Short communication
Head-to-head comparison of two rapid high-throughput automated electrochemiluminescence immunoassays targeting total antibodies to the SARS-CoV-2 nucleoprotein and spike protein receptor binding domain

https://doi.org/10.1016/j.jcv.2021.104784Get rights and content
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Highlights

  • First manufacturer-independent head-to-head comparison of Elecsys-N and Elecsys-S.

  • Evaluated during the exponential growth phase of the epidemic’s second wave.

  • 100 % specificity of both assays on 572 pre−COVID-19 samples.

  • High overall (98.68 %) and positive agreement (95.16 %) with kappa value of 0.996.

  • Concomitant over sequential Elecsys-N/Elecsys-S use recommended.

Abstract

Background

Accurate anti-SARS-CoV-2 assays are needed to inform diagnostic, therapeutic, and public health decisions. The first manufacturer-independent head-to-head comparison of two rapid high-throughput automated electrochemiluminescence double-antigen sandwich immunoassays targeting total anti-SARS-CoV-2 antibodies against two different viral proteins, Elecsys Anti-SARS-CoV-2 (Elecsys-N) and Elecsys Anti-SARS-CoV-2 S (Elecsys-S) (Roche Diagnostics), was performed in a routine setting during the exponential growth phase of the epidemic’s second wave.

Methods

The diagnostic specificity of Elecsys-N and Elecsys-S was initially evaluated on a panel of 572 pre−COVID-19 samples, showing 100 % specificity of both assays. Elecsys-N/Elecsys-S head-to-head comparison used 3,416 consecutive blood samples from individuals that were tested for the presence of anti-SARS-CoV-2 within commercial out-of-pocket serologic testing.

Results

Elecsys-N/Elecsys-S head-to-head comparison showed overall agreement of 98.68 % (3,371/3,416; 95 % CI, 98.23–99.03 %), positive agreement of 95.16 % (884/929; 95 % CI, 93.52–96.41 %), and a high kappa value of 0.996 (95 % CI, 0.956–0.976). Previous SARS-CoV-2 PCR positivity was identified in 14/24 (58.3 %) Elecsys-N negative/Elecsys-S positive individuals and in 4/21 (19.0 %) Elecsys-N positive/Elecsys-S negative individuals.

Conclusion

The first Elecsys-N/Elecsys-S head-to-head comparison showed excellent agreement of two highly specific and rapid high-throughput automated anti-SARS-CoV-2 assays. An important question is whether laboratories offering two different antibody assays could benefit from combining the assays; if so, should use be concomitant or sequential—and, in the latter case, in which order? Based on our results, we favor concomitant over sequential Elecsys-N/Elecsys-S use when testing individuals for anti-SARS-CoV-2 antibodies in high-incidence settings; for example, during the exponential or stationary growth phase of the COVID-19 epidemic.

Keywords

SARS-CoV-2
COVID-19
Antibody
Electrochemiluminescence
Immunoassay

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