Abandoning a Race-biased Tool for Kidney Diagnosis

On August 16, Yale New Haven Health System (YNHHS) stopped using a common method for measuring its patients’ kidney health, one that assessed Black patients differently from white patients. Glomerular Filtration Rate has been an indicator of kidney health for decades. The estimated GFR (eGFR) is a standard diagnostic test performed by taking a blood sample and plugging patient characteristics into an equation. The key word is “estimate.” The equation is inherently imprecise.

“The eGFR tool was validated using a P30 model. This means that at any given eGFR calculated value a +/- 30% range exists where the actual measured GFR (mGFR) of the patient is,” says Louis Hart, MD, assistant professor of pediatrics (hospital medicine) at Yale School of Medicine and medical director in the Office of Health Equity at YNHHS. A normal rate is more than 60 ml/min/1.73 m2. “For example, your eGFR might say 60, but your actual measured GFR (mGFR) might be 60, 42, or even 78. It’s far from perfect.”

Hart explains that eGFR is a crude estimate in the acute setting and is much better at measuring the progression of kidney disease over the course of several months and years. “It’s not a tool to be used once or twice and to make a snap judgment," he says. "But that’s how we were using it. It makes no sense to try and create artificial racial precision in such an inherently imprecise estimate tool. It’s like we think we’ve built a GPS system and we’re going to tell you the street address you’re on, when in reality we have a compass that can barely tell you what country you’re in.”

The equation was conceived in a 1999 Annals of Internal Medicine paper. By taking into account age, height, gender, weight, creatinine, and race, the equation could more easily estimate glomerular filtration rate than ever before.

Researchers found patients observed to be Black—their identity was not always self-reported—showed different rates from non-Black patients. They saw these differences not as unjust racial health care disparities, but rather as fundamental biological differences between Black and non-Black patients’ bodies. Providing no evidence for how this could be biologically plausible, researchers hypothesized it was because Black patients have more muscle mass than white patients and added a race modifier to their equation to make this disparity in their dataset better fit their new mathematical model.

In the following years, this equation became widely accepted and used throughout medicine in the United States. It was adopted by Yale New Haven Hospital in 2003.

“This equation increases our estimate of Black patients’ kidney function by 21% relative to non-Black patients, regardless of other factors,” says Hart. “We use an equation that artificially makes their kidneys look healthier and thus might delay their qualification for public health insurance for dialysis, or referral to a nephrologist, or to become eligible to list for organ transplantation.” Hart says it is sickening to see the impact of this racialized equation and how it denies access to the very same patients who are most likely to need comprehensive kidney care. In the United States, African Americans are four times more likely to develop kidney failure than white patients, yet this racially biased eGFR equation makes Black patients’ kidneys look “healthier” for longer.

Jennifer Tsai, MD, MEd, a fourth-year emergency medicine resident at Yale, led a recent study published in eClinicalMedicine to estimate what impact removing the race modifier would have on Black Americans. According to the findings, 3.3 million Black Americans would cross the threshold for diagnosis of chronic kidney disease stage 3, 300,000 more would qualify for beneficial nephrologist referral, and 31,000 more would become eligible for transplant evaluation and waitlist inclusion.

“When you imagine 300,000 Black people across the United States possibly being able to access or not access a kidney transplant based on this antiquated race correction that most scholars agree is defunct and harmful, that puts into perspective how important it is to change,” she says.

Medical students were at the forefront of change. Inspired by Naomi Nkinsi’s leadership at the University of Washington School of Medicine in eliminating the race modifier at her own institution in 2020, students and residents at Yale began to band together.

In October 2020, the movement to change the eGFR equation gained more momentum at Yale as medical students mounted increasing resistance to race-based medicine. That same month, Jessica Cerdeña, PhD, now an MD candidate, and Tsai published a paper in the Lancet on race-conscious medicine, drawing further attention to the issue. After noticing Yale’s caution on the subject, Cerdeña and many others urged the nation’s leading kidney organizations—the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN)—to make a change. Two months prior, NKF and ASN had formed a joint task force to reassess the race modifier.

“A lot of the early work was done by trainees,” says Tsai. “But to have somebody who is in a position of power who is cognizant of these issues and wants to change them is a totally different ballgame from a group of medical students trying to pick away at system level issues.”

In September 2021, the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Diseases released a statement recommending adoption of the eGFR equation without a race variable. A paper published in the New England Journal of Medicine two months later proposed new equations. The following April, a Clinical Chemistry paper provided practical guidance for laboratory medicine, putting in specific parameters for programming the eGFR equation. However, an error was found with an equation and an errata notice was issued, leading labs to be wary of rushing toward implementation.

Throughout this time, Cerdeña kept in close contact with those involved, continuing to prompt Yale to act. After careful consideration of the new research and the pioneering efforts of students, residents, and junior faculty, YNHHS implemented the new equation across its hospital system on Aug. 16, 2022.

“I don’t want that success to undermine how much work still has to be done,” says Tsai. “This is one level of implementation, but on a larger scale, health care providers are still making decisions using race corrections—not only in kidney care but also across medicine.”

“This is just a drop in the bucket,” says Cerdeña. “It won’t eliminate disease disparities, but it’s a step in the right direction.” Cerdeña would like to see policy changes that influence toxic environmental exposures, experiences of stress, and racialization that arises from policing, mass incarceration, and ongoing economic oppression.

“There are studies that can be done,” she says. “We have the population health data; we have an inventory of different policies that have been tried at the county, state, and federal levels where we can see the outcomes that can inform interventions. It’s not as simple as changing an equation, but that’s where I think the money needs to go.”

Hart recommends changing our perspective on medicine in America. He points out that the U.S. is one of the few countries that consistently use racialized clinical decision support tools, like eGFR, FRAX, STONE, VBAC, and many more. He says we need to acknowledge medicine’s sobering past of racially separate and unequal care in our country with honesty, humility, and the determination to say that we can and must do and be better in the future.

“A lot of things we are holding as pillars of pedagogy,” Hart says, “are vestigial and were penned and designed by people who are a far cry from the needs of modern medicine today. Unless we start to think more intentionally about why we do the things we do and why things are the way they are, we are doomed to be haunted by the structured consequences of our past unjust and biased decisions.”

“It’s a process that happens commonly throughout medicine,” says Tsai. “There are all kinds of critical algorithms and diagnostic tools that take race into account, explicitly or implicitly.” She lists cardiovascular algorithms, hypertension drug treatment guidelines, and even how urinary tract infections or kidney stones are diagnosed in children as methodologies that are candidates for correction.

“I do think teaching and physician training are part of the issue,” she continues. “When we teach that race is biological and that it’s something that changes how your kidney works, what your blood vessels do, how your heart beats, how thick your skin is—these are all false ideas that contribute to research and practices that are disparate in terms of what you do when the patient in front of you is Black or white.”

Tsai urges health care providers to see patients as complicated humans in a context of political and economic inequality rather than reducing them to group-based characteristics. “The solution to this is not color blindness,” she says. “Race has really tremendous and far-reaching consequences in terms of how you navigate the health care system and what kind of outcomes you experience. When you really get into it and understand the controversies and why this happened, I think it is an access point for opening up so many other conversations about issues in other areas of medicine.”