Evaluation and modelling of the performance of an automated SARS-CoV-2 antigen assay according to sample type, target population and epidemic trends

The Lumipulse® G SARS-CoV-2 Ag assay performance was evaluated on prospectively collected saliva and nasopharyngeal swabs (NPS) of recently ill in- and outpatients and according to the estimated viral load. Performances were calculated using RT-PCR positive NPS from patients with symptoms ≤ 7 days and RT-PCR negative NPS as gold standard. In addition, non-selected positive NPS were analyzed to assess the performances on various viral loads. This assay yielded a sensitivity of 93.1% on NPS and 71.4% on saliva for recently ill patients. For NPS with a viral load > 103 RNA copies/mL, sensitivity was 96.4%. A model established on our daily routine showed fluctuations of the performances depending on the epidemic trends but an overall good negative predictive value. Lumipulse® G SARS-CoV-2 assay yielded good performance for an automated antigen detection assay on NPS. Using it for the detection of recently ill patient or to screen high-risk patients could be an interesting alternative to the more expensive RT-PCR.

Diagnostic Performance of a Rapid Antigen Test Compared with the Reverse Transcription Polymerase Chain Reaction for SARS-CoV-2 Detection in Asymptomatic Individuals Referring to a Drive-in Testing Facility

Quick and reliable identification of severe acute respiratory syndrome coronavirus SARS-CoV-2 in the population is required to manage the COVID-19 pandemic. This is a prospective observational study of diagnostic accuracy. Paired swab samples from 317 asymptomatic individuals referring to a drive-in testing facility were tested in parallel by means of the rapid antigen test developed by Jiangsu Bioperfectus Technologies and routine nucleic acid detection. Overall specificity was 100% and sensitivity was 49% but reached 87% at higher viral loads (Ct < 25). In this study, the antigen detection test showed high specificity and good sensitivity in asymptomatic individuals carrying higher viral loads. The assay performance worsened with lower viral loads, making it useful when a rapidly deployable test is essential and to assess a potential risk of immediate transmission in the community, but not recommended for testing asymptomatic individuals.

COVID-19 Antibody Detection and Assay Performance Using Red Cell Agglutination

We recently developed a red cell based assay to detect SARS-CoV-2 antibodies in human plasma. In the current study, we show the hands-on application of this assay in a group of COVID-19 convalescent plasma donors and healthy individuals.

A bridging assay for detection and characterization of anti-drug antibodies to dostarlimab, a new anti-PD-1 therapeutic monoclonal antibody

Dostarlimab (JEMPERLI) is a humanized anti-programmed death 1 (PD-1) immunoglobulin (Ig)G4-kappa monoclonal antibody that binds to the PD-1 receptor and competitively inhibits binding of its ligands, PD-L1 and PD-L2. Dostarlimab was recently approved in the USA and the European Union. Because dostarlimab is a macromolecular therapeutic, it has the potential to elicit the formation of anti-drug antibodies, which have the capability to impact the drug’s safety and efficacy and to alter pharmacokinetics. The immunogenic potential of dostarlimab remains unknown, and it was therefore necessary to develop analytical assays to detect and characterize anti-drug antibodies as a key component in the mitigation of immunogenicity risk. Here, we present the development and optimization of a 3-tiered electrochemiluminescense bridging assay for the investigation of dostarlimab clinical immunogenicity. In this work, the full details of the method, statistical data analysis and cut point determinations, assay performance during clinical sample analysis, and associated regulatory expectations are discussed. The full validation of this 3-tier anti-drug antibody assay enabled dostarlimab immunogenicity evaluation in clinical studies. Trial registration: Clinicaltrials.gov, NCT02715284. Registered 9 March 2016

Assessing Biomarker Stability and Assay Performance Parameters for the Use of Biomarkers in Mental Disorders; A Study of Early Stage Biomarker Assay Method Development

Within the field of psychiatry the development of biomarker based assay methods is relatively young. Recent efforts focused on combining several biomarkers within a panel to increase discriminative power. However, most biomarker panels have failed to advance to the stage of clinical application. An important prerequisite is a proper sampling and storage procedure, based on a priori identified stability properties of all biomarker/body fluid combinations present in the panel. Second, is the performance requisites of the assays in use, such as Enzyme-Linked Immunosorbent Assays (ELISA), in order to assure reliable results within and between runs. In this study, we analyzed 24 biomarker assays in 32 biomarker/body fluid combinations. Each biomarker body fluid combination was tested for stability and assay performance. We found hampering stability in almost all cases expect three biomarkers in urine and three in serum. Variability in biomarker stability either indicates decreased biomarker stability or issues in assay performance. This study indicates that basic biomarker/body fluid combination stability provides a good starting point for biomarker panel assay development. However, assay performance plays an important role in the correct interpretation of those results. Along the way of assay development, other quality assurance parameters might be implemented focused on a fit for purpose principle ultimately providing reliable data necessary for diagnostical method implementation.

Antibody Responses to SARS-CoV-2 Infection—Comparative Determination of Seroprevalence in Two High-Throughput Assays versus a Sensitive Spike Protein ELISA

Robust assay development for SARS-CoV-2 serological testing requires assessment of asymptomatic and non-hospitalised individuals to determine if assays are sensitive to mild antibody responses. Our study evaluated the performance characteristics of two high-throughput SARS-CoV-2 IgG nucleocapsid assays (Abbott Architect and Roche) and The Binding Site (TBS) Anti-Spike IgG/A/M ELISA kit in samples from healthcare workers (HCWs). The 252 samples were collected from multi-site NHS trusts and analysed for SARS-CoV-2 serology. Assay performance was evaluated between these three platforms and ROC curves were used to redefine the Abbott threshold. Concordance between Abbott and TBS was 66%. Any discrepant results were analysed using Roche, which showed 100% concordance with TBS. Analysis conducted in HCWs within 58 days post-PCR result demonstrated 100% sensitivity for both Abbott and Roche. Longitudinal analysis for >100 days post-PCR led to sensitivity of 77.2% and 100% for Abbott and Roche, respectively. A redefined Abbott threshold (0.64) increased sensitivity to 90%, producing results comparable to TBS and Roche. The manufacturer’s threshold set by Abbott contributes to lower sensitivity and elevated false-negative occurrences. Abbott performance improved upon re-optimisation of the cut-off threshold. Our findings provided evidence that TBS can be used as bespoke alternative for SARS-CoV-2 serology analysis where high-throughput platforms are not feasible on site.

Impact of thyroglobulin and thyroglobulin antibody assay performance on the differential classification of DTC patients

Context Measurements of thyroglobulin (Tg) and Tg antibodies are crucial in the follow-up of treated differentiated thyroid cancer (DTC) patients. Inter-assay differences may significantly impact follow-up. Objective The aim of this multicenter study was to explore the impact of Tg and Tg antibody assay performance on the differential classification of DTC patients, as described in national and international guidelines. Design Four commonly used Tg and Tg antibody assays were technically compared to reflect possible effects on patients with DTC follow-up. Storage stability at different storage temperatures was also investigated for LIAISON® and Kryptor assays, as this is an underexposed topic in current literature. Results B.R.A.H.M.S. assays yield approximately 50% lower Tg values over the whole range compared to the DiaSorin and Roche assays investigated. These differences between assays may result in potential misclassification in up to 7% of patients if fixed cut-offs (e.g. 1 ng/mL) are applied. Poor correlation was also observed between the Tg antibody assays, when the method-specific upper limits of normal are used as cut-offs. Storage of Tg and Tg antibodies was possible for three to four weeks at -20 °C and -80 °C. Calibration of the assays, however, was found to be crucial for stable results over time. Conclusions Technical aspects of Tg and Tg antibody assays, including inter-assay differences, calibration and standardization, and cut-off values, may have a significant clinical impact on the follow-up of DTC patients.