Health Equity

November 17, 2022

VUMC adopts updated kidney function equation to better guide patient care decisions

In December Vanderbilt University Medical Center will again update the equation used for estimating kidney function with the goals of improving health equity and better guiding patient care decisions.

In July 2020, Vanderbilt University Medical Center was one of the first institutions in the United States to remove race from an equation used to estimate kidney function through the calculation of an estimated glomerular filtration rate (eGFR), and in December the Medical Center will again update the equation used for calculating eGFR with the goals of improving health equity and better guiding patient care decisions.

“VUMC began using the MDRD [(Modification of Diet in Renal Disease] calculation without a race co-efficient to assess kidney function in 2020,” said Joe Wiencek, PhD, assistant professor of Pathology, Microbiology and Immunology and VUMC Core Laboratory service line medical director. “We will begin using the CKD-EPI 2021 equation, which also does not include a race co-efficient, in December. This equation is expected to be more accurate than the MDRD equation for all adult patients, ages 18 and older, particularly for individuals with higher GFR levels.”

In September 2021, a joint task force of the National Kidney Foundation and the American Society of Nephrology (NKF-ASN) recommended that all laboratories and healthcare systems nationwide adopt the new Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2021 equation to move toward a uniform method of diagnosing and monitoring kidney disease in adults that is independent of race.

Historically, in equations used for calculating eGFR, Black individuals have been assigned higher values than non-Black individuals. In 2020, Vanderbilt students, residents and faculty pointed out that a social construct such as race should not be used in an equation that is estimating a biologic process. This led to the Medical Center removing race as a variable in the calculation of eGFR.

Eliminating the race-based adjustment has several important clinical implications: it allows for more timely diagnosis, appropriate referral for treatment of early kidney disease, better disease management, earlier transplant listing, and more appropriate medication decisions for Black patients.

“Removing a race adjustment factor from the calculation of renal disease severity is an important change that will help ensure more equitable access to renal transplantation,” said Seth Karp, MD, H. William Scott Jr. Professor, chair of the Section of Surgical Sciences and director of the Vanderbilt Transplant Center.

The National Kidney Foundation estimates that more than 37 million adults in the U.S. have kidney disease. Of these, it is estimated that 90% are unaware that they have kidney injury or diminished kidney function. A disproportionate number of people living with and at increased risk for developing kidney disease are from populations that routinely face health disparities and inequities in healthcare delivery, including persons of Black or African American, Hispanic or Latino, American Indian or Alaska Native, Asian American, or Native Hawaiian or Other Pacific Islander descent.

Black or African American individuals are almost four times more likely than non-Black persons to develop kidney failure, and Hispanic persons are 1.3 times more likely than non-Hispanic individuals to have kidney failure, according to the National Kidney Foundation. Risk factors for kidney disease include diabetes, high blood pressure, heart disease, obesity and a family history of kidney disease.

“The underdiagnosis of kidney disease hinders access to treatment which negatively affects health outcomes and having an accurate eGFR result is essential for managing kidney disease,” said Beatrice Concepcion, MD, associate professor of Medicine, Division of Nephrology and Hypertension and medical director of the VUMC Adult Kidney and Pancreas Transplant Program. “Use of the CKD-EPI 2021 equation without a race coefficient is expected to increase access to specialized kidney care and improve eligibility for kidney transplant waitlisting, particularly for Black individuals.”

“VUMC has already taken the lead in removing the race coefficient, and now we are leading the community to use a refined equation that allows more accurate assessment of kidney function at earlier stages of kidney disease,” said T. Alp Ikizler, MD, Catherine McLaughlin Hakim Professor, professor of Medicine and director of the Division of Nephrology and Hypertension. “This will allow recognition of individuals at risk for progressive kidney disease such as Blacks and Hispanics and allow the implementation of our multiple preventive strategies to improve their health.”

The national task force also recommended the increased, routine and timely use of the laboratory test cystatin C (combined with serum creatinine) to confirm eGFR in clinical decision-making. VUMC is also following this recommendation.

“Although the CKD-EPI 2021 creatinine equation is a reasonably accurate estimate for most individuals, using creatinine to approximate kidney function is not ideal in certain patients such as those with high or low muscle mass,” said Concepcion. “Checking a cystatin C level can provide a more accurate estimate of kidney function in these patients.”

Cystatin C is a protein that slows down the breakdown of other protein cells in the body, and kidney dysfunction leads to a higher level of cystatin C in the blood. Cystatin C-based estimates for GFR are believed to be less influenced by muscle mass or diet than creatinine-based estimates.

VUMC clinical providers have received communication from the VUMC Diagnostic Laboratory to explain the change to the CKD-EPI 2021 equation. The eGFR test using the updated equation is included in both the basic and comprehensive metabolic panels ordered by clinical staff and is part of a creatinine diagnostic order and a renal panel order. In a patient’s My Health at Vanderbilt list of test results, the test using the updated equation will appear as eGFRcr.

“The implementation of this new equation at VUMC demonstrates the importance and value of bringing together key stakeholders from the laboratory and other medical disciplines to efficiently enact evidence-based changes that will no doubt result in improved patient care,” Wiencek said.