Examining commonly used equations for estimating the glomerular filtration rate (GFR) in a healthy cohort of children and adolescents

<title>Abstract</title> Background In this study, we compared established equations for estimating the glomerular filtration rate (GFR) in a cohort of healthy children and adolescents and aimed to evaluate the equations’ validity. Methods Blood, urine, and anthropometric data from 4,776 healthy participants (0.25–21 years) were analyzed. The glomerular filtration rate was estimated (eGFR) using the revised Schwartz Bedside (2009), the Cystatin C- and Serum Creatinine- based Schwartz equation, the Chronic Kidney Disease in Children (CKiD) equation, the Chronic Kidney Disease in Children (CKiD) equation, the 3 versions of the U25 (U25cys, U25scr, U25ave), the Grubb equation, and the Cystatin C-Creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI). The resulting eGFR distributions were compared, and the percentages of eGFR values within the expected physiological eGFR range were calculated stratified by age and sex. Subsequently, age ranges with implausible distributions were identified. Results CKiD, Schwartz, and U25ave yielded the highest proportion of eGFRs within the expected range (75–135 mL/min/1.73m²) and showed consistent values across age groups without large jumps. Bland-Altman analysis indicated that the average U25 and CKiD had the lowest bias compared with Schwartz (-2.93 and − 4.79). U25cys and U25scr also exhibited low bias, while Grubb, Bedside, and CKD-EPI had larger biases, overestimating eGFR. Males showed higher eGFRs than females. Conclusion We found that the CKiD, Schwartz, and combined U25 resulted in the most plausible eGFR distributions for a healthy pediatric cohort. Estimates from simpler equations such as Bedside and Grubb were less plausible.