. Serum level of cystatin C (MW 13 000) depends on the glomerular filtration and on the production by nucleated cells. S-cystatin C was proposed as a better glomerular filtration rate marker than serum creatinine or creatinine clearance. Possibilite to avoid urine collection in children is another important advantage. The aim of the study was to estimate reliability of the test in the kidney transplant paediatric patients. Methods and Results. We measured cystatin C on Monarch 2000 IL by particle-enhanced turbidimetric assay using commercial kit provided by DAKO. We analysed S-cystatin C levels in three groups: 19 children before kidney transplantation (A), 25 paediatric patients after kidney transplantation (B), 20 children hospitalized on intensive care unit (C). Creatinine was measured by enzymatic method on ADVIA 1650 Bayer. We demonstrated significant correlation between S-cystatin C and creatinine levels is both groups A (r 2 =0.865, P<0.0001) and C (r 2 =0.812, P<0.05). Correlation coefficient was much lower for group B (r 2 =0.689, P<0.005). Cystatin C levels were compared with creatinine clearance (ml/s per 1.72 m 2 ) and we found a very poor negative correlation in groups C (r 2 =0.24, P<0.05) and B (r 2 =0.036, P<0.006). In group A there was significant correlation between S-cystatin C and creatinine clearance (r 2 =0.769, P<0.05). Negative correlation coefficient between calculated creatinine clearance (according Schwartz) and S-cystatin C was (r 2 =0.76, P<0.005) in group B and (r 2 =0.75, P<0.005) in group C. Conclusion. There is a significant correlation between S-cystatin C and creatinine levels in both groups: in group before kidney transplantation and in patients hospitalized at intensive care reanimation unit. In the group after kidney transplantation correlation coefficient is much lower.

        Key words: Backgroundcystatin C. glomerular filtration rate, creatinine clearance, kidney transplantation.