title: Relationship between serum cystatin C and creatinine in kidney and liver transplant patients.
abstract: 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 creatinine/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.
authors.affiliation: Laboratorio Central, Hospital Clínico Universitario, Santiago de Compostela, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Hermida
authors.forename: Rafael
authors.initials: R
authors.lastname: Romero
authors.forename: J Carlos
authors.initials: JC
authors.lastname: Tutor
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002908:Chronic Disease; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis / Q000601:surgery; D016030:Kidney Transplantation; D016031:Liver Transplantation; D008297:Male; D008875:Middle Aged
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D003404:Creatinine