High clinical performance and quantitative assessment of antibody kinetics using a dual recognition assay for the detection of SARS-CoV-2 IgM and IgG antibodies

Abstract

Objectives Several serological SARS-CoV-2 immunoassays have been developed recently but require external validation before widespread use. This study aims at assessing the analytical and clinical performance of the iFlash® anti-SARS-CoV-2 chemiluminescence assay for the detection of both IgM and IgG antibodies. The kinetics of the antibody response was also evaluated. Design & Methods The precision, carry-over, linearity, limit of blank, detection and quantification were assessed. Sensitivity analysis was performed by using 178 sera collected from 154 RT-PCR confirmed COVID-19 patients. The specificity analysis was performed from 75 selected non-SARS-CoV-2 sera with a potential cross-reaction to the SARS-CoV-2 immunoassay. Results This iFlash® SARS-CoV-2 assay showed excellent analytical performance. After 2 weeks since symptom onset, the sensitivities for IgM and IgG were 62.2% (95% CI: 52.3–71.2%) and 92.9%% (95% CI: 85.7–96.7%), respectively by using the cut-off provided by the manufacturer. After cut-off optimization (i.e. >2.81 for IgM and >4.86 for IgG), the sensitivity for IgM and IgG were 81.6 (95% CI: 72.7–88.1%) and 95.9% (95% CI: 89.4–98.7%), respectively. Optimized cut-off for IgG improved the sensitivity to reach 100% (95%CI: 87.6–100) from 28 days since symptom onset. Conclusions This study shows that the iFlash® SARS-CoV-2 assay from YHLO biotechnology, has satisfactory analytical performance. Nevertheless, the sensitivity of the IgM is limited for a proper clinical use compared to IgG. The determination of anti-SARS-CoV-2 IgG antibodies from 28 days since symptom onset was associated with high sensitivity, especially using optimized cut-offs (i.e. 100%).

An Original ELISA-Based Multiplex Method for the Simultaneous Detection of 5 SARS-CoV-2 IgG Antibodies Directed against Different Antigens

“…Use of serological testing to evaluate seroprevalence, to identify convalescent plasma donors, to monitor herd immunity and for risk predictions have also been proposed [ 3 , 7 ]. A wide range of serology immunoassays have been developed to complement the rRT-PCR, with different SARS-CoV-2 antigen targets and formats [ 2 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. The main SARS-CoV-2 antigens used are the nucleocapsid protein (N) and the spike protein (S) [ 10 , 16 , 17 , 18 ].…”

Sustained SARS-CoV-2 nucleocapsid antibody levels in nonsevere COVID-19: a population-based study

“…Commercially available tests detect antibodies of different antibody isotypes (i.e., total antibodies, IgG, IgA, or IgM) directed against various antigenic targets (i.e., spike protein (S) and nucleocapsid antigen (N)) [4]. Specific IgM have been shown to increase from day 0 to 17 and then gradually decrease from day 18 to 62 [4,5]. However, it is not known whether rapid decay of the SARS-CoV-2 antibodies directed against the RBD of the S protein can be extrapolated to other assays and beyond 90 days of symptom onset [1,6,7].…”

Radioligand Assay-Based Detection of Antibodies against SARS-CoV-2 in Hospital Workers Treating Patients with Severe COVID-19 in Japan

“…The results of ELISA and neutralizing antibody titration were consistent with those of RLA. Moreover, CLIA, commercialized and validated by other researchers [ 3 , 4 ], showed consistency in results with RLA. Therefore, RLA was considered to detect anti-SARS-CoV-2 IgG reliably.…”

“…To further validate the RLA results, CLIA measurements using an automatic analyzer were also performed because it had been validated by other researchers [ 3 , 4 ] and was available for research use. For CLIA, 201 samples were selected, including nine samples from patients with COVID-19, all 22 samples from the hospital staff having 1.0 or more index values by RLA, 169 negative samples having less than 1.0 index values by RIA from the hospital staff, and one blood donor sample with slightly high counts.…”