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

BackgroundGlomerular 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).MethodsWe examined 96 children (median age 9.2years (range 0.25-17.5)) with CKD stages 1-5. A 7-point iohexol clearance (GFR7p) was defined as the reference method (median mGFR 66mL/min/1.73m(2), range 6-153). Ten different eGFR equations, with or without body height, were evaluated: Schwartz(bedside), Schwartz(CKiD), Schwartz(cysC), CAPA, LMREV, (LMREV + 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).ResultsIn the group with mGFR below 60mL/min/1.73m(2), the Schwartz(cysC) equation had the lowest median bias (interquartile range; IQR) 3.27 (4.80) mL/min/1.73m(2) and the highest accuracy with P10 of 44% and P30 of 85%. In the group with mGFR above 60mL/min/1.73m(2), the Schwartz(CKiD) presented with the lowest bias 3.41 (13.1) mL/min/1.73m(2) and P10 of 62% and P30 of 98%. Overall, the Schwartz(cysC) had the lowest bias -1.49 (13.5) mL/min/1.73m(2) and both Schwartz(cysC) and Schwartz(CKiD) showed P30 of 90%. P10 was 44 and 48%, respectively.ConclusionsThe 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 RegistrationClinicalTrials.gov, Identifier NCT01092260, https://clinicaltrials.gov/ct2/show/NCT01092260?term=tondel&rank=2