For the past few years, experts have criticized — and defended — the use of race in calculating an important number for people with kidney disease: the estimated glomerular filtration rate (eGFR). As a Black woman who has lived with kidney disease for decades, I learned the hard way that race should not be part of this equation.
Kidney disease usually develops over a number of years, and eGFR is a valuable way to monitor its trajectory. Although the maximum eGFR value can be greater than 100, it’s easy to think of it as akin to a percentage, representing a person’s kidney function compared to “normal.” The higher the eGFR, the better the kidneys are functioning.
Doctors in a variety of medical specialties use the eGFR to quickly identify people with reduced kidney function, which is important for medical decision-making.
Calculators consider the level of serum creatinine, a natural breakdown product of muscle tissue, in the blood as well as age, gender, and other criteria to determine a patient’s number. Race became part of the calculation in 1999. With all other variables being equal, a Black person’s eGFR would be higher than a non-Black person’s by about 16%.
At the time, studies showed that Black people tended to have more creatinine in their blood, allegedly because they are more muscular (a notion that has since been discredited). That belief led policymakers to advocate using a different eGFR formula for Black people that de-emphasizes creatinine and more accurately represents their “real” kidney function.
I believe that the proponents of the race-enhanced formula for eGFR genuinely intended it to be helpful to Black people with kidney disease. But it likely harmed more than it helped.
For most of my life, I have self-identified as a Black person. So I was more than a little surprised in 2016 when a DNA analysis from Ancestry.com said I had only 48% African ancestry. Technically, then, using the non-Black eGFR would have been more appropriate for me.
More to the point: Identifying as not Black would have helped me get on the kidney transplant list sooner.
To explain: For a non-Black person with a creatinine level of 1.40, which is on the high side, the eGFR formula calculates their kidney function as 39% of normal. This puts them in Stage 3B of chronic kidney disease, which is moderately bad. But a Black person with that same creatinine level would have an eGFR of 45%, putting them in the less-dire Stage 3A. In this scenario, the non-Black individual is closer to qualifying for a kidney transplant than the Black individual, even though they have the same creatinine levels.
It turns out that the use of a race-based measure of eGFR means it would take about two extra years for a Black individual’s kidney function to decline to a point at which they can be evaluated for a kidney transplant.
Had I not been a Black person, my eGFR would have been low enough for me get evaluated for a transplant earlier than I did. Instead I had an unplanned “crash into dialysis” before my transplant workup was completed. Although I ultimately received a kidney transplant in 2010, the data show that people who receive transplants without going on dialysis have better long-term outcomes.
In 2018, as part of my work leading patient engagement at the University of Washington’s Kidney Research Institute, I was trying to attract a more diverse population to join the Community Advisory Boards for the Kidney Precision Medicine Project research study. That’s when I came across this comparison of kidney disease stages by race/ethnicity in a report by Susanne B. Nicholas, Kamyar Kalantar-Zadeh, and Keith C. Norris:
It shows that while early-stage chronic kidney disease is similar across racial and ethnic groups, Black people are almost four times more likely than white people to develop end-stage kidney disease (Stages 4-5), which requires regular dialysis or a kidney transplant.
One explanation for this is that the racially tilted eGFR has caused thousands of Black people with kidney problems to wait longer to be recognized as being in bad-enough shape to get on the transplant list. And make no mistake: Those years waiting can significantly affect one’s trajectory for recovery.
Based on the race-based eGFR calculations used after 1999, Black people and their doctors might have believed their kidneys were working better than they really were, and so might’ve made decisions about medications, diets, and lifestyle that could have worsened kidney damage or created other medical risks.
In July 2020, the National Kidney Foundation and the American Society of Nephrology assembled a task force to evaluate the use of race in kidney testing. This September, it recommended that the racial variable be removed from the eGFR formula. I had the honor to be one of two patients on that task force.
Race is a social construct, not a biological one. The National Institute of Health’s Human Genome Project has demonstrated that there are no biological differences between races. Armed with this evidence and the new eGFR recommendation, I expect doctors to ensure that their Black patients with potential kidney disease get true readings of their kidneys’ health and the same level of care and consideration that non-Black patients have received since 1999.
We now have data that give new insights about kidney disease, and new ways of calculating kidney function are under investigation.
As poet Maya Angelou said, “I did then what I knew how to do. Now that I know better, I do better.”
Glenda V. Roberts works at the University of Washington’s Kidney Research Institute; Center for Dialysis Innovation; and the Justice, Equity, Diversity, and Inclusion Center for Transformative Research.
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