Importance of anti-SARS-CoV-2 assay antigenic composition as revealed by the results of the Belgian external quality assessment (EQA) scheme

Alena Moerman, Kris Vernelen, Bernard China, Arnaud Capron, Dorien Van Den Bossche, Joachim Mariën, Kevin K Ariën, Jos Van Acker, Marie-Luce Delforge, Marijke Reynders, An Boel, Melissa Depypere, Natasja Van Gasse, Sara Vijgen, Jonathan Brauner, Barbara Dujardin, Elizaveta Padalko

Research output: Contribution to journalA1: Web of Science-articlepeer-review


We report on sample IS/17575 since it generated highly divergent results in the Belgian SARS-CoV-2 serology external quality assessment scheme. Sample IS/17575 was serum originating from a 30 years old male patient. 124 diagnostic laboratories analysed this sample. A total of 168 results was returned (including 5 doubles). Overall, 38 were positive. All tests against S1 were positive except the Euroimmun IgG ELISA and the Ortho clinical Diagnostics VITROS IgG CLIA. All tests against S1/S2 (Liaison, Diasorin) resulted in a signal above cutoff. Assays against RBD, mostly generate a negative result. An exception are the Wantai SARS-CoV-2 ELISA's. All tests targeting N protein were negative. The survey shows, when >6 months post-infection, assays targeting at least S1, and preferably S1 combined with S2, are the most sensitive. This finding accentuates the necessity of external quality assessment schedules and importance of antigenic composition of serologic SARS-CoV-2 assays.

Original languageEnglish
Article number115561
JournalDiagnostic Microbiology and Infectious Disease
Issue number2
Number of pages6
Publication statusPublished - 2022


  • Adult
  • Antibodies, Viral/immunology
  • Antigens, Viral/immunology
  • Belgium
  • COVID-19/diagnosis
  • COVID-19 Serological Testing/methods
  • Coronavirus Nucleocapsid Proteins/immunology
  • Diagnostic Tests, Routine
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Immunoglobulin A/immunology
  • Immunoglobulin G/immunology
  • Immunoglobulin M/immunology
  • Male
  • Phosphoproteins/immunology
  • SARS-CoV-2/immunology
  • Sensitivity and Specificity
  • Spike Glycoprotein, Coronavirus/immunology


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