ABSTRACT
Since the pandemic occurred due to the emergence of SARS-CoV-2, there has always been a demand for a simple and sensitive diagnostic kit for detection of SARS-Cov-2 infection. In January 2020, WHO approved the Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) for detecting the presence of Covid-19 genetic material in individuals. Till date many diagnostic kits have arrived in the market for quantification of SARS-CoV-2 antibodies. In spite of being the gold standard method of Covid-19 detection, there are some drawbacks associated with RT-PCR which leads to false-negative results. Hence, in order to fulfil the need for an antibody testing kit for evaluating seroconversion and immunity acquisition in the population, an efficient, highly specific and sensitive assay, Chimera Soochak, an enzyme-linked immunoassay (ELISA) Kit has been developed. It works on the principle of detecting IgG antibodies developed specifically against the S1-RBD by employing a recombinant strain of S1-RBD produced in the HEK293 cell line. The developed kit was validated using different modes and methods to attain the utmost confidence on the samples collected from patients. The validation methodology included, validation with known samples, blind study, third-party validation, validation using WHO Reference Panel and comparison with FDA approved Surrogate virus neutralization kit. The kit was found successful in detecting IgG against the S1-RBD of SARS-CoV-2. The kit had been validated on multiple parameters. A total of 900 samples had been tested by using this kit and it has exhibited the sensitivity, specificity and accuracy for all the above-mentioned parameters.
Subject(s)
COVID-19 , SARS-CoV-2 , Antibodies, Viral , HEK293 Cells , Humans , Sensitivity and SpecificityABSTRACT
Background and Objectives: There are limited published data on association of results from commercial serological anti-SARS-CoV-2 IgG antibody CLIA (chemiluminescent immunoassay) assays with neutralizing antibodies. This study was undertaken with an objective to correlate sample-to-cut-off (S/Co) ratio of CLIA antibody tests with inhibition activity, which may then serve as a valuable guide for labelling plasma as COVID convalescent plasma (CCP) for therapy and assessing vaccine efficacy. Materials and Methods: A total of 139 donor serum samples who were previously RT-PCR positive and had recovered completely from COVID-19 at least 28 days prior to collection of samples were recruited at three sites. The samples were analysed for S/Co ratio and per cent inhibition activity with VITROS SARS-CoV-2 IgG chemiluminescent assay and GenScript cPass SARS-CoV-2 Surrogate Virus Neutralization Test (sVNT) kit, respectively. Linear regression equation and receiver operating characteristic (ROC) curve were used to check the proposed model of comparing S/Co with per cent inhibition. Results: The results indicate very good correlation between the S/Co ratio of the chemiluminescent IgG assay and the neutralization activity depicted by per cent inhibition on sVNT assay. S/Co ratio of 4·04 (low-titre) and 8·19 (high-titre) correlated with 30% and 68% inhibition, respectively. Conclusion: Chemiluminescent SARS-CoV-2 IgG assay can be used as a semi-quantitative test, with a cut-off of >8·19S/Co ratio for selecting donors for convalescent plasma therapy and assessing efficacy of vaccination.