus 2 self-testing with antigen-detecting rapid diagnostic tests in attendees of educational settings. Results: 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". Conclusion: 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.

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.

OBJECTIVE: To define the relationship of SARS-CoV-2 antigen, viral load determined by RT-qPCR, and viral culture detection. Presumptively, viral culture can provide a surrogate measure for infectivity of sampled individuals and thereby inform how and where to most appropriately deploy antigen and nucleic acid amplification-based diagnostic testing modalities. METHODS: We compared the antigen testing results from three lateral flow and one microfluidics assay to viral culture detection and viral load determination performed in parallel in up to 189 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. RESULTS: Antigen tests were predictive of viral culture positivity, with the LumiraDx microfluidics method showing enhanced sensitivity (90%; 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 of 0.94 to 0.97 and 0.92, respectively. 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. Adjusting for sample dilution inherent in our study design, sensitivities of antigen tests were ≥95% for detection of viral culture positive samples with viral loads >106 genome copies/mL, although specificity of antigen testing was imperfect. DISCUSSION: Antigen testing results and viral culture were correlated. For culture positive samples, the sensitivity of antigen tests was high at high viral loads that are likely associated with significant infectivity. Therefore, our data provides support for use of antigen testing in ruling out infectivity at the time of sampling.

Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease With False-Positive Results in SARS-CoV-2 Antigen Tests: A Case Report.

A 23-year-old man presented with headache, fever, and urinary retention. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen tests were positive, but SARS-CoV-2 polymerase chain reaction (PCR) results were negative. MRI showed long spinal cord lesions. Due to positive serum and cerebrospinal fluid myelin oligodendrocyte glycoprotein (MOG) antibodies, we made the diagnosis of MOG-associated disease. We concluded that the antigen tests were false positives because SARS-CoV-2 IgM and IgG were not elevated. Although the mechanism behind the false-positive results is unclear, physicians should consider the possibility of a false-positive result in the SARS-CoV-2 antigen test.

Development of a rapid, simple, and sensitive point-of-care technology platform utilizing ternary NanoLuc.

Point-of-care tests are highly valuable in providing fast results for medical decisions for greater flexibility in patient care. Many diagnostic tests, such as ELISAs, that are commonly used within clinical laboratory settings require trained technicians, laborious workflows, and complex instrumentation hindering their translation into point-of-care applications. Herein, we demonstrate the use of a homogeneous, bioluminescent-based, split reporter platform that enables a simple, sensitive, and rapid method for analyte detection in clinical samples. We developed this point-of-care application using an optimized ternary, split-NanoLuc luciferase reporter system that consists of two small reporter peptides added as appendages to analyte-specific affinity reagents. A bright, stable bioluminescent signal is generated as the affinity reagents bind to the analyte, allowing for proximity-induced complementation between the two reporter peptides and the polypeptide protein, in addition to the furimazine substrate. Through lyophilization of the stabilized reporter system with the formulated substrate, we demonstrate a shelf-stable, all-in-one, add-and-read analyte-detection system for use in complex sample matrices at the point-of-care. We highlight the modularity of this platform using two distinct SARS-CoV-2 model systems: SARS-CoV-2 N-antigen detection for active infections and anti-SARS-CoV-2 antibodies for immunity status detection using chemically conjugated or genetically fused affinity reagents, respectively. This technology provides a simple and standardized method to develop rapid, robust, and sensitive analyte-detection assays with flexible assay formatting making this an ideal platform for research, clinical laboratory, as well as point-of-care applications utilizing a simple handheld luminometer.

COVID-19 contagious health care personnel 5-day early return-to-work program.

BACKGROUND: COVID-19 contagious health care personnel (HCP) who are self-isolating for a 10-day period increases burden to workforce shortages. Implementation of a 5-day early return-to-work (RTW) program may reduce self-isolation periods, without increasing transmission risk, during the COVID-19 pandemic. DESIGN AND METHODS: This observational cohort quality improvement study included newly diagnosed COVID-19 HCP at a multifacility health care system. The program allowed HCP to return to work 6 days after date of a positive test result if they were not immunocompromised, had mild and improving symptoms, and self-reported a SARS-CoV-2 antigen negative test on day 5. RESULTS: Between January 4 and April 3, 2022, 1,023 HCP self-enrolled and 344 (33.6%) self-reported negative test results. Among these, 161 (46.8%) self-reported negative test results on day 5 and were eligible for early RTW on day 6. A total of 714 days were saved from missed work in self-isolation. The number of tests purchased, dispensed, and reported per day of HCP time saved was 4.4. No transmission events were observed originating from HCP who participated in early RTW. CONCLUSION: Implementing a 5-day early RTW program that includes HCP self-reporting SARS-CoV-2 antigen test results can increase staffing availability, while maintaining a low risk of SARS-CoV-2 transmission.

Antigen Coverage Presented by MHC Class I Has a Negative Correlation with SARS-CoV-2-Induced Mortality.

The COVID-19 pandemic has caused a health crisis worldwide; therefore, it is necessary to understand the factors related to its prognosis. In this study, we hypothesized that SARS-CoV-2-derived antigens presented by MHC class I may correlate with mortality in COVID-19 because they induce adaptive immune responses. Antigen coverage at the national level was inferred using country-specific HLA allele frequencies and relative predictions of binding antigens. We performed regression analysis between antigen coverage and the death rate due to COVID-19 across countries and found a negative correlation, although it was statistically significant only in HLA-B. This negative correlation was corroborated in multiple regression analysis with known risk factors, such as the prevalence of underlying disease. Furthermore, we analyzed antigen coverage in accordance with SARS-CoV-2 domains and identified a significant negative correlation when it was derived from the spike domain, which is reported to be favorable for COVID-19 prognosis. Taken together, the results indicate that the antigen coverage of SARS-CoV-2 specifically presented by HLA-B may act as a favorable factor when explaining COVID-19-induced mortality.

Mass Screening of SARS-CoV-2 With Rapid Antigen Tests in a Receding Omicron Wave: Population-Based Survey for Epidemiologic Evaluation.

BACKGROUND: The COVID-19 Omicron BA.2 epidemic wave in Hong Kong peaked in the first quarter of 2022. Following the implementation of stringent public health measures, the daily number of reported cases fell from over 50,000 to below 2000. Although outbreaks steadily receded, the government rolled out a 3-day "voluntary universal rapid testing" campaign to invite all citizens to self-perform a rapid antigen test (RAT) daily to identify undetected prevalent infections. OBJECTIVE: This study aimed to evaluate the uptake and results of RAT mass screening to estimate the population's residual epidemic burden and assess the risk of further transmission. METHODS: A cross-sectional study comprising an open web-based population-based survey was conducted a week after the RAT campaign. Participants were asked to report their COVID-19 vaccination and infection history and the RAT performance and test result during the period. They were also invited to report their coliving individuals' test performance and results. Reasons for nonuptake were enquired. Testing and positive rates were age-adjusted. Determinants of undergoing RAT were identified using univariable and multivariable logistic regression models. RESULTS: In total, particulars from 21,769 individuals were reported by 8338 participants. The overall age-adjusted testing rate was 74.94% (95% CI 73.71%-76.18%), with over 80% of participants in the age groups between 45-84 years having self-performed RAT during the campaign period. After age-adjustment, 1.03% (95% CI 0.86%-1.21%) of participants tested positive. The positive rates in the age groups between 20-29 years and >84 years exceeded 2%. Taking into account the positive rate and 5819 reported cases during the period, the cases identified in the campaign might account for 7.65% (95% CI 6.47%-9.14%) of all infections. Testers were more likely to be female, older, not previously diagnosed with COVID-19, and have received COVID-19 vaccination. Adjusting for the number of household members, those living with a child aged <12 years and whose household members were also tested were more likely to have self-performed an RAT. Main reasons for not performing an RAT included the absence of symptoms (598/1108, 53.97%), disbelief of the appropriateness of the campaign as an antiepidemic measure (355/1108, 32.04%), and a recent COVID-19 diagnosis (332/1108, 29.96%). CONCLUSIONS: The residual population burden remained substantial in spite of the clear evidence of a receding epidemic wave. Despite caution in generalization to the Hong Kong population, the high participation rate in mass screening indicated that the voluntary RAT was well accepted, making it a feasible option for implementation as a complementary means of public health surveillance.

Impact of mass rapid antigen testing for SARS-CoV-2 to mitigate Omicron outbreaks in China.

We analysed the effectiveness of various non-pharmaceutical interventions in containing the 2022 Omicron outbreak in China. The results show that the Rapid Antigen Test contributed to containing the outbreak, reducing the reproduction number by 0.788 (95% CI:-0.306, 1.880) in studied cities.

Viral load may impact the diagnostic performance of nasal swabs in nucleic acid amplification test and quantitative antigen test for SARS-CoV-2 detection.

INTRODUCTION: Compared to nasopharyngeal swabs (NPS), there has been insufficient evaluation of the diagnostic performance of nasal swabs (NS) for the detection of severe acute respiratory coronavirus 2 (SARS-CoV-2) in the nucleic acid amplification test (NAAT) and quantitative SARS-CoV-2 antigen test (QAT). METHODS: We prospectively compared healthcare worker-collected and flocked NS within nine days after symptom onset to paired NPS to detect SARS-CoV-2 in NAAT and QAT on the fully automated Lumipulse system. The agreement between sample types was evaluated, and cycle threshold (Ct) values and antigen levels were used as surrogate viral load measures. RESULTS: Sixty sets of NPS and NS samples were collected from 40 patients with COVID-19. The overall agreements between NAAT and QAT samples were 76.7% and 65.0%, respectively. In NAAT, the Ct value of NS was significantly higher, 5.9, than that of NPS. Thirty-nine (95.1%) NS tested positive in 41 positive-paired NPS with Ct ≤ 30. The negative correlation was observed between antigen levels of NS in QAT and Ct values of NS in NAAT (r = -0.88). In QAT, the antigen level of NS was significantly lower than that of NPS. Thirty-six (90.0%) NS tested positive in 40 positive-paired NPS with antigen levels >100 pg/mL, which were collected significantly earlier than those with antigen levels ≤100 pg/mL. CONCLUSIONS: In NAAT and QAT, NS had limited performance in detecting SARS-CoV-2 compared to NPS. However, NS may be helpful for patients with COVID-19 with high viral loads or those in the early stages of the illness.

The Detection of SARS-CoV2 Antigen in Wastewater Using an Automated Chemiluminescence Enzyme Immunoassay.

The SARS-CoV-2 virus, which is driving the current COVID-19 epidemic, has been detected in wastewater and is being utilized as a surveillance tool to establish an early warning system to aid in the management and prevention of future pandemics. qPCR is the method usually used to detect SARS-CoV-2 in wastewater. There has been no study using an immunoassay that is less laboratory-intensive than qPCR with a shorter turnaround time. Therefore, we aimed to evaluate the performance of an automated chemiluminescence enzyme immunoassay (CLEIA) for SARS-CoV-2 antigen in wastewater. The CLEIA assay achieved 100% sensitivity and 66.7% specificity in a field-captured wastewater sample compared to the gold standard RT-qPCR. Our early findings suggest that the SARS-CoV-2 antigen can be identified in wastewater samples using an automated CLEIA, reducing the turnaround time and improving the performance of SARS-CoV-2 wastewater monitoring during the pandemic.