Evaluation of Cystatin C and Performance of Cystatin C Based Equations for Calculating GFR in Management of Chronic Kidney Disease Patients

Background: Glomerular Filtration Rate (GFR) is the best overall index for the assessment of kidney function in both health and disease state. Several studies suggested that CKD-EPI Creatinine˗Cystatin C equation 2012 (published by CKD-EPI group) performed better than equation based on either of these marker alone and gives more accurate estimation of GFR. Methods: The study was performed on 109 CKD patients. Serum creatinine and cystatin c levels were measured in same patients. GFR was estimated using 5 equation (Larsson, hoek, le bricon, filler, CKD-EPI Cystatin c) that are based on serum cystatin c, and three equations (Cockcroft – Gault, MDRD and CKD-EPI Creatinine) based on serum creatinine. We evaluated the new CKD-EPI Creatinine˗Cystatin C equation 2012 (published by CKD-EPI group) with other equations in a population of north Indian in classifying CKD across body mass index, diabetes, and hypertension status. Results: The ROC curve analysis showed significant (p<0.001) diagnostic accuracy of all GFR estimating equation with highest being of Cystatin C (AUC=0.986) followed by Larsson and Hoek (AUC=0.974), Creatinine and MDRD (AUC=0.961), CG (AUC=0.916), Filler (AUC=0.842) and Lebricon (AUC=0.736) the least. Our data showed that serum cystatin C correlated better with GFR than did creatinine. Conclusion: Cystatin C is a potential marker of kidney function in patients of chronic kidney disease. The equations containing both serum creatinine and serum Cystatin C are more accurate than other equations for estimating GFR. Cystatin C along with creatinine may be used for routine diagnostic use in chronic kidney disease patients. Key words: Chronic Kidney Disease (CKD), Glomerular Filtration Rate (GFR), Serum creatinine, cystatin c, Cockcroft- gault equation, MDRD