Understanding African American and non-African American eGFR laboratory results

Glomerular filtration rate (GFR) is the best way to measure how well your kidneys are working, but this test is complicated and cannot be easily done in a doctor’s office. To get around this, laboratories use mathematical equations to estimate the glomerular filtration rate instead of measuring it. This is why laboratories report estimated GFR or eGFR.

Two commonly 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 in the blood.

Creatinine is a waste product that comes from the normal wear and tear on your body’s muscles and also from the foods you eat. Everyone has creatinine in their bloodstream. However, creatinine levels can differ between people. This reason for this difference may not only be related to kidney disease – it may be affected by several other factors, such as age, sex, and body weight.

Race was originally included in eGFR calculations because clinical trials demonstrated that people who self-identify as Black/African American can have, on average, higher levels of creatinine in their blood. It was thought the reason why was due to differences in muscle mass, diet, and the way the kidneys eliminate creatinine. Since a patient’s race is not always used when laboratory tests are ordered, laboratories used different eGFR calculations for African American and non-African American and included both numbers in their lab results.

The use of race in calculating eGFR has been a subject of debate. Race is not a biological concept, but a social construct. Using race as a factor for calculating eGFR does not account for the diversity within communities of color. Also, people who self-identify as multiracial might not want to be put in a single racial bucket.

In 2020, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) formed a joint task force to review the use of race in eGFR calculations. On September 23, 2021, the Task Force announced a new race-free calculation for estimating eGFR. The National Kidney Foundation is working with the nation’s laboratories to get this new calculation into use as quickly as possible.  The NKF is also creating materials to show how this new equation may impact patient care.

Estimated GFR is one of the key tests for diagnosing kidney disease. The earlier kidney disease is detected, the better the chance of managing it or keeping your condition from getting worse. Your eGFR informs healthcare professionals about your kidney function and helps them to recommend the best treatments for you. For instance, eGFR results are used in the following ways:

• Confirming that kidney function is normal for a potential living kidney donor
• Making sure the right dose of medicine is used
• Enrollment in clinical trials that use kidney function as an inclusion or exclusion criterion
• Making sure the right type of imaging tests and dyes are used
• When to refer someone to a nephrologist or kidney doctor
• If and when to plan for dialysis
• When to start an evaluation for a kidney transplant

Although the NKF alone cannot solve all inequalities, the NKF is working to help identify, confront and reverse them. NKF advocates for making affordable healthcare more available and making sure that communities of color are not left behind. NKF’s CARES helpline is available to all people with kidney disease. NKF’s educational offerings include the impact of kidney disease on diverse communities, and the reasons why communities of color have been disproportionately affected by COVID-19. NKF is committed to continuing its work to address inequalities in kidney health.