Evaluation of 32 rapid tests for detection of antibodies against SARS-CoV-2

Point of care detection of SARS-CoV-2 antibodies and neutralisation capacity-lateral flow immunoassay evaluation compared to commercial assay to inform potential role in therapeutic and surveillance practices

Introduction

As the COVID-19 pandemic moves towards endemic status, testing strategies are being de-escalated. A rapid and effective point of care test (POCT) assessment of SARS-CoV-2 immune responses can inform clinical decision-making and epidemiological monitoring of the disease. This cross-sectional seroprevalence study of anti-SARS-CoV-2 antibodies in Irish healthcare workers assessed how rapid anti-SARS-CoV-2 antibody testing can be compared to a standard laboratory assay, discusses its effectiveness in neutralisation assessment and its uses into the future of the pandemic.

Methods

A point of care lateral flow immunoassay (LFA) detecting anti-SARS-CoV-2 spike (S)-receptor binding domain (RBD) neutralising antibodies (Healgen SARS-CoV-2 neutralising Antibody Rapid Test Cassette) was compared to the Roche Elecsys/-S anti-SARS-CoV-2 antibody assays and an in vitro surrogate neutralisation assay. A correlation between anti-spike (S), anti-nucleocapsid (N) titres, and in vitro neutralisation was also assessed.

Results

1,777 serology samples were tested using Roche Elecsys/-S anti-SARS-CoV-2 assays to detect total anti-N/S antibodies. 1,562 samples were tested using the POC LFA (including 50 negative controls), and 90 samples were tested using an in vitro ACE2-RBD binding inhibition surrogate neutralisation assay. The POCT demonstrated 97.7% sensitivity, 100% specificity, a positive predictive value (PPV) of 100%, and a negative predictive value (NPV) of 61% in comparison to the commercial assay. Anti-S antibody titres determined by the Roche assay stratified by the POC LFA result groups demonstrated statistically significant differences between the "Positive" and "Negative" LFA groups (p < 0.0001) and the "Weak Positive" and "Positive" LFA groups (p < 0.0001). No statistically significant difference in ACE2-RBD binding inhibition was demonstrated when stratified by the LFA POC results. A positive, statistically significant correlation was demonstrated between the in vitro pseudo-neutralisation assay results and anti-S antibody titres (rho 0.423, p < 0.001) and anti-N antibody titres (rho = 0.55, p < 0.0001).

Conclusion

High sensitivity, specificity, and PPV were demonstrated for the POC LFA for the detection of anti-S-RBD antibodies in comparison to the commercial assay. The LFA was not a reliable determinant of the neutralisation capacity of identified antibodies. POC LFA are useful tools in sero-epidemiology settings, pandemic preparedness and may act as supportive tools in treatment decisions through the rapid identification of anti-Spike antibodies.

Applications of nanobodies in the prevention, detection, and treatment of the evolving SARS-CoV-2

Global health and economy are deeply influenced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its newly emerging variants. Nanobodies with nanometer-scale size are promising for the detection and treatment of SARS-CoV-2 and its variants because they are superior to conventional antibodies in terms of cryptic epitope accessibility, tissue penetration, cost, formatting adaptability, and especially protein stability, which enables their aerosolized specific delivery to lung tissues. This review summarizes the progress in the prevention, detection, and treatment of SARS-CoV-2 using nanobodies, as well as strategies to combat the evolving SARS-CoV-2 variants. Generally, highly efficient generation of potent broad-spectrum nanobodies targeting conserved epitopes or further construction of multivalent formats targeting non-overlapping epitopes can promote neutralizing activity against SARS-CoV-2 variants and suppress immune escape.

Seroprevalence of SARS-CoV2 Infections in Health Care Personnel in a Long-Term Care Institution After the First Wave of the Pandemic: A Cross-Sectional Study

BACKGROUND

At the time of our study, occupational health evidence specific for long-term care employees was mostly lacking. The purpose of this study was to determine the proportion of positive cases in employees after the first COVID-19 wave in May 2020. We also determined the prevalence of asymptomatic cases.

METHOD

The study population included all health care workers (HCW) employed at one mid-size long-term hospital in Spain (May 2020). A cross-sectional study design included an interviewer-administered self-reported questionnaire (including sociodemographic questions, risk factors for COVID-19 complications such as hypertension or diabetes, and previous polymerase chain reaction [PCR] results) and antibody determination (Biozek rapid test). Data were analyzed using Student's t, Fisher, and chi-square tests. Two multivariate logistic models were created to evaluate exposure factors and symptoms separately on the outcome of having had COVID-19.

FINDINGS

Of the 97% of workers who participated (580/596), 300 (51.7%) suffered symptoms of COVID-19, 161 (27.8%) of the rapid antibody tests were positive for IgM and/or IgG, 160 (27.6%) workers had at least one risk factor, and 32 (19.0%) of the 168 SARS-CoV-2-positive cases were asymptomatic. The proportion of negative or unavailable PCRs, with positive antibody, was 11.7% (56/477). Casual contact without protection (odds ratio [OR]: 1.9, 95% confidence interval [CI]: 1.1-3.4), doctor occupation (OR 3.3, 95% CI: 1.1-10.2), and nursing assistant occupation (OR 2.5, 95% CI: 1.2-5.8) were independently associated with SARS-CoV-2 infection.

CONCLUSION

Physicians and nursing assistants in a long-term care setting were at a higher risk of SARS-COV-2 infection over other occupations in the first wave of the pandemic, especially when in contact with patients without protection. Almost one-fifth of the workers with a positive PCR test for SARS-COV-2 were asymptomatic and seroprevalence (27.8%) was well below the approximated herd immunity cutoff (60-70%). Essential workers in long-term care must be monitored frequently by Employee Health Service and should be required to wear personal protective equipment including a fit-tested N-95 while in close contact with patients and coworkers.

Clinical Chemistry and Laboratory Medicine celebrates 60 years – narrative review devoted to the contribution of the journal to the diagnosis of SARS-CoV-2

This review is an integral part of the special issue for the 60 years of the journal Clinical Chemistry and Laboratory Medicine (CCLM). The aim of the review is to highlight the role of the clinical laboratory since the emergence of the “severe acute respiratory syndrome coronavirus 2” (SARS-CoV-2), which causes Coronavirus disease 2019 (COVID-19), with special focus on the contribution of the journal in generating knowledge in SARS-CoV-2 diagnosis. As of October 30, 2022, a total of 186 CCLM publications were dedicated to COVID-19. Of importance, major International Federation of Clinical Chemistry (IFCC) guidelines related to the diagnosis of COVID-19 were published in CCLM. Between early-2020 and late October 2022, COVID-19 publications represented around 27% of all articles in CCLM, highlighting the willingness of the editorial board to help the field in order to better describe and diagnose this new emerging disease. First launched in 1963 under the name “Zeitschrift für Klinische Chemie”, the Journal was entirely devoted to clinical chemistry in the strict sense. The various topics published in relation to COVID-19 including its diagnosis, its impact on biochemical or hematological measures, as well as biosafety measures, is the perfect example that shows that the journal has greatly diversified over time.

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.

Disease Prevalence Matters: Challenge for SARS-CoV-2 Testing

While sensitivity and specificity are important characteristics for any diagnostic test, the influence of prevalence is equally, if not more, important when such tests are used in community screening. We review the concepts of positive/negative predictive values (PPV/NPV) and how disease prevalence affects false positive/negative rates. In low-prevalence situations, the PPV decreases drastically. We demonstrate how using two tests in an orthogonal fashion can be especially beneficial in low-prevalence settings and greatly improve the PPV of the diagnostic test results.