Comparison of Two Automated Immunoassays for the Detection of SARS-CoV-2 Nucleocapsid Antibodies

Abstract

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel member of the coronavirus family that caused the global coronavirus 2019 (COVID-19) pandemic. The prevalence remains largely unknown because of early testing supply shortages. Although it cannot currently be used to determine level of immunity, antibody testing can contribute to epidemiological studies, identify convalescent plasma donors, or satisfy curiosity about previous exposure to the virus. Methods 407 samples collected from hospitalized inpatients with and without a confirmed SARS-CoV-2 infection, 170 remnant clinical specimens collected and frozen prior to the COVID-19 outbreak, and paired serum and plasma samples from 23 convalescent plasma donors were used to determine performance characteristics of the Abbott SARS-CoV-2 IgG and Roche Elecsys Anti-SARS-CoV-2 assays. The sensitivity, specificity, imprecision, interferences, and sample stability were determined. These assays were then used to characterize the antibody response in serial samples from 20 SARS-CoV-2 positive inpatients. Results Both assays exhibited 100% specificity (95% CI; 99.05 – 100.00), giving no positive results in 170 specimens collected before July 2019 and 215 specimens from patients without a confirmed SARS-CoV-2 infection. Differences between platforms were most notable in SARS-CoV-2 positive samples. Roche offered higher sensitivity in convalescent plasma donors at 95.7% (95% CI; 78.1 – 99.9) versus 91.3% (95% CI; 72.0 – 98.9) but Abbott detected antibodies in two immunocompromised patients whereas Roche did not. The Roche and Abbott platforms also exhibited different trends in antibody signal for a subset of patients. Conclusions Both the Abbott and Roche platforms offer excellent specificity but different trends in antibody signal may reflect qualitative differences in the types of antibodies recognized by the two assays. Negative serologic results do not exclude previous SARS-CoV-2 infection.

SARS-CoV-2 Serology Status Detected by Commercialized Platforms Distinguishes Previous Infection and Vaccination Adaptive Immune Responses

“…The Roche S-antibody test and the Diazyme NAbs assay detect SARS-CoV-2 infected patients with similar sensitivity (PPA) and specificity (NPA) as previously validated SARS-CoV-2 serology assays (23)(24)(25); all four commercial serology platforms had PPAs of 100% for patients tested ≥ 15 days a post-PCR positive result. Since the Roche S-antibody and Roche N-antibody assays are performed on the same platform, clinical laboratories can utilize a single analyzer to implement the CDC's recommended screen and confirm approach when testing low disease prevalence populations for past exposure to SARS-CoV-2 (26).…”

A comparison of SARS-CoV-2 nucleocapsid and spike antibody detection using three commercially available automated immunoassays

“…Roche had the lowest overall sensitivity, but several samples that were negative via the Roche assay and positive via the Abbott assay came from two immunocompromised patients receiving chemotherapy or anti-CD20 monoclonal therapy. The samples from the patient receiving anti-CD20 monoclonal antibody therapy were positive via the Beckman assay, however the samples from the patient receiving chemotherapy remained consistently negative [ 8 ],. Exclusion of the 15 samples from these two patients gave Abbott, Beckman, and Roche overall sensitivities of 98%, 95%, and 98% respectively.…”

“…The Roche assay detects anti-nucleocapsid IgG, IgM, and IgA antibodies, the Abbott assay detects anti-nucleocapsid IgG antibodies, and the Beckman assay detects anti-spike IgG antibodies (see Supplemental Table 1 for additional assay details). Additional details can be found in our previous study [ 8 ],.…”

“…Previously, we evaluated the Abbott SARS-CoV-2 IgG and Roche Elecsys Anti-SARS-CoV-2 total antibody assays, both which target the nucleocapsid protein [ 8 ],. To supplement our previous report, we have compared the performance of the Beckman-Coulter Access IgG spike protein assay to our previous report of Abbott and Roche assays.…”

Review of SARS-CoV-2 Antigen and Antibody Testing in Diagnosis and Community Surveillance

“…These publications demonstrated very low false-positive rates across multiple test manufacturers and platforms by testing sera from either well characterized SARS-CoV-2 PCR-negative patients, or samples collected prior to December 2019, the generally accepted date associated with SARS-CoV-2 spread. 14 , 15 , 16 , 17 …”