Because Black adults tend to have a higher serum creatinine level than other racial or ethnic groups, for years the equation for calculating estimated glomerular filtration rate included an adjustment for Black race. That changed with the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) race-free equation. It is widely believed that race is a social and nonbiological construct and including race in the eGFR calculation may contribute to disparities in chronic kidney disease care.
The clinical implications of this change are not yet understood, so James D. Oliver III, MD, and others examined the effect that the adoption of the race-free equation has had on CKD prevalence in a diverse US military population. Their research was published in Kidney Medicine.
Their study used data from adults in the US Military Health System (MHS) from 2016 to 2019. The data of 1,502,607 adults were included in the complete case analysis, and the data of 1,970,433 adults were included in an imputed race analysis. Subjects in the complete case analysis had a median age of 40 years and were 18.8% Black, 35.4% female, and 50.2% active-duty military.
The study outcome was CKD stages 3-5, defined as the last eGFR persistently <60 mL/min/1.73 m2 for ≥90 days. Cumulatively, 3008 Black adults and 12,147 non-Black adults were reclassified or restratified by the 2021 equation. With the introduction of the 2021 equation, the median change in eGFR was –8 mL/min/1.73 m2 in Black adults and +4 mL/min/1.73 m2 in non-Black adults. The number of Black adults with CKD stages 3-5 increased by 58.1%, from 4,147 to 6,556 (change in crude prevalence from 1.47% to 2.32%). The number of non-Black adults with CKD stages 3-5 decreased by 30.4%, from 27,596 to 19,213 (change in crude prevalence from 2.26% to 1.58%).
Results were similar in the imputed race analysis. Cumulatively, among adults with CKD stages 3-5 by at least one equation, 45.8% of Black adults were reclassified to more advanced stages of CKD and 44.0% of non-Black adults were reclassified to less severe stages. The 2021 equation could have consequences in clinical management for approximately 45% of the population with CKD in the MHS.
Limitations of the study include potential underestimation of CKD stages 3-5 prevalence, missing data on race in the nonactive-duty population, and underestimation of overall CKD prevalence because albuminuria was not included in the criteria for CKD. Finally, future clinical effects of the revised equation are speculative, and there may be unforeseen risks or benefits to its adoption.
In summary, the authors found that adopting the 2021 CKD-EPI equation in the MHS reclassifies many Black adults into CKD stages 3-5 or into more advanced CKD stages; the new equation has the opposite effect on non-Black adults. While the researchers acknowledged the race-free calculation may help address disparities in kidney care and outcomes, there are risks to its adoption. “It might be important after implementation of the 2021 CKD-EPI equation to perform active surveillance of desired clinical outcomes and unintended consequences among different racial and ethnic groups,” they wrote. “As recognized by the [National Kidney Foundation-American Society of Nephrology] Task Force, an ultimate goal is better assessments of eGFR by cystatin C and the development of next-generation race-independent markers of kidney function.”
Source: Kidney Medicine
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