Determination of optimum levels of binding antibody units (BAU) of new quantitative chemiluminescent immuno-assay (CLIA) in COVID-19 vaccinated volunteer blood donors.

BACKGROUND: For assessment of COVID-19 vaccine efficacy, neutralization activity of anti-SARS-CoV-2 antibody is measured. This study was undertaken to determine optimum levels of binding antibody units (BAU/ml) in new quantitative chemiluminescent assay (CLIA) that corresponded to neutralizing potential (30% inhibition) of sVNT assay. METHODS: Ninety-one blood samples were analyzed by CLIA and sVNT assays. Test samples (n = 75) were collected from blood donors post-2nd vaccination dose, while control samples (n = 16) were archived pre-COVID donor samples. Correlation between CLIA and sVNT was calculated and receiver operating characteristic (ROC) curve was drawn and analyzed. RESULTS: Results indicated excellent correlation between 57.5 BAU/ml on CLIA and 30%inhibition on sVNT assay. ROC curve analysis revealed that the area under the curve (AUC) was 0.971. DISCUSSION: The present study determined that 57.5 BAU/ml on CLIA corresponded to 30% inhibition on sVNT assay. Periodic quantitative analysis.

Analytical and clinical performance evaluation of enhanced chemiluminescence-based fourth-generation HIV combo assay: Report from tertiary health-care setup in North India.

INTRODUCTION: HIV fourth-generation assay, designed for the detection of HIV p24 antigen along with anti-HIV antibodies of both immunoglobulin M and immunoglobulin G type against HIV 1 and HIV 2 viral antigens, have helped in the early detection of HIV infection and supports in minimizing the transmission risk in the acute phase of infection. The objective of this study was to evaluate the analytical and clinical performance of HIV fourth-generation assay based on enhanced chemiluminescence technology. MATERIALS AND METHODS: The analytical performance of the assay was evaluated in terms of accuracy, precision, limit of detection, type of sample (serum vs. plasma), cross-reactivity (with other transfusion transmissible infections markers), and interference (with endogenous substances). Proficiency control material included kit-controls, archived known positive donor samples, third-party controls, and World Health Organization (WHO)/National Institute for Biological Standards and Controls (NIBSC, MHRA, UK) controls. The clinical performance was evaluated using routine donor and patient samples received during the study period. RESULTS: HIV fourth-generation assay showed reliable and reproducible results measured in terms of coefficient of variation % with kit-controls, archived known positive donor samples, third-party controls, and WHO international standards for anti-HIV 1 and 2 antibodies, HIV1 p24 antigens and HIV2 p26 antigen controls. The analytical sensitivity of the HIV fourth-generation assay was found to be 0.1 IU/mL of HIV1 p24 antigen control and there was no cross-reactivity or interference observed. In the clinical performance of the assay, HIV fourth-generation assay showed reliable performance in both donor and patient samples. CONCLUSION: HIV fourth-generation assay meets the requirements for its use as a screening assay for HIV infection based on the analytical and clinical performance of the assay.

Correlation of sample-to-cut-off ratio of anti-SARS-CoV-2 IgG antibody chemiluminescent assay with neutralization activity: a prospective multi-centric study in India.

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.