CALCA and infection: In addition, to investigate the potential additive impact of an increased PCT concentration and infection on survival, we further stratified the 906 patients into 4 subgroups based on whether the PCT concentration was ≥ 0.39 ng/mL at POD 5 or the patient was infected or not: PCT low/infection (−) (n = 737), PCT high/infection (−) (n = 118), PCT low/infection ( +) (n = 38) and PCT high/infection ( +) (n = 13), respectively.