Diagnostic value of cystatin C for diagnosis of early renal damages in type 2 diabetic mellitus patients: The first experience in Iran

Background: Diabetic nephropathy (DN) is one of the most important complications of diabetes mellitus. Now-a-days, cystatin C (CysC) is introduced as a new marker for diagnosis of renal damages; however, use of this marker in clinical laboratories is still controversial. The present study was aimed to evaluate the diagnostic value of serum CysC for early detection or monitoring treatment of kidney damages in the Kurdish people with type 2 diabetes mellitus. Materials and Methods: Glomerular filtration rate (GFR) was estimated by Modification of Diet in Renal Disease formula. Serum CysC and urine microalbumin were also measured in 126 diabetic and healthy subjects. Blood glycated hemoglobin (Hb) also measured in all healthy and diabetic patients. Two independent samples t-test, Mann-Whitney U-test, one-way ANOVA, and Kruskal-Wallis test, as well as Pearson/Spearman correlation coefficient statistical tests were used as appropriate. Results: Serum CysC was higher (1312.41 ng/ml) in diabetic patients with GFR < 60 ml/min than other subjects (993.25 ng/ml) (patients with normal kidney function and healthy subjects). A borderline significant correlation between CysC and estimating GFR (r(s) = -0.16, P = 0.05) but highly significant with microalbumin (r(s) = 0.22, P = 0.014) was observed. Serum CysC sensitivity, negative and positive predictive values were 100 and 4%. Conclusion: CysC cover variation of GFR and urine microalbumin, but it cannot be used as a surrogating marker of glycated Hb. According to our results, it seems that serum CysC is a useful marker for screening of DN; but it cannot be used for monitoring of treatment in diabetic patients.