Figure 1. Correlation Between Spike Receptor-Binding Domain (S-RBD) IgG and Neutralizing Antibody Titers in 139 Patients Analyzed Simultaneously With Both Methods (172 Serum Samples).

The dotted line represents the fitted line plot with 95% CIs. kBAU indicates kilo–binding antibody units; PRNT₅₀, highest dilution resulting in a reduction of the control plaque count greater than 50% on the Plaque Reduction Neutralization Test.