Performance of the European Kidney Function Consortium (EKFC) creatinine-based equation in United States cohorts

Estimating glomerular filtration rate (GFR) is important in daily practice to assess kidney function and adapting the best clinical care of patients with and without chronic kidney disease. The new creatinine-based European Kidney Function Consortium (EKFC) equation is used to estimate GFR. This equation was developed and validated mainly in European individuals and based on a rescaled creatinine, with the rescaling factor (Q-value) defined as the median normal value of serum creatinine in a given population. The validation was limited in Non-Black Americans and absent in Black Americans. Here, our cross-sectional analysis included 12,854 participants from nine studies encompassing large numbers of both non-Black and Black Americans with measured GFR by clearance of an exogenous marker (reference method), serum creatinine, age, sex, and self-reported race available. Two strategies were considered with population-specific Q-values in Black and non-Black men and women (EKFC_PS) or a race-free Q-value (EKFC_RF). In the whole population, only the EKFC_PS equation showed no statistical median bias (0.14, 95% confidence interval [-0.07; 0.35] mL/min/1.73m²), and the bias for the EKFC_RF (0.74, [0.51; 0.94] mL/min/1.73m²) was closer to zero than that for the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI₂₀₂₁) equation (1.22, [0.99; 1.47]) mL/min/1.73m²]. The percentage of estimated GFR within 30% of measured GFR was similar for CKD-EPI₂₀₂₁ (79.2% [78.5%; 79.9%]) and EKFC_RF (80.1% [79.4%; 80.7%]), but improved for the EKFC_PS equation (81.1% [80.5%; 81.8%]). Thus, our EKFC equations can be used to estimate GFR in the United States incorporating either self-reported race or unknown race at the patient's discretion per hospital registration records.