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. 2021 Sep 15;9(2):e00731-21. doi: 10.1128/Spectrum.00731-21

FIG 4.

FIG 4

Correspondence of Luminex assays for different antigens and isotypes. (A) S-, RBD-, and N protein-specific IgG, measured in serum (n = 509, left) and saliva (n = 430, right) in the Luminex assay, expressed as MFI. S and N are plotted against each other, and RBD-positive samples are shown in orange. The red dotted lines are the cutoff values to discriminate positive and negative measurements for S and N. (B) SARS-CoV-2 S-specific IgG and IgA in serum (n = 487, left) and saliva (n = 413, right) measured in the Luminex assay, expressed as MFI. IgG and IgA are plotted against each other to reveal the correspondence between the two isotypes. Samples that were also positive in the Wantai RBD total antibody assay are shown in blue. S, trimeric SARS-CoV-2 spike protein; RBD, monomeric receptor binding domain of the SARS-CoV-2 spike; N, SARS-CoV-2 nucleocapsid protein; MFI, median fluorescence intensity.