Implementing and Evaluating the New Race-Free Equation to Assess Kidney Function

In early 2022, Cleveland Clinic formally adopted the recently retooled race-free estimated glomerular filtration rate (eGFR) formula for consistent use across the enterprise.

This decision followed a recommendation by the National Kidney Foundation and the American Society of Nephrology (NKF-ASN) Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease to adopt a new equation: the eGFR 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI).

The task force engaged with nearly 100 experts from seven countries for more than a year before arriving at their decision. They evaluated 26 possible equations and published data. In addition, they spoke with patients, healthcare workers, and trainees before concluding that widespread adoption of the CDK-EPI equation, a race-free formula, was the best approach.

Crystal Gadegbeku, MD, Department Chair of Kidney Medicine at Cleveland Clinic and task force member, says, “As a group, we unanimously agreed that race should not be considered as a factor in estimating GFR. We recognize what a genetic mosaic we all are. Not only is race a poor proxy for genetics, but it’s a social construct. So taking race out of the eGFR equation makes sense.”

The newly recommended formula

CKD-EPI is a creatinine-based equation that excludes race, but includes age and sex.

For clinical decisions where greater accuracy is essential, the task force recommends using cystatin C combined with serum creatinine, cystatin C alone equation, or measured GFR test to confirm kidney function.

Although cystatin C has never required a race modifier to estimate kidney function, it’s not available at every center. “With an estimate of over 200 million measurements performed annually, we need a tool for everyday use in all clinical practice settings, not only to manage kidney disease but for assessment across the spectrum of kidney function,” says Dr. Gadegbeku.

Emphasis on estimate

While the CKD-EPI formula can estimate kidney function, primary care physicians shouldn’t base critical medical decisions on a single number. Instead, estimates should be used as a guide in making treatment decisions. Dr. Gadegbeku advocates for reporting a GFR range so that physicians and patients understand that these are not precise measurements.

Implications for care

Emilio Poggio, MD, Medical Director of the Kidney Transplant Program at Cleveland Clinic, and colleagues are now focusing on evaluating the performance of the new equation in persons interested in kidney donation.

In a recent retrospective cohort study of nearly 300 living kidney donors, the research team examined four different equations with and without the race variable. “We found that the new formula performed very well when estimating kidney function and even better when we included cystatin C,” he explains.

Accuracy is essential in the living kidney donor population to ensure their candidacy. “We need to ensure that the function of their remaining kidney is good and able to maintain its function long term.”

In July 2022, the United Network for Organ Sharing (UNOS) announced that transplant hospitals are now required to adopt the new equation for appropriate assessment in potential kidney donors and recipients.

“The old equation may overestimate GFR in Black patients, which could inadvertently delay transplant evaluation for Black candidates compared to non-Black candidates with similar creatinine values,” explains Dr. Poggio.

He adds, “We are encouraged by the findings we’ve seen so far, but it is also important to note that while the implementation of race-free GFR reporting is a step in the right direction, the use of this equation alone will not completely solve the complex issue of racial disparity in kidney transplantation.”