Analytical and Clinical Evaluation of the Semiquantitative Elecsys Anti-SARS-CoV-2 Spike Protein Receptor Binding Domain Antibody Assay on the Roche cobas e602 Analyzer.

OBJECTIVES: To analytically and clinically evaluate the semiquantitative Elecsys anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein antibody (S-Ab) assay on the Roche cobas e602 analyzer. METHODS: The S-Ab assay is a 1-step, double-antigen sandwich electrochemiluminescent immunoassay that semiquantitatively measures total IgG, IgM, and IgA antibodies specific for the receptor binding domain of SARS-CoV-2 spike protein in serum or plasma. The S-Ab assay was evaluated for precision, linearity, interference (by hemoglobin, bilirubin, triglycerides, and biotin), cross-reactivity, and clinical performance, and was compared to the qualitative Elecsys anti-nucleocapsid (N-Ab) immunoassay, a lateral flow device that qualitatively detects S-Ab and N-Ab, and an anti-spike enzyme-linked immunosorbent assay (ELISA). RESULTS: S-Ab assay is precise, exhibits linearity from 0.4 to 250 U/mL, is unaffected by significant cross-reactivity or interferences, and qualitatively demonstrates greater than 90% concordance with N-Ab assay and lateral flow device. Readouts of S-Ab assay correlate with ELISA, which in turn correlates strongly with SARS-CoV-2 virus neutralization assay, and exhibit 100% sensitivity and specificity for COVID-19 patient samples obtained at or more than 14 days after PCR positivity. CONCLUSIONS: The S-Ab assay is a robust clinical test for qualitative and semiquantitative detection of seropositivity following SARS-CoV-2 infection or spike-encoding mRNA COVID-19 vaccination.

SARS-CoV-2 Infection Severity Is Linked to Superior Humoral Immunity against the Spike.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently causing a global pandemic. The antigen specificity of the antibody response mounted against this novel virus is not understood in detail. Here, we report that subjects with a more severe SARS-CoV-2 infection exhibit a larger antibody response against the spike and nucleocapsid protein and epitope spreading to subdominant viral antigens, such as open reading frame 8 and nonstructural proteins. Subjects with a greater antibody response mounted a larger memory B cell response against the spike, but not the nucleocapsid protein. Additionally, we revealed that antibodies against the spike are still capable of binding the D614G spike mutant and cross-react with the SARS-CoV-1 receptor binding domain. Together, this study reveals that subjects with a more severe SARS-CoV-2 infection exhibit a greater overall antibody response to the spike and nucleocapsid protein and a larger memory B cell response against the spike.IMPORTANCE With the ongoing pandemic, it is critical to understand how natural immunity against SARS-CoV-2 and COVID-19 develops. We have identified that subjects with more severe COVID-19 disease mount a more robust and neutralizing antibody response against SARS-CoV-2 spike protein. Subjects who mounted a larger response against the spike also mounted antibody responses against other viral antigens, including the nucleocapsid protein and ORF8. Additionally, this study reveals that subjects with more severe disease mount a larger memory B cell response against the spike. These data suggest that subjects with more severe COVID-19 disease are likely better protected from reinfection with SARS-CoV-2.

Evaluation of the Truvian Easy Check COVID-19 IgM/IgG Lateral Flow Device for Rapid Anti-SARS-CoV-2 Antibody Detection.

OBJECTIVES: To evaluate the analytical and clinical performance of the Truvian Easy Check coronavirus disease 2019 (COVID-19) IgM/IgG anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody test.Serologic assays have become increasingly available for surveillance through the Food and Drug Administration emergency use authorization in the ongoing COVID-19 global pandemic. However, widespread application of serologic assays has been curbed by reports of faulty or inaccurate tests. Therefore, rapid COVID-19 antibody tests need to be thoroughly validated prior to their implementation. METHODS: The Easy Check device was analytically evaluated and its performance was compared with the Roche Elecsys anti-SARS-CoV-2 antibody assay. The test was further characterized for cross-reactivity using sera obtained from patients infected by other viruses. Clinical performance was analyzed with polymerase chain reaction-confirmed samples and a 2015 prepandemic reference sample set. RESULTS: The Easy Check device showed excellent analytical performance and compares well with the Roche Elecsys antibody assay, with an overall concordance of 98.6%. Clinical performance showed a sensitivity of 96.6%, a specificity of 98.2%, and an overall accuracy of 98.1%. CONCLUSIONS: The Easy Check device is a simple, reliable, and rapid test for detection of SARS-CoV-2 seropositivity, and its performance compares favorably against the automated Roche Elecsys antibody assay.

Analytical and Clinical Evaluation of the Automated Elecsys Anti-SARS-CoV-2 Antibody Assay on the Roche cobas e602 Analyzer.

OBJECTIVES: To evaluate the analytical and clinical performance of the automated Elecsys anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody (Elecsys Ab) assay on the Roche cobas e602 analyzer. With the ongoing global coronavirus disease 2019 (COVID-19) pandemic, widespread and routine serologic testing of SARS-CoV-2 remains a pressing need. To better understand its epidemiologic spread and to support policies aimed at curtailing further infections, reliable serologic testing is crucial for providing insight into the dynamics of the spread of COVID-19 on a population level. METHODS: The presence of anti-SARS-CoV-2 antibodies in polymerase chain reaction-positive, confirmed COVID-19 patient samples was determined using the Elecsys Ab assay on the Roche cobas e602 analyzer. The precision and cross-reactivity of the Elecsys Ab assay were characterized and its performance was compared against the EuroImmun IgA/IgG antibody (EuroImmun Ab) assay. Calculated sensitivity, specificity, and positive and negative predictive values were assessed. RESULTS: The Elecsys Ab assay demonstrated good precision, had no cross-reactivity with other viral samples, and showed 100% concordance with the EuroImmun Ab assay. Excellent clinical performance with respect to sensitivity, specificity, and positive and negative predictive values was observed. CONCLUSIONS: The Elecsys Ab assay is a precise and highly reliable automated platform for clinical detection of seropositivity in SARS-CoV-2 infection.

Evaluation of the EUROIMMUN Anti-SARS-CoV-2 ELISA Assay for detection of IgA and IgG antibodies.

As the Coronavirus 2019 (COVID-19) pandemic evolves, the development of immunoassays to help determine exposure and potentially predict immunity has become a pressing priority. In this report we present the performance of the EUROIMMUN enzyme-linked immunosorbent assay (ELISA) for semi-quantitative detection of IgA and IgG antibodies in serum and plasma samples using recombinant S1 domain of the SARS-CoV-2 spike protein as antigen. Specimens from patients, with and without COVID-19 infection, were tested at the University of Chicago Clinical Microbiology and Immunology Laboratory. Of 86 samples from SARS-CoV-2 PCR-negative patients, including 28 samples positive for common human coronavirus strains, 76 tested negative and 10 tested positive for IgA (88.4% agreement, 95% CI: 79.9-93.6) while 84 tested negative and 2 tested positive for IgG (97.7% agreement, 95% CI: 91.9-99.6). Of 82 samples from SARS-CoV-2 PCR-positive patients, 14 tested negative and 68 tested positive for IgA (82.9% agreement, 95% CI: 73.4-89.5) while 27 tested negative and 55 tested positive for IgG (67.1% agreement, 95% CI: 56.3-76.3). Of samples collected ≥4 days after positive PCR, 38 of 42 (90.5% agreement, 95% CI: 77.9-96.2) were positive for IgA, and 42 of 42 (100% agreement, 95% CI: 91.6-100) were positive for IgG, respectively. The EUROIMMUN Anti-SARS-CoV-2 ELISA Assay demonstrated good sensitivity for detection of IgA and excellent sensitivity for detection of IgG antibodies from samples collected ≥4 days, after COVID-19 diagnosis by PCR. This assay demonstrated good specificity for IgA and excellent specificity for IgG and demonstrated only borderline cross reaction in 2 of the 28 samples from patients with common human coronaviruses infection, types NL63 and OC43.