Interpretive discrepancies caused by target values inter-batch variations in chemiluminescence immunoassay for SARS-CoV-2 IgM/IgG by MAGLUMI

J Med Virol. 2021 Mar;93(3):1805-1809. doi: 10.1002/jmv.26612. Epub 2020 Nov 1.


Plasma specimens from coronavirus disease 2019 patients were double-tested for anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies by two different batches of MAGLUMI 2019-nCov immunoglobulin M/immunoglobulin G (IgM/IgG) assays to evaluate IgM/IgG levels, qualitative interpretation, antibody kinetics, and linearity of diluted specimen. Here we show that (i) high-level IgM specimens need to be diluted with negative human plasma but not kit diluents and (ii) measured anti-SARS-CoV-2 IgM/IgG concentrations are substantially higher with later marketed immunoassay batch leading to (iii) the change of qualitative interpretation (positive vs. negative) in 12.3% of specimens measured for IgM, (iv) the informative time-course pattern of antibody production only when data from different immunoassay batches are not combined.

Keywords: CLIA; anti-SARS-CoV-2 IgG; anti-SARS-CoV-2 IgM; inter-assay batch variation; interpretative inconsistency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Viral / immunology
  • COVID-19 / blood*
  • COVID-19 / immunology*
  • COVID-19 Testing / methods
  • Humans
  • Immunoassay / methods
  • Immunoglobulin G / blood*
  • Immunoglobulin G / immunology*
  • Immunoglobulin M / blood*
  • Immunoglobulin M / immunology*
  • Luminescence
  • Luminescent Measurements / methods
  • SARS-CoV-2 / immunology*
  • Sensitivity and Specificity


  • Antibodies, Viral
  • Immunoglobulin G
  • Immunoglobulin M