Figure 4. Receiver operating characteristic (ROC) curves of serum CNPY2 isoform 2, CEA and CA19-9 considered separately and for the combined use of all three in predicting colorectal cancer (CRC). The area under the ROC curve (AUC) of the combination of all 3 was 0.786 (95% CI :0.740-0.832, P<0.001). The AUC comparison by the DeLongs Algorithm indicated that the AUC of the combined use of all 3 markers was greater than that of each marker detected respectively.