Fig. 5.

Comparison of dried blood microsampling and phlebotomy for blood collection. (A) Dried-blood microsampling. The dot plot shows RBD-specific IgG antibody binding determined by ELISA with samples collected by finger stick utilizing Mitra microsamplers from subjects that tested PCR-negative (n = 50, circles) or PCR-positive for SARS-CoV-2 infection (n = 12, triangles). The horizontal line represents the cut-off value of the assay, calculated as in the legend to Fig. 4. (B) Correlation between ELISA results obtained from the same subjects by phlebotomy and by finger stick and Mitra microsampling. The correlation plot shows results obtained with samples from 16 subjects (13 seropositive and 3 seronegative for SARS-CoV-2 infection). Assays were performed in technical duplicates. The Pearson correlation coefficient (R²) of the comparison is also shown. In both panels, each symbol represents one study subject.