Fig. 2.

a A calibration plot of the predicted and observed probabilities of anastomotic leakage after anterior resection for rectal cancer. The x-axis shows the predicted probability of anastomotic leakage, and the y-axis shows the observed probability of anastomotic leakage. The nomogram had a bootstrapped-concordance index of 0.72 and was well calibrated. b We validated the nomograms with an external independent validation set, and the receiver operating characteristic curve for the prediction model area under the curve was 0.723