CALCA and infection: For model 2, when PCT was combined with either CRP or WBC, the model showed statistically significant predictive value for postoperative infection with an AUC of 0.72 (95 % CI: 0.55–0.86) (p = 0.014) for the PCT and WBC combination, and an AUC of 0.71 (95 % CI: 0.57–0.86) (p = 0.008) for the PCT and CRP combination.