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

Should We Switch to the U25 Creatinine and CysC eGFR to Monitor Pediatric Kidney Transplant Recipients?

“…This approach leads to overestimating GFR in lean patients and underestimating GFR in obese patients [22]. Using the exact weight may also lead to substantial variability of the regression analysis between the mGFR and the biomarker, especially if the mGFR is >60 mL/min/1.73 m 2 [12]. Moreover, the Haycock [21] formula for calculating the body surface area (published in 1978), the Mosteller formula [23] (published in 1987), and the Dubois formula [24] (published in 1916) may be outdated because of the acceleration of growth in the past three decades [25].…”

“…Although many formulae exist, and few are externally validated, KDOQI/KDIGO recommends the CKiD U25 formula for people <18 years of age and the CKD-EPI for older patients based on both biomarkers [11]. A limitation of the CKiD U25 formula soon became apparent because it was derived from children, adolescents, and young adults with a decreased GFR at <75 mL/min/1.73 m 2 [12]. Any regression analysis only works well in the range where the data are generated [13].…”

“…Any regression analysis only works well in the range where the data are generated [13]. Switching from the CKiD U25 formula to the adult CKD-EPI formula leads to an implausible increase in eGFR [12,14,15]. Using age-and sex-based average creatinine measurements, Hans Pottel introduced the full age spectrum (FAS) formula, derived from GFR measurements of 735 children and adolescents, 4371 adults, and 1764 older adults in Europe.…”

“…Since most patients had an mGFR below 75 mL/min/1.73 m 2 , the U25 CKiD formula worked reasonably well. However, this may differ in the normal or hyperfiltration range, where several manuscripts have outlined problems[12,14], and the work by Lindvig et al[20], requires some points:…”