Estimating glomerular filtration rate in children: evaluation of creatinine- and cystatin C-based equations

Background Glomerular filtration rate (GFR) estimated by creatinine- and/or cystatin C-based equations (eGFR) is widely used in daily practice. The purpose of our study was to compare new and old eGFR equations with measured GFR (mGFR) by iohexol clearance in a cohort of children with chronic kidney disease (CKD). Methods We examined 96 children (median age 9.2 years (range 0.25–17.5)) with CKD stages 1–5. A 7-point iohexol clearance (GFR7p) was defined as the reference method (median mGFR 66 mL/min/1.73 m 2 , range 6–153). Ten different eGFR equations, with or without body height, were evaluated: Schwartz bedside , Schwartz CKiD , Schwartz cysC , CAPA, LM REV , (LM REV + CAPA) / 2, FAS crea , FAS cysC , FAS combi , FAS height . The accuracy was evaluated with percentage within 10 and 30% of GFR7p (P10 and P30). Results In the group with mGFR below 60 mL/min/1.73 m 2 , the Schwartz cysC equation had the lowest median bias (interquartile range; IQR) 3.27 (4.80) mL/min/1.73 m 2 and the highest accuracy with P10 of 44% and P30 of 85%. In the group with mGFR above 60 mL/min/1.73 m 2 , the Schwartz CKiD presented with the lowest bias 3.41 (13.1) mL/min/1.73 m 2 and P10 of 62% and P30 of 98%. Overall, the Schwartz cysC had the lowest bias − 1.49 (13.5) mL/min/1.73 m 2 and both Schwartz cysC and Schwartz CKiD showed P30 of 90%. P10 was 44 and 48%, respectively. Conclusions The Schwartz cysC and the combined Schwartz CKiD present with lower bias and higher accuracy as compared to the other equations. The Schwartz cysC equation is a good height-independent alternative to the Schwartz CKiD equation in children and can be reported directly by the laboratory information system. Clinical Trial Registration ClinicalTrials.gov , Identifier NCT01092260, https://clinicaltrials.gov/ct2/show/NCT01092260?term=tondel&rank=2