Testing kidney function with race-free values offers a better health picture

The use of a race coefficient in the equation to test kidney function traces back to an old study that had serious limitations.

Black/African Americans have a higher rate of chronic kidney disease than their white counterparts. They are more than three times as likely to develop kidney failure. Yet for many years, the results from a common kidney test were race-adjusted by health systems nationwide. That may have contributed to health disparities for Black individuals with kidney disease.

Dr. Susanne Nicholas, MD, MPH, PhD, is chair of the UCLA Nephrology Racial and Health Equity Committee.

More recently, health professionals at UCLA and other top health centers began to rethink this approach. On June 1, UCLA Health adopted a new, race-free method of calculating the results of this test.

“Nationally, UCLA is one of the leaders in making this positive change,” says Susanne Nicholas, MD, MPH, PhD, chair of the UCLA Nephrology Racial and Health Equity Committee.

Race-based eGFR values

Glomerular filtration rate (GFR) is a measure of how fast a person’s kidneys are filtering waste and excess water from the blood. This indicates how well the kidneys are working. Measuring GFR directly is a cumbersome process and impractical for routine use.

Instead, health professionals measure blood levels of creatinine, a waste product that’s filtered by the kidneys. Then they use an equation that factors in age and sex — and, until recently, race — to calculate an estimated GFR (eGFR). A higher eGFR value indicates better kidney function.

The use of a race coefficient in the equation traces back to a study from 1998. It showed that Black people had higher serum (blood) creatinine levels, on average, than whites. Unfortunately, the study had serious limitations. It didn’t look at why groups may have differed in their creatinine levels. Plus, it didn’t account for the fact that individuals who self-identify as Black are diverse, genetically and biologically.

Nonetheless, researchers relied on this flawed science to develop a widely used formula that included a coefficient for Black patients.

“Using the 2009 CKD-EPI eGFR formula, all Black individuals automatically got a 16% increase in their eGFR,” says Lu Song, PhD, DABCC, FACB, chief of Clinical Chemistry at UCLA Health. “Imagine two people — one Black, one not — who are the same age and sex and have the same serum creatinine level.

"Let’s say the person who is non-Black has an eGFR of 55 mL/min/1.73 m2, in the stage 3 of chronic kidney disease. For a person who is Black, eGFR would be artificially increased to 64 mL/min/1.73 m2, which is in the stage 2 of chronic kidney disease.”

Grappling with unintended consequences

That boost in eGFR for Black individuals had important implications for kidney care.

“If a patient’s eGFR is higher, it offers false confidence that their kidney function is better,” says Dr. Nicholas. “That patient may not be monitored as closely by their health care provider or referred for kidney disease education as soon.”

eGFR values also help determine when patients are placed on kidney transplant lists.

“We usually refer patients to be evaluated for kidney transplantation when their eGFR is around 20 or lower,” says Dr. Nicholas. “Consider two people with the same age, sex and serum creatinine level. A white individual who has an eGFR of 20 mL/min/1.73 m2 may be referred. But a Black individual whose eGFR is 23 mL/min/1.73 m2 due to the race coefficient may miss out on being referred at the appropriate time.”

Filtering out racial bias

By 2020, the use of race-based eGFR values was under growing scrutiny. The National Kidney Foundation and the American Society of Nephrology formed a joint task force to look into the issue.

Dr. Lu Song, PhD, DABCC, FACB, is chief of clinical chemistry at UCLA Health.

At UCLA, Dr. Nicholas and Dr. Song were already discussing a move away from this practice. Simply dropping the race coefficient wasn’t the best option, however. That would have meant applying a formula based only on non-Black individuals to everyone. So, they waited for a formula that could be applied to everyone to be published by the study team who had access to the original data — and they prepared for the change.

In late 2021, the task force published guidelines recommending a new formula for eGFR. It’s based on data from all study participants, both Black and non-Black individuals. The coefficient once used to raise the eGFR values of Black patients is now gone.

“Without that race coefficient, we have a much better idea of an individual’s kidney function,” says Dr. Nicholas.

As a kidney specialist, Dr. Nicholas spearheaded the switch to report race-free eGFR values at UCLA Health. She coordinated with Dr. Song, who oversees the labs where the testing is done. They also worked with the information technology team to change how eGFR values appear in the electronic health record.

Patients and providers now see just a single eGFR number that is calculated based on age, gender and creatinine levels for everyone. A separate eGFR number for Black/African Americans, which was reported in the past, is no longer there.

“It’s one sign of our ongoing commitment to lowering barriers to kidney care and reducing health disparities,” Dr. Nicholas says.

Learn more about kidney care and research at UCLA Health.

Related:

UCLA research uncovers racial differences in children’s chronic kidney disease

What’s it like to donate a kidney? A sister shares her story

UCLA kidney-transplant patient now fights for a new cause


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