A performance comparison of two (electro) chemiluminescence immunoassays for detection and quantitation of serum anti‐spike antibodies according to SARS‐CoV‐2 vaccination and infections status

Abstract

The information provided by SARS‐CoV‐2 spike (S)‐targeting immunoassays can be instrumental in clinical‐decision making. We compared the performance of the Elecsys® Anti‐SARS‐CoV‐2 S assay (Roche Diagnostics) and the LIAISON® SARS‐CoV‐2 TrimericS IgG assay (DiaSorin) using a total of 1176 sera from 797 individuals, of which 286 were from vaccinated‐SARS‐CoV‐2/experienced (Vac‐Ex), 581 from vaccinated/naïve (Vac‐N), 147 from unvaccinated/experienced (Unvac‐Ex), and 162 from unvaccinated/naïve (Unvac‐N) individuals. The Roche assay returned a higher number of positive results (907 vs. 790; p = 0.45; overall sensitivity: 89.3% vs. 77.6%). The concordance between results provided by the two immunoassays was higher for sera from Vac‐N (ϰ: 0.58; interquartile ranges [IQR]: 0.50−0.65) than for sera from Vac‐Ex (ϰ: 0.19; IQR: −0.14 to 0.52) or Unvac‐Ex (ϰ: 0.18; IQR: 0.06−0.30). Discordant results occurred more frequently among sera from Unvac‐Ex (34.7%) followed by Vac‐N (14.6%) and Vac‐Ex (2.7%). Antibody levels quantified by both immunoassays were not significantly different when <250 (p = 0.87) or <1000 BAU/ml (p = 0.13); in contrast, for sera ≥1000 BAU/ml, the Roche assay returned significantly higher values than the DiaSorin assay (p < 0.008). Neutralizing antibody titers (NtAb) were measured in 127 sera from Vac‐Ex or Vac‐N using a S‐pseudotyped virus neutralization assay of Wuhan‐Hu‐1, Omicron BA.1, and Omicron BA.2. The correlation between antibody levels and NtAb titers was higher for sera from Vac‐N than those from Vac‐Ex, irrespective of the (sub)variant considered. In conclusion, neither qualitative nor quantitative results returned by both immunoassays are interchangeable. The performance of both assays was found to be greatly influenced by the vaccination and SARS‐CoV‐2 infection status of individuals.

SARS-CoV-2-reactive antibody waning, booster effect and breakthrough SARS-CoV-2 infection in hematopoietic stem cell transplant and cell therapy recipients at one year after vaccination

“…Finally, no patients died from SARS-CoV-2 breakthrough infection in the current series, confirming a significant reduction in the severity of SARS-CoV-2 VOCs, and notably, that breakthrough SARS-CoV-2 infection did not increase all-cause mortality. This study should be interpreted in light of certain limitations, such as the absence of neutralizing antibody testing, absence of cellular immune response analyses, the lack of molecular data regarding SARS-CoV-2 variants in patients with breakthrough infections and the use of different serological tests although most of them tend to correlate [39][40][41][42][43][44]. Another limitation was that only 12% of the current series were recently treated.…”

“…This study should be interpreted in light of certain limitations, such as the absence of neutralizing antibody testing, absence of cellular immune response analyses, the lack of molecular data regarding SARS-CoV-2 variants in patients with breakthrough infections and the use of different serological tests although most of them tend to correlate [ 39 – 44 ]. Another limitation was that only 12% of the current series were recently treated.…”

Vaccine-induced SARS-CoV-2 antibody response: the comparability of S1-specific binding assays depends on epitope and isotype discrimination

“…Other groups pointed out the inherent limitations of harmonization to the WHO IS, especially for SARS-CoV-2 binding assays that differ significantly in target antigen (N vs. S protein) and isotype specificity (IgG vs. IgM) ( 40 , 59 , 73 – 75 ). However, the early and widespread adoption of the WHO standard and the wide availability of conversion factors for commercial SARS-CoV-2 assays led to the following erroneous conclusion: conversion to BAU/ml allows the harmonization of two given SARS-CoV-2 binding assays.…”

Antibody‐dependent NK‐cell and neutralizing antibody responses against the Spike protein of Wuhan‐Hu‐1 and Omicron BA.1 SARS‐CoV‐2 variants in vaccinated experienced and vaccinated naïve individuals

“…Serum SARS‐CoV‐2‐S IgGs were measured using the LIAISON® SARS‐CoV‐2 TrimericS IgG assay (DiaSorin) 25 . Total antibodies against the receptor binding domain (RBD) were quantitated by the Roche Elecsys® Anti‐SARS‐CoV‐2 S test (Roche Diagnostics) 26 .…”

“…Serum SARS-CoV-2-S IgGs were measured using the LIAISON ® SARS-CoV-2 TrimericS IgG assay (DiaSorin). 25 Total antibodies against the receptor binding domain (RBD) were quantitated by the Roche Elecsys ® Anti-SARS-CoV-2 S test (Roche Diagnostics). 26 Neutralizing antibodies (NtAb) targeting the S protein were quantitated using a GFP-expressing vesicular stomatitis virus pseudotyped with the Wuhan-Hu-1 and Omicron BA.1 variants, as previously described.…”