A Comparison Between Serum Cystatin C And Creatinine In Estimation Of Residual Glomerular Filtration Rate In Dialysis Patients

Objective :To assess the application value of serum Cystatin C in evaluating residual renal function (RRF) of dialysis patients.Methods :Plasma and urine samples of 61 Hemodialysis and 34 peritoneal dialysis patients were used to determine serum creatinine (Scr) and urine creatinine (Ucr) and Cystatin C concentration respectively, Urine of complete interdialytic interval was collected. We applied creatinine clearance rate (Ccr) in dialysis patients as the measured RRF. We investigated if serum cystatin C could give a good estimation of eGFR1 in dialysis patients and compared it to the measured RRF, as well as to the eGFR2 estimate obtained with the modified Modification of Diet in Renal Disease (MDRD) formula.Results : The Cystatin C,RRF,eGFR1 based on Cystatin C,eGFR2 based on Scr in hemodialysis(HD) group was 5.92±0.75mg/L,3.37±0.99 ml/min/1.73m2,2.83±0.46 ml/min/1.73m2,6.20±1.77ml/min/1.73m2 respectively, and in peritoneal dialysis(PD) group was 5.79±0.95mg/,3.78±1.01ml/min/1.73m2,3.35±0.64ml/min/1.73m2,7.29±1.28ml/min/1.73m2 respectively. All dialysis patients Cystatin C and Scr concentration raised with following RRF descent, but Cystatin C concentration rise was more stable than Scr. Significant negative correlation was observed between RRF and Cystatin C,Scr, (r=-0.53, P<0.05 and r=-0.46,P<0.05)in HD group,PD dialysis group also had the similar results(r=-0.71, P<0.05 and r=-0.63,P<0.05). In HD group, the deviation between eGFR based on cystatin C and Scr to RRF was 0.53±0.77ml/min/1.73m2 and 2.83±1.62ml/min/1.73m2 respectively, in PD group, was 0.43±0.72 ml/min/1.73m2 and 3.51±1.1ml/min/1.73m2,the difference of eGFR1 and eGFR2 based on Cystatin C,Scr respectively was statistical significance (P<0.05).The correlation coefficient between eGFR derived from Cystatin C and Scr formula to RRF was 0.69 and 0.63 respectively in hemodialysis group, and 0.74 and 0.58 respectively in peritoneal dialysis patients. Conclusions:Cystatin C estimated dialysis patients RRF accurately and precisely, it was more suitable for estimation of RRF than Scr in dialysis patients when no 24 h urine sample is available.