The Application Value Of Serum Cystatin C For Diagnosing Early Diabetic Nephropathy

Objective: To explore the value of the applicability of serum cystatinC for diagnosing early diabetic nephropathy.Methods: A total of 145 diabetes mellitus were selected with strict criteria to prevent confounders. The patients were divided into those with normo-, micro-, and macroalbuminuria ( ACR<30, 30-299, and≥300mg/g, respectively) . Serum cystatin C,albuminuria,serum creatinine,urine creatinine were measured , and ACR and endogenous creatinine clearance rate were calculated. 64 of the total patients had measured the 99mTc-DTPA clearance,they were divided into 3 groups according to the classification of CKD according to their 99mTc-DTPA clearance, stages 1 , 2 , and 3 (≥90 , 89-60 , and 59-30 ml/min/1.73m2, respectively ) . We made the 99mTc-DTPA clearance as the gold standard , compared the correlation among 99mTc-DTPA clearance and serum cystatin C,serum creatinine,endogenous creatinine clearance rate ,and carried ROC analysis,and compared their area under the curve . We also made ACR as the standard,compared the correlation among diabetic nephropathy and serum cystatin C,serum creatinine,endogenous creatinine clearance rate and then carried ROC analysis on serum cystatin C .Results: Serum cystatinC is unaffected by sex , age , BMI , and HbA1C(p>0.05). Serum cystatinC increased significantly in patients from normo- to macro- and micro- to macroalbuminuria (p< 0.01) . Serum creatinine also increased (p < 0.01) , but only in micro- to macroalbuminuira group increased obviously . Serum cystatinC was also significantly increased in patients with stage 1 to 3 and stage 2 to 3 groups in CKD classification ( p<0.01) . Serum creatinine also increased (p<0.01),but only in CKD 2 to CKD 3 group increased obviously . Endogenous creatinine clearance rate decreased with the development of the course(p<0.01). Serum cystatin C,serum creatinine,endogenous creatinine clearance rate all had correlation with the 99mTc-DTPA clearance(r=-0.804,-0.367,0.728 ,p<0.01) . The 99mTc-DTPA clearance was considered to be the gold standard , with a cut-off value of 90 ml/min/1.73m2 , the area under the curve was 0.917 for serum cystatinC, and 0.696 for serum creatinine , and 0.816 for endogenous creatinine clearance rate (all p<0.01). With a cut-off value of the 99mTc-DTPA clearance at 60 ml/min/1.73m2 , the area under the curve was 0.933 for serum cystatinC , and 0.718 for serum creatinine , and 0.917 for endogenous creatinine clearance rate (all p<0.01). In discriminating ACR , while with a cut-off value of 30mg/g, the area under the curve was 0.747 for serum cystatinC (p <0.01) . With a cut-off value of 300mg/g , the area under the curve was 0.816 for serum cystatin C (p <0.01).Conclusions: Among serum cystatinC,serum creatinine,endogenous creatinine clearance rate, serum cystatinC can evaluate the glomerular filtration rate with the best saitivity,reliability in those subjected early diabetic nephropathy, and it can also evaluate the albumin-to-creatinine ratio to some extent .