Comparative assessment of SARS-CoV-2 serology in healthcare workers with Abbott Architect, Roche Elecsys and The Binding site ELISA immunoassays. (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serology testing is key for assessing seroprevalence and antibody response post-vaccination in immunocompromised patients. Here we performed a comparison between two high-throughput nucleocapsid assays (Abbott SARS-CoV-2 IgG and Roche Elecsys Anti-SARS-CoV-2) and The Binding Site (TBS) anti-Spike IgG/A/M- SARS-CoV-2 ELISA kit. 236 samples were collected across 2 sites, Portsmouth Hospital University NHS Trust (PHU) and The Dudley Group NHS Trust. We derived concordance, agreement and assay performance as well as using receiver operating characteristic (ROC) curves to redefine the assay threshold of the Abbott assay. Result concordance between the Abbott and TBS was 66%. Discrepant samples were analysed using the Roche assay which showed 100% agreement with the TBS assay. In samples analysed >58 days post-PCR, the sensitivity of Abbott and Roche was 100%. In samples analysed >100 days post-PCR the sensitivity of the Abbott assay dropped to 77.2% but remained at 100% for the Roche assay. A redefined Abbott threshold of 0.64 increased the sensitivity to 90% giving results similar to the Roche and TBS assays. In conclusion, this study demonstrated Abbott assay had a lower sensitivity in comparison to TBS and Roche. This study established TBS can be implemented as a viable alternative for SARS-CoV-2 serology testing where high-throughput assays are not available on site. Furthermore, anti-spike assays, such as TBS, could be used to monitor vaccination responses to deduce SARS-CoV-2 population-immunity. Further optimization studies are required to evaluate the performance characteristics of these assays which could facilitate widescale sero-epidemiological surveillance.

Validation of a combined ELISA to detect IgG, IgA and IgM antibody responses to SARS-CoV-2 in mild or moderate non-hospitalised patients (preprint)

BackgroundFrequently SARS-CoV-2 results in mild or moderate disease with potentially lower concentrations of antibodies compared to those that are hospitalised. Here, we validated an ELISA using SARS-CoV-2 trimeric spike glycoprotein, with targeted detection of IgG, IgA and IgM (IgGAM) using serum and dried blood spots (DBS) from adults with mild or moderate disease. MethodsTargeting the SARS-CoV-2 trimeric spike, a combined anti-IgG, IgA and IgM serology ELISA assay was developed using 62 PCR-confirmed non-hospitalised, mild or moderate COVID-19 samples, [≥]14 days post symptom onset and 624 COVID-19 negative samples. The assay was validated using 73 PCR-confirmed non-hospitalised COVID-19 and 359 COVID-19 negative serum samples with an additional 81 DBSs, and further validated in 226 PCR-confirmed non-hospitalised COVID-19 and 426 COVID-19 negative clinical samples. ResultsA sensitivity and specificity of 98.6% (95% CI, 92.6-100.0), 98.3% (95% CI, 96.4-99.4), respectively, was observed following validation of the SARS-CoV-2 ELISA. No cross-reactivities with endemic coronaviruses or other human viruses were observed, and no change in results were recorded for interfering substances. The assay was stable at temperature extremes and components were stable for 15 days once opened. A matrix comparison showed DBS to correlate with serum results. Clinical validation of the assay reported a sensitivity of 94.7% (95% CI, 90.9-97.2%) and a specificity of 98.4% (95% CI, 96.6-99.3%). ConclusionsThe human anti-IgGAM SARS-CoV-2 ELISA provides accurate and sensitive detection of SARS-CoV-2 antibodies in non-hospitalised adults with mild or moderate disease. The use of dried blood spots makes the assay accessible to the wider community. Supplementary MaterialNo