According to a new study led by UC San Francisco and Hennepin County Medical Center in Minneapolis, using equations to determine kidney function that do not account for race adjustments would result in Black patients getting more time before their kidneys fail on the transplant waitlist when compared to similar durations for white patients.
The researchers compared the period between becoming eligible for the waitlist and developing kidney failure in their study, which was published in the journal CJASN on September 19, 2022, for Black and white patients.
“The earlier a patient is waitlisted prior to kidney failure, the higher priority the patient has in getting a transplant and the more likely a patient could potentially avoid dialysis,” said first author Elaine Ku, MD, of the UCSF Division of Nephrology and of the Department of Epidemiology and Biostatistics. “Patients who avoid dialysis, or do it for a short period, generally have better outcomes than those on dialysis in the long term,” she said.
Estimated glomerular filtration rate, or eGFR, is used in a method to determine who is eligible for the kidney transplant waitlist. It takes into account the patient’s age and sex while measuring creatinine, a byproduct of the breakdown of muscle tissues.
Previously, Black individuals had a higher eGFR despite having a similar creatinine level because the eGFR formulae included a race adjustment. This is justified by past research showing that Black people may naturally have greater levels of creatinine.
Recognizing Race as Social Construct Prompts Criteria Review
However, the American Society of Nephrology and the National Kidney Foundation this year advised the elimination of these race modifiers, which alter kidney function upward by 16% in Blacks, in recognition of race as a social construct rather than a biological one.
The earlier a patient is waitlisted prior to kidney failure, the higher priority the patient has in getting a transplant and the more likely a patient could potentially avoid dialysis. Patients who avoid dialysis, or do it for a short period, generally have better outcomes than those on dialysis in the long term.
Elaine Ku
The current transplant waitlist requirement for patients regardless of race is eGFR 20 ml/min, significantly lower than 90 ml/min or higher, which is considered normal.
The researchers examined two novel eGFR formulas that do not take race into account: one used creatinine alone, the traditional test, and the other utilized both creatinine and cystatin, a more recent blood test that is expected to provide more accurate results when kidney function is higher.
Using the eGFR creatinine formula, they found that among 350 Black patients, kidney failure was reached at an average 23 months, versus an average 22 months for 122 white patients, which the researchers describe as not having a statistically significant difference.
When they examined the results of the eGFR creatinine-cystatin formula, they discovered that kidney failure was experienced on average by 289 Black patients at the age of 21 months, as opposed to 152 White patients at the age of 26 months. This difference was not statistically significant, but it was more divergent than the eGFR creatinine formula results.
“These findings suggest that the new creatinine-cystatin equation, but not the creatine equation, is still associated with differences in pre-emptive wait time by race,” said Ku.
“Our data suggest that using the race-free creatinine equation to determine waitlist eligibility is the strategy that may reduce racial differences in access to pre-emptive wait-time accrual the most, though our findings require additional confirmation in other cohorts,” she said.
Ku was the lead author of a previous study that suggested that putting Black patients on the transplant waitlist at a little higher kidney function threshold than white patients would enhance racial equity in transplant availability.
According to other studies, Black patients with chronic kidney disease deteriorate more quickly and are more frequently submitted for transplant evaluation later than white patients.
