Prospects of Using Cystatin C As an Early Predictor of Diabetic Nephropathy

Hypothesis/aims of study. Using early non-invasive markers of diabetic nephropathy (DN) in clinical practice is important to early start of nephroprotective therapy and leads to improving the quality of life, while decreasing disability and mortality of diabetic patients. The aim of the study was to estimate the potential of using serum cystatin C and glomerular filtration rate (GFR) calculated by CKD-EPIcys and CKD-EPIcr-cys equations for an early diagnosis of DN in type 1 diabetic (T1D) women who were planning pregnancy or were in the I trimester of pregnancy. Study design, materials, and methods. 47 T1D women were examined, of whom 25 individuals were pregnant and 22 ones were planning pregnancy. In all patients, glycated hemoglobin and serum cystatin C levels were determined, GFR was estimated by the creatinine clearance test, MDRD, CKD-EPIcr, CKD-EPIcys, and CKD-EPIcr-cys equations, with diabetes training done. Results. The pregnant group and the planning pregnancy group were distinguished by glycated hemoglobin (p = 0.001), serum creatinine (p = 0.001), and GFR estimated by the creatinine clearance test (р = 0.017), CKD-EPIcr (р = 0.005), and CKD-EPIcr-cys (р = 0.046) equations. There was no difference in urinary creatinine, serum cystatin C, and GFR estimated by CKD-EPIcys equation and daily urinary protein excretion between the study groups. Most pregnant women (87.5%) were in stage C1 and only 12,5% in stage C2 as determined by estimated GFR using the CKD-EPIcr formula, which was significantly different compared to the planning pregnancy group, where the percentage of women in stages C1 and C2 was comparable (р = 0.002). In addition, most pregnant patients were in stage C1, while most of the patients planning pregnancy were referred to stage C2 by GFR estimated by CKD-EPIcysequation. Stage C3a was diagnosed in the both study groups only when CKD-EPIcys equation for GFR estimation was used. Most women from both groups were in stage C1 when GFR was estimated by the creatinine clearance test, the percentage ratio of patients in stages C1 and C2 in both groups being comparable. Conclusion. Our results demonstrated that serum cystatin C and GFR estimation by CKD-EPIcys equation could improve nephropathy diagnostic accuracy among T1D patients with a normal serum creatinine level and intact GFR based on creatinine level.