The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has elicited a surge in demand for serological testing to identify previously infected individuals. In particular, antibody testing is crucial in identifying COVID-19 convalescent plasma (CCP), which has been approved by the Food and Drug Administration (FDA) under the Emergency Use Authorization (EUA) for use as passive immune therapy for hospitalized patients infected with COVID-19. Currently, high-titer CCP can be qualified by Ortho's Vitros COVID-19 IgG antibody test (VG).


To explore the use of an efficient testing method to identify high-titer CCP for use in treating COVID-19 infected patients and track COVID-19 positivity over time.


We evaluated an ELISA-based method that detects antibodies specific to the SARSCoV-2 receptor binding domain (RBD) with individual and pooled plasma samples and compared its performance against VG. Using the pooled RBD-ELISA (P-RE) method, we also screened over 10,000 longitudinal healthy blood donor samples to assess seroprevalence.


P-RE demonstrates 100% sensitivity in detecting FDA-defined high-titer samples when compared to VG. Overall sensitivity of P-RE when compared to VG and our individual sample RBD-ELISA (I-RE) were 83% and 56%, respectively. When screening 10,218 healthy blood donor samples by P-RE, we found the seroprevalence correlated with the local infection rates with a correlation coefficient of 0.21 (P< .001).


Pooling plasma samples can be used to efficiently screen large populations for individuals with high-titer anti-RBD antibodies, important for CCP identification.

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Author notes

*Drs. Boyd and Pham contributed equally to this work.

-This work was supported by an Early Postdoc. Mobility Fellowship Stipend to Wirz from the Swiss National Science Foundation (SNSF).

-Boyd has consulted for Regeneron, Sanofi and Novartis on topics unrelated to this study, owns shares in AbCellera Biologics, and has patents awarded or submitted related to immunoglobulin gene analysis. The other authors have no relevant financial interest in the products or companies described in this article.