Across the world, medical tests are being adjusted according to patients’ skin colour – with shocking consequences, writes Layal Liverpool, a science writer, who, in The Guardian, describes how she helped overturn one of the pernicious assumptions of race-based healthcare.
Liverpool writes:
My younger sister is an elite 400m sprinter who has competed internationally for 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, generally 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 gave a list of factors which could be responsible for raised creatinine levels. One was “Afro-Caribbean race”.
“Could my race be affecting my creatinine level?” my sister asked me.
I was about to stumble on an answer. 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 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 it was alive and well.
Adjusting results
My first clue came in 2021 via a US-based study highlighting issues associated with a widespread practice of adjusting routine kidney test results based on race. In brief: if a doctor wants to assess a patient’s kidney health, they usually start with a test measuring the level of the waste product creatinine in their blood, the same 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 indicate kidney problems. In the worst cases, when the kidneys aren’t functioning correctly, toxic waste products build up in the body – which is fatal without treatment like dialysis or a kidney transplant.
What I gleaned was that the most widely used eGFR equations globally included a specific multiplier applied to increase eGFR values for black people. After the application of this adjustment, a black patient would end up with a higher eGFR than a non-black patient with the same blood test results.
Additionally, the study showed the removal of the race adjustment could improve the accuracy of kidney failure risk prediction among black adults.
I remembered my sister had had a similar test done in the UK the previous year. She showed me some photographs of it. Printed 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 this guidance? If race is a social construct, why is it being treated as a biological one? Are there similar race adjustments in other areas of medicine? Might this be causing harm to black patients? What is the medical definition of “black” anyway?
More questions
I was not the first person to raise these questions. In addition to Dorothy Roberts, kidney doctors like 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.
Students, who were still being taught race-based practices in medical school, began to increasingly question their teachers. Among those was Naomi Nkinsi, a medical student at the University of Washington.
When I interviewed her in 2021, Nkinsi walked me through the history behind various race adjustments, saying two equations were commonly used to calculate eGFR, both of which included adjustments for black race.
The first, called MDRD, was developed in the 1990s. “This equation looks at various factors that can impact someone’s kidney functioning. And one that is built into the equation is black race,” she said.
“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.”
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 than those who identified as white.
“From this they said, ‘Oh, well, if they have higher creatinine, it must mean black people have a higher muscle mass,’” Nkinsi told me.
However, the MDRD study included only 1 628 participants: 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 than 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 said.
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 depend on equations that are now being recognised to be built on faulty science,” said Nkinsi.
Slowly unfolding
Around this time, I discovered preliminary research from a study led by kidney doctors Rouvick Gama and Kate Bramham at King’s College London. Their work showed that eGFR equations with race adjustments over-estimated actual GFR in black patients, compared with results using a more invasive but more accurate method.
Gama told me the over-estimation 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 – which is reflected in UK health statistics.
“If you’re black, you’re three- to five-fold more likely to end up with end-stage kidney disease,” Bramham said. “Almost certainly we’re not recognising it enough.”
Similarly, in the US, 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 thinks the race adjustment is a contributing factor to that disparity.
“It means we’re missing kidney disease in black people. For a black person to be identified as having kidneys that are sick, they actually need to be sicker than a non-black person. That means later access to specialised care, to things like transplant, like Medicaid coverage for kidney care. That leads to worse health outcomes.”
In the US, it is estimated that 13 people die daily 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 means their chances of even getting on to the transplant list have been limited.
I began contacting health bodies I thought might be responsible for setting this sort of medical guidance.
Guidelines
In May 2021, I contacted the CDC (US Centres for Disease Control and Prevention) to clarify what their guidance was. They said current US guidelines came from Kidney Disease Improving Global Outcomes (KDIGO) – “a global organisation that develops and implements evidence-based clinical practice guidelines in kidney disease”.
I downloaded KDIGO’s guidelines and saw 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 the scientific rationale 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 didn’t give up.
Nkinsi had told me she had questioned her teachers at medical school the first time her class was taught about eGFR. “When we were presented in the lecture with, ‘Ok, so we’re using the MDRD equation, you have to adjust for race,’ I thought, ‘Wait a minute, that doesn’t make sense,’” she said.
“In our physiology lecture, no one ever said black kidneys work differently. What is the physiology?”
No one could give Nkinsi a straight answer.
Origin of adjustment
She started digging, and discovered the concerning origin of the race adjustment in the MDRD study.
“In medicine, and as scientists, we are supposed to pride ourselves on gaining new information, 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,” she said.
“Medical students and younger physicians …are taught these equations, these facts, and you’re not taught to question where this information comes from.”
Thankfully, Nkinsi did question things, and when she realised they were fishy, she demanded action from UW Medicine, where she was enrolled at the University of Washington.
In response to her 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 to make this move. Others 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 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 said it was updating that guideline and 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 the recommendation to “correct” eGFR for people of African-Caribbean or African family origin was still there.
It was accompanied by a note saying 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 called to let me know 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 NICE was due to publish its updated guideline soon. I forwarded Gama and Bramham’s research article to NICE, and asked if they were aware of the findings.
The response finally came. NICE had decided to remove the race adjustment from its recommendations on calculating eGFR.
It would publish its updated guideline the next morning. I was delighted, as were Gama and Bramham.
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 March this year, KDIGO also updated its guidelines to remove its recommendation to adjust eGFR based on race.)
• This is an edited extract from Systemic: How Racism Is Making Us Ill by Layal Liverpool, published by Bloomsbury.
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