How kidney testing is affected by racial bias

The glomerular filtration rate (GFR) is a blood test used to measure kidney function. It is also an important test for diagnosing kidney disease. An estimated glomerular filtration rate (eGFR) is an equation used as a primary method for identifying and managing kidney disease. The equation includes age, sex, race and bodyweight to estimate kidney function.

The practice of using race as a component of eGFR rates has garnered much discussion within the medical community. A racial multiplier is used in the eGFR equation and calculates higher values for African American patients.

In 2020, the American Society of Nephrology (ASN) and the National Kidney Foundation (NKF) created a task force to re-examine race in the eGFR calculations used to diagnose kidney disease.

Why race has been a part of the eGFR

The eGFR is calculated from the amount of creatinine in our blood, a waste product produced during normal metabolism and muscle turnover in our bodies. Creatinine levels vary among individuals and are influenced by multiple variables, including age, sex, diet and medications.

Historically, race was included in eGFR calculations based on findings from previous clinical studies demonstrating higher average creatinine levels in people identifying as African American. Muscle mass, diet and kidney elimination of creatinine were considered possible factors for these results. Muscle mass, in particular, was a curious variable because it varies so widely between individuals regardless of race.

One study about the accuracy of eGFR calculations purported that “previous studies have shown that on average, black persons have greater muscle mass than white persons.”

Another study showed that removing the race factor from a standard eGFR calculation would hypothetically result in about one-third of African American patients with chronic kidney disease being reassigned to a more severe stage of disease.

The alternative to the eGFR

eGFR calculations can play an integral role in medical decision-making, management and overall patient care. The use of race in eGFR calculations has caused controversy because race is a societal concept instead of a biological one.

Furthermore, using race in eGFR calculations does not account for the diversity within minority communities. Using race in eGFR calculations may also unjustly and forcibly assign people identifying as multiracial to a single race. In light of the flaws with eGFR, many institutions have moved to stop relying on the eGFR for analyzing kidney function and are using the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation. This equation uses creatinine, sex, and age and excludes a race variable.

I am hopeful that changes such as these will continue to improve medical care, strengthen physician-patient relationships and further dispel racial biases in the medical profession and beyond.

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