Race Coefficient Alters Kidney Disease Stage in Many Black Patients

Mitchel L. Zoler, PhD

April 07, 2021

The race coefficient routinely used in US practice for more than two decades to upwardly adjust the estimated glomerular filtration rate (eGFR) of African American and Black patients unequivocally places many at a higher level of renal function than they would have without the adjustment.

What remains unclear, however, is whether this affects the medical care they receive and their ultimate clinical outcomes.

The latest evidence of the power wielded by the race coefficient when calculating eGFR for people who self-identify as Black comes in a study of 786,712 Black US veterans with any inpatient or outpatient visit to a VA health system facility in 2019.

Assessment of each of these veterans, as well as more than 3 million veterans from other racial groups also seen in 2019, showed that not applying the race coefficient reclassified 36% of Black veterans into a worse stage of chronic kidney disease (CKD) compared with the CKD category their eGFR placed them in with the race coefficient applied, Yun Han, PhD, and associates reported in a poster presented at the 2021 Spring Clinical Meetings (SCM21) of the National Kidney Foundation (NKF).

As an example of how this could influence diagnosis and treatment, the analysis more specifically showed that among Black veterans with an eGFR calculated as 60-89 mL/min/1.73m2 when using the race coefficient, 24% were reclassified as having stage 3 CKD with an eGFR of 45-59 mL/min/1.73m2 when the race coefficient wasn't used.

(The coefficient in the eGFR formula most often used today, the Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] equation, inflates eGFR by 15.9% compared with what it would be without adjustment, and applies to people who self-identify as Black.)

Data "Seem to Align"

The scope of effect in this newest study confirms earlier reports from similar analyses.

A 2020 report detailed that the same exercise applied to a single US health system population of about 57,000 patients, including 2225 African Americans, documented a 33% rate of reclassification overall when the race coefficient wasn't used.

The new data reported at SCM21 "seem to align in terms of the reclassification statistics," commented Malika L. Mendu, MD, a nephrologist and executive medical director of Clinical Operations at Brigham and Women's Hospital in Boston, Massachusetts, and a coauthor of the 2020 report.

Another pair of similar analyses that used two additional US populations, published in early 2021, also showed that dropping the race coefficient reclassified significant numbers of Black individuals.

No Obvious Disparities in Care?

But the new analysis also showed no "obvious disparities in care" as a result of applying the race coefficient, said Han, a nephrology researcher at the University of Michigan in Ann Arbor, and coauthors in their SCM21 poster.

The findings leave uncertainty as to "whether removal of the Black race coefficient would help improve clinical outcomes for Black US veterans," they state.

Their uncertainty stems from the pattern of three markers of care they examined to gauge the quality of medical management for CKD that the veterans received: the incidence of nephrology consults, measurement of albuminuria, and treatment with an ACE inhibitor or ARB, two drug classes that are a cornerstone of CKD treatment.

Overall, and regardless of whether or not the race coefficient was applied, a greater proportion of Black veterans received each of these three markers of care than their White counterparts, said Han and colleagues.

However, Mendu commented, "I'm not sure the questions were asked in a way to get to whether there are disparities in care delivery."

The 2020 report she coauthored concluded that "use of racial correction in eGFR can potentially impact care for African American patients with advanced CKD," a hypothesis that remains valid, she said in an interview.

In 2020, the NKF and American Society of Nephrology formed a task force to make recommendations about continued use of a race coefficient when calculating eGFR.

A statement from the NKF last month said an interim report from the task force would release within a few weeks.

SCM21: Abstract 242. Presented April 6, 2021.

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