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Serological testing for SARS-CoV-2 antibodies in clinical practice: a comparative diagnostic accuracy study
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  • Michael Horn,
  • Hulda R. Jonsdottir,
  • Daniel Brigger,
  • Lauro Damonti,
  • Franziska Suter-Riniker,
  • Olga Endrich,
  • Tanja Fröhlich,
  • Martin Fiedler,
  • Carlo Largiadèr,
  • Jonas Marshall,
  • Benjamin Weber,
  • Alexander Eggel,
  • Michael Nagler
Michael Horn
Inselspital Universitatsspital Bern
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Hulda R. Jonsdottir
Inselspital Bern Universitatsklinik fur Rheumatologie Immunologie und Allergologie
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Daniel Brigger
Inselspital Bern Universitatsklinik fur Rheumatologie Immunologie und Allergologie
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Lauro Damonti
Universitat Bern Institut fur Infektionskrankheiten
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Franziska Suter-Riniker
Universitat Bern Institut fur Infektionskrankheiten
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Olga Endrich
Inselspital Universitatsspital Bern
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Tanja Fröhlich
Inselspital Universitatsspital Bern
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Martin Fiedler
Inselspital Universitatsspital Bern
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Carlo Largiadèr
Inselspital Universitatsspital Bern
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Jonas Marshall
Universitat Bern Institut fur Infektionskrankheiten
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Benjamin Weber
Labor Spiez
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Alexander Eggel
Inselspital Bern Universitatsklinik fur Rheumatologie Immunologie und Allergologie
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Michael Nagler
Inselspital Universitatsspital Bern
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Abstract

Background: Serological tests are a powerful tool in the monitoring of infectious diseases and the detection of host immunity. However, manufacturers often provide diagnostic accuracy data generated through biased studies and the performance in clinical practice is essentially unclear.  Objectives: We aimed to determine the diagnostic accuracy of various serological testing strategies for (a) identification of patients with previous coronavirus disease-2019 (COVID-19) and (b) prediction of neutralizing antibodies against SARS-CoV-2 in real-life clinical settings.  Methods: We prospectively included 2’573 consecutive health-care workers and 1’085 inpatients with suspected or possible previous COVID-19 at a Swiss University Hospital. Various serological immunoassays based on different analytical techniques (enzyme-linked immunosorbent assays, ELISA; chemiluminescence immunoassay, CLIA; electrochemiluminescence immunoassay, ECLIA; lateral-flow immunoassay, LFI), epitopes of SARS-CoV-2 (nucleocapsid, N; receptor-binding domain, RBD; extended RBD, RBD+; S1 or S2 domain of the spike [S] protein, S1/S2), and antibody subtypes (IgG, pan-Ig) were conducted. A positive real-time PCR test from a nasopharyngeal swab was defined as previous COVID-19. Neutralization assays with live SARS-CoV-2 were performed in a subgroup of patients to assess neutralization activity (n=201).  Results: The sensitivity to detect patients with previous COVID-19 was ≥85% in anti-N ECLIA (86.8%) and anti-S1 ELISA (86.2%). Sensitivity was 84.7% in anti-S1/S2 CLIA, 84.0% in anti-RBD+ LFI, 81.0% in anti-N CLIA, 79.2% in anti-RBD ELISA, and 65.6% in anti-N ELISA. The specificity was 98.4% in anti-N ECLIA, 98.3% in anti-N CLIA, 98.2% in anti-S1 ELISA, 97.7% in anti-N ELISA, 97.6% in anti-S1/S2 CLIA, 97.2% in anti-RBD ELISA, and 96.1% in anti-RBD+ LFI. The sensitivity to detect neutralizing antibodies was ≥85% in anti-S1 ELISA (92.7%), anti-N ECLIA (91.7%), anti-S1/S2 CLIA (90.3%), anti-RBD+ LFI (87.9%), and anti-RBD ELISA (85.8%). Sensitivity was 84.1% in anti-N CLIA, and 66.2% in anti-N ELISA. The specificity was ≥97% in anti-N CLIA (100%), anti-S1/S2 CLIA (97.7%), and anti-RBD+ LFI (97.9%). Specificity was 95.9% in anti-RBD ELISA, 93.0% in anti-N ECLIA, 92% in anti-S1 ELISA, and 65.3% in anti-N ELISA. Diagnostic accuracy measures were consistent among subgroups.  Conclusions: The diagnostic accuracy of serological tests for SARS-CoV-2 antibodies varied remarkably in clinical practice, and the sensitivity to identify patients with previous COVID-19 deviated substantially from the manufacturer’s specifications. The data presented here should be considered when using such tests to estimate the infection burden within a specific population and determine the likelihood of protection against re-infection.

Peer review status:IN REVISION

29 Jul 2021Submitted to Allergy
02 Aug 2021Assigned to Editor
02 Aug 2021Submission Checks Completed
03 Aug 2021Reviewer(s) Assigned
22 Aug 2021Review(s) Completed, Editorial Evaluation Pending
26 Aug 2021Editorial Decision: Revise Minor