The Clinical Applicability Of Serum And Urinary Cystatin C In Diabetic Nephropathy

[OBJECTIVE] To evaluate the clinical applicability of the serum and urinary Cystatin C(Cys C) in early diabetic nephropathy.[METHODS] Serum and urinary samples were obtained from 109 cases with diabetes and 26 cases with pre-diabetes.Serum and urinary Cys C were determined by Particle-enhanced turbidimetric immunoassay (PETIA).All patients were divided into three groups according to different level of 24hours'urinary albumin excretion(UAE),such as group normal UAE(DM1),group microalbumin (DM2) and group macroalbumin(DM3).Serum creatine(SCr),blood urea nitrogen(BUN),urinaryα1-MG,urinaryβ2-MG were also measured for every patient. Meanwhile, glomerular filtration rate(GFR) measured by 99mTc-DTPA clearance was considered to be the Gold Standard . Correlation between GFR and serum Cys C,SCr,BUN was compared, the area under the Receiver Operating Characteristic Curve (AUCROC) and the Likehood Ritio(LR) were used for evaluating the reliability of serum Cys C. Also, the correlation between urinary Cys C and urinaryα1-MG,β2-MG was analyzed, and the positive rate of the three parameters was compared.The control group contained 48 healthy persons. [RESULTS]Serum Cys C in group DM2 and DM3 was significantly higher than control group's(P<0.05),while SCr and BUN were significantly higher than control group's just in group DM3(P<0.05).The significant correlation between GFR and serum Cys C,SCr,BUN was found(P<0.05),and that of between GFR and serum Cys C was the most strongest.The AUCROC of the serum Cys C,SCr and BUN was 0.944,0.778,0.746 ,respectively,and there was significant statistical difference between serum Cys C and SCr,BUN, respectively(P<0.05).The likehood rate of serum Cys C was the best in the three parameters. Urinary Cys C and urinaryα1-MG,β2-MG in three groups were all significantly higher than control group's(P<0.05),and the statistical difference of the three parameters among three groups were also significant(P<0.05). The significant correlation between urinary Cys C and urinaryα1-MG,β2-MG was found(P<0.05),but the positive rate of urinary Cys C was significantly higher than urinaryβ2-MG in group DM1,and than urinaryα1-MG,β2-MG in group DM3(P<0.05).[CONCLUSIONS] 1.Serum Cys C is a more sensitive and reliable parameter of GFR than SCr and BUN in early diabetic nephropathy.2.Urinary Cys C is more sensitive to reflect the tubular injury of the early diabetic nephropathy than urinaryα1-MG andβ2-MG.