Researchers identify preferable GFR equations with, without race coefficient
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The Chronic Kidney Disease Epidemiology Collaboration 2021 equation for estimating GFR proved to be the least biased and most accurate GFR equation among potential living donors, according to data published in Kidney Medicine.
While the improvements remained among subgroups of Asian, Hispanic and white patients, researchers found the improved performance was not seen among Black patients.
“In our data, when compared to the older Chronic Kidney Disease Epidemiology Collaboration 2009 (CKDEPI09) and Modification of Diet in Renal Disease (MDRD) equations with race adjustments included, the new Chronic Kidney Disease Epidemiology Collaboration 2021 (CKDEPI21) equation improved accuracy and precision but introduced a greater degree of bias for Black individuals,” David Alex Goodson, MD, MPH, from the department of internal medicine at the University of California Davis Medical Center, and colleagues wrote.
In a cross-sectional study, researchers examined 637 potential living kidney donors (51.5% self-identified as white; 29.2% self-identified as Hispanic; 13.5% self-identified as Asian; 5.8% self-identified as Black) from the University of California Davis Medical Center. Patients had serum creatinine concentration measurement and GFR measurement by iohexol plasma clearance between October 2016 and December 2020.
Researchers measured GFR using the MDRD equation, the CKDEPI09 equation and the CKDEPI21 equation. The MDRD and CKDEPI09 equations were assessed with and then without the race coefficient, while the CKDEPI21 equation does not include one.
Primary outcomes of the study included equation bias, precision, accuracy and accurate classification of GFR as equal to or greater than 80 mL/min/1.72 m2 or less than 80 mL/min/1.72 m2. Researchers compared GFR estimation equation performance to GFR measured by iohexol clearance.
Analyses revealed the median bias of the CKDEPI-21 equation underestimated the GFR measured by iohexol by 2.8 mL/min/1.73 m2. Overall, it was less biased and more accurate than the other eGFR equations, except among the subgroup of Black patients, in which the bias underestimated the GFR measured by iohexol by 9 mL/min/1.73 m2. Further, the MDRD equation performed the worst compared with the other equations among all subgroups in the study.
Researchers identified the total misclassification of a GFR either greater than or less than 80 mL/min/1.73 m2 was 16.3% for CKDEPI21 and 16% for CKDEPI09 (with race adjustment).
“Our data suggest that in the aggregate, the GFR estimates generated by the CKDEPI21 equation are less biased and more accurate than earlier estimates of GFR function in the potential living donor population. Precision is slightly reduced compared to previous estimates, but the difference is likely clinically insignificant. The superiority of the CKDEPI21 GFR estimates is reflected in measures of bias and accuracy that are maintained regardless of whether or not estimates are normalized to a body surface area of 1.73 m2,” Goodson and colleagues wrote. They added, “Our findings suggest that, among the Black subgroup, removal of the race coefficient [...] produces GFR estimates with more bias than when race coefficients are included. This is consistent with previous analyses.”
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