Unexpected high frequency of unspecific reactivities by testing pre-epidemic blood specimens from Europe and Africa with SARS-CoV-2 IgG-IgM antibody rapid tests points to IgM as the Achilles heel.

Abstract

We aimed to evaluate the rates of false-positive test results of three rapid diagnostic tests (RDTs) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific immunoglobulin G (IgG) and IgM detection. Two serum panels from patients hospitalized in Paris, France, and from patients living in Bangui, Central African Republic, acquired before the 2019 COVID-19 outbreak, were tested by 3 CE IVD-labeled RDTs for SARS-CoV-2 serology (BIOSYNEX® COVID-19 BSS [IgG/IgM]; SIENNA™ COVID-19 IgG/IgM Rapid Test Cassette; NG-Test® IgG-IgM COVID-19). Detectable IgG or IgM reactivities could be observed in 31 (3.43%) of the 902 IgG and IgM bands of the 3 RDTs used with all pre-epidemic sera. The frequencies of IgG/IgM reactivities were similar for European (3.20%) and African (3.55%) sera. IgM reactivities were observed in 9 European and 14 African sera, while IgG reactivity was observed in only 1 African serum (15.1% vs. 0.66%). The test NG-Test® IgG-IgM COVID-19 showed the highest rates of IgG or IgM reactivities (6.12% [18/294]), while the test BIOSYNEX® COVID-19 BSS (IgG/IgM) showed the lowest rate (1.36% [4/294]). Some combinations of 2 RDTs in series allowed decreasing significantly the risk of false-positive test results. Our observations point to the risk of false-positive reactivities when using currently available RDT for SARS-CoV-2 serological screening, especially for the IgM band, even if the test is CE IVD-labeled and approved by national health authorities, and provide the rational basis for confirmatory testing by another RDT in case of positive initial screening.

• Authors: Ralph-Sydney Mboumba Bouassa, Hélène Péré, Serge Tonen-Wolyec, Jean De Dieu Longo, Sandrine Moussa, Francois-Xavier Mbopi-Keou, Christian Diamant Mossoro-Kpinde, Gérard Grésenguet, David Veyer, Laurent Bélec
• Journal: Journal of medical virology (J Med Virol) Vol. 93 Issue 4 Pg. 2196-2203 (04 2021) ISSN: 1096-9071 [Electronic] United States
• PMID: 33107601 (Publication Type: Journal Article)
• Copyright: © 2020 Wiley Periodicals LLC.

Chemical References

• Antibodies, Viral
• Immunoglobulin G
• Immunoglobulin M

Topics

• Adult
• Africa
• Aged
• Aged, 80 and over
• Antibodies, Viral (blood)
• COVID-19 (blood, diagnosis, epidemiology, virology)
• COVID-19 Testing (methods)
• Central African Republic
• Europe
• False Positive Reactions
• Female
• France
• Humans
• Immunoglobulin G (blood)
• Immunoglobulin M (blood)
• Male
• Middle Aged
• Pandemics
• SARS-CoV-2 (immunology, isolation & purification)
• Sensitivity and Specificity
• Seroepidemiologic Studies
• Serologic Tests (methods)