Relationship between serum cystatin C and creatinine in kidney and liver transplant patients

Background: The results obtained for serum cystatin C, which has been proposed as a novel marker of glomerular filtration rate (GFR), in kidney and liver transplant are still very limited. In our study, the relationship between serum cystatin C and creatinine in kidney and liver transplant patients was investigated. Methods: Serum cystatin C and creatinine concentrations were determined in 182 samples from 52 kidney transplant patients and 71 samples from 28 liver transplant patients at 1 -9870 days post-transplantation time. Eighty-seven serum samples from 66 patients with different types of chronic kidney disease were also analysed. Results: The serum creatinine (r= -0.517, p < 0.001) and cystatin C (r= - 0.409, p < 0.001) concentrations were negatively correlated with the post-transplantation time in the kidney transplant patients. In the liver transplant patients, the correlation between these variables is not statistically significant. The creatinine/cystatin C ratio in the liver transplant group is significantly lower than in the other group of patients (p<0.001). This ratio in the kidney transplant patients groups is significantly lower than in the kidney disease group (p<0.001). In the kidney transplant patients the creatinine/cystatin C ratio and the post-transplantation time were negatively correlated (r= -0.523,p<0.001); however, in the liver transplant patients the correlation between these variables was not significant. Conclusions: In the groups of kidney disease and kidney transplant patients, as renal function decreases, there is an increase in the creatininc/cystatin C ratio. This may be due to the fact that, since creatinine is eliminated by glomerular filtration and tubular secretion, as renal function is impaired, its serum concentration increases to a greater extent than that of cystatin C, which is only eliminated by glomerular filtration. In the liver transplant patients, the creatinine/cystatin C ratio is lower than in the other groups. This may be due to better preserved renal function, lower muscular mass and a reduced rate of creatine formation and creatinine production in some of these patients. The serum cystatin C would be a better GFR marker than the widely used creatinine in liver transplant patients. (C) 2002 Elsevier Science B.V. All rights reserved.