Development and validation of the Elecsys Anti-SARS-CoV-2 immunoassay as a highly specific tool for determining past exposure to SARS-CoV-2

Abstract

Background: The Elecsys® Anti-SARS-CoV-2 immunoassay (Roche Diagnostics) was developed to provide an accurate and reliable method for the detection of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated the sensitivity, specificity, and cross-reactivity of the Elecsys Anti-SARS-CoV-2 immunoassay. Methods: The performance of the Elecsys Anti-SARS-CoV-2 immunoassay was assessed at Roche Diagnostics (Penzberg, Germany). Sensitivity was evaluated using anonymised residual frozen samples from patients who had previously tested positive for SARS-CoV-2 infection by polymerase chain reaction (PCR); one or more consecutive samples were collected from patients at various timepoints after PCR confirmation. Specificity was evaluated using anonymised unselected residual frozen samples from routine diagnostic testing or from blood donors; all samples were collected before December 2019 and thus deemed negative for SARS-CoV-2-specific antibodies. Cross-reactivity was evaluated using anonymised frozen samples containing a wide range of potentially cross-reacting analytes, which were purchased from commercial vendors. For sensitivity and specificity, point estimates and 95% confidence intervals (CIs) were calculated. Results: Sensitivity of the Elecsys Anti-SARS-CoV-2 immunoassay in 496 samples from 102 patients with prior PCR-confirmed SARS-CoV-2 infection was 99.5% (95% CI 97.0-100.0) at ≥14 days after PCR confirmation. Overall specificity in 10,453 samples from routine diagnostic testing (n = 6305) and blood donors (n = 4148) was 99.80% (95% CI 99.69-99.88). Only 4/752 samples containing potential cross-reacting analytes were reactive with the Elecsys Anti-SARS-CoV-2 immunoassay, resulting in an overall specificity in this cohort of 99.5% (95% CI 98.6-99.9). Conclusion: The Elecsys Anti-SARS-CoV-2 immunoassay demonstrated a sensitivity of 99.5% at ≥14 days after PCR confirmation and a very high specificity of 99.80%. Our findings support the use of the Elecsys Anti-SARS-CoV-2 immunoassay as a tool for the identification of past SARS-CoV-2 infection, including in populations with a low disease prevalence.

Multicenter evaluation of two chemiluminescence and three lateral flow immunoassays for the diagnosis of COVID-19 and assessment of antibody dynamic responses to SARS-CoV-2 in Taiwan

“…Many automated or point-of-care serological tests have been rapidly manufactured to meet the urgent clinical and epidemiological needs to cope with the unprecedented spread and tremendous impact of the COVID-19 pandemic [ 14 , 15 , 17 ]. An ideal serological test for SARS-CoV-2 should have a high diagnostic sensitivity, low or no cross-reactivity with other existing antibodies, and a high sample throughput to prevent the delay of timely therapeutic decisions due to false-negative results, erroneous assumption of immunity to SARS-CoV-2 due to false-positive result, and facility collapse due to staff burn-out [ 31 ].…”

“…An ideal serological test for SARS-CoV-2 should have a high diagnostic sensitivity, low or no cross-reactivity with other existing antibodies, and a high sample throughput to prevent the delay of timely therapeutic decisions due to false-negative results, erroneous assumption of immunity to SARS-CoV-2 due to false-positive result, and facility collapse due to staff burn-out [ 31 ]. Previous studies have reported a high performance of various serological tests after the plateau phase of antibody formation, mostly 3 weeks after symptom onset [ 11 , 14 , 15 , 18 ]. Our study, however, found diverse diagnostic sensitivities for the different serological test.…”

“…Cross-reaction with autoantibodies or antibodies responding to other microorganisms, resulting a false-positive result in a serological test is important and should be comprehensively evaluated for accurate interpretation of test results. Previous studies have reported cross-reactivity with sera containing antibodies positive for CMV, Epstein–Barr virus (EBV), and systemic lupus erythematous in the Roche Test [ 15 , 16 ]. Our study further identified that cross-reactivity occurred not only in the Roche Test but also in the Abbott Test.…”

“…Elecsys® Anti-SARS-CoV-2 is an electrochemiluminescence immunoassay using the recombinant N protein for the detection of antibodies (including IgG) against SARS-CoV-2 with Cobas e immunoassay analyzers (Roche Diagnostics Basel, Switzerland) [ 15 , 26 ]. SARS-CoV-2 IgG, a chemiluminescent microparticle immunoassay, qualitatively detects IgG antibodies to the SARS-CoV-2 nucleocapsid protein (N protein) in human serum and plasma using the ARCHITECT i System (Abbott Laboratories, IL, USA) [ 14 , 27 ].…”

Seroprevalence of COVID-19 in Taiwan revealed by testing anti-SARS-CoV-2 serological antibodies on 14,765 hospital patients

“…In this study, out of 14,765 hospital patients screened by using Elecsys Anti-SARS-CoV-2 Assay we discovered 25 individuals with positive results and among them only 11 were tested positive based on forward confirmation using Academia Sinica ELISA assay. The possible reasons for discrepancy between these two assays include that Elecsys Anti-SARS-CoV-2 Assay had been demonstrated to have cross-reactivity with cytomegalovirus and Epstein-Barr virus IgM/IgG antibodies [17] . Of note, the observation that three patients with highest Elecsys Assay COI values (patients 8, 11, 13 in Fig.…”