Analysis of the predictive value of serum Cys-C and IL-6 levels for acute kidney injury in patients with acute respiratory distress syndrome

Objective: To evaluate serum cystatin C (Cys-C) and interleukin-6 (IL-6) for predicting acute kidney injury (AKI) in patients with acute respiratory distress syndrome (ARDS). Methods: This retrospective study analyzed 220 ARDS patients (78 with AKI, 142 without). Serum Cys-C and IL-6 levels were measured. Correlations with renal function indicators were analyzed. Patients were stratified by biomarker median levels to compare AKI incidence. Logistic regression identified AKI risk factors, and ROC curves assessed diagnostic performance. Results: Serum Cys-C and IL-6 levels were significantly higher in the AKI group and correlated with worse renal function. High Cys-C/IL-6 expression groups had a significantly increased AKI incidence. APACHE II score, Cys-C, and IL-6 were independent risk factors for AKI, while eGFR was protective. The combination of Cys-C and IL-6 showed the best diagnostic performance. Conclusion: Serum Cys-C and IL-6 are significantly elevated in ARDS patients with AKI. Although each marker individually correlates with AKI, their combination demonstrates a stronger association. Given the retrospective design and exclusion of patients with early AKI, these findings are strictly associative and hypothesis-generating, not predictive. The combination offers additive associative value for identifying ARDS patients who subsequently develop AKI, but this requires prospective validation before any clinical application.