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

Chew, Ka Lip; Tan, Shaun S.; Saw, Sharon; Pajarillaga, Anastacia; Zaine, Suzzana; Khoo, Candy; Wang, Weixuan; Tambyah, Paul; Jureen, Roland; Sethi, Sunil K.

OBJECTIVE: This study aimed to evaluated the diagnostic performance of the Abbott Architect SARS-CoV-2 IgG assay in COVID-19 patients. METHODS: Residual sera from 177 symptomatic COVID-19 positive patients, and 163 non-COVID-19 patients were tested for antibody with the Abbott SARS-CoV-2 IgG assay (Abbott Diagnostics, Chicago, US). 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 since onset of clinical illness. The clinical sensitivity at ≤6 days was 8.6% (7/81; 95% CI: 3.8 – 17.5%), 7-13 days: 43.6% (17/39; 95% CI: 28.2 – 60.2%), 14-20 days: 84.0% (21/25; 95% CI: 63.1 – 94.7%), and ≥21 days: 84.4% (27/32; 95% CI: 66.5 – 94.1%). Clinical sensitivity was higher in the ≥14 days group compared to <14. There were no differences between the 14-20 days and ≥21 days group; 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 early stages of disease but improved from 14 days after onset of clinical infection.