#466 Comparison of CKDEPI vs EKFC equations in estimating glomerular filtration rate in kidney transplant recipients
Authors: Belotto Miguel Martínez , Ortega María José , Rodríguez María , Escagedo Clara , García Cristina , Pasache José Enrique , López del Moral Covadonga , Valero Rosalía , Belmar Lara , de la Oliva Valentín María , Ruiz Juan Carlos , Rodrigo Emilio 
Published: May 2024

Abstract

Background and Aims
In 2020, European Kidney Function Consortium (EKFC) proposed a new equation that estimates glomerular filtration rate (GFR) in European population. Using creatinine and age, as well as CKDEPI, EKFC gives an estimation which has been demonstrated to correlate better to measured GFR, particularly at extreme ages. CKDEPI equation is the most common equation used in our clinical practice. Few studies have compared EKFC with CKDEPI, particularly in kidney transplant (KT) recipients. Our objective is to compare estimation of GFR with EKFC and CKDEPI in KT patients.

Method
We conduct a retrospective observational study including all consecutive KT performed at our centre from 1993 to 2022 with survival greater than one year, and laboratory tests at third month and one-year post-transplant. Using Creatinine and Age we calculate estimated GFR (eGFR) by CKDEPI and EKFC equations. We compare both results in terms of correlation and agreement in the global sample and classifying by subgroups according to a) Sex, b) Age by 10-year sections, c) Body Mass Index (BMI) as WHO classification and d) presence or absence of Diabetes Mellitus (DM). We use SPSS as statistics program.

Results
We include 968 KT, depicted in Table 1. CKDEPI and EKFC at 3rd month and EKFC at one-year have a non-normal distribution (Kolmogorov-Smirnov test with p = 0.003, p = 0.035 and p = 0.002, respectively), contrary to normality in CKDEPI at one year (p = 0.058). Levene test for homogeneity of variances shows no differences (3rd month p = 0.102, one year p = 0.165), as well as in subgroups. We perform, besides Mann-Whitney, Student's T-test despite limitations over means without significant differences in any subgroup.
Mean global difference at 3rd month is 0.23 ml/min greater by CKDEPI. There are no relevant differences between subgroups related to DM and BMI. We can describe a difference between women (0.85 ml/min) and men (0.05 ml/min), and it is larger in 20-30 years group (3.4 ml/min) and in 70-80 years (2.74 ml/min). As measure of agreement, Intraclass Correlation Coefficient (ICC) shows excellent correlation in all subdivisions (Cronbach's Alpha statistic (CA) &gt; 0.99), without significant decrease in any subgroup; minimum ICC = 0.987 is in 20-30 years group, and maximum ICC = 0.999 in 40-60 years. Bland-Altman plot is shown in Fig. 1, where we appreciate a negative bias in low eGFR against a positive in higher values.
Mean global difference at one-year eGFR is 0.25 ml/min greater by CKDEPI. We observe a difference between women (0.75 ml/min) and men (0.04 ml/min), larger in 20-30 years group (2.94 ml/min) and 70-80 years (2.27 ml/min) without significance. ICC shows excellent correlation without significant decrease in any subgroup; minimum ICC = 0.992 is in 20-30 years group, and maximum ICC = 0.999 in 50-60 years.

Conclusion
We find no significant differences between means in eGFR by CKDEPI and EKFC. We observe a tendency to a greater estimation in women than in men. Both CKDEPI and EKFC equations for eGFR show an excellent concordance in our cohort of KT but differences in scatter analysis in Bland-Altman plot, greater in higher values of eGFR. ICC and CA are both slightly minor in the extreme age groups of our cohort. It matches what described in major studies; these differences may be not clinically relevant in this age range group but are probably greater in patients beyond this range.