For those with end-stage kidney disease (ESKD), a transplant is the only way to avoid dialysis. In the United States, kidney transplant eligibility is determined from a single number known at the estimated glomerular filtration rate (eGFR). 

While eGFR indicates the health of a person’s kidneys, it is determined differently for Black individuals. Learn more about eGFR and how it may negatively affect Black patients’ opportunity to receive a transplant.* 

What Is Estimated Glomerular Filtration Rate (eGFR)?

Used often by nephrologists (“kidney doctors”), eGFR is a calculation to measure a patient’s kidney function. The equation consists of serum creatinine (a specific waste product in the blood), age, sex, and race. While eGFR is an estimate and may not be completely accurate, it saves doctors time and less hassle of directly measuring the filtration rate. 

In the United States, there are only two race variables for the eGFR equations: “Black” and “non-Black.” Kidney experts everywhere are starting to see this as a problem. 

Why Is Race Part of the Estimating Equation?

In the 1990s, researchers developed the eGFR equation and determined certain characteristics, such as gender, age and race, were factors in kidney function. 

​​“And they found that Black participants in that study, compared to White participants at the same measured GFR or kidney function, had higher levels of serum creatinine,” said Dr. Amaka Eneanya.

Since researchers knew a more muscular body leads to increased creatinine levels, they theorized that Black people were more muscular and would naturally have higher creatinine levels than their White counterparts. While this theory has been debunked, the researchers created the eGFR equation that gave Black patients better eGFR results than other populations. 

How Is the eGFR Equation Creating Inequity?

There are many critics of the eGFR equation for Black individuals as it is leading to inequity in qualifying for transplant. 

“We’re assigning Black patients to have better kidney function, so there’s a delay in terms of when they can actually get referred to be evaluated for a kidney transplant,” Eneanya said.

Moreover, the studies that led to the eGFR creations had faults. Including the use of the debunked theory that Black individuals were more muscular, the studies also lacked ethnic diversity. 

“There weren’t a high number, for instance, of Asian participants or Latinx and Hispanic participants,” Eneanya said. “And so they kind of lumped all of those participants together with the white participants. So it really became a Black versus non-Black investigation for these studies.”

What Can Be Done to Fix the Problem?

It is clear among kidney experts that eGFR equations are a problem causing inequity for Black patients. Dr. Andrew Levy, an expert who participated in the original studies in the 1990s, has realized that too much emphasis was put on the race variable.

Levy believes a new blood biomarker may be effective in estimating GFR and replacing the race factor. 

“Cystatin C is a protein that’s made by all cells,” said Levey. “We don’t understand as much what governs how much it’s made, but we do find that the level of cystatin in the blood is related a little bit to age and a little bit to sex-less related than creatinine-but it doesn’t appear to be related to race at all.” Dr. Levy and other experts believe Cystatin C is slightly better than creatinine as it is less affected by what a person eats or how old someone is. 

While addressing the eGFR equation is just one inequity Black individuals face in kidney care, it is hopefully a start to real action taking place in the healthcare racial divide. 

*Ahébée, S. (2021, July 30). How a clinical tool meant to predict kidney function could be hurting Black patients. WHYY. https://whyy.org/segments/how-the-egfr-tool-could-be-hurting-black-patients/