Is systemic racism in medicine putting Black people’s lives at risk?

My younger sister is an elite 400-metre sprinter who has competed internationally for Great Britain. In early 2020, she told me about some blood test results she had recently received – her creatinine level was a bit higher than normal – a potential indicator of a kidney problem. That wasn’t particularly surprising; creatinine is a waste product produced by muscles and so athletes, who tend to be more muscular on average, commonly have higher-than-average levels of the compound in their blood without this being associated with kidney problems. She had also shared her blood test results with a sports doctor. He confirmed that creatinine is derived from muscle metabolism and that levels are proportional to muscle mass. He also gave a list of factors that he said could be responsible for raised creatinine levels. One of those listed was “Afro-Caribbean race”. “Could my race be affecting my creatinine level?” my sister asked me.

I was about to stumble on an answer to my sister’s question. I was at the beginning of an investigation into what I now refer to as “race-based medicine” – the practice of adjusting medical tests based on a person’s race or ethnicity. I had first learned about it in a 2015 Ted Talk by US academic and author Dorothy Roberts, but I had assumed it would be a thing of the past by now. I soon discovered that race-based medicine is alive and well.

My first clue came in 2021 via a US-based study that highlighted issues associated with a widespread practice of adjusting routine kidney test results based on a person’s race. In brief: if a doctor wants to assess a patient’s kidney health, they will usually start with a test that measures the level of the waste product creatinine in their blood – the same blood test my sister had. The medic conducting the analysis will then plug that blood test result into an equation that calculates the patient’s estimated glomerular filtration rate (eGFR) – the rate at which the kidneys filter waste – an important indicator of how well the kidneys are functioning. Broadly speaking, more creatinine in the blood suggests a lower filtration rate by the kidneys. If a patient’s eGFR is too low, that could be a sign of a kidney problem. In the worst cases, when the kidneys aren’t functioning correctly, toxic waste products build up in the body – a condition that is fatal without treatment such as dialysis or a kidney transplant.

What I gleaned from the study was that the most widely used eGFR equations globally included a specific multiplier that was applied to increase eGFR values for Black people. After the application of this adjustment, a Black patient would end up with a higher eGFR compared with a non-Black patient with the same blood test results. Not only that, but the study showed that the removal of the race adjustment could improve the accuracy of kidney failure risk prediction among Black adults.

I remembered that my sister had had a similar test done in the UK the previous year. She showed me some photographs of it. Printed in brackets above her results was the phrase: “If Black multiply result by 1.21.”

I had so many questions. Where did the Black race adjustment in eGFR come from? How many other countries have similar medical guidance? If race is a social construct, why is it being treated as a biological one? Are there similar race adjustments still being used in other areas of medicine? Might this be causing harm to Black patients? What is the medical definition of “Black” anyway?

The list went on. Fortunately, I was by no means the first person to raise any of these questions. In addition to Dorothy Roberts, kidney doctors such as Vanessa Grubbs and Nwamaka Eneanya in the US have long been calling for the elimination of race-based medical practices entirely, highlighting the lack of evidence to support them. Their calls received renewed attention in 2020, as medical institutions clamoured to publish Black Lives Matter statements in the wake of George Floyd’s murder and worldwide anti-racism protests. Students, who were still being taught race-based practices in medical school, began to increasingly question their teachers. Among those asking questions was Naomi Nkinsi, a medical student at the University of Washington.

When I interviewed her in 2021, Nkinsi patiently walked me through the history behind various race adjustments used in medicine. She explained that there were two equations commonly used in medicine to calculate eGFR, both of which included adjustments for Black race. The first of these equations, called MDRD, was developed in the 1990s. “This equation looks at a variety of factors that can impact someone’s kidney functioning. And one that is built into the equation is Black race,” Nkinsi told me. “So, if someone is identified as being Black – and there’s no specification as to whether they’re self-identified or if the physician says, ‘Oh, this person looks Black’ – then their eGFR calculation is adjusted by 1.21,” she said. The same three digits from my sister’s test result sheet.

The digits that constitute the Black race adjustment in the MDRD equation originate from a small US study by the same name conducted in 1999, which found that study participants who self-identified as African American had higher levels of creatinine in their blood on average compared with those who identified as White.

“From this they said, ‘Oh, well, if they have higher creatinine, it must mean that Black people have a higher muscle mass,’” Nkinsi told me. However, the MDRD study included only 1,628 participants, only 197 of whom identified as African American. “It’s based on this one observation they found out of a very, very small population,” said Nkinsi. Moreover, there is limited evidence to support the secondary assumption that Black people have more muscle mass compared with White people.

In 2009, an updated eGFR equation – the second of the two most widely used equations – was developed based on a larger study called CKD-EPI. But the assumption that it was necessary to adjust for Black race was carried through from the MDRD study, Nkinsi explained. Indeed, both the MDRD and CKD-EPI equations for calculating eGFR contain a Black race multiplier (in the MDRD equation the multiplier is 1.212, whereas in the CKD-EPI equation it is 1.159). “So we have all of these aspects of medicine that are dependent on equations that are now being recognised to be built on faulty science,” said Nkinsi. Not just faulty, but potentially harmful.

Around the same time I met Nkinsi, I came across preliminary research from a UK study led by kidney doctors Rouvick Gama and Kate Bramham at King’s College London. Their work showed that eGFR equations with race adjustments overestimated actual GFR in Black patients, compared with results using a more invasive but more accurate method. Gama told me that the overestimation of kidney health because of race adjustment could have serious consequences for Black patients. “It could lead to delay in diagnosis of chronic kidney disease,” he said, and therefore delays in treatment – something that is reflected in UK health statistics. “If you’re of Black ethnicity, you’re three- to five-fold more likely to end up with end-stage kidney disease,” Bramham told me. “Almost certainly we’re not recognising it enough,” she said.

There is a similar picture in the US, where, according to the National Kidney Foundation, Black or African American people are more than three times as likely as White people to develop kidney failure. Nkinsi told me she thought that the race adjustment was a contributing factor to that disparity. “What it means is that we’re missing kidney disease in Black people,” she said. “For a Black person to be identified as having kidneys that are sick, they actually need to be sicker than a non-Black person,” she emphasised. “That means you have later access to specialised care, later access to things like transplant, later access to things like Medicaid coverage for kidney care. That leads to worse health outcomes for Black people,” she said.

In the US, it is estimated that 13 people die every day while waiting for a kidney transplant. Black or African American transplant candidates wait longer on average than White transplant candidates for kidney and other organ transplants – and use of race adjustment in calculating eGFR has meant that their chances of getting on to the transplant list in the first place have been limited.

As I learned more about the use of race adjustment in eGFR and its potential harms for Black people, I began contacting some of the health bodies I thought might be responsible for setting this sort of medical guidance.

In May 2021, I sent a request to the CDC [Centers for Disease Control and Prevention] in the US to clarify what their guidance was. I received a response explaining that the current guidelines in the US came from Kidney Disease Improving Global Outcomes (KDIGO) – “a global organisation that develops and implements evidence-based clinical practice guidelines in kidney disease,” according to the CDC. I downloaded KDIGO’s guidelines. I was once again greeted with the same instruction that had been printed on my sister’s eGFR results, to multiply the patient’s eGFR by a specific numerical factor “if Black”.

My heart sank. This was a global organisation, so its guidance would be relied upon internationally. I asked KDIGO to explain what the scientific rationale was behind its recommendation to use race adjustment in eGFR calculations. I received a response, curtly stating: “KDIGO is not in a position to comment on the rationale used to determine the adjustment in eGFR calculations.” I felt deflated, but I didn’t give up.

When I had spoken to Nkinsi, she told me about how she had questioned her teachers at medical school the first time her class was taught about eGFR. “When we were presented in lecture with, ‘OK, so we’re using the MDRD equation, you have to adjust for race,’ I was like, ‘Wait a minute, that doesn’t make sense,’” Nkinsi told me. “In our physiology lecture, no one ever said that Black kidneys work differently,” she pointed out. “What is the physiology?” No one could give Nkinsi a straight answer. “They were just kind of like, ‘Well, this is how we do things,’” she said. Nkinsi wasn’t satisfied, and started digging, which is how she discovered the concerning origin of the race adjustment in the MDRD study. “One study can change the trajectory of so much of what we do, because it’s further grandfathered in,” she sighed.

“In medicine, and as scientists, we are supposed to pride ourselves on gaining new information, looking at how the world is changing, getting new data and saying, ‘OK, what are we doing?’ Nothing we do is solid, right? Everything is supposed to be able to be questioned. But, unfortunately, medicine is very hierarchical. It’s based on this kind of false meritocracy, where for the longest time, White men are running everything – and you can’t question your superiors. Medical students and younger physicians are supposed to just take things as they’re taught. You’re taught these equations, you’re taught these facts, and you just kind of perpetuate them,” said Nkinsi. “You’re not taught to question where this information is coming from.”

Thankfully, Nkinsi did question things, and when she realised they were fishy, she demanded action from UW Medicine, the medical school where she was enrolled at the University of Washington. In response to Nkinsi’s calls, in 2020 UW Medicine announced it would transition away from the use of race adjustment in eGFR calculations. It was not the first or the last medical institution in the US to make this move. Other institutions also abolished the race adjustment, and in 2021 the National Kidney Foundation and the American Society of Nephrology established a joint task force to “examine the inclusion of race in the estimation of GFR”.

Inspired by Nkinsi’s success, I contacted the UK’s National Institute for Health and Care Excellence (Nice) in June 2021, regarding its guideline on calculating eGFR, which at the time recommended applying “a correction factor to GFR values […] for people of African-Caribbean or African family origin”. Nice told me it was in the process of updating that guideline and reassured me that “there was some consideration in the update about adjustment based on the characteristics you have highlighted”. Nice shared a link to the draft of the updated guidance, which was to be published two months later, in August 2021. I was disappointed to see that the recommendation to “correct” eGFR for people of African-Caribbean or African family origin was still there. It was accompanied by a note saying that future research should explore the use of “factors other than ethnicity” as biological markers. At this point, I decided that the best thing I could do was put my head down and write up my report for New Scientist.

A few weeks after my article was published, Gama and Bramham got in touch to let me know that their preliminary study, highlighting the potential harms of race adjustment in eGFR to Black patients in the UK, had been published in a scientific journal. It was August 2021, and I knew that Nice was due to publish its updated guideline soon. I forwarded Gama and Bramham’s research article to my contact at Nice, and asked whether Nice was aware of their findings. The response I had been waiting for finally came. Nice had made the decision to remove the race adjustment from its recommendations on calculating eGFR. It would publish its updated guideline the following morning. I was delighted, as were Gama and Bramham. “This is a really important opportunity to stop race-based medicine,” Bramham told me at the time.

It finally felt as if there was movement in the right direction. I wrote up a report on the guideline change for New Scientist, and contacted the UK Kidney Association to get its reaction to the news. “We welcome and support this change,” said Paul Cockwell, president of the association. “Ethnicity and race are social constructs and do not match genetic categories,” he said.

On the other side of the Atlantic, there had also been some movement. A few weeks after Nice published its updated guidelines, the National Kidney Foundation and the American Society of Nephrology formally established a consensus against the use of race adjustment in kidney function equations in the US. (In March this year, KDIGO also updated its guidelines to remove its recommendation to adjust eGFR based on race.)

“It is exciting to see that such a big change is being made,” Nkinsi told me. “There’s a concern that once institutions around the country are making this change, they’re not going to go deeper and look at other ways in which Black patients are getting inadequate kidney care,” she said. “The concern is that institutions will see this as, ‘OK, now we’re not racist any more.’”

• This is an edited extract from Systemic: How Racism Is Making Us Ill by Layal Liverpool, published by Bloomsbury (£22). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply