Clinical Utility of Urinary Cystatin C in Early Screening and Staging of Diabetic Kidney Disease in Type 2 Diabetes

Objectives: Diabetic kidney disease (DKD) is a major complication of Type 2 diabetes mellitus (T2DM). Early detection is critical to prevent renal function decline and improve outcomes, but conventional biomarkers (e.g., urinary albumin-to-creatinine ratio [UACR] and estimated glomerular filtration rate [eGFR]) have limited sensitivity for early-stage kidney damage. Urinary cystatin C (UcyC) is a protein marker of impaired tubular reabsorption and a promising biomarker for early tubulointerstitial injury in DKD. This study assessed the clinical utility of UcyC for early detection and staging of DKD and compared its diagnostic performance with that of serum cystatin C (CysC). Methods: This prospective study included 102 patients with T2DM who were enrolled at The People's Hospital of Chizhou, China, between May 2022 and October 2025. The participants were classified as having T2DM without kidney disease (T2DM without KD) or DKD based on UACR and eGFR. The DKD group was divided into early DKD (EDKD) and clinical DKD (CDKD). Demographic and laboratory data were obtained from the hospital's medical records. Multivariate logistic regression analyses independent risk factors of DKD. Correlation analysis and receiver operating characteristic (ROC) curve analyses assess diagnostic accuracy and disease staging effectiveness of DKD. Results: < 0.001), paralleling advancing kidney impairment severity. Logistic regression quantified > 350-fold higher DKD risk per 10-fold logUcyC increase. UcyC demonstrated strong positive correlation with UACR and inverse correlation with eGFR, reinforcing its utility for tracking disease progression. Notably, ROC analysis confirmed superior staging accuracy versus CysC (AUC 0.830 vs. 0.691) and enhanced sensitivity plus negative predictive value for early DKD detection. Conclusion: UcyC, a noninvasive and highly sensitive biomarker for renal injury, could be valuable for early screening, assessing risk levels, and potentially guiding treatment personalization in DKD. This may streamline diagnosis and help tailor management plans for patients with DKD.