Clinical Impact of the Refit CKD-EPI 2021 Creatinine-Based eGFR Equation

BACKGROUND: The National Kidney Foundation recently endorsed the refit Chronic Kidney Disease Collaboration (CKD-EPI) equation for estimated glomerular filtration rate (eGFR) using creatinine, age and sex [2021 eGFR_Cr(AS)] without a coefficient for race. We evaluated the impact of adopting the 2021 eGFR_Cr(AS) equation or a variation of the 2009 CKD-EPI eGFR equation without race [2009 CKD-EPI eGFR_Cr(ASR-NB)] compared to the original CKD-EPI eGFR [2009 eGFR_Cr(ASR)]. METHODS: The studied population included patients with a clinically ordered iothalamate clearance (n ¼ 33 889). Bias was assessed as the difference between measured and estimated GFR, P30 was defined as the percentage of estimates within 30% of measured GFR, and concordance was determined according to relevant clinical thresholds. RESULTS: Among Black patients, the median bias for 2009 eGFR_Cr(ASR), 2009 eGFR_Cr(ASR-NB), and 2021 eGFR_Cr(AS) was -1.32 mL min-¹ (1.73 m²)-¹ (95CI -2.46 to -0.26), -8.81 mL min-¹ (1.73 m²)-¹ (95CI -9.93 to -7.58), and -6.08 mL min-¹ (1.73 m²)-¹ (95CI -7.18 to -4.92), respectively. The median bias among non-Black patients was -0.15 m min-¹ (1.73 m²)-¹ (95CI -0.84 to -0.08) for 2021 eGFR_cr(AS) compared to -3.09 mL min-¹ (1.73 m²)-¹ (95CI -3.17 to -3.03) for the 2009 eGFR_Cr(ASR). P30 and concordance were not significantly different in either racial group. The net reclassification improvement at a measured GFR <20 mL min-¹ (1.73 m²)-¹ was 6.4% (95CI 0.36 to 12.4) for Black patients and -5.1% (95CI -6.0 to -4.1) for non-Black patients using the 2021 eGFR_Cr(AS) equation. CONCLUSIONS: Overall, the change in reported eGFR was minimal. However, these changes led to significant reclassification improvements at lower eGFR, which will indirectly improve equitable access to CKD resources.