RESUMEN
OBJECTIVE: To determine the diagnostic accuracy and cut-off values of serum cystatin C as early diagnostic biomarker of diabetic kidney disease. STUDY DESIGN: Cross-sectional analytical study. PLACE AND DURATION OF STUDY: Department of Pathology, Army Medical College, Rawalpindi in collaboration with Endocrinology Department, Military Hospital (MH), Rawalpindi from November 2015 to November 2016. METHODOLOGY: One hundred and nineteen diagnosed patients of type 2 diabetes mellitus were enrolled in the study from the outpatient Endocrinology Department of the MH Rawalpindi. Fifty disease-free controls were also included. Fasting blood samples of the patients and controls were analysed for creatinine by Jaffé's kinetic method and estimated GFR was calculated using MDRD-based equation for GFR. Serum cystatin C was estimated by quantitative turbidimetric method. RESULTS: Serum cystatin C was higher in the diabetic group (mean = 1.022 ±0.33 mg/dl) as compared to the control group (mean = 0.63 ±0.14 mg/dl). ROC curve analysis, keeping less than 60 ml/min/1.73 m2 GFR (CKD-MDRD based) as reference value of the stat variable/gold standard; revealed an area under the curve of 0.914 (95% CI 0.85-0.98) and at optimal sensitivity of 88.2% and specificity of 84.8% the established cut-off of serum cystatin C was 1.26 mg/L. CONCLUSION: Cystatin C is an accurate biomarker of diabetic kidney disease with good sensitivity and specificity.