Comparison of cystatin C- and creatinine-based glomerular filtration rate formulas with inulin clearance in pediatric renal transplantation.

Background: It has been suggested that plasma cystatin C (Cyst-C) concentrations provide better indicators of changes in glomerular filtration rate (GFR) than plasma creatinine concentration (PCr).

Methods: We compared the performance of five equations--2009 Schwartz, Local Schwartz, Larsson, Le Bricon, and Schwartz Combined--in 60 renal transplant children by calculating the mean bias, Pearson correlation coefficient (R) and determination (R2), 10% (P10) and 30% (P30) accuracies, and Bland-Altman plots. GFR was measured by inulin clearance.

Results: For the whole population, R2 was slightly lower for formulas based on Cyst-C or PCr, but the mean bias was lower, and P10 and P30 were greater, than using combined Schwartz equation. However, the mean estimated GFR by Schwartz 2009, Local Schwartz, and Schwartz combined equations was not statistically different from the mean inulin clearance measurement.

Conclusions: In our pediatric transplant population, the combined Schwartz formula exhibited better performance to estimate GFR than formulae based on Cyst-C or combined PCr.