Estimating glomerular filtration in young people

Abstract

Background: Creatinine-based equations are the most used to estimate glomerular filtration rate (eGFR). The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), the re-expressed Lund-Malmö Revised (r-LMR) and the European Kidney Function Consortium (EKFC) equations are the most validated. The EKFC and r-LMR equations have been suggested to have better performances in young adults, but this is debated.

Methods: We collected data (GFR) measured by clearance of an exogenous marker (reference method), serum creatinine, age and sex from 2366 young adults (aged between 18 and 25 years) both from Europe and the USA.

Results: In the European cohorts (n = 1892), the bias (in mL/min/1.73 m²) was systematically better for the EKFC and r-LMR equations compared with the CKD-EPI equation [2.28, 95% confidence interval (1.59; 2.91), -2.50 (-3.85; -1.76), 17.41 (16.49; 18.47), respectively]. The percentage of estimated GFR within 30% of measured GFR (P30) was also better for EKFC and r-LMR equations compared with the CKD-EPI equation [84.4% (82.8; 86.0), 87.2% (85.7; 88.7) and 65.4% (63.3; 67.6), respectively]. In the US cohorts (n = 474), the bias for the EKFC and r-LMR equations was better than for the CKD-EPI equation in the non-Black population [0.97 (-1.69; 3.06), -2.62 (-5.14; -1.43) and 7.74 (5.97; 9.63), respectively], whereas the bias was similar in Black US individuals. P30 results were not different between the three equations in US cohorts. Analyses in sub-populations confirmed these results, except in individuals with high GFR levels (GFR ≥120 mL/min/1.73 m²) for whom the CKD-EPI equation might have a lower bias.

Conclusions: We demonstrated that both the EKFC and r-LMR creatinine-based equations have a better performance than the CKD-EPI equation in a young population. The only exception might be in patients with hyperfiltration.

Keywords: creatinine; glomerular filtration rate; young adult.

Figure 1:

(A–F) Bias and P30 for the different equations according to age in the European, non-Black US and Black US cohorts. The grey area indicates the region where bias was zero ±5 mL/min/1.73 m² or P30 was ≥75%.

Figure 2:

The Bland and Altman plots [absolute (A, C) or relative (B, D) bias] in the European cohorts for the EKFC (A, B) and CKD-EPI equations (C, D). The red line is the bias (mean difference) and the limits of agreement are between the green dotted lines. The grey dotted lines are corresponding to the zero bias line and the ±30% limits.

Figure 3:

The Bland and Altman plots [absolute (A, C) or relative (B, D) bias] in the non-Black US cohorts for the EKFC (A, B) and CKD-EPI equations (C, D). The red line is the bias (mean difference) and the limits of agreement are between the green dotted lines. The grey dotted lines are corresponding to the zero bias line and the ±30% limits.