Performance characteristics of five immunoassays for SARS-CoV-2: a head-to-head benchmark comparison

Abstract

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic in 2020. Testing is crucial for mitigating public health and economic effects. Serology is considered key to population-level surveillance and potentially individual-level risk assessment. However, immunoassay performance has not been compared on large, identical sample sets. We aimed to investigate the performance of four high-throughput commercial SARS-CoV-2 antibody immunoassays and a novel 384-well ELISA. Methods We did a head-to-head assessment of SARS-CoV-2 IgG assay (Abbott, Chicago, IL, USA), LIAISON SARS-CoV-2 S1/S2 IgG assay (DiaSorin, Saluggia, Italy), Elecsys Anti-SARS-CoV-2 assay (Roche, Basel, Switzerland), SARS-CoV-2 Total assay (Siemens, Munich, Germany), and a novel 384-well ELISA (the Oxford immunoassay). We derived sensitivity and specificity from 976 pre-pandemic blood samples (collected between Sept 4, 2014, and Oct 4, 2016) and 536 blood samples from patients with laboratory-confirmed SARS-CoV-2 infection, collected at least 20 days post symptom onset (collected between Feb 1, 2020, and May 31, 2020). Receiver operating characteristic (ROC) curves were used to assess assay thresholds. Findings At the manufacturers' thresholds, for the Abbott assay sensitivity was 92·7% (95% CI 90·2–94·8) and specificity was 99·9% (99·4–100%); for the DiaSorin assay sensitivity was 95·0% (92·8–96·7) and specificity was 98·7% (97·7–99·3); for the Oxford immunoassay sensitivity was 99·1% (97·8–99·7) and specificity was 99·0% (98·1–99·5); for the Roche assay sensitivity was 97·2% (95·4–98·4) and specificity was 99·8% (99·3–100); and for the Siemens assay sensitivity was 98·1% (96·6–99·1) and specificity was 99·9% (99·4–100%). All assays achieved a sensitivity of at least 98% with thresholds optimised to achieve a specificity of at least 98% on samples taken 30 days or more post symptom onset. Interpretation Four commercial, widely available assays and a scalable 384-well ELISA can be used for SARS-CoV-2 serological testing to achieve sensitivity and specificity of at least 98%. The Siemens assay and Oxford immunoassay achieved these metrics without further optimisation. This benchmark study in immunoassay assessment should enable refinements of testing strategies and the best use of serological testing resource to benefit individuals and population health. Funding Public Health England and UK National Institute for Health Research.

Antibody Status and Incidence of SARS-CoV-2 Infection in Health Care Workers

“…The incidence of SARS-CoV-2 infection was inversely associated with baseline anti-spike and anti-nucleocapsid antibody titers, including titers below the positive threshold for both assays, such that workers with high “negative” titers were relatively protected from infection. In addition to the 24 seronegative health care workers with a previous positive PCR test, it is likely that other health care workers with baseline titers below assay thresholds, which were set to ensure high specificity, 23 had been previously infected with SARS-CoV-2 and had low peak postinfection titers or rising or waning responses at testing. 5 …”

“…Serologic investigations were performed with use of an anti-trimeric spike IgG enzyme-linked immunosorbent assay (ELISA), developed by the University of Oxford, 23 , 24 and an anti-nucleocapsid IgG assay (Abbott). See the Supplementary Appendix , available with the full text of this article at NEJM.org, for details on the assays and PCR tests.…”

Estimated SARS-CoV-2 Seroprevalence in the US as of September 2020

“…For one, persons with asymptomatic or mild infection may mount a less robust immune response than persons with more severe disease. [35][36][37][38] Further, declines in SARS-CoV-2 antibodies following infection have been observed. [35][36][37][38][39] The kinetics of waning antibodies also appear to differ by type of assay, viral target, and severity of infection 35,40 We do not yet understand the association of these factors with estimating seroprevalence in the population or interpreting changes in seroprevalence over time.…”

Humoral Responses and Serological Assays in SARS-CoV-2 Infections

“…Drawbacks of LFAs include their higher cost-per-test rate, their inability to analyze multiple samples simultaneously, their general lack of quantitative data, and importantly, a several-fold reduced sensitivity when compared to non-rapid testing methods (71,72). Although RDTs are theoretically ideal for POC usage, recent studies have demonstrated that many newly developed RDTs for SARS-CoV-2 have failed to meet the necessary standards for sensitivity and specificity when compared to non-rapid testing (71)(72)(73)(74)(75)(76). Therefore, for research purposes, LFAs are not the ideal choice.…”