Clinical evaluation of serological IgG antibody response on the Abbott Architect for established SARS-CoV-2 infection

OBJECTIVE: This study aimed to evaluate the diagnostic performance of the Abbott Architect SARS-CoV-2 IgG assay in COVID-19 patients. METHODS: Residual sera from 177 symptomatic SARS-CoV-2-positive patients and 163 non-COVID-19 patients were tested for antibody with the Abbott SARS-CoV-2 IgG assay (Abbott Diagnostics, Chicago, USA). Clinical records for COVID-19 patients were reviewed to determine the time from onset of clinical illness to testing. RESULTS: Specificity of the assay was 100.0% (95%CI: 97.1–100.0%). The clinical sensitivity of the assay varied depending on time from onset of symptoms, increasing with longer periods from the onset of clinical illness. The clinical sensitivity at ≤6 days was 8.6% (7/81; 95%CI: 3.8–17.5%), at 7–13 days 43.6% (17/39; 95%CI: 28.2–60.2%), at 14–20 days 84.0% (21/25; 95%CI: 63.1–94.7%), and at ≥21 days 84.4% (27/32; 95%CI: 66.5–94.1%). Clinical sensitivity was higher in the ≥14-day group compared to <14 days. There were no differences between the 14–20-day and ≥21-days groups; the combined clinical sensitivity for these groups (≥14 days) was 84.2% (49/57; 71.6–92.1%). CONCLUSION: The Abbott SARS-CoV-2 IgG test has high specificity. Clinical sensitivity was limited in the early stages of disease but improved from 14 days after the onset of clinical symptoms.