Serum Cystatin C As An Efficacious Marker Of Renal Function In Kidney Transplant Recipients

BACKGROUND Efficacious monitoring the transplanted kidney function can early detect the renal impairments caused by infections or acute rejections(AR).Nowadays,the extensively used renal markers are blood urea nitrogen(BUN)and creatinine(Cr),while their low-sensitivity and low-specificity couldn't satisfy the clinical needs.Recently,Cystatin C(Cys C)appears as an ideal glomerular filtration rate(GFR)marker and has been recommended by most renal experts at home and abroad for clinical application.OBJECTIVE To compare the clinical application of Cys C and serum Cr as a marker of renal function in kidney post-transplant patients,especially when infections or acute rejections occur.METHODS 65 renal transplant recipients(36 ones with stable renal function;16 ones with acute rejections;and 13 ones with infections)were enrolled in this study.The serum samples were collected both before and the day 1,2,3,4,5,6, 7,14,21,28 after the transplantation,and also the days of infections or rejections occurrence.At the same time 30 healthy persons and 30 infected patients without kidney transplantations were served as controls.Cys C levels were measured with particle-enhanced nephelometirc immunoassays(PENIA)and serum Cr was measured by autoanalyzer.Software SPSS(version 11.0)was used to do the statistic analyses and Software MedCalc(version 9.0)was used to draw the receiver operating characteristic(ROC)curves and the corresponding analyses.RESULTS1.The concentrations of Cys C were(0.71±0.06)mg/L for healthy persons and (0.87±0.13)mg/L for the infected patients without kidney transplantations, and there were no significant differences between them(P=0.32).2.Cys C and Cr decreased obviously in the first 3 days with the recovery of transplanted renal function(69.2%,74.7%,75.8%for Cys C and 38.4%,74.5%, 81.4%for Cr(P＜0.01)).There were no significant differences between the following days(each P＞0.05).3.When acute rejections occur,Cys C increased by 148.9%and(2.7±1.8)days earlier than Cr.When infections occur,Cys C increased by 39.4%and(4.4±1.5)days earlier than Cr.4.Compared with the levels of stable state,Cys C increased by 38.7%and 108.5%during infection and rejection periods(P＜0.0001),while Cr increased by 34.2%and 89.5%respectively(P＜0.001).5.During day 3 to day 28 after transplantation,there was a positive correlation between Cys C and Cr(r=0.785,P＜0.0001).6.According to the ROC analysis,the cut-offvalue of rejection group for Cys C and Cr were 1.79 mg/L and 122μmol/L respectively.The sensitivity,specificity, positive predictive value,negative predictive value,coincidence and AUC of rejection group for Cys C were 100%,76.70%,64.29%,100%,81.25%,0.962,and all better than that for Cr(P＜0.05).Similarly the cut-off value of infection group for Cys C and Cr were 1.64 mg/L and 121μmol/L respectively. The sensitivity,specificity,positive predictive value,negative predictive value, coincidence and AUC of infection group for Cys C were 83.33%,62.22%,45.71%,92.11%,69.50%,0.804,but there was no statistic difference between Cys C and Cr(P＞0.05).CONCLUSIONS1.Cys C is a new serum marker for estimating the transplanted kidney function.2.When acute rejections and infections occur,Cys C changed earlier and greater than Cr.So Cys C is more sensitive than Serum Cr to detect early renal function impairment.3.Cys C is superior to Cr in detecting the acute rejection occurance and reflecting the renal function impairment sensitively,specifically and accurately during the kidney post-transplantation with better sensitivity,specificity,positive predictive value,negative predictive value,coincidence and AUC.4.Cys C can be used as an ideal marker of GFR for clinical monitoring for its quick,accurate,convenient and autoanalysable detection by PENIA.