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. 2022 Jan 28;17(1):e0262957. doi: 10.1371/journal.pone.0262957

Fig 1. Detection of SARS-CoV-2 specific antibodies.

Fig 1

Plasma samples collected from study volunteers were tested by ELISA against SARS-CoV-2 RBD, full length S protein and N protein. Panel A shows results with plasma from three representative subjects with confirmed COVID-19 infection along with negative, high positive and low positive control samples. Panel B shows results from eight study subjects without a PCR-based confirmatory test. The horizontal line represents the cutoff value for positivity based on reactivity with S or RBD for plasma samples collected from healthy control volunteers prior to October, 2019. The cutoff value was set at two standard deviations above the mean optical density of the plasma samples collected from healthy control volunteers prior to October, 2019. Optical density readings were normalized against the level of the high positive standard run on each ELISA.