Analytical and clinical performances of five immunoassays for the detection of SARS-CoV-2 antibodies in comparison with neutralization activity

Abstract

Background Reliable high-throughput serological assays for SARS-CoV-2 antibodies are urgently needed for the effective containment of the COVID-19 pandemic, as it is of crucial importance to understand the strength and duration of immunity after infection, and to make informed decisions concerning the activation or discontinuation of physical distancing restrictions. Methods In 184 serum samples from 130 COVID-19 patients and 54 SARS-CoV-2 negative subjects, the analytical and clinical performances of four commercially available chemiluminescent assays (Abbott SARS-Cov-2 IgG, Roche Elecsys anti-SARS-CoV-2, Ortho SARS-CoV-2 total and IgG) and one enzyme-linked immunosorbent assay (Diesse ENZY-WELL SARS-CoV-2 IgG) were evaluated and compared with the neutralization activity achieved using the plaque reduction neutralization test (PRNT). Findings Precision results ranged from 0.9% to 11.8% for all assays. Elecsys anti-SARS-CoV-2 demonstrated linearity of results at concentrations within the cut-off value. Overall, sensitivity ranged from 78.5 to 87.7%, and specificity, from 97.6 to 100%. On limiting the analysis to samples collected 12 days after onset of symptoms, the sensitivity of all assays increased, the highest value (95.2%) being obtained with VITRO Anti-SARS-CoV-2 Total and Architect SARS-CoV-2 IgG. The strongest PRNT 50 correlation with antibody levels was obtained with ENZY-Well SARS-CoV-2 IgG (R 2 adj = 0.569). Interpretation The results confirmed that all immunoassays had an excellent specificity, whereas sensitivity varied across immunoassays, depending strongly on the time interval between symptoms onset and sample collection. Further studies should be conducted to achieve a stronger correlation between antibody measurement and PRNT 50 in order to obtain useful information for providing a better management of COVID-19 patients, effective passive antibody therapy, and developing a vaccine against the SARS-CoV-2 virus. Funding None.

Persistence of Anti-SARS-CoV-2 Antibodies Depends on the Analytical Kit: A Report for Up to 10 Months after Infection

“…Whether the antibodies measured with commercial assays have a neutralizing capacity is paramount for indicating the potential level of protective immunity against SARS-CoV-2 infection. Recently, Padoan et al found that the Ortho S1 IgG (R 2 adj = 0.544) and DiaSorin S1 + S2 IgG (R 2 adj = 0.402) assays were more correlated to neutralization activity compared with the Ortho S1 total antibody (R 2 adj = 0.117) and Roche NCP total antibody (R 2 adj = 0.046) assays [ 6 ]. The fact that anti-NCP assays showed a low correlation with the neutralizing capacity was expected as neutralizing antibodies are directed against the spike protein that is responsible for enabling the entry of the virus into the cells that express ACE-2 [ 22 ].…”

“…Compared with commercial immunoassays, only neutralization activity assays reliably measure the actual protective immunity of antibodies [ 6 ]. However, neutralization activity assays are only reserved for specialized laboratories and require a high workload, skillful operators, expensive installations, crucial biosafety measures and have, to date, a low throughput.…”

Evaluation of the automated LIAISON® SARS-CoV-2 TrimericS IgG assay for the detection of circulating antibodies

“…While molecular tests and rapid antigen tests are targeted for early diagnosis, serology tests play a different and perhaps even larger role by supporting epidemiological studies, furthering the understanding of longitudinal immunity, and in assessing the efficacy of vaccine development [5]. The efficient use of serology tests in understanding immunity, both in response to disease or vaccination, requires evaluation of any given assay's diagnostic performance and discriminative ability [6,7].…”

Analytical and clinical performances of a SARS-CoV-2 S-RBD IgG assay: comparison with neutralization titers

“…A high-throughput PRNT method was used for the fast and accurate quantification of neutralizing antibodies in plasma samples collected from patients exposed to SARS-CoV-2, as described elsewhere (12). Briefly, after heat-inactivation, samples were diluted in Dulbecco modified Eagle medium (DMEM) and then mixed with a virus solution containing 20-25 focus-forming units (FFUs) of SARS-CoV-2.…”