The Evalution Of Serum Cystatin C In The Diagnosing Renal Function Impairment

Objective: The main function of the renal is to excrete metabolite and regulate the balance among the water, electrolyte and acid-base so as to keep the stability of the internal environment of the organism. This is fulfilled by the glomerular fitration and the tubular reabsorption and secretion, of which the glomerular filtration play an important role. Hence, it is important that the function of glomerular filtration is measured accurately and conveniently in clinical work. At present, the parameter in clinic which are used to measure glomerular filtration have limitation. Serum Cystatin C is a proteinase inhinbitor with a low molecular weight, its serum level are mainly dependent on glomerular fitration rate, it is an ideal parameter to reflect the function of glomerular filtration. The aim of this article is to evaluate the applicability of serum Cystatin C in patients with renal impairment.Methods: Serum samples were abtained from 98 patients with renal diseases, 50 cases from health checkers to determin the inference intervals, Serum Cystatin C concentration was determined by enzyme linked immunosorbent assay (ELISA), Serum creatinine (Scr) by Jaffe method and Creatinine clearance rate (Ccr) was estimated, glomerular filtration rate (GFR) by 99mTc-DTPA clearance was considered to be a Gold Standard, 98 patients were divided into four groups according to the level of GFR. The correlation between GFR and the above three parameters were compared, the area under the Receiver Operating Charateristic curve (AUCROC) and the likelihood ratio (LR) were used for evaluating the reliability of Cystatin C.Results:(1) In four groups, the significant correlation were found between GFR and Cystatin C, Scr, Ccr, and that of between GFR and Cystatin C was the most strongest.(2) The AUCROC for Cystatin C, Scr, Ccr was 0.989, 0.926, 0.942 respectively, and there was significant statistical differentce between Cystatin C and Scr(P<0.05), but no statistical difference between Cystatin C and Ccr(P>0.05).(3) Likelihood ratio of serum Cystatin C was the best among the above three parameters.Conclusions: Serum Cystatin C determination is a parameter of reflecting glomerular filtration function more accurately and reliably than Scr and Ccr in patients with impaired renal function and there is guidance purpose for diagnosing various renal disease patients with earlier renal impairment.Significance: The measurement of serum Cystatin C improve the renal function monitoring. It is valuable to monitor the toxic effect of drugs and to find out the earlier renal impairment of patients with hypertension, diabetes and renal transplantation, it is also objective to reflect the renal function of the old aged, children ,pregnancy women and malnutritional patients.