Task Force Reviewing Race Modifier in eGFR Issues Interim Report

Mitchel L. Zoler, PhD

April 13, 2021

The race coefficient now used in calculating estimated glomerular filtration rate (eGFR) in US patients who self-identify as Black will soon change, says a task force established to examine the issue. The point was made in an interim report the task force released on April 9.

The task force is not yet ready to say what changes it will recommend but promises a final report "soon," likely by the summer of 2021.

In its interim report, the task force ― which began work in August 2020 ― spelled out some of the data it has compiled, the lessons learned, and a framework for making its recommendations. The report makes 30 statements of evidence and values and identifies 26 approaches for reducing bias and improving accuracy when calculating eGFR. The task force, jointly created by the National Kidney Foundation and the American Society of Nephrology, will declare one of them to be best within the next few months.

"It's quite complex" to parse out an optimal balance for a widely usable equation that accurately estimates renal function while taking into account diverse features across the US population that can bias the result, said task force co-chair Cynthia Delgado, MD, in a session that reviewed the interim report during the National Kidney Foundation (NKF) 2021 Spring Clinical Meetings.

"We can't just drop" the race modifier, and the new equation needs to be widely acceptable and practical in the clinical community, where eGFR is a mainstay for tracking renal function starting at the primary care level, explains Delgado, a nephrologist with the University of California, San Francisco.

Two Sides to Dropping the Race Coefficient

The interim report highlights the multiple layers at play regarding this issue.

"Many assert that removing race from eGFR would achieve better health and healthcare equity by mitigating disparities, particularly for African Americans who experience faster progression to kidney failure and lower rates of transplantation," the report notes.

Dropping the race coefficient, which in the currently recomended eGFR equation boosts the level in Blacks by a factor of about 16%, "could result in earlier identification and management of kidney diseases and referral for specialist care."

But the report also acknowledges the contrarian view, that "removing race may create or perpetuate other disparities" among Blacks by inappropriately underestimating their GFR.

The tricky goal for the task force is to "find an approach that embraces the substantial diversity of the US population and promotes social and health equity without creating new, or worsening current, health disparities," the report says.

"Using the race coefficient might lead to delayed referral for kidney transplant," because in typical practice, important management decisions are often based on small shifts in eGFR, noted Mukta Baweja, MD, a nephrologist at Mount Sinai Hospital, New York City, who is a task force member.

But removing the race coefficient "could create additional inequity" by, for example, making the patient ineligible to receive important treatments, such as metformin and sodium-glucose cotransporter 2 inhibitors.

Estimated GFR Is a Rough Estimate

Task force members highlight the substantial ambiguity that limits the accuracy of eGFR. The current standard for calculating eGFR, the CKD-EPI equation, introduced in 2009, has what's known as p30 accuracy, which means that the value it estimates is intended to fall within 30% of a person's actual GFR were that rate to be measured directly. Study findings show that the CKD-EPI equation fails to meet this goal in 15% of Black persons and in 11% of people who do not self-identify as Black.

The upshot is that for a person with an eGFR of 60 mL/min/1.73m2 ― an important cut point that distinguishes mild from moderate chronic kidney disease ― the actual GFR could lie between 42 mL/min/1.73m2 and 78 mL/min/1.73m2, noted Wendy L. St. Peter, PharmD, a task force member and professor of pharmacy at the University of Minnesota, Minneapolis, Minnesota.

The eGFR equations "are relatively inaccurate at an individual level," she emphasized.

Ideally, important clinical decisions should involve further assessment of renal function beyond the calculation of eGFR, observes St. Peter, a task force member speaking during the session at the NKF 2021 Spring Clinical Meetings.

One simple step is to not index eGFR to body size by dividing by 1.73m2, a number intended to reflect average body size.

Experts already discourage use of the 1.73m2 index factor when using eGFR to determine appropriate drug dosing for a patient, St. Peter says.

Get It Right

"Getting it right — having reliable and consistent estimates — is critical to the effective practice of nephrology and all of medicine," stress Harold I. Feldman, MD, and Josephine P. Briggs, MD, in an editorial that accompanies the interim report.

The task force's efforts have broader implications, write Feldman, editor in chief of the American Journal of Kidney Diseases, and Briggs, editor in chief of the Journal of the American Society of Nephrology, the journals that both published the interim report.

This process "should serve as a starting point to robustly address and reverse the unacceptable excessive burden of kidney disease in people within racial minority communities," they say in their editorial.

"The use of race in clinical algorithms, such as for the estimation of GFR, normalizes and reinforces the misconception of race as a biological determinant of health and disease," comments Paul M. Palevsky, MD, president of the National Kidney Foundation, in a written statement.

"This is not to say that clinicians should ignore race and ethnicity. Doing so would blind us to the disparities and inequities present in health and healthcare. But we must not conflate the societal effects of race and racism on health, healthcare and kidney diseases with physiologic and pathophysiologic determinants of health," Palevsky writes.

US Labs Await Guidance

Once the task force's recommendations come out later this year, "the National Kidney Foundation and American Society of Nephrology have assured us that they will do their best to mount an effort to implement the recommendations," said Neil R. Powe, MD, co-chair of the task force.

He and other task force members expect a very receptive audience.

"We won't need to sell this to any laboratories. They are very eager to hear the recommendations," says Delgado.

"The laboratory community in general, both large commercial labs and labs at academic medical centers and community hospitals, are all anxiously awaiting the recommendations," agrees W. Greg Miller, PhD, a professor of pathology at Virginia Commonwealth University, Richmond, Virginia, and a task force member. "The lab community is prepared to change. They just need guidance on what makes the most sense to do."

Regardless of this willingness, "it will probably take a couple of years for full implementation of the recommendations, for a variety of technical reasons," Miller said.

Delgado, Powe, Feldman, Briggs, and Palevsky have disclosed no relevant financial relationships. Baweja has an employment relationship with Premier, Inc. St. Peter receives honoraria from Integritas Group and OptumLabs. Miller is a consultant to Baebies.

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