Cystatin C-estimated glomerular filtration rate in pediatric autologous hematopoietic stem cell transplantation.

Formal evaluation of kidney function is essential to determine chemotherapy dosing based on established treatment protocols in children undergoing autologous stem cell transplantation. Cystatin C has been widely studied as a marker of the glomerular filtration rate (GFR), although data regarding its use in stem cell transplantation are limited. We evaluated the performance of cystatin C-based equations and determined their sensitivity to detect a nuclear GFR of <100 mL/min/1.73 m(2) in children undergoing autologous transplantation. We performed a retrospective cohort analysis in 16 children undergoing 26 transplantations using a modified Bland-Altman analysis to account for repeated measures. Cystatin C-based equations published by Hoek, Le Bricon, Rule, Filler, Zappitelli, Larsson, and Schwartz (the New Chronic Kidney Disease in Children formula, New CKiD formula) were evaluated and compared to the creatinine-based modified Schwartz equation. We found that cystatin C-based equations demonstrated improved sensitivity to detect a nuclear GFR of <100 mL/min/1.73 m(2) compared to the creatinine-based modified Schwartz equation, which significantly overestimated GFR. Most cystatin C-based equations, however, tended to underestimate the nuclear GFR. The New CKiD formula, combining cystatin C and creatinine, offered a sensitivity of 100% and a specificity of 95% for detecting a nuclear GFR <100 mL/min/1.73 m(2). Institutions using cystatin C-based GFR estimation should be aware of the specific prediction formula and GFR measurement techniques available at their center, as each method's performance can vary considerably. As more research becomes available, this easily measured marker should become a valuable component of GFR estimation, providing cost savings (a nuclear GFR is 5.5 times more costly than a cystatin C) and reducing radiation exposure.