Study explores racial disparities in healthcare outcomes

A younger sister, an elite 400-metre sprinter who has competed internationally for Great Britain, informed the author in early 2020 that a recent blood test revealed a creatinine level slightly above the normal range, a potential indicator of a kidney problem. The sister had also consulted a sports doctor who confirmed that creatinine is derived from muscle metabolism and that levels are proportional to muscle mass, listing factors that could be responsible for elevated levels, including “Afro-Caribbean race.”

The author was beginning an investigation into “race-based medicine,” the practice of adjusting medical tests based on a person’s race or ethnicity, a concept initially learned about in a 2015 Ted Talk by US academic and author Dorothy Roberts. A US-based study in 2021 highlighted issues with adjusting routine kidney test results based on race. Typically, doctors assess kidney health by measuring creatinine levels and calculating the estimated glomerular filtration rate (eGFR), which indicates how well the kidneys filter waste. Lower eGFR values can signal kidney problems, and untreated kidney dysfunction can lead to toxic waste buildup.

The study revealed that eGFR equations globally often included a multiplier applied to increase eGFR values for Black people. This adjustment resulted in a higher eGFR for Black patients compared to non-Black patients with the same blood test results. The study also suggested that removing the race adjustment could improve the accuracy of kidney failure risk prediction among Black adults.

The author’s sister had a similar test in the UK the previous year, which included the phrase: “If Black multiply result by 1.21.”

The author investigated the origin of the Black race adjustment in eGFR, the prevalence of similar practices internationally, and the potential for harm to Black patients. Kidney doctors Vanessa Grubbs and Nwamaka Eneanya in the US have long called for the elimination of race-based medical practices, highlighting the lack of evidence to support them.

A medical student, Naomi Nkinsi at the University of Washington, explained that two commonly used eGFR equations included adjustments for Black race. The first, MDRD, developed in the 1990s, incorporated Black race as a factor. This adjustment stemmed from a 1999 US study that found higher creatinine levels among African American participants compared to White participants, leading to the assumption of greater muscle mass. However, the MDRD study included only a small population, and evidence supporting the assumption of greater muscle mass in Black people is limited.

An updated eGFR equation, CKD-EPI, developed in 2009, also carried through the race adjustment from the MDRD study. Preliminary research from a UK study led by kidney doctors Rouvick Gama and Kate Bramham at King’s College London showed that eGFR equations with race adjustments overestimated GFR in Black patients. Gama noted that this overestimation could lead to delayed diagnosis and treatment of chronic kidney disease, contributing to the fact that people of Black ethnicity are three- to five-fold more likely to end up with end-stage kidney disease.

In the US, Black or African American people are more than three times as likely as White people to develop kidney failure. Nkinsi emphasized that the race adjustment meant that Black patients needed to be sicker to be identified as having kidney problems, potentially delaying access to specialized care and transplant opportunities.

The Centers for Disease Control and Prevention (CDC) in the US referred the author to Kidney Disease Improving Global Outcomes (KDIGO), a global organization that develops clinical practice guidelines. KDIGO’s guidelines recommended adjusting eGFR for people of African-Caribbean or African family origin.

Inspired by Nkinsi’s efforts, the author contacted the UK’s National Institute for Health and Care Excellence (Nice), which initially maintained the race adjustment in its guidelines. However, after the author’s article was published and Gama and Bramham’s research was shared, Nice removed the race adjustment from its recommendations.

The National Kidney Foundation and the American Society of Nephrology also established a consensus against the use of race adjustment in kidney function equations in the US, and KDIGO subsequently updated its guidelines to remove the recommendation.