Statement of Problem: SARS-CoV-2 serology testing is key for assessing seroprevalence and antibody response post-vaccination in immunocompromised patients. Consequently, several immunoassays have been designed to meet global laboratory infrastructures. However, immunoassay performance has been primarily elucidated through severe COVID-19 patient-samples, whereby, combination of high viral-load and robust immune-responses could overestimate assay sensitivities. Therefore, accurate detection of both asymptomatic and non-hospitalised individuals is pivotal for SARS-CoV-2 serological assay development. We therefore evaluated the Abbott, Roche and TBS immunoassays in nonhospitalised healthcare workers to identify both assay sensitivities and redefine assay thresholds required for optimisation.
Methodology: 252 samples were collected from Portsmouth Hospital University NHS Trust (PHU) and The Dudley Group NHS Trust and analysed for SARS-CoV-2 serology. 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.
Findings: 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.
Conclusion: This study demonstrated Abbott assay had a lower sensitivity in comparison to TBS and Roche. Our findings 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 optimisation studies are required to evaluate the performance characteristics of these assays which could facilitate widescale sero-epidemiological surveillance.