Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Qualitative IgG Assays: The Value of Numeric Reporting.

CONTEXT: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG testing is used for serosurveillance and will be important to evaluate vaccination status. Given the urgency to release coronavirus disease 2019 (COVID-19) serology tests, most manufacturers have developed qualitative tests. OBJECTIVE: To evaluate clinical performance of six different SARS-CoV-2 IgG assays and their quantitative results to better elucidate the clinical role of serology testing in COVID-19. DESIGN: Six SARS-CoV-2 IgG assays were tested using remnant specimens from 190 patients. Sensitivity and specificity were evaluated for each assay with the current manufacturer's cutoff and a lower cutoff. A numeric result analysis and discrepancy analysis were performed Results: The specificity was >93% for all assays, and sensitivity was >80% for all assays (≥ 7 days post-polymerase chain reaction [PCR] testing). Inpatients with more severe disease had higher numeric values compared to health care workers with mild or moderate disease. Several discrepant serology results were those just below the manufacturers cutoff. CONCLUSIONS: SARS-CoV-2 IgG antibody testing can aid in the diagnosis of COVID-19 especially with negative PCR. Quantitative COVID-19 IgG results are important to better understand the immunological response and disease course of this novel virus and to assess immunity as part of future vaccination programs.