Comparison of estimated and measured GFR in pediatric CKD patients transitioning from adolescence to adulthood: results from KNOW-PedCKD

Background Accurate estimation of glomerular filtration rate (eGFR) is essential for managing pediatric chronic kidney disease (CKD). While multiple eGFR equations are used clinically, their reliability in adolescents transitioning to adulthood with pediatric-onset CKD remains uncertain. This study aimed to evaluate the accuracy of 10 eGFR equations against measured GFR (mGFR) values in South Korean adolescents and young adults with CKD using data from the KoreaN Cohort Study for Outcome in Patients With Pediatric Chronic Kidney Disease (KNOW-PedCKD) cohort. Methods Patients aged ≥ 15 years who underwent mGFR testing were included in the KNOW-PedCKD study. mGFR was determined using plasma clearance of ⁵¹ Cr-EDTA or ^99m Tc-DTPA. Ten eGFR equations (U25 _Cr , U25 _CysC , U25 _Cr-cysC , Schwartz _Cr , CKiD _Cr-cysC , FAS _Cr -Age, FAS _Cr -Ht, FAS _CysC , CKD-EPI _Cr , and CKD-EPI _Cr-CysC ) were compared with concurrent mGFR values. Performance was assessed using bias, precision, accuracy (percentage within 10% and 30% of the mGFR), and Spearman’s correlation coefficient. Results The analysis encompassed 187 mGFR measurements from 82 patients (median age 18.4 years, interquartile range (IQR) 16.5–20.8; 75.9% male). Median mGFR was 48.3 ± 33.5 ml/min/1.73 m ² . Overall, the U25 _Cr-CysC showed the most balanced performance, with low bias (1.9 mL/min/1.73m ² ), high precision (SD 10.5), 32.6% accuracy within 10%, 67.4% within 30%, and strong correlation (ρ = 0.97). FAS _Cr -Ht equations exhibited the highest accuracy (77.0%), and the lowest bias (-0.44), with slightly lower precision (SD 12.5). Both equations performed constantly across adolescents and young adult subgroups. In contrast, CKD-EPI _Cr equation consistently overestimated GFR with the highest bias and lowest accuracy. Conclusions The eGFR equations covering children — particularly U25 _Cr-CysC and FAS _Cr -Ht equations — provide more reliably estimate GFR than adult equations in Korean adolescents and young adults with CKD. These findings support the use of age-spanning formulas during transitional care to improved clinical accuracy and continuity.