Cystatin C and creatinine after successful kidney transplantation in children

Background: Serum creatinine is commonly used for the monitoring of allogra ft function following renal transplantation (RTX). Due to lower muscle mass , creatinine production rate is reduced in children, thus decreasing its se nsitivity for the detection of allograft dysfunction. In children, the seru m concentration of cystatin C, a low molecular weight protein of 13.3 kDa, reflects glomerular filtration rate independent of age, height and body com position. We, therefore, sought to assess the potential of cystatin C as a marker of allograft function in children. Methods: Cystatin C and creatinin e were measured in parallel at least daily in 24 children (14 boys, 10 girl s; mean age 10.5 +/- 5.1 years) during hospitalization after successful RTX . Cystatin was determined immunoturbidimetrically, creatinine enzymatically . Results: Within one hour after RTX, cystatin C (mean +/- SE) almost halve d from 6.69 +/- 0.45 mg/l to 3.69 +/- 0.38 mg/l while creatinine declined f rom 862 +/- 65.4 to 633 +/- 62.9 mu mol/l. Following a nadir of 1.82 +/- 0. 18 mg/l on day 2, there was a secondary increase in cystatin C concentratio ns to 2.69 +/- 0.35 mg/l on day 10. Creatinine concentrations continued to decline until day 9 reaching 80.5 +/- 13.1 mu mol/l. Day-to-day variation a t steady-state was comparable. In the course of 9 acute rejection episodes, both parameters rose in parallel, the increase in creatinine concentration being much greater. Conclusion: Cystatin C was an early indicator of allog raft function following successful RTX in children. It did not prove superi or to creatinine for the recognition of acute allograft dysfunction, howeve r.