Comparing Results of Five Glomerular Filtration Rate-Estimating Equations in the Korean General Population: MDRD Study, Revised Lund-Malmö, and Three CKD-EPI Equations

Abstract

Background: Estimated glomerular filtration rate (eGFR) is a widely used index of kidney function. Recently, new formulas such as the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations or the Lund-Malmö equation were introduced for assessing eGFR. We compared them with the Modification of Diet in Renal Disease (MDRD) Study equation in the Korean adult population.

Methods: The study population comprised 1,482 individuals (median age 51 [42-59] yr, 48.9% males) who received annual physical check-ups during the year 2014. Serum creatinine (Cr) and cystatin C (CysC) were measured. We conducted a retrospective analysis using five GFR estimating equations (MDRD Study, revised Lund-Malmö, and Cr and/or CysC-based CKD-EPI equations). Reduced GFR was defined as eGFR <60 mL/min/1.73 m².

Results: For the GFR category distribution, large discrepancies were observed depending on the equation used; category G1 (≥90 mL/min/1.73 m²) ranged from 7.4-81.8%. Compared with the MDRD Study equation, the other four equations overestimated GFR, and CysC-based equations showed a greater difference (-31.3 for CKD-EPI(CysC) and -20.5 for CKD-EPI(Cr-CysC)). CysC-based equations decreased the prevalence of reduced GFR by one third (9.4% in the MDRD Study and 2.4% in CKD-EPI(CysC)).

Conclusions: Our data shows that there are remarkable differences in eGFR assessment in the Korean population depending on the equation used, especially in normal or mildly decreased categories. Further prospective studies are necessary in various clinical settings.

Keywords: CKD-EPI equation; Estimated glomerular filtration rate; MDRD Study equation; Revised Lund-Malmö equation.

Fig. 1. Bland-Altman plots of estimated glomerular filtration rate (eGFR) calculated by the MDRD Study equation and others (n=1,482). (A) CKD-EPI_Cr equation. (B) LM_Revised equation. (C) CKD-EPI_CysC equation. (D) CKD-EPI_Cr-CysC equation. The solid gray lines represent the mean difference and dashed lines depict±1.96 SD. A negative difference suggests an overestimation of GFR by each equation compared with the value obtained by the MDRD Study equation. For ease of display, the maximum scale on the vertical axis of (A) and (B) was limited to 30, while that on (C) and (D) was limited to 90 depending on the distribution of the eGFR difference between equations.