A simple height-independent equation for estimating glomerular filtration rate in children.

Background: The chronic kidney disease (CKD) classification system for children is similar to the CKD classification system for adults, using estimated glomerular filtration rate (eGFR) combined with fixed cut-off values of 60, 30, and 15 ml/min/1.73 m(2) for CKD stages III, IV, and V, respectively. To estimate GFR in children, eGFR-equations are used that require serum creatinine (Scr), but also height information, which is normally not available in clinical laboratory databases.

Methods: This retrospective study is based on data from two different databases, one that has previously been used to develop the Flanders Metadata equation for children and one database including 353 children who underwent (51)Cr-EDTA GFR, serum creatinine, height, and weight measurements.

Results: A height-independent eGFR equation based on the concept of a population-normalized Scr, presented before for adults, is extended to children: eGFR = 107.3/(Scr/Q), with Q the median Scr for healthy children of a particular age. This equation is validated against direct measurements of GFR, and against the updated Schwartz and Flanders Metadata equation.

Conclusions: The new simple height-independent equation performs very well and should make (mass) screening of kidney function in children easier.