The Clinical Applicability Of Serum Cystatin C In Early Diabetic Nephropathy

Objective: Correlation between Cystatin C and UAER, e GFR was compared, To evaluate whether the serum Cystatin C can be the sensitive index of the early diagonosis of early diabetic nephropathy.Methods: 136 type 2 diabetes cases diagnosed in accordance with WHO1999 diagnosis and classification of diabetes mellitus from January 2014 to September 2014 were analysed. Among them, 73 patients were male, 63 patients were female, and the age between 40~75 years. Patients were enrolled without thyroid disease, infections, tumor, hematuria Diabetic Ketoacidosis, or Hyperosmolar Hyperglycemic syndrome. We count the amount of urine specimens of 24 hours, take l0 ml of them to detect the urine albumin excretion rate. We also measured height and weight of patients to calculate body mass index(BMI) and the blood pressure. We also measured cystatin C(Cys C), fasting plasma glucose(FPG), glycohemoglobin(GHB), triglycerides(TG), total cholesterol(TC), apo-lipoprotein A1(Apo A1), apo-lipoprotein B(Apo B), low density lipoprotein cholesterol(LDL-C), high density lipoprotein cholesterol(HDL-C), blood urea nitrogen(BUN), serum creatinine(SCr), and Uric acid(UA).And then calculated glomerular filtration rate by a simplified MDRD equation. According to 24 hour urinary albumin excretion rate, all patients were divided into three groups: no diabetic nephropathy group(Normal albuminuria group, UAER<30mg/24h), early-stage diabetic nephropathy group(microalbuminuria group, UAER=30mg-300mg/24h), and clinical diabetic nephropathy group(macroalbuminuria group, UAER>300 mg/24h). Compare the different indicators’ detection rate of renal dysfunction at different levelsof proteinuria. Analyze the correlation between Cys C, e GFR, SCr, BUN, UA and UAER in early diabetic nephropathy. The patients are divided into two groups by e GFR : e GFR ≥ 60ml/min/l.73m2 group and e GFR <60ml/min/1.73m2 group. Between the two groups, serum cystatin C and other indicators were compared and analyzed statistically. Evaluate the diagnostic performance of Cystatin C by ROC curves.Results: 1. With the increase of the amount of urinary albumin, serum cystatin C increased, e GRF decreased,. 2. Positive rate of renal function increased with increased UAER. Positive rates were different among the three groups significantly. 3. The levels of Serum Cys C in microalbuminuria group and macroalbuminuria group was significantly higher than Normal albuminuria group’s(P<0.05), while the levels of SCr was significantly higher than Normal albuminuria group’s just in macroalbuminuria group(P<0.05). 4. Cys C and e GFR had a good negative correlation in early diabetic nephropathy(r=-0.589, p<0.05). Cys C anduaer had a good positive correlation in early diabetic nephropathy(r =0.541, p<0.05). 5. The significant correlation between UAER and serum Cys C, SCr, e GFR was found in early stage diabetic nephropathy group.(r=0.541,P<0.05; r=0.507,P<0.05, r=-0.465, P<0.05), and that of between UAER and serum Cys C was the most strongest. 6. The level of Cys C whose e GFR less than 60ml/min/l.73m2 was significantly higher than the patient whose e GFR more than 60ml/min/l.73m2. 7. When GFR<60ml/min and GFR<90ml/min, AUC ROC of Cys C was bigger than that of UAER. 8. When UAER>30mg/24, AUC ROC of Cys C was bigger than that of Scr.Conclusion:There is a good correlation between the Serum Cystatin c and Glomerular filtration rate and urinary albumin excretion rate in early diabetic nephropathy group. Cysctatin-c can be used as an indicator in early diagnosis of diabetic nephropathy as a new biomarker of Glomerular filtration rate.