eGFR stands for estimated glomerular filtration rate. This estimate of kidney function can help doctors diagnose and treat kidney disease. The formulas currently used for eGFR modify results based on whether or not you are Black.

Kidney disease is when your kidneys no longer effectively filter waste and excess fluids from your blood. The National Institute of Diabetes and Digestive and Kidney Diseases estimates that over 37 million people in the United States are currently living with kidney disease.

The Black community is disproportionately affected by kidney disease. In fact, Black people make up an estimated 35 percent of people with kidney failure in the United States.

Adjusting eGFR based on race can have serious health and social implications. Keep reading as we break down the use of race in determining eGFR, its impact, and how this is changing.

eGFR is an estimation of how well your kidneys are working to filter your blood. Lower scores are associated with lower levels of kidney function.

The result of a blood test for creatinine, a waste product made by your muscles, is used to calculate eGFR. Kidneys that are functioning well filter creatinine from the blood and into the urine, where it’s eventually expelled from the body.

However, kidneys that aren’t functioning well don’t filter creatinine into the urine efficiently. Because of this, creatinine levels in the blood are higher.

The formula to calculate eGFR uses the results of a serum creatinine test, but it also uses additional factors like your age, sex assigned at birth, and body size. Doctors have also historically used race as a part of this formula as well. More on that soon.

The results of an eGFR calculation tell your doctor about the stage of your kidney disease. This can help them determine what types of treatment may be effective at slowing or halting its progression.

As mentioned above, eGFR is calculated using a formula. Today, two of the most commonly used ones are:

  • the Modification of Diet in Renal Disease (MDRD) formula, developed in 1999
  • the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula, developed in 2009

To determine eGFR, both of these formulas incorporate a variety of factors, including your:

  • results from a serum creatinine test
  • age
  • sex assigned at birth
  • body size
  • race, specifically whether or not you are Black

So, why exactly is race used to help determine eGFR? The answer to this question involves research observations that are now decades old.

In 1998, before the development of common eGFR formulas, results from the National Health and Nutrition Examination Survey found that, on average, Black people had higher serum creatinine levels than people of other races.

Research from 1999 also observed that serum creatinine levels in Black participants were higher than in white participants with the same calculated GFR value. This led to the idea that factors influencing serum creatinine may differ between racial groups.

When the MDRD equation was developed in 1999, it used race as a modifier to help better predict GFR in Black individuals. This is an extra number value of about 1.2, called a coefficient. The eGFR is multiplied by the coefficient to get the final result.

However, more recent research from 2008 found that high creatinine levels in Black individuals are likely due to factors besides muscle mass and nutrition status, as originally thought.

In 2009, the development of the CKD-EPI equation also used race as a modifier. The coefficient for this equation is slightly lower than the one used for the MDRD equation.

Since the cause of these differences is unclear, further research will be needed to understand them. As such, measures that are more clearly understood would serve as better indicators of kidney function.

Including race in eGFR calculations has caused much debate. The rationale for its use is based on differences in serum creatinine levels that experts still don’t fully understand.

Including race in the calculation of eGFR can also have serious potential health effects for Black people.

A race modifier is used to determine eGFR only in Black people. Because of this, if you’re Black, your calculated eGFR will automatically be higher than someone of another race with the same serum creatinine, age, and body size.

As such, using race to determine eGFR can result in overestimating your kidney function. This can result in a missed or late diagnosis of kidney disease. A missed or late diagnosis is potentially dangerous, as kidney disease disproportionately affects Black people.

According to the National Kidney Foundation, Black people are 3 to 4 times more likely than white people to develop kidney failure. While the exact reason for this is unknown, it may be due to a variety of factors including:

  • diabetes
  • high blood pressure, or hypertension
  • a family history of kidney disease or associated conditions
  • unequal access to healthcare

There are additional issues with race-based eGFR calculations as well. For example, using race for eGFR:

  • implies that race is a biological construct, when it’s actually a social construct
  • automatically applies an across-the-board adjustment that doesn’t account for the great amount of diversity that’s found within the Black community
  • places people who identify as multiracial into a single racial category that’s not reflective of their identity

Removing race from eGFR

The outlook for kidney disease improves with early detection. So, it’s possible that removing the race modifier from eGFR calculations will help doctors identify and treat kidney disease more quickly and effectively in Black individuals.

In fact, a 2020 study found that when race wasn’t considered in eGFR, 743 out of 2,225 Black people with kidney disease (33.4 percent) would be reclassified to a more severe disease category. This can have a significant impact on the type of care a person with kidney disease receives.

Removing race from eGFR determination isn’t without potential drawbacks, however. It’s also possible that removing the race modifier may lead to overdiagnosis of kidney disease in some people. This could lead to:

  • unnecessary treatments
  • additional medical bills
  • inability to take some medications that are hard on the kidneys, such as some diabetes drugs

One strategy to determine eGFR in a way that isn’t influenced by race would be to use a biomarker other than creatinine in the calculation. Researchers are currently working on alternative formulas that don’t rely on creatinine.

Some institutions have already stopped using race in the calculation of eGFR. Some examples include the University of Washington Medical Center and the University of Vanderbilt Medical Center. Further change is also on the way.

In 2020, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) put together a task force to review the use of race as a part of calculating eGFR. And in 2021, the task force proposed a new calculation to estimate GFR.

The new eGFR 2021 CKD EPI creatinine equation estimates kidney function without race as a factor. Instead, it uses a blood test to measure creatinine in order to estimate GFR. It also uses a urine test for albumin, a protein created by the liver, to calculate urine to creatinine ratio.

The task force also recommended testing cystatin C levels and combining them with serum, or blood, creatinine to confirm the GFR score.

The NKF and ASN are urging all laboratories and healthcare systems across the country to adopt this new measure as soon as possible. They hope a move toward a more consistent test to diagnose and stage kidney diseases — independent of race — will help people get the care they need.

If you have any risk factors for kidney disease, speak with a healthcare professional about whether these tests might be helpful for you.

eGFR is used to estimate kidney function and help diagnose and treat kidney disease.

Currently, determining eGFR uses a race modifier based on whether or not you are African American. This modifier was based on research observations about serum creatinine levels that are now decades old.

Using race to help calculate eGFR can have harmful consequences. This is because it can lead to an overestimation of kidney function in Black people, potentially delaying vital diagnosis and treatment.

However, change is coming. An NKF and ASN task force has recently released a final recommendation for a way to determine eGFR that’s not based on race. They hope that this will be an important first step in improving equity in the diagnosis and treatment of kidney disease.