Changes to eGFR Calculation and What that Means for People Living with Kidney Disease
September 23, 2021, 12:30pm EDT
Having an accurate eGFR result is essential for managing kidney disease (KD). Important decisions like diagnosing KD, determining drug dosing, when to see a kidney doctor, find out eligibility for a kidney transplant, and when to start dialysis involve eGFR test results.
Over the past year and a half, we’ve been leading the effort to develop race-free eGFR (estimated glomerular filtration rate) test results while maintaining the accuracy of the test. People living with KD, particularly those self-identifying as Black or African American, need to be aware that a new approach to calculating eGFR may have an impact on their kidney disease care.
What is eGFR?
Your glomerular filtration rate (GFR) is a way to check how well your kidneys are working and GFR can be either estimated or measured. Measured glomerular filtration rate (mGFR) is the best way, but the test is complicated and cannot be done routinely in a doctor’s office. In daily practice, most doctors rely on a mathematical calculation to estimate a person’s GFR instead of directly measuring it. And this is the reason laboratories report estimated GFR or eGFR.
Until now, the two most often used estimating equations for eGFR are the CKD MDRD (Modification of Diet in Renal Disease) and the CKD EPI (Chronic Kidney Disease Epidemiology Collaboration) equations. Using these math equations, eGFR is calculated from the amount of creatinine that is found in the blood.
Creatinine is a waste product that comes from the normal wear and tear on your body’s muscles and from the foods you eat. Everyone has creatinine in their bloodstream. However, creatinine levels can differ between people. The reason for this difference is not only due to kidney diseases – it can also be affected by other factors, such as age, sex, and body weight.
Why is the eGFR calculation being changed?
Using calculations to make accurate estimations is common in the medical field. It’s a reliable, non-invasive way to identify certain illnesses and have a warning about potential risks. For example, another kind of calculation uses factors such as a mother’s age, weight, previous pregnancy history, and alcohol and drug use to estimate the risks associated with pregnancy and giving birth.
In the past some medical calculations, like the Chronic Kidney Disease Modification of Diet in Renal Disease (CKD MDRD) and the 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation, included race in their estimates. Just because you have the same skin color as someone else doesn't mean everything else about your body is the same. Using race in the eGFR equations is no longer an acceptable way to estimate GFR.
In July 2020, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) formed the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Diseases. In April 2021, the Task Force published an interim report called Special Article: Reassessing the Inclusion of Race in Diagnosing Kidney Diseases: An Interim Report from the NKF-ASN Task Force in the Journal of the American Society of Nephrology (JASN) and the American Journal of Kidney Diseases (AJKD). The interim report provided a review of the many challenges that exist in identifying, finding, and promoting alternative methods for diagnosing kidney diseases.
On September 24, the Task Force’s Final Report recommended the use of the new eGFR 2021 CKD EPI creatinine equation that estimates kidney function without using race. The Task Force also recommended increased use of cystatin C combined with creatinine for a reliable way to check kidney function.
The final report was drafted with a lot of input from hundreds of people, including patients and their family members, medical students, health professionals, and scientists. After much work, the Task Force agreed to use an eGFR calculation that does not include race in the estimate. This new eGFR calculation will make sure that laboratories, doctors, patients, and public health officials can make better and more informed decisions, which will lead to greater health equity and more personalized care for patients with kidney diseases.
What can you do now?
It’s expected that it will take some time for labs, hospital systems, physician practices, and academic institutions to incorporate the new calculations into their results for doctors and patients. While these changes are taking place, we, at the NKF, are taking steps to quickly update our patient and healthcare professional resources, including our eGFR calculator, which can be used to calculate non-race-based eGFR until the new calculation becomes the standard.
Access the GFR calculator here. To use the calculator, you will need the serum creatinine value from your latest laboratory tests. If the eGFR calculator provides you with a number that is different from your latest laboratory tests, we suggest that you contact your doctor to see how this change will impact care for your kidney disease.