Estimation of Glomerular Filtration Rate and Predicting Diagnostic Accuracy of Cystatin C and Creatinine in Detection of Renal Function among Longstanding Type-2 Diabetics

Introduction: Estimation of Glomerular Filtration Rate (GFR) is dependent on Serum Creatinine (SCr). Though, a sudden decrease in GFR would not result in rapid rise in concentrations of SCr, as they are imprecise but it leads to the over diagnosis of Chronic Kidney Disease (CKD).
Aim: To calculate GFR using Cystatin-C (Cys-C) based formulas to contrast its accuracy with SCr based formulas and to predict the diagnostic accuracy of Cys-C in patients with diabetes. Materials and Methods: A total 48 type-2 diabetic patients were diagnosed with CKD and their GFR was assessed using the Cystatin-C and SCr. GFR was measured and estimated using three equations (Cockcroft-Gault (CG), Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CDK-EPI), that are based on SCr and three equations (LeBricon, Grubb and Hoek) based on Cys-C among the 48 CKD patients. The filtration rate was measured using labelled diethylenetriaminepentaacetic acid(99mTc-DTPA) renal scan method as the standard for comparison. The Receiver Operating Characteristics (ROC) analysis was used to evaluate the diagnostic accuracy of the filtration rate.
Results: A significant association was observed (p=0.0001) among both the estimates which were equivocal when compared with measured iGFR, SCr and Cys-C based GFR estimate. A greater difference of Area Under the Curve (AUC) was observed between SCr (0.765±0.07) and Cys-C (0.569±0.09) (p=0.04) in the ROC analysis at a creatinine clearance <60 mL/min/m2.
Conclusion: SCr and Cys-C based formulae has equivocal performance in estimating GFR. SCr could be a better marker to estimate GFR among patients with Cr clearance <60 mL/min/m2.