Value of serum cystatin C in estimating renal function in children with non‐renal solid organ transplantation

Children with non-renal solid organ transplants are surviving longer, but outcome is complicated by CKD. Accurate and frequent renal function monitoring is imperative to recognize and institute measures early to reverse, prevent, or arrest progression. This study of 59 children determined the accuracy (P30), bias, sensitivity and specificity between measured renal function by NM-GFR, and estimated GFR by three formulas: Filler (serum cystatin C), mSchwartz (serum creatinine), and CKiD (serum cystatin C, creatinine, urea, and height). Mean GFR by all formulas differed significantly from NM-GFR. Filler and mSchwartz formulas significantly increased the proportion of patients with GFR ≥ 90 mL/min/1.73 m2 (CKD stage 1) while decreasing those with GFR 60–89 mL/min/1.73 m2 (CKD stage 2). All formulas overestimated GFR. CKiD showed the highest P30 and lowest bias (79.7%; 6.9 mL/min/1.73 m2) followed by Filler (67.7%; 19.9 mL/min/1.73 m2) and Schwartz (57.6%; 26.8 mL/min/1.73 m2) for all GFR values. All formulas performed best with GFR ≥ 90 mL/min/1.73 m2, but CKiD was the only formula to achieve 91.1% accuracy. All formulas showed high sensitivities, but low specificities at NM-GFR cutoff at 90. Thus, GFR estimated by CKiD followed by Filler formula is an adequate method to monitor renal function closely and frequently in these children.