Limitations of U25 CKiD and CKD-EPI eGFR formulae in patients 2–20 years of age with measured GFR > 60 mL/min/1.73 m2—a cross-sectional study

When applying Pierce U25 formula for estimating glomerular filtration rate (eGFR), we observed a higher proportion of eGFR < 90 mL/min/1.73 m2 (chronic kidney disease (CKD) stage 2). We compared agreement and accuracy of the Pierce U25 (ages 2–25), Pottel (ages 2–100), and CKD-EPI (ages 18–100) formulae to GFR measurements. Post hoc analysis of the three eGFRs compared to 367 99m technetium-diethylene-triamine penta-acetic acid (99Tc DTPA) GFR measurements (240 patients) using 3 sampling points and Brockner/Mørtensen correction (body surface area calculation based on ideal weight) on simultaneous serum creatinine and cystatin C measurements. Overall, the U25 formula performed well with a Spearman r of 0.8102 (95