Evaluation of serological tests for detecting SARS-CoV-2 antibodies: implementation in assessing post vaccination status

BackgroundThe anti-SARS-CoV-2 immunological assays have promising applications in the control and surveillance of the current COVID-19 pandemic. Therefore, large number of serological assays are developed in the commercial market to measure SARS-CoV-2 antibodies, which requires evaluation before their application in large scale. ObjectivesTo evaluate the performances of commercially available serological assays for detecting SARS-CoV-2 antibodies. MethodsThe study compared the performances of six different methods for detection of antibodies against SARS-CoV-2 which includes (i) Genscript SARS-CoV-2 surrogate virus neutralization test kit [Test A] (ii) Diasorin - SARS-CoV-2 S1/S2 IgG detection [Test B] (iii) Alinity SARS-CoV-2 IgG II [Test C] (iv) Diasorin - SARS-CoV-2 TrimericS IgG [Test D] (v) Roche Elecsys Anti-SARS-CoV-2 - cobas [Test E] (vi) AESKULISA (AESKU Enzyme Linked Immunosorbent Assay) [Test F] against the gold standard Plaque Reduction Neutralization Test (PRNT). ResultsTest E had the highest sensitivity and Test A had the highest specificity The ROC for tests A, C, D and E showed optimum cut-offs that differed from the manufacturers recommendation. Test D had the best performance considering all the performance indicators with the highest agreement with the PRNT results. Parallel testing of test A with test D and test B had the optimum performance. ConclusionSerological assays that are commercially available are very promising and show good agreement with the standard PRNT results. Studies on large samples for optimization of the assay cut-off values and cost-effective evaluations on parallel testing methods are needed to make recommendations on these commercial assays. ImportanceSerological assays that are commercially available are very promising and this paper adds new knowledge about the optimization of these kits for evaluating post vaccination antibodies status. It highlights the positive and negative aspects of each of these assays in terms of sensitivity, specificity, positive and negative predictive values, and the agreement of results with the standard neutralization test. When serological assays are being used to assess post-vaccine immune status, a balance of all parameters needs to be considered rather than emphasizing only on high specificity. This is particularly relevant in the current situation where vaccination is happening around the globe, high sensitivity assays will result in reporting a lower percentage of false negative reports and avoids panic about lack of vaccine response. It is important that we understand the strengths and limitations of commercially available serological assays for better application of these tests to understand immune response and the duration of protection post vaccination.