- The glomerular filtration rate (GFR) — a measure of kidney function — is usually calculated by looking at the levels of creatinine or cystatin C in the body.
- Age, sex, and race are all factors in current estimated GFR (eGFR) calculations that employ creatinine or cystatin C to calculate this figure.
- However, the use of race in these computations is increasingly being questioned. This is because race is a social construct rather than a biological one.
- A new study has compared the accuracy of race-based GFR-estimating equations to new equations that do not take race into account.
Racial disparities in medical practice are nothing new.
However, in the healthcare profession, discussions about inequities have just lately taken on a new importance.
One example is a growing understanding of the dangers of using race as a criterion for kidney disease diagnosis and treatment.
Scientists have discovered that employing race-free equations for determining kidney function — while still analyzing creatinine and cystatin C — resulted in more accurate findings and lower discrepancies between Black and non-Black persons, according to a recent research.
Dr. Neil Powe, MPH, MBA, leader of the University of California San Francisco Medicine Service at the Priscilla Chan and Mark Zuckerberg San Francisco General Hospital, talked with Medical News Today.
The study’s findings, he added, demonstrate the need of recruiting a broad group of people for any clinical research that informs medical interventions.
“We found a path forward for estimating kidney function that was a victory for patients, a victory for valuing evidence-based medicine, and a victory for the trainees who were troubled by using race to estimate GFR.”
– Dr. Neil Powe
“We need to do more to discover the drivers of health disparities and do our best to devise interventions to address them,” he concluded.
The findings of the study were published in The New England Journal of Medicine.
Developing race-free eGFR equations
The present Chronic Kidney Disease Epidemiology Collaboration equations for predicting kidney function were compared to two new equations that did not take race into account.
Medical experts presently employ three formulae to determine GFR. The first uses creatinine (eGFRcr), the second uses cystatin C (eGFRcys), and the third uses both (eGFRcr-cys).
The researchers used data from two development datasets to create the new race-free eGFR equations:
- There were 8,254 participants in 10 trials for serum creatinine, with 31.5 percent of them being Black.
- There were 5,352 individuals in 13 trials for both serum creatinine and cystatin C, with 39.7% of them being Black.
All individuals were at least 18 years old, and race was mostly self-reported in most research.
The researchers employed the same coefficients for age, sex, and creatinine levels in the first set of new equations as in the present eGFRcr and eGFRcr-cys equations. When computing eGFR, they eliminated the Black race coefficient and allocated non-Black people’ eGFRcr and eGFRcr-cys values to Black persons.
The researchers fully removed race as a variable for computing eGFR in the second set of equations.
The researchers examined the performance of the present and new equations using a validation dataset of 12 studies that comprised 4,050 individuals, 14.3% of whom were Black.
Furthermore, the researchers compared the old and new equations in order to determine the prevalence of chronic renal disease in a representative sample of individuals in the United States.
The data comes from 4,563 people who took part in the National Health and Nutrition Examination Survey in the 1999–2000 and 2001–2002 cycles.
Validating the findings of the research
The current eGFRcr equation overstated observed GFR in Black individuals by 3.7 milliliters (ml) per minute per 1.73 meters squared (m2) in the validation dataset, according to the authors. It overstated non-Black individuals’ measured GFR by 0.5 ml per minute per 1.73 m2 on average.
The authors found that the measured GFR in Black individuals was overestimated by a median of 7.1 ml per minute per 1.73 m2 in the first novel equation, where they attributed eGFRcr values for non-Black persons to Black people.
In addition, the race-free eGFRcr equation underestimated measured GFR in Black individuals by 3.6 ml per minute per 1.73 m2, while overestimating measured GFR in non-Black participants by 3.9 ml per minute per 1.73 m2.
Furthermore, the current eGFRcr-cys equation underestimated observed GFR in Black individuals by a median of 2.5 per minute per 1.73 m2 and by a median of 0.6 per minute per 1.73 m2 in non-Black participants.
In an unexpected surprise, the two new eGFRcr-cys equations (non-Black coefficient and race-free) showed a lesser bias in Black participants, a comparable bias in non-Black participants, and a smaller differential bias overall than the corresponding new eGFRcr equations.
The new eGFRcr equations, but not the new eGFRcr-cys equations, raised population estimates of CKD prevalence among Black participants while yielding similar or lower prevalence among non-Black participants when compared to the present eGFRcr equation.
As a result of their observations, the authors came to the following conclusion:
“New eGFR equations that incorporate creatinine and cystatin C but omit race are more accurate and led to smaller differences between Black participants and non-Black participants than new equations without race with either creatinine [eGFRcr] or cystatin C alone [eGFRcys].”
To put it another way, the new eGFRcr-cys (non-Black coefficient and race-free) equations were more successful in reducing renal disease overdiagnosis and underdiagnosis.
What are the opinions of the experts?
Experts were contacted by MNT for their thoughts on the study.
Dr. Eniola Bada, a senior house officer at the Birmingham Women’s and Children’s NHS Foundation Trust in England, is optimistic about the study’s findings. The findings, she told MNT, might lead to an earlier identification of impaired renal function among African-Americans:
“[Another] clinical implication [of this study] is that [Black] people who have been on a level of care such as watchful waiting can have their management escalated to dialysis or transplant, thereby potentially improving their clinical outcomes.”
The study’s design, according to the authors, is its strength. It develops and validates new race-free equations for predicting GFR using different big datasets that contain both Black and non-Black subjects.
The research, however, is not without flaws. To begin with, the research divides race into two categories: Black and non-Black, which fails to appropriately reflect the variety within and across ethnic groupings. Furthermore, several of the studies utilized by the researchers to construct the new equations were outdated, and none of them were conducted in representative populations.
Furthermore, in the validation trials, there were fewer Black participants than non-Black individuals, which might lead to less exact estimations of accuracy in Black persons. Furthermore, there was insufficient representation of ethnic groups other than Black and White.
Finally, the researchers only looked at data from adults who didn’t have any major comorbid illnesses. As a result, the findings may not apply to those who have more serious conditions.
Regardless of flaws, one thing is clear: the findings of this study emphasize racial disparities in medical treatment while simultaneously proposing a remedy that might one day have major therapeutic implications.
Dr. Bada’s final comments on the study provide pause for thought. She said, “the beauty of science is in its evolution, and as such, scientists, healthcare workers, and the public should be committed to evaluating our current clinical practices, especially the ones that seem ‘not right,’ and we just might find something that is better for everyone.”