Intraindividual variability of the modified Schwartz and novel CKiD GFR equations in pediatric renal transplant patients

Tsampalieros A, Lepage N, Feber J. Intraindividual variability of the modified Schwartz and novel CKiD GFR equations in pediatric renal transplant patients. Pediatr Transplantation 2011: 15: 760–765. © 2011 John Wiley & Sons A/S. Abstract: GFR in children can be obtained from a formula using SCr and height or various formulas including serum CysC. Recently, two new GFR formulas have been developed: (i) height and SCr—mSchwartz GFR and (ii) height, SCr, CysC, and serum urea (CKiD GFR). While these formulas proved to be accurate when compared to the gold standard, their use in children post-kidney Tx is yet to be assessed. A total of 1174 blood samples (urea, SCr and CysC) were analyzed from the post-Tx period in 24 Tx children (12 boys, median age = 8.6 yr) currently followed at our institution. CKiD GFR and mSchwartz GFR were compared using Bland–Altman analysis and the CV. The mSchwartz GFR overestimated the CKiD GFR (mean bias = 1.09 ± 0.14; 95% limits of agreements from 0.82 to 1.36). Median CV of CKiD GFR (10.3%) was significantly lower than that of mSchwartz GFR (15.0%), p = 0.04, and negatively correlated with the slope of GFR (r2 = 0.34, p = 0.0026). In conclusion, CKiD GFR has a significantly lower intraindividual variation than mSchwartz GFR and may be better suited for longitudinal follow-up of patients post-Tx.