Evaluation of the Omicron variant by RT-PCR and rapid antigen testing (ExacTest™ COVID-19 Antigen Rapid Test)

Purpose: The present study aims to compare the results of the COVID-19 rapid antigen test (ExacTest™ COVID-19 Antigen Rapid Test) and real-time polymerase chain reaction (RT-PCR) test in samples of people suspected of coronavirus disease (COVID-19). Materials and methods: Among the samples submitted between January 2022 and March 2022 with suspicion of COVID-19, 299 samples subject to simultaneous COVID-19 RADT (Rapid Antigen Detection Test) and RT- PCR were evaluated retrospectively. The Real-Time PCR test was studied with the DS CORONEX COVID-19 Multiplex Real time-qPCR Test Kit (DS Nano and Biotechnology Product Tracing and Tracking Co., Turkey) and the rapid antigen test was studied by the immunochromatographic method with ExacTest™ COVID-19 Antigen Rapid Test Cassette kit (General Diagnostica inc., California, USA). Ag-RDT test results were evaluated with the fluorescent immunoassay analyzer (FIATEST Analyzer, Hangzhou Alltest Biotech Co., Ltd. China). Results: RT-PCR test was positive in 53 (17.7%) samples. The RADT's sensitivity was found 88.7 (95% Cl 77.0-95.7), specificity 98.0 (95% Cl 95.3-99.3), positive predictive value 90.4 (95% Cl 79.7-95.8), negative predictive value 97.6 (95% Cl 95.0-98.8), and accuracy 96.3 (95% Cl 93.5-98.2). Sample sensitivities of patients under and over 18 years of age have been identified as 75 (95% Cl 19.4-99.4) and 89.8 (95% Cl 77.8-96.6), respectively. The sensitivity of patients with and without symptoms was 95.5 (95% Cl 77.2-99.9) and 83.9 (95% Cl 66.3-94.6), respectively. For samples with a cycle threshold (Ct) of <20, 20-<25, 25-<30 and 30-<35, the concordance of testing was 100%, 92.9%, 78.9% and 80%, respectively. Conclusion: The rapid antigen kit studied complies with the use criteria recommended by the World Health Organization and is quite useful for the rapid diagnosis of symptomatic patients in COVID-19. © 2022, Pamukkale University. All rights reserved.

Inpatient Admission Pathway for Patients with Rheumatological Disorders

Background/Aims Rheumatology is a complex specialty covering many conditions of varying severity, from muscle pain through inflammatory arthritis such as Rheumatoid arthritis (RA) and connective tissue diseases. Most of the conditions can be managed in an outpatient/day case setting. However, acutely ill patients require safe and prompt inpatient management including specific intravenous infusions. This need to be done urgently and cannot wait to be accommodated through the Infusion unit at our hospital. Historically Medicine Acute Admission Unit has been the route to bring in these patients. However, operational bed pressures faced challenges leading to instances of delayed treatment with complications including fatality. This led to creating a direct inpatient admission pathway to the specialist ward. Methods Ward Matron designed the following robust pathway for direct patient admission to our specialist Rheumatology ward, Jevington ward. This was implemented in February 2022 after discussion and agreement with Clinical Lead consultant, pharmacist, clinical site managers and other colleagues. Rheumatology team and nurses covered the ward during working hours and by the on-call team out of hours. The overall responsibility remained with the rheumatology team. The referrals accepted only after completing appropriate paperwork. Patients carried out Lateral Flow Test (LFT) at home prior to admission. We ensured negative results and followed the Trust COVID 19 screening protocols. Subsequent screenings were done according to the updated guidelines. The planned assessment and treatments were carried out by the ward team complying with BSR/ EULAR Guidelines, infusion protocols such as standard and continuous Iloprost Infusion Protocols of the Trust. Results We assessed the delay in patient's admission, length of stay, patient outcome and experience after implementing the pathway. The significant change has been in the time to admit;from two weeks in 2018 & 19 to two days this year. This is reflected in the patient feedback. All our acutely ill patients were assessed, treated and discharged promptly on this specialist ward. Conclusion This pathway allowed safe and prompt treatment, prognosis and excellent experience for acutely ill patients with rheumatological disorders. This additionally enabled reduced length of stay supporting financial sustainability of the Trust. (Table Presented).

Anti-N SARS-CoV-2 assays for evaluation of natural viral infection.

BACKGROUND: The 2019 coronavirus (COVID-19) epidemic, required the development of different diagnostic tests. While reverse transcriptase real-time PCR (RT-PCR) remains the first-line test of choice in acute infection diagnosis, anti-N antibodies serological assays provide a valuable tool to differentiate natural SARS-CoV-2 immunological response from that induced by vaccination, thus the goal of our study was to evaluate three serological tests agreement for these antibodies detection. METHODS: Three anti-N different tests were examined in 74 sera from patients referred or not COVID infection: immunochromatographic rapid test (Panbio™ COVID-19 IgG/IgM Rapid Test Device Abbott, Germany), ELISA kit (NovaLisa® SARS-CoV-2 IgG and IgM NovaTech Immunodiagnostic GmbH, Germany) and ECLIA immunoassay (Elecsys® Anti-SARS-CoV-2 Roche Diagnostics, Manheim, Germany). RESULTS: Qualitative comparison of the three analytical methods revealed a moderate agreement between ECLIA immunoassay and immunochromatographic rapid test (Cohen kappa coefficient κ = 0.564). Correlation analysis indicated weak positive correlation between total Ig (IgT) detected by ECLIA immunoassay and IgG by ELISA test (p < 0.0001), the analysis of ECLIA IgT and IgM ELISA detected, showed no statistical correlation. CONCLUSION: Comparison between of three analytical systems available for anti-N SARS-CoV-2 IgG and IgM antibodies showed a general agreement when compared to detect total and G class immunoglobulins, while doubtful or discordant results have been highlighted for IgT and IgM class. Anyway, all the tests examined provide reliable results to assess the serological status of SARS-CoV-2 infected patients.

Evaluation of a new lateral flow assay for the quantitative detection of Anti-SARS- CoV- 2 specific IgG

Background: Antibody testing for COVID-19 may represent an interesting tool to document past SARS-CoV- 2 infections, both in individual patients with suspected COVID-19 symptoms or late-stage complications who had no (conclusive) PCR test. In addition, measuring SARS-CoV- 2 antibodies may offer a prognostic value and convey information on protective immunity in vaccination trials. The objective of the study is the evaluation of a rapid test for the quantitative interpretation of Anti-SARS- CoV- 2 IgG compared with other in-vitro methods. Method(s): The Anti-SARS- CoV- 2 LFA (Lateral Flow Assay) is a rapid test for the quantitative measurement of IgG antibodies to SARS-CoV- 2 in human serum, plasma and whole blood within 20 minutes. The complexes of Anti-SARS- CoV- 2 antibodies from patient's sample and coloured conjugate are retained at the test line by the complete SARS-CoV- 2 Spike Protein. The use of a special scanner system provides the opportunity of quantitative interpretation of the results, by using calibration curve established with "First WHO International Standard for anti-SARS- CoV- 2 immunoglobulin (human)". Result(s): Serum samples were taken from the serum bank at Dr. Fooke Laboratorien GmbH and tested for Anti-SARS- CoV- 2 IgG by the newly developed LFA (Dr. Fooke Laboratorien GmbH). The results were compared with established assay methods like Anti-SARS- CoV- 2 ELISA IgG (Dr. Fooke Laboratorien GmbH and Euroimmun). Good agreements were observed. Sensitivity and specificity between the newly developed LFA and Anti-SARS- CoV- 2 ELISA IgG of Dr. Fooke / Euroimmun were found at 0.95/0.88 and 1.00/0.93, respectively. The calibration curve established with "First WHO International Standard for anti-SARS- CoV- 2 immunoglobulin (human)" shows a reproducibility of > 90%. Conclusion(s): The Anti-SARS- CoV- 2 LFA shows comparable results to the ELISA systems of Dr. Fooke Laboratorien and Euroimmun. By the use of small amounts of serum, plasma or whole blood (10muL) the patients receive a fast and reliable result. A calibration curve, established with "First WHO International Standard for anti-SARS- CoV- 2 immunoglobulin (human)" offers the comparability to quantitative ELISA systems.

Rapid Detection of Sars Cov-2 Infection in Comparision with Rt-Pcr in Tertiary Care Hospital

Objectives: The goal of the present study was to assess the SARS-CoV-2 antigen detection test's performance features and compare them to the real-time reverse transcription polymerase chain reaction (RT-PCR) test, the gold standard test for the diagnosis of COVID-19 cases. Method(s): From October 2020 to May 2021, patients attending the OPD, including those undergoing surgery, at a Tertiary Care Teaching Hospital in Telangana provided 1000 respiratory samples, primarily nasopharyngeal swabs. A skilled technician had collected two nasopharyngeal swabs from each person in a COVID sample collection room while wearing personal protective equipment and following strict infection control procedures. One swab was used for the rapid antigen test given by the standard Q COVID-19 Ag test kit and placed into the extraction buffer tube. Second swab was kept in the viral transport medium and used for AllplexTM 2019-nCoV Assay (Seegene, Korea), which targets envelope gene (E), and RNA dependent RNA polymerase (RdRp) and nucleocapsid (N) genes of SARS CoV-2, was used for SARS-CoV-2 RNA detection according to the manufacturer's instructions. Result(s): Out of 1000 samples tested for COVID-19, 623 (63.7%) were males and 377 (36.3%) were females. Out of 1000 samples, 347 samples were RT-PCR positive and 653 were RT-PCR negative. Out of 347 RT-PCR samples positive, 341 were Rapid antigen test positive samples and six were negative. Overall sensitivity and specificity are 98.27% and 99.85%, respectively. Conclusion(s): The real-time RT-PCR assay's sensitivity and specificity were comparable to those of the rapid assay for SARS-CoV-2 antigen detection. It can be utilized for contact tracing measures to control the COVID-19 pandemic in places such as border crossings, airports, interregional bus and train stations, and mass testing campaigns needing quick findings. This is especially true in areas with a high prevalence of the disease.Copyright © 2023 The Authors. Published by Innovare Academic Sciences Pvt Ltd.

Experimental SARS-CoV-2 human challenge in young adults

Rationale: To establish a novel SARS-CoV-2 human challenge model enabling controlled investigation of pathogenesis, correlates of protection and efficacy testing of interventions. Method(s): Thirty-six healthy 18-29-year-old subjects, without evidence of previous infection or vaccination, received 10 TCID50 of a wild-type virus (SARS-CoV-2/human/GBR/484861/2020) intranasally. Following inoculation, subjects resided in a high-containment quarantine, with 24-hour medical monitoring. The study's main objectives were to identify a virus dose that induced well-tolerated infection in >50% of subjects and assess virus and symptoms over time. AEs and longitudinal disease profiles are presented. Result(s): Eighteen of thirty-four evaluable (~53%) subjects became infected and developed serum antibodies. Viral load rose steeply and peaked ~5 days post-inoculation (PI). Virus was first detected in the throat but rose to significantly higher levels in the nose, peaking at ~8.87 log10 copies/ml (median, 95% CI [8.41,9.53]). Viable virus was recoverable from the nose up to ~10 days PI, on average. Mild-to-moderate symptoms were reported by 16 (89%) infected subjects, beginning 2-4 days PI. Anosmia or dysosmia developed in 15 (83%) subjects. Results from lateral flow tests were associated with viable virus and modelling showed that twice-weekly rapid antigen tests could diagnose infection before 70-80% of viable virus had been generated. There were no overt lung function changes, CT abnormalities, or SAEs. Conclusion(s): This novel SARS-CoV-2 challenge of 18-29-year-olds was considered safe. Viral kinetics over the course of primary infection was established, with implications for public health recommendations and strategies to impact transmission.

Successful Kidney Transplantation from Covid-19 Positive Donors

Introduction: Covid-19 results in a wide spectrum of illness ranging from asymptomatic, mild to severe respiratory disease and multi-organ involvement. Transplant recipients are at increased risk of severe Covid-19. The risk of transmission from a Covid-19 positive donor to recipient in kidney transplantation is unknown. National Health Service Blood and Transplant, UK recommended respiratory polymerase chain reaction (PCR) testing for all donors for Covid-19 and advice against organ donation if positive within the last 28 days. However, a recent amendment of guideline (www.odt.nhs.uk, POL304/3) supports organ donation from selected donors with positive or indeterminate SARS-CoV-2 PCR results. Method(s): We report two cases of kidney transplantation including one unvaccinated recipient where donors had tested SARS-CoV-2 PCR positive. Result(s): 1: Mrs A is a 38-year old Caucasian with end-stage kidney disease (ESKD) secondary to reflux nephropathy, established on haemodialysis (HD). She had declined Covid-19 vaccinations. The donor died of traumatic brain injury and he had a positive lateral flow test 3 weeks prior. The PCR test was positive. Decision was made to proceed with deceased donor kidney transplantation. She was high immunological risk with a HLA antibody calculated reaction frequency (CRF) of 79%, donor specific antibody negative. She was given Basiliximab induction followed by Tacrolimus, Mycophenolate Mofetil and steroids. Graft function was immediate and at 3 week post-transplant, she is well with excellent graft function and no evidence of Covid-19. 2: Mrs B is a 63-year old Asian with ESKD secondary to diabetes and hypertension. She was established on HD and fully vaccinated (three doses of Pfizer-BNT162b2 mRNA vaccine). The donor died of subarchnoid haemorrhage. He had a positive lateral flow test 15 days prior with flu-like symptoms. Respiratory PCR for SARS-CoV-2 was positive. The decision was to proceed with deceased donor transplantation. She was low immunological risk with a HLA antibody CRF of 0%. There were no peri-operative complications and she had immediate graft function. She had Basiliximab induction and was discharged on Tacrolimus and Mycophenolate mofetil with prednisolone withdrawn on day 7 (our low immunological risk protocol). At 3 week post-transplant, she is well with no evidence of Covid-19 and excellent graft function. Conclusion(s): We report 2 cases of kidney transplantation from Covid-19 positive donors in whom the cause of death was not Covid-19 pneumonia. Covid-19 status of the donor was discussed with the patients who both consented. Neither recipient developed Covid-19 in the early post-transplant period, despite being heavily immunosuppressed. Although there remains a theoretical risk, there are no reports of transmission of Covid-19 to kidney transplant recipients from positive donors. Prophylactic antivirals or monoclonal antibodies for the recipient post-transplant or spike antibody test to guide decision making are not currently recommended. We used clinical details of the donor and virology advice which accounts for PCR cycle threshold value to make a decision to transplant. The outcomes of 2 patients reported along with similar experience from other centres is encouraging and supports use of kidneys from selected SARS-CoV-2 positive deceased donors after obtaining virological advice and appropriate consent. No conflict of interestCopyright © 2023

Evaluation of five immunoassays and one lateral flow immunochromatography for anti-SARS-CoV-2 antibodies detection.

INTRODUCTION: In order to deal with the current pandemic caused by the novel SARS-CoV-2 coronavirus several serological immunoassays have been recently developed with the objective of being used as a complementary diagnostic tool and to support the RT-PCR technique currently considered the "gold-standard" method. However, these new assays need to be evaluated and validated. The purpose of this study was to assess the performance of five immunoassays (two ELISA and three CLIA assays) and one rapid immunochromatographic test for the detection of anti-SARS-CoV-2 antibodies. METHODS: Five semiquantitative immunoassays (MENARINI®, PALEX®, VIRCLIA®, ROCHE® and SIEMENS®) and one lateral flow rapid test (WONDFO®) were performed. A total of 124 samples were studied. Case serum samples (n=78) were obtained from COVID-19 patients confirmed by real-time RT-PCR/epidemiological-clinical-radiological criteria, and control non-SARS-CoV-2 samples (n=46) belonged to healthy healthcare workers involved in a seroprevalence study. RESULTS: Overall, the tests showed sensitivities around 70-90% and specificities greater than 95%, including the immunochromatographic test. In addition, we observed very good agreements among them, being better for the detection of IgG than for IgM antibodies (Cohen's kappa index of 0.95 for VIRCLIA® IgG with ROCHE®), as well as good diagnostic power of the tests as determined by the ROC curves. CONCLUSIONS: This study demonstrates the proper performance of the different immunoassays in order to be applied in the clinical practice as support in the diagnostic approach and in the development of vaccines and seroepidemiological studies of COVID-19.

Development of an Antigen Detection Kit Capable of Discriminating the Omicron Mutants of SARS-CoV-2.

INTRODUCTION: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread around the world, caused millions of deaths and a severe illness which poses a serious threat to human health. OBJECTIVE: To develop an antigen detection kit that can identify Omicron novel coronavirus mutants. METHODS: BALB/c mice were immunized with the nucleocapsid protein of SARS-CoV-2 Omicron mutant treated with ß-propiolactone. After fusion of myeloma cells with immune cells, Elisa was used to screen the cell lines capable of producing monoclonal antibodies. The detection kit was prepared by colloidal gold immunochromatography. Finally, the sensitivity, specificity and anti-interference of the kit were evaluated by simulating positive samples. RESULTS: The sensitivity of the SARS-CoV-2 antigen detection kit can reach 62.5 TCID50/mL, and it has good inclusiveness for different SARS-CoV-2 strains. The kit had no cross-reaction with common respiratory pathogens, and its sensitivity was still not affected under the action of different concentrations of interferences, indicating that it had good specificity and stability. CONCLUSION: In this study, monoclonal antibodies with high specificity to the N protein of the Omicron mutant strain were obtained by monoclonal antibody screening technology. Colloidal gold immunochromatography technology was used to prepare an antigen detection kit with high sensitivity to detect and identify the mutant Omicron strain.

Evaluation of an immunochromatography-based rapid antigen test, Inspecter Kowa® SARS-CoV-2, using saliva specimens for the detection of SARS-CoV-2.

BACKGROUND: In the context of the coronavirus disease 2019 (COVID-19) pandemic, a rapid and reliable point-of-care test is an essential tool for controlling the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In particular, an immunochromatography test (ICT) that uses saliva specimens for rapid antigen detection not only reduces the risk of secondary infections but also reduces the burden on medical personnel. METHODS: The newly developed salivary antigen test kit "Inspecter Kowa® SARS-CoV-2" is an ICT to which saliva specimens can be directly applied. We evaluated its usefulness in comparison with reverse transcription quantitative PCR (RT-qPCR) and the Espline® SARS-CoV-2 Kit for the detection of SARS-CoV-2 using nasopharyngeal swab specimens. In this study, 140 patients with suspected symptomatic COVID-19 who visited our hospital were enrolled, and nasopharyngeal swab and saliva specimens were collected after they consented to participate in the study. RESULTS: Inspector Kowa SARS-CoV-2 was positive in 45 of 61 (73.8%) saliva that were positive by RT-qPCR and the Espline® SARS-CoV-2 Kit was also positive in 56 of 60 (93.3%) Np swabs that were positive by RT-qPCR. Good antigen detection was achieved by ICT with saliva and nasopharyngeal swab specimens when viral load was ≥105 copies/mL, whereas detection sensitivity was low when viral load was <105 copies/mL, especially in saliva specimens. CONCLUSION: This ICT for the detection of SARS-CoV-2 salivary antigen is an attractive tool that does not require specialized equipment and allows patients to perform the entire process from sample collection to self-diagnose and to reduce the burden on medical care during a pandemic.

A false positive serology test of SARS­CoV­2 in a patient with Waldenström's macroglobulinemia: A case report.

The serology test of SARS-CoV-2 is one of the critical assays to make a diagnosis of SARS-CoV-2 infection. The gold immunochromatography assay (GICA) is a common measure to test SARS-CoV-2 specific IgG and IgM. The sensitivity and specificity of the assay are ~>80%. It has been reported that the result of GICA could be compromised in various situations, such as auto-immune diseases, Kawasaki disease, pregnancy or other conditions. However, following the European Hematology Association's consensus statement on the management of Waldenström's Macroglobulinemia (WM) patients, serological tests for SARS-CoV-2 specific IgM should not be affected by the total IgM or paraprotein levels. The present study reports a patient with duplicate positive serology tests of SARS-CoV-2 which is hypothesized to be due to monoclonal IgM caused by WM.

Silent Antibodies Start Talking: Enhanced Lateral Flow Serodiagnosis with Two-Stage Incorporation of Labels into Immune Complexes.

The presence of pathogen-specific antibodies in the blood is widely controlled by a serodiagnostic technique based on the lateral flow immunoassay (LFIA). However, its common one-stage format with an antigen immobilized in the binding zone of a test strip and a nanodispersed label conjugated with immunoglobulin-binding proteins is associated with risks of very low analytical signals. In this study, the first stage of the immunochromatographic serodiagnosis was carried out in its traditional format using a conjugate of gold nanoparticles with staphylococcal immunoglobulin-binding protein A and an antigen immobilized on a working membrane. At the second stage, a labeled immunoglobulin-binding protein was added, which enhanced the coloration of the bound immune complexes. The use of two separated steps, binding of specific antibodies, and further coloration of the formed complexes, allowed for a significant reduction of the influence of non-specific immunoglobulins on the assay results. The proposed approach was applied for the serodiagnosis using a recombinant RBD protein of SARS-CoV-2. As a result, an increase in the intensity of test zone coloration by more than two orders of magnitude was demonstrated, which enabled the significant reduction of false-negative results. The diagnostic sensitivity of the LFIA was 62.5% for the common format and 100% for the enhanced format. Moreover, the diagnostic specificity of both variants was 100%.

Lateral Flow Immunoassays for SARS-CoV-2.

The continued circulation of SARS-CoV-2 virus in different parts of the world opens up the possibility for more virulent variants to evolve even as the coronavirus disease 2019 transitions from pandemic to endemic. Highly transmissible and virulent variants may seed new disruptive epidemic waves that can easily put the healthcare system under tremendous pressure. Despite various nucleic acid-based diagnostic tests that are now commercially available, the wide applications of these tests are largely hampered by specialized equipment requirements that may not be readily available, accessible and affordable in less developed countries or in low resource settings. Hence, the availability of lateral flow immunoassays (LFIs), which can serve as a diagnostic tool by detecting SARS-CoV-2 antigen or as a serological tool by measuring host immune response, is highly appealing. LFI is rapid, low cost, equipment-free, scalable for mass production and ideal for point-of-care settings. In this review, we first summarize the principle and assay format of these LFIs with emphasis on those that were granted emergency use authorization by the US Food and Drug Administration followed by discussion on the specimen type, marker selection and assay performance. We conclude with an overview of challenges and future perspective of LFI applications.

Analytical sensitivity of six lateral flow antigen test kits for variant strains of SARS-CoV-2.

INTRODUCTION: The lateral flow antigen test is a useful tool for rapid diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The analytical sensitivity of six lateral flow antigen test kits was compared. METHODS: The limit of detection (LoD) and time to positive results were evaluated for six lateral flow tests including ImmunoArrow®, ESPLINE® SARS-CoV-2, QuickNavi™ COVID19 Ag, ImmunoAce® SARS-CoV-2, Panbio™ COVID-19 Ag Rapid Test Device, and SARS-CoV-2 Rapid Antigen Test using the heat-inactivated virus. The LoD of ImmunoArrow® against the Omicron variants was compared with that against the wild-type using recombinant proteins. RESULTS: ImmunoArrow® and ESPLINE® showed the lowest LoD. The time to positive results of all tests except for ESPLINE® was within 200 s in the evaluation at high dose of antigens (2.5 × 105 TCID50/mL) and 500 s in the evaluation at low dose of antigens (2.5 × 104 TCID50/mL). The LoD of ImmunoArrow® against the Omicron variants was the same concentration against the wild-type antigen. CONCLUSIONS: ImmunoArrow® detected SARS-CoV-2 antigens including the Omicron variants with good sensitivity among the six lateral flow antigen tests. These finding support that it can support the rapid diagnosis of COVID-19 with the good sensitivity.

Osmoprocessor for enabling highly sensitive biomarker detection via lateral flow assays

Lateral flow assays are low-cost devices suitable for point-of-care testing, particularly in low-resource settings. However, some of the lateral flow assays exhibit limited diagnostic utility because the assays can only sample <100uL specimen and the biomarker concentration is significantly lower than the assay detection limit, which compromise the sensitivity. To address the challenge, we have developed the osmoprocessor that statically and spontaneously concentrated biomarkers via osmosis. The specimen in the device interfaces with the aqueous polymer solution via a dialysis membrane. The polymer solution induces an osmotic pressure difference that extracts water from the specimen, while the membrane retains the biomarkers. The evaluation demonstrated that osmosis induced by various water-soluble polymers efficiently extracted water, ca. 15 mL/hr. The water transport kinetics can be adjusted by varying polymer molecular weights and mass concentrations. The osmoprocessor concentrated the specimens to improve the lateral flow assays' detection limits for the model analytes-human chorionic gonadotropin and SARS-CoV-2 nucleocapsid protein. The device processed a 10 mL specimen into a 100uL concentrated sample. Then, the lateral flow assays detected the corresponding biomarkers in the concentrated specimens. The test band intensities of the assays with the concentrated specimens were very similar to the reference assays with 100-fold concentrations. The mass spectrometry analysis estimated the SARSCoV- nucleocapsid protein concentration increased ca. 200-fold after the osmosis. With its simplicity and flexibility, this device demonstrates a great potential to be utilized in conjunction with the existing lateral flow assays for enabling highly sensitive detection of dilute target analytes.

Evaluation of five immunoassays and one lateral flow immunochromatography for anti-SARS-CoV-2 antibodies detection.

INTRODUCTION: In order to deal with the current pandemic caused by the novel SARS-CoV-2 coronavirus several serological immunoassays have been recently developed with the objective of being used as a complementary diagnostic tool and to support the RT-PCR technique currently considered the "gold-standard" method. However, these new assays need to be evaluated and validated. The purpose of this study was to assess the performance of five immunoassays (two ELISA and three CLIA assays) and one rapid immunochromatographic test for the detection of anti-SARS-CoV-2 antibodies. METHODS: Five semiquantitative immunoassays (MENARINI®, PALEX®, VIRCLIA®, ROCHE® and SIEMENS®) and one lateral flow rapid test (WONDFO®) were performed. A total of 124 samples were studied. Case serum samples (n=78) were obtained from COVID-19 patients confirmed by real-time RT-PCR/epidemiological-clinical-radiological criteria, and control non-SARS-CoV-2 samples (n=46) belonged to healthy healthcare workers involved in a seroprevalence study. RESULTS: Overall, the tests showed sensitivities around 70-90% and specificities greater than 95%, including the immunochromatographic test. In addition, we observed very good agreements among them, being better for the detection of IgG than for IgM antibodies (Cohen's kappa index of 0.95 for VIRCLIA® IgG with ROCHE®), as well as good diagnostic power of the tests as determined by the ROC curves. CONCLUSIONS: This study demonstrates the proper performance of the different immunoassays in order to be applied in the clinical practice as support in the diagnostic approach and in the development of vaccines and seroepidemiological studies of COVID-19.

The Proportion of Long-term Response to Anti-N IgG Antibody after 12 Months for COVID-19 Subclinical Infections and a Longitudinal Survey for COVID-19 Subclinical Infections in 2021.

Objective To examine the continuation of antibody prevalence status after 12 months and background factors in antibody-positive subjects following asymptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods We initially determined the SARS-CoV-2 anti-nucleocapsid protein immunoglobulin G (anti-N IgG) antibody prevalence in 1,603 patients, doctors, and nurses at 65 medical institutions in Kanagawa Prefecture, Japan. We then obtained consent from 33 of the 39 subjects who tested positive and performed follow-up for 12 months. Results Follow-up for up to 12 months showed that a long-term response of the anti-N IgG antibody could be detected in 6 of the 33 participants (18.2%). The proportions with hypertension, using an angiotensin-receptor blocker, and without a drinking habit were higher among the participants with a long-term anti-N IgG antibody response for up to 12 months than among those without a long-term antibody response. Conclusions The proportion of individuals with subclinical COVID-19 who continuously had a positive result for the anti-N IgG antibody at 12 months was low.