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Correlation of Automated Chemiluminescent Method with Enzyme-Linked Immunosorbent Assay (ELISA) Antibody Titers in Convalescent COVID-19 Plasma Samples: Development of Rapid, Cost-Effective Semi-Quantitative Diagnostic Methods

Authors Mendoza R, Silver M, Zuretti AR, Christian M, Das B, Norin AJ, Borgen P, Libien J, Bluth MH

Received 22 December 2020

Accepted for publication 23 February 2021

Published 17 March 2021 Volume 2021:12 Pages 157—164


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Professor Michael Shurin

Rachelle Mendoza,1 Michael Silver,2,3 Alejandro R Zuretti,1,4 Manan Christian,4 Ballabh Das,5 Allen J Norin,5 Patrick Borgen,6 Jenny Libien,1,4 Martin H Bluth4

1Department of Pathology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; 2School of Public Health, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; 3Department of Medicine, Maimonides Medical Center, Brooklyn, NY, USA; 4Department of Pathology, Maimonides Medical Center, Brooklyn, NY, USA; 5Department of Medicine, SUNY Downstate Health Sciences University, Brooklyn, NY, USA; 6Department of Surgery, Maimonides Medical Center, Brooklyn, NY, USA

Correspondence: Martin H Bluth
Blood Transfusion and Donor Services, Clinical Laboratories, Translational Research (Pathology), Maimonides Medical Center, 4802 10 th Avenue, Brooklyn, NY, 11219, USA
Email [email protected]

Background: We investigated the utility of an automated chemiluminescent SARS-CoV-2 IgG antibody assay platform in quantifying the amount of binding antibodies present in donated convalescent plasma.
Methods: A total of 179 convalescent plasma units were analyzed for the presence of SARS-CoV-2 IgG antibodies using the Beckman-Coulter chemiluminescent immunoassay (CLIA) platform. The equipment-derived numerical values (S/Co ratio) were recorded. Aliquots from the same units were subjected to enzyme-linked immunosorbent assay (ELISA) that detects IgG antibodies against the receptor-binding domain (RBD) of the SARS-CoV-2 S1 protein. The relationship between ELISA titers and CLIA S/Co values was analyzed using linear regression and receiver operating characteristics (ROC) curve.
Results: Twenty-one samples (11.7%) had S/Co values of less than 1.0 and were deemed negative for antibodies and convalescent plasma had S/Co values between > 1.0 and 5.0 (70/179, 39.1%). Fifteen units (8.4%) had negative ELISA titer. The majority of the units (95/179. 53.1%) had titers ≥ 1:1024. The sensitivities of ELISA to CLIA were comparable (90.5% vs 88.3%, respectively; p=0.18). There was positive linear correlation between CLIA S/Co values and ELISA IgG titer (Rho = 0.75; Spearman’s rank = 0.82, p-value = < 0.0001). The agreement between the two methods was fair, with a κ index of 0.2741. Using the ROC analysis, we identified a CLIA S/Co cutoff value of 8.2, which gives a sensitivity of 90% and a specificity of 82% in predicting a titer dilution of ≥ 1:1024.
Conclusion: The utility of automated antibody detection systems can be extended from simply a screening method to a semi-quantitative and quantitative functional antibody analysis. CLIA S/Co values can be used to reliably estimate the ELISA antibody titer. Incorporation of chemiluminescent-based methods can provide rapid, cost-effective means of identifying anti-SARS-CoV-2 antibody titers in donated plasma for use in the treatment of COVID-19 infection.

Keywords: COVID-19, ELISA, chemiluminescence, antibody, titers

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