To investigate the diagnostic performance of 3-month postoperative copeptin level for permanent CDI, we performed ROC curve analysis (AUC = 0.879, 95% CI = 0.801–0.958) and revealed several cutoff values of the 3-month postoperative copeptin level for diagnosing permanent CDI (Fig. 2b). This evidence concerns the gene AVP and clostridium difficile infection.