Abstract： Objective:To explore the predictive value and prognosis effect of calprotectin on acute kidney injury (AKI) in patients with sepsis.Methods:A prospective observational study was conducted. From December 2018 to November 2020, patients with sepsis admitted to the Emergency Department of China Rehabilitation Research Center were enrolled. General clinical data of patients were collected continuously, and the acute physiology and chronic health evaluationⅡ (APACHEⅡ) score, sequential organ failure assessment (SOFA) score and calprotectin were evaluated in 24 h after admission. The patients were divided into the AKI group and non-AKI group according to the occurrence of AKI within 7 days after admission. Calprotectin level and other clinical data were compared between the two groups. Logistic regression was used to analyze the risk factors for AKI in patients with sepsis, and receiver operating characteristic (ROC) curve was plotted to evaluate the predictive value of calprotectin for AKI in patients with sepsis. The patients with AKI were further divided into the survival group and death group according to the 28-day outcome, and the calprotectin levels between the two groups were compared.Results:A total of 207 patients with sepsis were enrolled, and the incidence of AKI was 68.12% (141/207). The level of calprotectin in patients with AKI was higher than that in patients without AKI [4.65 (3.25, 5.61) μg/mL vs. 3.42 (2.29, 4.09) μg/mL, P < 0.001]. Multivariable Logistic regression analysis showed that APACHEⅡ score ( OR=1.090, 95% CI: 1.043-1.139), C-reactive protein ( OR=1.004, 95% CI: 1.001-1.008) and calprotectin ( OR=1.590, 95% CI: 1.269-1.991) were independent risk factors for AKI in patients with sepsis. The area under ROC curve (AUC) of calprotectin for predicting AKI was 0.716 (95% CI: 0.643-0.788). The cutoff value of prediction was 4.63 μg/mL with the Yoden index of 0.405, which yielded a sensitivity of 0.511 and a specificity of 0.894. When calprotectin was combined with APACHE II score and SOFA score respectively, the predictive ability was significantly improved with the AUC of 0.768 (95% CI: 0.701-0.834) and 0.769 (95% CI: 0.701-0.837), respectively. We further divided patients with AKI into the survival group and non-survival group according to the 28-day outcome and there was no significant difference in calprotectin between the two groups [4.80 (3.40, 5.76) μg/mL vs. 4.19 (2.89, 5.29) μg/mL, P < 0.05]. Conclusions:The level of calprotectin in the AKI group is higher than that in the non-AKI group. Calprotectin can be regarded as an effective predictor of AKI in patients with sepsis, and the combination with APACHEⅡ score or SOFA score will improve its predictive efficacy. However, there is no significant difference in the concentration of calprotectin for patients with sepsis associated AKI with different prognosis.