Fig. 6

Procalcitonin data. a Estimated distribution functions for the non-diseased (open circles, dashed line) and the diseased individuals (filled circles, solid line). The grey lines mark the confidence regions and different studies are marked in different colours. The optimal threshold, derived from a maximization of the Youden index, is depicted as a solid vertical line. b Estimated densities and their point of intersection. Non-diseased (dashed line), diseased individuals (solid line). c Study-specific ROC curves. d Estimated SROC curve with the optimal threshold for equal weighting of sensitivity and specificity. Different studies are marked in different colours