A Comparative Study between Serum Cystatin C and Creatinine in Early Detection of Acute Kidney Injury

BACKGROUND: Acute kidney injury (AKI) is a common and grave clinical entity associated with significant morbidity and mortality, leading to prolonged hospitalization and increased healthcare expenses. Early diagnosis is often difficult as serum creatinine, the conventional biomarker of AKI, rises only after a considerable decline in glomerular filtration rate (GFR). Serum cystatin C (CysC) has emerged as an optimistic endogenous biomarker capable of detecting renal dysfunction earlier than creatinine. AIM: The aim of the study was to compare serum CysC and serum creatinine for the early detection of AKI. MATERIALS AND METHODS: This prospective, cross-sectional, diagnostic study was conducted in the Department of General Medicine, Shri Sathya Sai Medical College and Research Institute, Chengalpattu, Tamil Nadu, from March 2024 to October 2025. Adult patients at risk for developing AKI were enrolled. Serum CysC and serum creatinine levels were measured at admission, and patients were monitored for decline in estimated GFR and development of AKI according to Kidney Disease: Improving Global Outcomes criteria. Diagnostic accuracy, sensitivity, specificity, and predictive performance of both biomarkers were statistically analyzed. RESULTS: Serum CysC levels increased significantly earlier than serum creatinine in patients who developed AKI. CysC demonstrated greater sensitivity for early AKI detection and showed superior diagnostic performance in identifying the initial phase of renal injury. Receiver operating characteristic analysis revealed a higher area under the curve for CysC than for serum creatinine. Elevated CysC levels were also associated with worsening renal dysfunction, prolonged hospitalization, greater AKI severity, and need for dialysis. CONCLUSION: Serum CysC is a sensitive and reliable biomarker for the early detection of AKI when compared with serum creatinine. Its incorporation into routine clinical evaluation may facilitate earlier intervention and improve patient outcomes.