ACE2 and COVID-19: To address this need, we report here a rapid test, termed the CoVariant-SCAN (COVID-19 Variant S-ACE2–Competitive Antibody Neutralization) assay, that evaluates the ability of host nAbs to block the pathologic interaction between variants of viral RBD and human ACE2 within 1 hour from a drop of plasma (Fig. 1A).