Predictive Value of Serum Procalcitonin and APACHE-II Score for Acute Kidney Injury in Critically Ill Patients: A Prospective Cohort Study

Background: Acute kidney injury (AKI) is a common and highly fatal condition among patients treated in intensive care units (ICUs). This study aimed to investigate whether procalcitonin (PCT) levels and APACHE-II scores can predict the development of AKI in critically ill patients. Methods: This prospective cohort study was conducted in the General Intensive Care Unit of İzmir City Hospital. A total of 327 patients were included. Patients were divided into two groups according to the presence or absence of AKI. Continuous variables (age, PCT, albumin, CRP, and APACHE-II) were analyzed using either the Student’s t-test or the Mann–Whitney U test based on the Shapiro–Wilk normality test. Categorical variables were compared using the chi-square test. Variables found to be significant were entered into a forward binary logistic regression model. For subgroup analyses, patients were reclassified according to sepsis status. Results: The mean age of the study population was 68.09 ± 14.72 years, and 45.3% were female. In the entire cohort, age (p = 0.004), albumin (p = 0.005), CRP (p = 0.001), APACHE-II (p < 0.001), and PCT (p < 0.001) were significantly associated with AKI development. In logistic regression analysis, APACHE-II (p < 0.001; OR = 1.050) and PCT (p = 0.038; OR = 1.013) were identified as independent predictors of AKI. In patients without sepsis, age (p < 0.001), CRP (p = 0.001), PCT (p < 0.001), and APACHE-II (p = 0.003) remained significant, while albumin was not (p = 0.120). Among those with sepsis, only the APACHE-II score remained significant (p < 0.001). The overall model accuracy was 71.3%. Optimal cut-offs were ~0.29 ng/mL for PCT in all patients (sensitivity 78.4%, specificity 55.5%) and ~0.26 ng/mL in non-septic patients (61.5%, 64.3%), and 25 points for APACHE-II overall (58.6%, 75.1%). Conclusion: Serum PCT level and APACHE-II score are independent predictors of AKI development in ICU patients. The predictive power of PCT is particularly evident in non-septic patients. Evaluating PCT in conjunction with the APACHE-II score may provide clinical utility in the early identification of patients at high risk for kidney injury.