Changes have been made to the eGFR (estimated glomerular filtration rate) calculation.
Previously Black race was used in the eGFR calculation along with age, sex, and body type. However, in 2021, a task force led by the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) announced recommendations to remove Black race as a factor in the eGFR calculation. While labs have made this shift to update their lab value reports, you should check with your doctor to make sure they are not using race-based equations.
Here are answers to some questions you may have about what this change may mean for you or loved ones who have kidney disease:
What is eGFR?
eGFR (estimated glomerular filtration rate) is a measure of how well your kidneys are working. The eGFR is an estimated number to tell doctors what stage of kidney disease you have. This number comes from a blood test of creatinine in your blood.
Creatinine is a waste product in your blood that comes from your muscles. Healthy kidneys take creatinine out of your blood and send it out of your body through your urine. If your kidneys are not working the way they should, creatinine will build up in your blood. Your age, sex, and body weight can affect your muscle mass and the level of creatine in your blood. Your eGFR is based on your creatine and your age, sex, and body weight.
A normal eGFR is 90 or higher, as long as you don't have any other signs of kidney damage. If your eGFR is less than 90 for three months or more, your kidneys may not be working well. Use this chart to see what your eGFR may mean.
Stage 1: eFGR ≥ 90; kidneys work as well as normal
Stage 2: eGFR 60-89; mild kidney damage
Stage 3: eGFR 45-59; mild to moderate kidney damage
Stage 4: eGFR 30-44; moderate to severe kidney damage
Stage 5: eGFR < 15; kidney failure
eGFR is a mostly reliable test for doctors to know how well your kidneys are working. However, the eGFR may not be accurate if you are younger than 18, pregnant, very overweight, an amputee or very muscular. In addition, other tests such as an ultrasound or a kidney biopsy may be ordered to confirm kidney disease and potentially to find a cause.
Visit the American Kidney Fund website to learn more about eGFR and stages of kidney disease.
Why is eGFR important?
eGFR is a key test used to diagnose kidney disease and understand how your kidneys are working. Your eGFR helps your healthcare team make the best treatment plan for you. eGFR is used to:
- Decide when to refer you to a nephrologist or kidney doctor
- Prepare if and when to begin dialysis
- See if you can qualify for a transplant. Before you can be approved for a kidney transplant, most transplant centers require your eGFR to be 20 or less.
- Make sure the right dose of medicine is being used
- See if your kidney disease is getting worse or if you have an increased risk for complications
- Check if a potential living donor has kidneys that are working well
What change was made to the eGFR calculation and why?
Here is a sample of what your lab report may currently look like.
The lab report shows two eGFR calculations, one estimate for Black/African Americans and another for non-Black/African Americans. Since the lab may not know your race the report includes both numbers.
The eGFR calculation accounts for biological factors like age, sex, and body weight. In the past, race has also been used in the calculation. This was based on research studies which found that people who identified as Black or African American can have higher levels of creatinine in their blood. It was thought that this was due to differences in muscle mass.
We now understand that race is a social concept, meaning it was created by people as a system to classify individuals rather than reflect biology. The inclusion of race in the eGFR calculation doesn't consider the ancestral diversity among Black people or individuals who self-identify as being of mixed racial background.
A task force led by the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) was formed in 2020 to look into the use of race in the GFR test. The NKF-ASN Task Force asked patients, the community and kidney disease experts, including AKF's Medical Advisory Committee, to give advice on how to reduce bias in the equations that estimate how well kidneys work. In September 2021, the NKF-ASN Task Force announced recommendations to remove Black race in the eGFR calculation.
Are there are other tests to measure my how well my kidneys are working?
Researchers are working to find other tests that could replace eGFR and provide a better way to measure how well your kidneys are working. The NKF-ASN Task Force recommended the use of another test called cystatin C. Cystatin C is also measured with a blood test. Doctors can use both tests to see how your kidneys are working to help guide your care.
Your doctor may want to do additional tests to look for signs of kidney problems. Ask your doctor about these tests to check your kidneys.
- Urine tests: When your kidneys are damaged, protein may start to leak into your urine. This can be one of the earliest signs of kidney disease. One test is the urine albumin-to-creatinine ratio or UACR test. This measures how much albumin, a type of protein, and creatinine, a waste product, are in your urine. Another test is a 24-hour urine collection. This measures the creatinine in your urine to show how your kidneys are working over a 24-hour period.
- Blood test: Your blood urea nitrogen (BUN) level is based on a blood test that measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product that your body makes after it breaks down protein.
- Kidney ultrasound: One way your doctor can look at your kidneys is by doing a kidney ultrasound. A kidney ultrasound (also called a renal ultrasound) is a safe and painless test that uses sound waves to make images of your kidneys.
- Kidney biopsy: One way your doctor can see if your kidneys are damaged is to do a kidney biopsy. A kidney biopsy is a procedure where your doctors take a very small piece of your kidneys to look at it closely under a microscope.
What does this change mean for me?
Most US-based clinical lab companies, doctor's offices, and hospitals have updated their lab reports to remove the race-based calculation. However, you should check with your healthcare team to make sure they are not using race-based equations and learn how this may impact your care. If you are curious if your eGFR calculation has changed, you can find an online calculator which has been updated to use the non-race-based eGFR calculation.
Your doctors use your eGFR to guide your care such as your medicine dose, when to prepare for and start dialysis, and when you can qualify for a transplant. If your eGFR has changed, your healthcare team may want to make changes to your treatment plan. We recommend you talk with your healthcare team to ask if your eGFR has changed and to learn how this may change your care.