Fig. 3.

Scatterplot illustrating the relationship between antibody titre detected in plasma (x-axis) and the corresponding DBS-eluate (y-axis) (n = 1710). The correlation is calculated using the Spearman method. The dashed vertical line denotes the manufacturer's cut-off value for result classification. The dashed horizontal lines denote the empirically determined cut-off value (bold) for result classification with its boundary values (light). The solid line represents the LOESS (locally estimated scatterplot smoothing or local regression) modelling the association. The grey region is the 95% CI of the LOESS estimate.