Addressing False Positives in SARS-CoV-2 Serology Testing

There is a growing concern that false positive results could undermine the utility of SARS-CoV-2 serology testing by incorrectly reporting immunity to COVID-19.

The challenge with SARS-CoV-2 is that there are other coronavirus strains and a patient might already have antibodies to these strains which could cross-react with the antigens used in the SARS-CoV-2 test, leading to false positive results.

Several strategies can be used to overcome the specificity issue, including: (i) using multiple recombinant antigens to SARS-CoV-2 in an assay to collectively represent the immunodominant regions, (ii) pre-treating patient samples with antigens against the other strains of coronaviruses to remove cross-reacting antibodies and (iii) utilizing antigens that most closely resemble the native virus (e.g. contains post-translational modifications common to the virus).  Only a handful of tests for SARS-CoV-2 have appeared to successfully overcome the specificity challenges with specificity reaching 100% and sensitivity ranging from 87% to 99.5%.

Meridian’s new range of HEK293 and insect-cell expressed SARS-CoV-2 antigens help to overcome specificity issues in COVID-19 serology assays.  When expressed in human or insect cells, antigens are post-translationally modified (glycosylation and phosphorylation) and more closely resembling the native viral proteins.  This offers significant performance advantages over E. coli expressed formats.

Insect-Cell Expressed SARS-CoV-2 Ags

Product Name Cat. No.
SARS-CoV-2 Spike protein, S1 subunit 9556
SARS-CoV-2 Spike S1 NTD 9557
SARS-CoV-2 Spike S1 RBD Protein 9558
SARS-CoV-2 full length S2 9559
SARS-CoV-2 full length Nucleocapsid 9560

HEK293 Expressed SARS-CoV-2 Ags

Product Name Cat. No.
SARS-CoV-2 Spike S1 RBD Protein 9552
SARS-CoV-2 Spike protein, S1 Subunit 9553
SARS-CoV-2 Nucleocapsid 9554