Combination of pediatric and adult formulas yield valid glomerular filtration rate estimates in young adults with a history of pediatric chronic kidney disease

Abstract

As patients with chronic kidney disease (CKD) transition from pediatric nephrology care to adult care, their kidney function is clinically assessed by estimated glomerular filtration rate (eGFR) using both pediatric and adult equations, which may not be congruent. Here we evaluated commonly used eGFR equations and directly measured iohexol GFR (iGFR) among participants between ages 18 and 26 with a diagnosis of pediatric CKD in the Chronic Kidney Disease in Children (CKiD) cohort. The bedside serum creatinine (SCr)-only equation (CKiDSCr), the SCr-only CKD-EPI (CKD-EPISCr), the cystatin C (Cys)-only CKD-EPI (CKD-EPICys) and the combined SCr and Cys CKD-EPI (CKD-EPISCr-Cys) were compared with a) 279 measured iGFRs obtained from 187 participants and b) 548 eGFRs from the SCr and Cys-based CKiD equation (CKiDSCr-Cys) obtained from 219 participants. Among emerging adults with a median iGFR of 49 ml/min/1.73m2, the CKiDSCr-Cys equation had low bias (+1.5 ml/min/1.73m2) and high correlation (0.94), while CKiDSCr underestimated iGFR and CKiDSCr-Cys (-5.6 and -7.4 ml/min/1.73m2, respectively) and CKD-EPISCr had an overestimation bias (+8.2 and +6.1 ml/min/1.73m2, respectively). However, the CKD-EPICys and CKD-EPISCr-Cys exhibited strong agreement with both iGFR and CKiDSCr-Cys. GFR may also be validly estimated in this population by taking the simple average of CKiDSCr and CKD-EPISCr (average bias +1.3 compared to iGFR and -0.6 compared to CKiDSCr-Cys). Clinicians should be aware that individually the pediatric and adult SCr-based estimates of GFR had large discrepancies among emerging adults with pediatric CKD. Thus, when cystatin C is not available, we recommend the average of pediatric and adult SCr-based eGFR as a valid tool for clinical use.

Keywords: chronic kidney disease; clinical nephrology; glomerular filtration rate; pediatric nephrology; young adults.

Conflict of interest statement

Statement of Competing Financial Interests

None declared.

Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Agreement plot of CKiD eGFR based on serum creatinine and cystatin C (CKiDSCr-Cys) and directly measured iohexol GFR (iGFR) in the log scale among 279 person-visits from 187 young adults with a history of pediatric chronic kidney disease. The bolded grey line is a non-parametric spline based on 95% of the data; the ellipse region depicts the 90% confidence region of the data based on a bivariate normal distribution.

Figure 2

Agreement plot of the average of CKiD eGFR and CKD-EPI eGFR based on serum creatinine-only (CKiDSCr and CKD-EPISCr eGFR) and directly measured iohexol GFR (iGFR) in the log scale among 279 person-visits from 187 young adults with a history of pediatric CKD. The bolded grey line is a nonparametric spline based on 95% of the data; the ellipse region depicts the 90% confidence region of the data based on a bivariate normal distribution.

Figure 3

Agreement plot of the average of CKiD eGFR and CKD-EPI eGFR based on serum creatinine-only (CKiDSCr and CKD-EPISCr eGFR) and CKiDSCr-Cys in the log scale among 548 person-visits from 219 young adults with a history of pediatric CKD. The bolded grey line is a non-parametric spline based on 95% of the data; the ellipse region depicts the 90% confidence region of the data based on a bivariate normal distribution.