Comparison of different equations for estimated glomerular filtration rate in patients with chronic kidney disease

Abstract

Objective To compare different equations for estimated glomerular filtration rate (eGFR) in patients with chronic kidney disease (CKD). Methods Hospitalized patients with CKD from the nephrology department of the First Affiliated Hospital of Nanjing Medical University (Jiangsu Province Hospital) were recruited between December 2014 and May 2015. The calculations of eGFR and 24 h creatinine clearance rate (Ccr) were accomplished in three days after admission. The eGFRs were calculated separately using the 24 h creatinine clearance rate adjusted by the standard body surface area (Ccr_BSA), Cockcroft-Gault equation adjusted by the standard body surface area (eCcr_BSA), CKD-EPI creatinine equation (EPI_Cr), CKD-EPI cystatin C equation (EPI_CysC), CKD-EPI creatinine-cystatin C equation (EPI_Cr_CysC), simplified MDRD (MDRD) and China MDRD equations. The EPI_Cr_CysC equation was used as the standard and the precision and accuracy of the other six equations were compared and analyzed. Results A total of 403 CKD participants were enrolled in the study, with 228 male patients and a mean age of (54.9±18.4) years. The main primary diseases were chronic glomerulonephritis (43.7%) and diabetic nephropathy (13.2%). The median concentration of serum creatinine and cystatin C were 117.5 (69.7, 242.4) μmol/L and 1.80 (1.13, 3.31) mg/L, respectively. The median values of Ccr_BSA, eCcr_BSA, MDRD, China MDRD, EPI_Cr, EPI_CysC and EPI_Cr_CysC equations were 50.8 (21.1, 96.2), 51.9 (23.3, 93.2), 53.6 (23.0, 97.4), 52.2 (22.4, 94.1), 53.2 (22.1, 97.3), 35.1 (15.4, 67.0) and 49.1 (22.8, 82.3) ml·min-1·(1.73 m2)-1, respectively. There was well agreement among MDRD, China MDRD and EPI_Cr equations, while there were large differences between equations derived from CysC (EPI_Cr_CysC and EPI_CysC) and equations derived only from creatinine (EPI_Cr, MDRD, China MDRD, eCcr_BSA, Ccr_BSA equations). Compared with EPI_Cr_CysC equation (the reference equation), EPI_Cr equation showed the highest accuracy [percentage of other eGFR equation calculations that were >30% of the reference equation calculations (1-P30), 30.8%] while Ccr_BSA equation showed the lowest (1-P30, 42.4%). EPI_CysC equation showed the highest precision [inter-quartile range (IQR) of the difference, 11.7 ml·min-1·(1.73 m2)-1] while Ccr_BSA equation showed the lowest [IQR of the difference, 22.8 ml·min-1·(1.73 m2)-1]. Conclusions The agreement among equations derived only from creatinine is better; while it exhibits some differences between equations with cystatin C and equations derived only from creatinine. The accuracy of EPI_Cr equation is second only to EPI_Cr_CysC equation and it is currently the most suitable eGFR equation for clinical popularization of renal glomerular function assessment. Key words: Glomerular filtration rate; Renal insufficiency, chronic; Creatinine clearance