Accurate eGFR reporting for children without anthropometric data

Introduction Reporting estimated glomerular filtration rate (eGFR) instead of serum concentrations is advised in current guidelines. Most creatinine-based eGFR equations for children require height, a parameter not readily available to laboratories. Combining height-dependent creatinine- and cystatin C-based eGFR improves performance. Recently, a height-independent creatinine-based eGFR equation has been developed. Aim To compare the combination of height-independent creatinine- and cystatin C-based equations with a combination of equations using anthropometric data. Methods Retrospective analysis of 408 pediatric inulin clearance studies with simultaneous height, creatinine, cystatin C and urea measurements. eGFR calculation using the recalibrated Schwartz_crea (height-dependent), FASage (height-independent) and the Schwartz_cys equation. The means (Schwartz_crea + Schwartz_cys) / 2 and (FASage + Schwartz_cys) / 2 were compared with the CKiD3 equation incorporating cystatin C, creatinine, urea, height and gender in terms of %prediction error and accuracy. Results All three single parameter equations performed similarly (P₃₀ accuracy around 80%). (FASage + Schwartz_cys) / 2 (P₃₀ 89.2%) and (Schwartz_crea + Schwartz_cys) / 2 (P₃₀ 89.0%), performed comparably to CKiD3 (P₃₀ 90.0%). If the difference between the creatinine- and the cystatine C based eGFR was < 40%, P₃₀ accuracy of the mean exceeded 90%. Conclusion Combining the height-independent FASage and Schwartz_Cys equations substantially improves accuracy and performs comparably to height-dependent equations. This allows laboratories to directly report eGFR in children.