Researchers identify preferable eGFR equation without race coefficient
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The eGFR equation that includes creatinine and cystatin C but not the race coefficient may be preferable to the eGFR equation that only includes creatinine for measuring racial differences in the risk of kidney failure.
“[...] the use of race in GFR estimation and other clinical algorithms has been challenged because race is a social and not a biologic construct and does not fully capture the diversity within vs. between racial groups,” Orlando M. Gutiérrez, MD, MMSc, from the department of medicine and epidemiology at the University of Alabama at Birmingham, and colleagues wrote. They added, “This study examined whether GFR estimating equations based on different filtration markers (creatinine [eGFRcr] vs. cystatin C [eGFRcys] vs. both [eGFRcr-cys]) and equations that included or excluded race altered risk estimates for [kidney failure with replacement therapy] KFRT and mortality for Black compared with non-Black participants.”
In a retrospective individual-level data analysis, researchers evaluated 62,011 participants (20,773 individuals were Black; 41,238 individuals were not Black; mean age was 63 years; 53% were women) from eight U.S.-based cohorts. All cohorts included serum creatinine, cystatin C and follow-ups for KFRT and mortality between 1988 and 2018.
Researchers studied seven GFR estimating equations developed by the Chronic Kidney Disease Epidemiology Collaboration, but they primarily focused on the following equations: 2009 eGFRcr (age, sex and race), 2021 eGFRcr (age and sex), 2012 eGFRcys (age and sex) and 2021 eGFRcrcys (age and sex).
Adjusting for age and sex, researchers determined the prevalence of decreased eGFR at baseline and hazard ratios of KFRT and mortality in Black participants vs. participants who were not Black. Researchers used multivariable random-effects models to conduct meta-analyses across cohorts. Additionally, researchers analyzed each cohort.
Researchers considered KFRT, all-cause mortality and cardiovascular mortality as primary outcomes.
Overall, the prevalence ratio of eGFR less than 60 mL/min/1.73 m² comparing Black participants with participants who were not Black was 0.98 for eGFRcr with race, 0.95 for eGFRcys and 1.2 for eGFRcr-cys. However, the prevalence ratio was 1.8 for eGFRcr without race. Researchers determined a decreased eGFR correlated with significantly greater risk of KFRT and mortality for all equations.
Mean follow-up of 13 years showed 8% and 4% of Black participants and participants who were not Black, respectively, experienced KFRT, and 34% and 39%, respectively, died.
Similarly, the 5-year absolute risk differences for KFRT comparing Black participants with participants who were not Black were 1.4% for eGFRcr with race, 1.1% for eGFRcys and 1.3% for eGFRcr-crys vs. 0.37% for eGFRcr without race.
“In this retrospective analysis of eight U.S. cohorts including Black and non-Black individuals, the eGFR equation without race that included creatinine and cystatin C, but not the eGFR equation without race that included creatinine without cystatin C, demonstrated racial differences in the risk of KFRT and mortality throughout the range of eGFR,” Gutiérrez and colleagues wrote. “The eGFRcr-cys equation may be preferable to the eGFRcr equation without race for assessing racial differences in the risk of KFRT and mortality associated with low eGFR.”
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