Fig 1.

Schematic workflow of multiplexed in-solution protein array (MISPA) and SARS-CoV-2 Wuhan strain, receptor-binding domain (wRBD) antibody calibration. (A) Schematic workflow for MISPA. (B) SARS-CoV-2 wRBD antibody calibration using MISPA. Serially diluted anti-receptor-binding domain antibodies were tested in nine technical replicates in MISPA, along with quantitative PCR + samples collected in 2020 and pre-2019 samples (box indicates median and 25th–75th percentiles, whiskers max and min samples). The mean value of pre-2019 sample plus 3× standard deviation was set as a seropositivity cutoff (red dashed line). Positive percent agreement (PPA) and negative percent agreement (NPA) with clinical diagnosis for serum samples were 94.5% and 96.9%, respectively. SINR, spike-in normalized ratio.