Estimated Glomerular Filtration Rate

Estimated GFR Calculated Using the CKD-EPI Equation

See the prior memo, dated May 26, 2020.

Background

On July 5, 2022, the laboratories at UWMC-ML, UWMC-NW, HMC, and SCCA began using the Chronic Kidney Disease Epidemiology Collaboration 2021 equation (2021 CKD-EPI) to calculate estimated glomerular filtration rate (eGFR). This new equation is now recommended for estimating GFR from serum creatinine by the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN). The equation was modeled using the original CKD-EPI cohorts, but eliminated consideration of race as a variable. This has achieved a less biased approach to kidney function testing by recognizing that race is a social construct and an ineffective variable in the biomedical environment.

Why is this change being made?

In 2021, the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Diseases concluded that race should not be a parameter in GFR estimating equations.

What this means

In 2020, UW Medicine shifted from using the MDRD equation to estimate GFR to using a form of the original 2009 CKD-EPI equation that lacked the race variable. During the development of the 2021 CKD‑EPI equation, race was excluded from the putative statistical models used to predict measured GFR. As a result, there will be slight shifts in the calculated eGFR for all patients. As shown in the table, this could lead to the recategorization of many of our UW Medicine patients to a stage of CKD associated with better kidney function. A comparison of the performance of the 2009 equation without race coefficient (rows) and the 2021 CKD-EPI equation (columns) in our patient population is shown here:

Recommendation

No changes in ordering practices are indicated. However, a change in calculated eGFR before and on/after July 5, 2022 should be interpreted with this calculation change in mind.

For additional information, please contact Andy Hoofnagle, MD PhD, Director of UWMC Chemistry (ahoof@uw.edu), or Geoff Baird, MD PhD, Director of HMC Chemistry (gbaird@uw.edu).

Inker LA, et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. N Engl J Med 2021, 385:1737-1749. 34554658

Ghuman JK, et al. Impact of Removing Race Variable on CKD Classification Using the Creatinine-Based 2021 CKD-EPI Equation. Kidney Med 2022, 4:100471. 35756325