Decision on Race Multiplier in CKD in Blacks 'Has Real Consequences'

Mitchel L. Zoler, PhD

October 23, 2020

Eliminating the race multiplier from calculation of the estimated glomerular filtration rate (eGFR) of more than 2000 African Americans in a Boston-based health system led to reclassification of a third to a more severe stage of chronic kidney disease (CKD).

The findings document the important clinical consequences that dropping the race multiplier can have, say Salman Ahmed, MD, MPH, of Brigham and Women's Hospital, Boston, Massachusetts, and colleagues, in their study published online October 15 in J Gen Intern Med.

Skipping the race multiplier when calculating eGFR in people who self-identified as African American also led to a 16% increase in the total number diagnosed with any stage of CKD. And it reclassified 64 patients (3%) as having an eGFR of ≤ 20 mL/min/1.73m2, which meant they had end-stage renal disease and became potential candidates for a kidney transplant.

These results "highlight the meaningful impact that continued use of the race multiplier has on classification of African American patients with CKD, their stage of CKD, and the care they receive, especially with respect to transplantation," said senior author Mallika L. Mendu, MD, a nephrologist at Brigham and Women's Hospital.

"The 33% rate of CKD reclassification is a meaningful change, and was surprising and concerning to all of us involved with the study. The magnitude of the race multiplier's impact illustrates that the decision to use or not use it has real and important consequences," she noted in an interview.

Race Multiplier an "Urgent" Issue

The study used data collected from more than 56,000 patients, 2225 of whom self-identified as African American, in a CKD registry maintained by the Partners Healthcare system run by Mass General Brigham in the Boston area.

The analyses looked at the impact of applying or not applying the race multiplier coefficient on the classification of patients by CKD severity.

The concept of systematically up-adjusting the eGFR for African Americans dates to the 1999 introduction of the Modification of Diet in Renal Disease equation, which used a multiplier of 1.212. The multiplier remained but at the reduced rate of 1.159 when the most recent eGFR equation came out in 2009, the Chronic Kidney Disease Epidemiology Collaboration formula.

The new findings "provide the necessary data on the impact of the race multiplier," and "highlight the urgency of addressing the inclusion of the race multiplier at a national level given its potential impact on a significant number of African Americans," explained  Mendu.

Routine use of the multiplier and its frequent effect of minimizing the estimated severity of CKD in African Americans has "care-delivery implications," she stressed.

In their report, the authors highlight that none of the 64 patients reclassified as having end-stage renal disease by dropping the multiplier in fact received a transplant referral.

Results Don't Support Choosing, or Losing, the Race Multiplier

These new analyses from Boston show "a magnitude of reclassification" that is "very surprising," commented Rajnish Mehrotra, MD, professor and interim head of nephrology at the University of Washington School of Medicine in Seattle.

"Their findings tell me that they have a large proportion of patients who are close to the cut-off values" for various stages of CKD.

But he also cautioned that the findings, "while interesting, do not support any proposition to use or not use the race multiplier."

His rationale is that it's already known that eGFR is, as the term says, only an estimate. It's an inherently imprecise extrapolation from serum creatinine levels, and hence, "neither of the two estimates, with or without race correction, is the gold standard," Mehrotra explained in an interview.

Mendu and most other nephrologists agree that eGFR is imprecise and always requires confirmation with more reliable metrics.

"Markers like cystatin C, which does not involve racial classification, can and should be used for all patients regardless of their race given the imprecision of eGFR," Mendu noted.

The Race Multiplier Helps Some Patients

Boosting measured eGFR with the multiplier can also have potentially positive consequences.

If not used and African American patients are routinely diagnosed with lower eGFRs this "could lead to less access to important medications" that require minimum eGFR levels, such as metformin, commented Neil F. Powe, MD, professor of medicine at the University of California, San Francisco.

He cites a recent report and editorial that highlight the risk faced by Blacks because of a contraindication set by the US Food and Drug Administration in 2016 to not give metformin when eGFR drops below 30 mL/min/1.73m2.

"It would be awful if elimination of the race coefficient set Blacks back by recreating disparities in use of this important diabetes drug," Powe said in an interview.

"We need a more comprehensive picture of the benefits and harms of elimination of the race coefficient, including the impact on patients of the loss of consistency of measurement and reporting of kidney function across institutions," added Powe, who is also chief of medicine at Zuckerberg San Francisco General Hospital.

He pointed to another finding from the Boston study that identified other problems faced by African Americans with CKD and falling renal function.

Among Black patients in the study, 156 had eGFRs ≤ 20 mL/min/1.73m2 even when the default multiplier was used, which made all 156 candidates for renal transplant, but only 19% had a transplant evaluation, referral, or were waitlisted.

"This suggests that there are far more powerful drivers of disparities for Blacks" than the race multiplier, Powe emphasized.

Seeking a National Approach by the End of 2020?

In a recent commentary, Powe calls for national guidelines that could bring an evidence-based and consistent approach to determining eGFR.

Working toward that goal, Powe serves as cochair of a task force formed in August 2020 by the National Kidney Foundation and the American Society of Nephrology, which is charged with coming up with recommendations on how to deal with the race multiplier by the end of 2020. Mendu also serves on the task force.

Earlier this year, several US health systems announced they had eliminated routine reporting of eGFR values using the race modifier or strongly discouraged its use.

This included the Mass General Brigham system in Boston, the University of Washington system in Seattle, and the Vanderbilt University Medical Center system in Nashville, as reported by Medscape Medical News.

But once the task force formed in August, "many health systems paused on further decisions until the task force makes its recommendations," Mendu explained.

"Our study makes it clear that this is an urgent issue impacting a large percentage of African American patients with CKD. The real consequence of potentially delaying transplantation referrals for African Americans needs to be addressed," she concluded.

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