The first sign something was wrong with Curtis Warfield came in 2005, when lab tests found protein in his urine during a routine checkup. In 2012, Warfield was diagnosed with stage 3 kidney disease. Two years later, he began dialysis.
“When you’re diagnosed, you sit there like a deer in the headlights. You don’t know what’s going on. You don’t know what’s going to happen next,” Warfield said. “You know, you have this disease.”
Warfield is a black man, 52 years old, in good health with no family history of kidney disease. As his condition worsened and he pursued treatment options, he unknowingly experienced a form of racism: a mathematical equation that accounted for his race when estimating his kidney function.
This equation, called the estimated glomerular filtration rate, or eGFR, is an important variable that helps guide the course of treatment for the approximately 37 million people with kidney disease nationwide. The eGFR equation estimates a person’s kidneys’ ability to filter blood, taking into account a person’s age, gender and levels of creatinine, a waste product naturally produced by the body that is cleared through the kidneys. But it has long involved a controversial variable: race.
If a person self-identifies as black, the equation adjusts their score, thereby increasing it. Other races are not accounted for in the equation. Therefore, black people have higher eGFR scores than people of other races. These scores, which assess kidney function, can influence physicians’ treatment recommendations. The lower the score, the more likely the patient is to start dialysis or even receive a kidney transplant.
As the disparities faced by black people with kidney disease are more widely studied, race-based eGFR is increasingly being challenged by nephrologists, prominent kidney disease organizations and, most importantly, medical students, who are asking educators about the distinction Biological basis of blacks and whites.
Since receiving a transplant in 2015, Warfield has been a voice for other kidney patients. Ethnicity was incorporated into eGFR, resulting in two new equations for estimating renal function.
The new, race-neutral formula came out last fall. In February of this year, the United Network for Organ Sharing (UNOS), a nonprofit organization that manages the U.S. organ donation and transplantation system, proposed abandoning the use of racialized eGFR in favor of a race-neutral eGFR. As a result, kidney care in the United States is at a watershed moment, transcending the equation of entrenched, institutional racism.
Experts on a National Kidney Foundation task force say removing race from kidney evaluations is a critical step toward reducing disparities in kidney disease and treatment. Black Americans are at disproportionate risk for kidney diseases such as high blood pressure, diabetes and heart disease. Although black people make up less than 14% of the U.S. population, they account for 35% of dialysis patients, according to the National Kidney Foundation.
“Black people are less likely to be referred for a transplant even when they are on dialysis. When referred, they are much less likely to be listed. Once listed, they are much less likely to receive a kidney transplant . There are differences every step of the way,” said Rajnish Mehrotra, MD, chief of nephrology at Harborview Medical Center and professor of nephrology and medicine at the University of Washington.
Mehrotra said these differences underlie an increasing number of questions medical students have been asking over the past few years, particularly when it comes to equations students are learning to assess kidney function.
“They were told in class that there’s an equation where if you’re black, it reports a different number if you’re not black. They question that premise, like, ‘What’s the evidence that there’s a difference?'” Meher Rotella said. “So the deeper we looked for evidence supporting differential coverage by race, we concluded that the evidence supporting this was simply not strong.”
Mehrotra’s school, Washington University School of Medicine, became one of the first institutions to remove the race variable from the eGFR equation as early as June 2020.
But there is a broader movement underway involving kidney specialists’ top professional societies, the National Kidney Foundation and the American Society of Nephrology, as well as patient advocates (including Warfield), clinicians, scientists and laboratory technicians, The goal of all meetings is to phase out racialized eGFR in favor of a race-neutral approach.
In June 2021, a year after Washington Medical Center abandoned racialized eGFR, a task force composed of these organizations issued an interim report questioning the use of race as a factor in diagnosing kidney care.
The report states that the racial variable in eGFR is based on research in the 1990s. The Modification of Diet in Renal Disease (MDRD) study, published in 1999, was one of the first studies to include black people—earlier equations for estimating kidney function were based entirely on information from white male patients—and found higher serum creatinine levels, according to the task force. Black adults died at higher rates than white adults, the authors wrote in the report.
When the MDRD was created, adjusting math for race was seen as progress because including black people in studies was itself progress, the report said.
But there’s a troubling reason why blacks have higher creatinine levels in MDRD: Early research showed that “blacks, on average, have greater muscle mass than whites.” The three studies cited were each published in 1977 , 1978, and 1990, black and white study participants were compared on different health measures, including serum creatinine kinase and whole-body potassium concentrations. These studies all suggest that blacks need a separate reference standard, attributing differences in outcomes to differences in racial biology.
Today, these conclusions will be challenged.
“Our understanding of race has evolved over the past quarter-century,” said Paul Palevsky, MD, president of the National Kidney Foundation and a professor at the University of Pittsburgh, one of the lead organizations on the task force. “Race is not based on biology but is more of a social construct.”
In September 2021, the task force released two new equations for estimating kidney function. Neither included race as a factor. One of these is very similar to the racialized eGFR that measures creatinine. Another equation adds a second test that measures cystatin C, another chemical in the blood used as a filtering marker.
The reason these two equations are recommended is that while creatinine testing is available at nearly all laboratories across the country, cystatin C is not, resulting in higher prices and reduced access to testing. Palevsky said the process of moving lab practices to the new standards is ongoing, and he expects major labs to make changes in the coming months.
“In medicine, it typically takes about ten years from the time a clinical practice guideline or recommendation is issued to when it actually enters clinical care,” Palevsky said. “What we’re seeing in this case is the rapid implementation of a new equation.”
Palevsky and Mehrotra agreed that the new equation was slightly less accurate than the old one. But these estimates are only estimates and should be used as part of a more comprehensive clinical analysis of an individual’s health and needs.
As racial disparities in medicine continue to be studied and understood, taking race into account in health care decisions can have corrosive effects that extend beyond the individual and their diagnosis, Palevkes said. “When we teach medical students and residents, if we use race-based algorithms, we reinforce to them this concept, this false concept, that race is a biological determinant of disease,” Palevsky said. but it is not the truth.
Systemic racism impacts health outcomes for Black people in many different ways, from experiencing the chronic stress of racism to limited access to healthy foods to bias among health care providers. These problems are deep-seated and require ongoing solutions.
However, Palevsky said the new eGFR equation is a step in the right direction.
“Will it solve the problem of disparities in kidney care? I think we fool ourselves into thinking that a simple change in the equation is going to solve many, many deep-rooted problems,” Palevsky said. “Of course, simply changing the equation won’t solve the problems of inequality, many of which are rooted in historical racism.”
Only large-scale investments in the health of poor communities can meaningfully close these gaps. But nonetheless, the eGFR equation is still a meaningful step forward for black people with kidney disease. Warfield said the benefits of the new eGFR equation extend beyond the equation itself.
“It opens eyes and doors to other disparities that are going on, at least in the kidney community, and gets people talking and looking at everything that’s going on,” Warfield said. “It’s nice to know that patient voices are now at the table and Be heard, not just decided by the medical community.”
