Clinical Implications of Removing Race From Estimates of Kidney Function

Abstract

This study uses NHANES data to compare estimated glomerular filtration rate from serum creatinine (eGFRcr) values calculated with vs without race as a variable, and to estimate the number of patients for whom nephrologist referrals and drug and renal replacement recommendations would change as a result according to KDIGO guidelines and Medicare benefit policies.

Over the past year, medical centers across the US have removed race adjustment from estimated glomerular filtration rate from serum creatinine (eGFRcr), with many now reporting the “White/other” value for all patients. These changes follow calls to reconsider the use of race in estimating kidney function¹ and in medicine broadly.² We analyzed potential changes in recommended care using eGFRcr with and without race among Black individuals in the US (individuals who are not Black would not be affected).

Methods

We used data from the National Health and Nutrition Examination Survey (NHANES) characterizing a cross-sectional sample of the noninstitutionalized US population from 2001 to 2018, with response rates from 48.8% to 79.6%. Laboratory measurements, including serum creatinine, were collected in mobile examination centers, and demographic variables, including race/ethnicity, were self-reported in personal interviews. Participants provided written consent using a protocol approved by the National Center for Health Statistics Research Ethics Review Board.

We computed eGFRcr using the Chronic Kidney Disease (CKD) Epidemiology Collaboration (CKD-EPI) equation³ with and without its race coefficient for Black individuals. We then estimated the number of Black adults whose care could change as recommended by Kidney Disease: Improving Global Outcomes (KDIGO)³ and the Medicare Part B benefit policy.⁴ Evaluated changes include CKD diagnoses, CKD stage reclassifications and related drug recommendations, nephrologist referrals, Medicare coverage, kidney donation, and kidney transplantation. Outcomes are defined in the eAppendix in the Supplement. Analyses were performed using R version 4.0.0.

Results

The study cohort comprised 9522 nonpregnant, non-Hispanic Black adults; 50.5% self-identified as women and the median age was 45 years. After removal of race, median eGFR decreased from 102.9 mL/min/1.73 m² to 88.8 mL/min/1.73 m²; the median change was −14.1 mL/min/1.73 m² (Figure).

Figure. Changes in Reported eGFR for Black Adults Following Removal of Race From eGFRcr.

All Black adults would experience a decrease in reported estimated glomerular filtration rate (eGFR) of 13.7% (computed from the Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]) race coefficient as 1 − 1/1.159). Median eGFR was 102.9 mL/min/1.73 m² with race and 88.8 mL/min/1.73 m² without race; the median eGFR change was −14.1 mL/min/1.73 m². The 25th percentile for the change in eGFR was −16.5 mL/min/1.73 m², and the 75th percentile for the change in eGFR was −11.5 mL/min/1.73 m². Data are from the 2001-2018 National Health and Nutrition Examination Survey (NHANES). eGFRcr indicates estimated glomerular filtration rate from serum creatinine.

Removing race may increase the prevalence of CKD among Black adults from 14.9% to 18.4% (difference, 3.5% [95% CI, 3.2%-3.9%]) (Table). Concurrently, 29.1% (95% CI, 26.4%-32.0%) of Black adults with existing CKD may be reclassified to more severe stages of disease, with significant clinical and pharmacologic implications. Affected drugs include angiotensin-converting enzyme inhibitors, β-blockers, warfarin, cisplatin, metformin, and sodium-glucose cotransporter-2 inhibitors. The prevalence of CKD stage 3b or higher may change from 2.3% to 3.5%, affecting 1.2% (95% CI, 1.0%-1.5%) of Black adults. Similarly, the prevalence of CKD stage 4 or higher may change from 1.0% to 1.3%, affecting 0.29% (95% CI, 0.18%-0.43%) of Black adults.

Table. Potential Implications for Black Adults in the US Following Removal of Race From eGFRcr^a.

Implicationb	eGFR range, mL/min/1.73 m2	No. in NHANES (weighted %)		Absolute change, weighted % (95% CI)
		Including race	Removing race
CKD diagnosis	<60	1646 (14.9)	2051 (18.4)	3.5 (3.2-3.9)
Ineligible to donate kidney	<60	3848 (38.5)	4088 (40.6)	2.1 (1.8-2.4)
Reclassification: CKD stage 3b or higher and related drug recommendationsc	<45	282 (2.3)	439 (3.5)	1.2 (1.0-1.5)
Medical nutrition therapy covered	13-50	724 (5.0)	789 (5.5)	0.47 (0.37-0.60)
Reclassification: CKD stage 4 or higher and related drug recommendationsd	<30	120 (1.0)	155 (1.3)	0.29 (0.18-0.43)
Referral to nephrologist	<30	357 (3.2)	384 (3.4)	0.22 (0.13-0.35)
Kidney disease education covered	15-29	33 (0.22)	52 (0.36)	0.14 (0.07-0.25)
Eligible for kidney transplant waiting list	<20	74 (0.66)	82 (0.71)	0.051 (0.02-0.10)

Abbreviations: CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; eGFRcr, estimated glomerular filtration rate from serum creatinine; KDIGO, Kidney Disease Improving Global Outcomes; NHANES, National Health and Nutrition Examination Survey.

^aThe total sample consisted of 9522 nonpregnant Black adults derived from the 2001-2018 NHANES. Proportions and 95% CIs are adjusted to be representative of the US population using the NHANES survey weights and design. Sample counts were not survey adjusted.

^bOutcomes are defined in the eAppendix in the Supplement (including non-eGFR inclusion or exclusion criteria) and ordered by the number of affected individuals (absolute change).

^cRecommendations from KDIGO² for eGFR less than 45: dose reduction for angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, aldosterone antagonists, and direct renin inhibitors.

^dRecommendations from KDIGO² for eGFR less than 30: contraindication for metformin, sodium-glucose cotransporter-2 inhibitors, cisplatin, and nonsteroidal anti-inflammatory drugs; dose reduction for β-blockers, macrolides, warfarin, and low-molecular-weight heparins.

Following race removal, 3.4% of Black adults may be referred to specialist care instead of 3.2% (difference, 0.22% [95% CI, 0.13%-0.35%]). Medicare would cover 5.5% of Black adults for medical nutrition therapy instead of 5.0% (difference, 0.47% [95% CI, 0.37%-0.60%]). Similarly, 0.36% of Black adults would be covered for kidney disease education instead of 0.22% (difference, 0.14% [95% CI, 0.07%-0.25%]).

Computing eGFRcr without race may raise the proportion of Black adults eligible for the kidney transplant wait list from 0.66% to 0.71%, newly qualifying 0.051% (95% CI, 0.02%-0.10%) of Black adults for transplantation. Conversely, the proportion of kidney donor candidates deemed “not acceptable” would change from 38.5% to 40.6%, newly disqualifying 2.1% (95% CI, 1.8%-2.4%) of Black adults from kidney donation.

Discussion

Removal of race adjustment may increase CKD diagnoses among Black adults and enhance access to specialist care, medical nutrition therapy, kidney disease education, and kidney transplantation, while potentially excluding kidney donors and prompting drug contraindications or dose reductions for individuals reclassified to advanced stages of CKD. This potential for benefits and harms must be interpreted in light of persistent disparities in care,³ documented biases of eGFRcr without race,⁵ and the historical misuse of race as a biological variable to further racism.²

This study had several limitations. First, many institutions use the Modification of Diet in Renal Disease (MDRD) equation. Removal of the larger race coefficient in the MDRD (1.212 vs 1.159 in CKD-EPI) would lead to larger decreases in eGFR and more individuals crossing relevant thresholds. Second, some institutions have removed race using methods other than universalizing the “White/other” equation. Third, eGFR does not determine care for all patients. Clinical judgment,⁶ unbiased confirmatory tests to corroborate eGFRcr, and varying adherence to guidelines may all influence how changes materialize.

Section Editor: Jody W. Zylke, MD, Deputy Editor.

Supplement.

eAppendix. Population Definitions and Non-eGFR Inclusion/Exclusion Criteria