Combined Measurement of Serum Cystatin C,~(99m)Tc-DTPA and Urine Microalbumin in Early Diagnosis of Type 2 Diabetic Nephropathy

Objective To demonstrate the clinical value of serum cystatin-C(CysC) in the assessment of renal function in type-2 diabetic nephropathy(T2DN) by comparing it with the glomerular filtration rate(GFR) measured by 99mTc-DTPA method.Methods From June 2010 to January 2011,76 patients with type 2 diabetes mellitus(T2DM) were classified into two groups according to their 24 h microalbuminuria(m-Alb) level: the normal albuminuric group(n=31) and the microalbuminuric group(n=45).GFR,Serum creatinine(Scr),CysC,and hemoglobin A1c(HbA1c) were measured.Thirty-eight healthy subjects were recruited as the control group,and statistical analysis was carried out.Results The CysC levels in the control group,the normal albuminuric group and the microalbuminuria group were respectively(1.1±0.6),(1.6±0.7) and(1.0±0.3) mg/L,with a significant difference among the three groups(P0.05).HbA1c level in the three groups were respectively(7.1±2.7)%,(7.9±3.1)% and(5.4±0.6)%,with a significant difference between the two diabetic groups and the control group(P0.05).Scr levels in the three groups were respectively(87.7±23.8),(93.7±38.4),(81.5±11.4) μmol/L;GFR levels in the three groups were respectively(80.9±23.0),(74.2±26.1),(79.3±19.7) mL/(min·1.73 m2);among the three groups the differences of both Scr and GFR were not significant.Both CysC and Scr were negatively correlated with GFR(r=-0.694,-0.692;P0.001),and CysC was positively correlated with Scr(r=0.903,P0.001).Conclusion Increased CysC may be an early indicator of incipient diabetic nephropathy,but the diagnostic accuracy of CysC is not superior to that of Scr in distinguishing between mildly and moderately reduced GFR.