eGFR using CKD-EPI (2021 update)

The original CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation was developed in 2009 in an effort to create a more precise formula to estimate glomerular filtrate rate (eGFR) from serum creatinine and other readily available clinical parameters, especially at when actual GFR is >60 mL/min per 1.73m ². A subsequent revision of this equation was published in 2021. The 2021 version, which is used by this tool, revised the equation based on more data and removed the racial component from the equation, which was found to overestimate GFR, especially in Black patients.

Researchers pooled data from multiple studies to develop and validate this new equation. They randomly divided 10 studies which included 8254 participants, into separate data sets for development and internal validation. 16 additional studies, which included 3896 participants, were used for external validation.

The CKD-EPI equations performed better than the MDRD (Modification of Diet in Renal Disease Study) equation, especially at higher GFR, with less bias and greater accuracy. When looking at NHANES (National Health and Nutrition Examination Survey) data, the median eGFR was 94.5 mL/min per 1.73 m ² vs. 85.0 mL/min per 1.73 m ², and the prevalence of chronic kidney disease was 11.5% versus 13.1%.

The CKD-EPI 2021 equation is:
eGFR = 142 x min(standardized Scr/K,1) ^α * max(standardized Scr/K,1) ^-1.200 * 0.9938 ^{age in years} * 1.012 [if female]

where:

• Scr = serum creatinine in mg/dL
• K = 0.7 (females) or 0.9 (males)
• α = -0.241 (females) or -0.302 (males)
• min(standardized Scr/K,1) = the minimum of Scr/K or 1
• max(standardized Scr/K,1) = the maximum of Scr/K or 1