Fig. 3

ROC curve analysis of preoperative and postoperative (24 h, 48 h and 72 h after surgery) plasma IL-6 levels for distinguishing POD. In this figure, an optimal value of plasma IL-6 levels determined preoperatively and postoperatively (24 h, 48 h and 72 h after surgery) was selected, which distinguished patients developing postoperative delirium with corresponding sensitivity and specificity values. ROC: receiver operating characteristic; POD: postoperative delirium; IL-6: interleukin-6