Application of combined detection of serum cystatin C and urinary NAG in early diagnosis of diabetic nephropathy

Cui Hongping; Zhao Ying; Huang Songling; Wu Haoneng

doi:10.3969/j.issn.1674-7151.2023.04.007

Abstract：Objective To investigate the application value of combined detection of serum cystatin C(CysC)and urinary N-acetyl-β-D-glucosidase(NAG)in the early diagnosis of diabetic nephropathy.Methods A total of 476 patients with type 2 diabetes mellitus in endocrinology department of the First Affiliated Hospital of Kunming Medical University from January to June 2023 were selected as research objects.According to different levels of urinary albumin(ALB)/creatinine(Cr)ratio(UACR),the patients were divided into non proteinuria group(UACR<30 mg/g Cr;329 cases),microalbuminuria group(30 mg/g Cr≤UACR<300 mg/g Cr;107 cases)and massive proteinuria group(UACR≥300 mg/g Cr;40 cases).Using a fully automated biochemical analyzer,the serum level of CysC was detected using latex agglutination method,urine NAG was detected using 2-chloro-4-nitrobenzene-N-acetyl-β-D-glucosamine substrate method,ALB was detected using immunoassay,and Cr was detected using enzyme method.The receiver operator characteristic(ROC)curve was drawn and the area under ROC curve(AUC)was calculated to investigate the diagnostic efficacy of serum CysC and urine NAG single and combined detection for diabetes nephropathy.Results There was no significant difference in the levels of CysC and urinary NAG between non proteinuria group and control group.The levels of CysC and urinary NAG in massive proteinuria group were significantly higher than those in microalbuminuria group,non proteinuria group and control group[CysC(mg/L):1.79±0.76 vs.1.21±0.778,0.83±0.23,0.79±0.13,urinary NAG(U/L):21.34±15.75 vs.15.61±13.01,11.80±8.78,10.26±5.43,all P<0.05],and the levels of CysC and urinary NAG in microalbuminuria group were significantly higher than those in non albuminuria group and control group(both P<0.05).ROC curve analysis showed that the AUC of combined detection of serum CysC and urine NAG for early diagnosis of diabetes nephropathy was 0.998,and 95%confidence interval(95%CI)was 0.996-1.000,which was significantly higher than those by serum CysC and urine NAG alone(AUC was 0.676,0.608,and 95%CI was 0.614-0.737,0.547-0.670,respectively).Conclusions There are significant differences in the levels of serum CysC and urine NAG among the tested subjects in each group,which are related to the severity of the condition.Serum CysC could be used as a diagnostic marker of diabetes nephropathy,but it does not have early diagnostic efficacy.Urinary NAG could be used as a serum marker for early diagnosis of diabetes nephropathy,and the combined detection of the two indicators could improve the early diagnostic efficacy of diabetes nephropathy.