For Black Americans, lack of 'rigorous scientific evidence' led to test that leaves some off kidney transplant list.
Nada Hassanein, USA TODAY
When her relative couldn’t get on the waiting list for a kidney transplant, Dr. Nwamaka Eneanya had to step in.
Tests showed his kidney function was not severe enough. But Eneanya, a physician who specializes in kidney disease treatment, knew better – the labs didn't show the true picture, and the condition runs in her family. She knew her loved one needed a transplant.
"I really had to advocate on behalf of that family member as a nephrologist, as someone who had the training that I had, to get them on the transplant list," she said.
For about two decades, the test used in the general population has overestimated kidney function in Black patients, masking the severity of their kidney disease, resulting in late diagnosis and delayed transplant referrals.
The calculation has drawn scrutiny, most recently from the American Kidney Fund. Last week, it endorsed a more equitable test proposed by a national task force of scientists.
Dr. Nwamaka D. Eneanya
The current most widely used test to estimate kidney function – estimated glomerular filtration rate or eGFR test – uses creatinine, a waste product in the blood created by muscle use, to calculate how well kidneys are working.
Black people in original studies to develop the test may have had nonbiological exposures that affected creatinine levels, such as medications or dietary differences – but scientists, trying to account for these differences seen in Black participants, deduced Black people had more "muscle mass," so had a higher baseline level of creatinine.
But that correlation hasn’t been substantiated by “rigorous scientific evidence,” experts wrote in a scientific editorial detailing the equation’s impact on systemic inequities in kidney transplants for Black patients, which published this year in the Journal of the American Medical Association.
Eneanya, a University of Pennsylvania Perelman School of Medicine professor and a member of the task force, said the assumption simply "doesn’t make sense." There is no evidence to support it.
“Why would Black patients have different kidney function than everybody else?” she said.
eGFR tests erroneously keep some off transplant list, experts say.
In the transplant inequities editorial, researchers noted the antiquated calculation “systematically raises” estimated kidney function by as much as 16% for Black people compared with patients of all other racial groups, “conferring an estimate of better kidney function for Black individuals.”
Still, other researchers recently argued in support of the equation. But Eneanya said the attempt at accuracy didn’t account for other races and lumped all Black people together into a separate category.
“We know that race can really introduce implicit bias into the clinical encounter, and we know that there are studies that have shown implicit bias has negatively affected Black individuals," said Eneanya, an author on a recent New England Journal of Medicine study that produced an inclusive equation.
“Hopefully, the way forward is that we won’t have any tools that lead with race or ethnicity, that we'll have real measures of structural racism.”
Black patients make up about 13% of the U.S. population, yet comprise more than a third of the nation’s 500,000 kidney failure patients, according to the National Institutes of Health.
Kidney failure is dubbed a “disease multiplier” because of the illnesses that often accompany it, such as diabetes and high blood pressure. Patients with kidney disease have been especially vulnerable to COVID-19.
Duke University professor and nephrologist Dr. Dinushika Mohottige, an author on the transplant inequities paper, said the racialized equation, embedded into clinical practice and education, is an example of structural racism.
“We have probably underdetected people who have chronic kidney disease and other concerning signs for rapidly progressing kidney failure or kidney disease… because of this overestimation of kidney function that has been specific to Black individuals,” Mohottige said. “There’s a litany of disparities in kidney disease that have plagued the United States for the past many decades."
A Black patient of Mohottige who came to learn about the calculation difference was appalled. The patient, in his 60s, told her, “It is not fair,” and had “extreme frustration that it was the first time he was hearing about it.”
Missed early detection can contribute to poor management of the disease, a lack of patient education, and limited access to medications or new treatments that could slow progression of the disease.
Dr. Dinushika Mohottige
Medical students in recent years were the first to question the equation disparity. Dr. Bessie Young remembers discussions with her students at the University of Washington, and as a health disparities researcher, epidemiologist and nephrologist, started to question it herself.
“Race is a social construct, a social-legal construct,” she said. In the kidney research however, “it was being used as a biologic construct, which it isn’t."
Kidney function is inherently difficult to measure. Doctors began using population-based function tests in clinical care when other tests were more expensive or cumbersome.
“We were making clinical decisions based on these estimates,” Young said. “We relied on them much more, but I think people always knew there was this bias.”
Eneanya, who helped write a "Grey's Anatomy" episode about the issue that aired last week, said researchers need to work together for a path forward.
“Leading with Black race, leading with race, is wrong in those circumstances,” she said. “Where we get into trouble is when we try to silo the biomedical sciences from other sciences … looking at Black people as kind of a different ‘species,’ it goes back to slavery. Us being resistant to that type of (integrated) scholarship is exactly how we got into this place.”
Dr. Bessie Young