National Projections for Clinical Implications of Race-Free Creatinine-Based GFR Estimating Equations

How histopathological diagnosis interacts with kidney ultrasound parameters and glomerular filtration rate

The evaluation of estimated GFR (eGFR) is a pivotal staging step in patients with chronic kidney disease (CKD), and renal ultrasound plays an important role in diagnosis, prognosis and progression of CKD. The interaction between histopathological diagnosis and ultrasound parameters in eGFR determination has not been fully investigated yet. The study examined the results of native kidney biopsies performed in 48 Italian centers between 2012 and 2020. The primary goal was if and how the histopathological diagnosis influences the relationship between ultrasound parameters and eGFR. After exclusion of children, patients with acute kidney injury and patients without measure of kidney length or parenchymal thickness, 2795 patients have been selected for analysis. The median values were 52 years for patient age, 11 cm for bipolar kidney diameter, 16 mm for parenchymal thickness, 2.5 g/day for proteinuria and 70 ml/min/1.73 m2 for eGFR. The bipolar kidney diameter and the parenchymal thickness were directly related with eGFR values (R square 0.064). Diabetes and proteinuria were associated with a consistent reduction of eGFR, improving the adjusted R square up to 0.100. Addition of histopathological diagnosis in the model increased the adjusted R square to 0.216. There is a significant interaction between histopathological diagnosis and longitudinal kidney diameter (P 0.006). Renal bipolar length and parenchymal thickness are directly related with eGFR. The magnitude of proteinuria and histopathological kidney diagnosis are associated with eGFR. The relationship between kidney length and the level of eGFR depends on the nature of the kidney disease.

Impact of Race-Free Glomerular Filtration Rate Estimations on CKD Prevalence in the US Military Health System: A Retrospective Cohort Study

Rationale & Objective

The 2021 CKD-EPI removes Black race as a factor in calculating the estimated glomerular filtration rate (eGFR). We assessed its effect on CKD prevalence in the demographically-diverse US Military Health System.

Study Design

A retrospective calculation of the eGFR from serum creatinine measured over 2016-2019 using both the 2009 and 2021 CKD-EPI equations.

Setting & Population

Multicenter health care network with data from 1,502,607 adults in the complete case analysis and from 1,970,433 adults in an imputed race analysis.

Predictors

Serum creatinine, age, sex, and race.

Outcome

CKD stages 3-5, defined as the last eGFR persistently < 60 mL/min/1.73m2 for ≥90 days.

Analytical Approach

The t test and Kruskal-Wallis test were used for continuous variables and Χ2 for categorical data.

Results

The population in the complete case analysis had a median age of 40 years and was 18.8% Black race and 35.4% female. With the 2021 equation, the number of Black adults with CKD stages 3-5 increased by 58.1% from 4,147 to 6,556, a change in the 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, a crude prevalence change from 2.26% to 1.58%. Similar results were seen with race imputation. 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 across eGFR thresholds that could change clinical management.

Limitations

Potential underestimation of CKD in individuals with only 1 measurement.

Conclusions

Adoption of the 2021 CKD-EPI equation in the Military Health System reclassifies many Black adults into new CKD stages 3-5 or into more advanced CKD stages, with the opposite effect on non-Black adults. This may have an effect on CKD treatment and outcomes in ways that are yet unknown.

Single-Ancestry versus Multi-Ancestry Polygenic Risk Scores for CKD in Black American Populations

Key Points

Background

CKD is a risk factor of cardiovascular disease and early death. Recently, polygenic risk scores (PRSs) have been developed to quantify risk for CKD. However, African ancestry populations are underrepresented in both CKD genetic studies and PRS development overall. Moreover, European ancestry–derived PRSs demonstrate diminished predictive performance in African ancestry populations.

Methods

This study aimed to develop a PRS for CKD in Black American populations. We obtained score weights from a meta-analysis of genome-wide association studies for eGFR in the Million Veteran Program and Reasons for Geographic and Racial Differences in Stroke Study to develop an eGFR PRS. We optimized the PRS risk model in a cohort of participants from the Hypertension Genetic Epidemiology Network. Validation was performed in subsets of Black participants of the Trans-Omics in Precision Medicine Consortium and Genetics of Hypertension Associated Treatment Study.

Results

The prevalence of CKD—defined as stage 3 or higher—was associated with the PRS as a continuous predictor (odds ratio [95% confidence interval]: 1.35 [1.08 to 1.68]) and in a threshold-dependent manner. Furthermore, including APOL1 risk status—a putative variant for CKD with higher prevalence among those of sub-Saharan African descent—improved the score's accuracy. PRS associations were robust to sensitivity analyses accounting for traditional CKD risk factors, as well as CKD classification based on prior eGFR equations. Compared with previously published PRS, the predictive performance of our PRS was comparable with a European ancestry–derived PRS for kidney traits. However, single-ancestry PRSs were less predictive than multi-ancestry–derived PRSs.

Conclusions

In this study, we developed a PRS that was significantly associated with CKD with improved predictive accuracy when including APOL1 risk status. However, PRS generated from multi-ancestry populations outperformed single-ancestry PRS in our study.

Care of Adults with Advanced Chronic Kidney Disease

Chronic kidney disease (CKD) impacts over 10% of the global population. Adults with CKD face significant morbidity and mortality. As kidney disease progresses, the risk of adverse outcomes increases. Here, we present an overview of strategies to care for adults with advanced CKD (stage 4-5 CKD, not receiving kidney replacement therapy). We aim to guide clinicians through several aspects of CKD care, ranging from recommended laboratory assessments to interdisciplinary support for patients as they plan for kidney replacement therapy (dialysis, transplantation, or conservative management). We incorporate considerations of health equity and person-centered care, empowering clinicians to deliver high-quality care to people with CKD.

Performance of race-neutral eGFR equations in patients with decompensated cirrhosis

The 2021 Chronic Kidney Disease Epidemiology Collaboration equation [CKD-EPI 2021] is a race-neutral equation recently developed and rapidly implemented as a reference standard to estimate glomerular filtration rate(GFR). However, its role in cirrhosis has not been examined especially in low GFR. We analyzed the performance of CKD-EPI 2021 compared to other equations with protocol-measured GFR (mGFR) in cirrhosis. We analyzed 2090 unique adult patients with cirrhosis undergoing protocol GFR measurements using iothalamate clearance from 1985 to 2015 when listed for liver transplantation at Baylor University in Dallas and Fort Worth, Texas. Using mGFR as a reference standard, the CKD-EPI 2021 was compared to CKD-EPI 2012, Modification of Diet in Renal Disease-4, Modification of Diet in Renal Disease-6, Royal Free Hospital, and GFR Assessment in Liver disease overall and in certain subgroups (ascites, mGFR ≤ 30 mL/min/1.73 m 2 , diagnosis, Model for End-Stage Liver Disease and gender). We examined bias (difference between eGFR and mGFR), accuracy (p30: eGFR within ± 30% of mGFR) and agreement between eGFR and mGFR categories. CKD-EPI 2021 had the second lowest bias across the entire range of GFR after GFR Assessment in Liver disease (6.6 vs. 4.6 mL/min/1.73 m 2 , respectively, p < 0.001). The accuracy of CKD-EPI 2021 was similar to CKD-EPI 2012 (p30 = 67.8% vs. 67.9%, respectively) which was higher than the other equations ( p < 0.001). It had a similar performance in patients with ascites, by diagnoses, Model for End-Stage Liver Disease subgroups, by gender, and in non-Black patients. However, it had a relatively higher overestimation in mGFR ≤ 30 mL/min/1.73 m 2 than most equations (18.5 mL/min/1.73m 2 , p < 0.001). Specifically, 64% of patients with mGFR ≤ 30 mL/min/1.73m 2 were incorrectly classified as a less severe CKD stage by CKD-EPI 2021. In Blacks, CKD-EPI 2021 underestimated eGFR by 17.9 mL/min/1.73 m 2 , which was higher than the alternate equations except for Royal Free Hospital ( p < 0.001). The novel race-neutral eGFR equation, CKD-EPI 2021, improves the GFR estimation overall but may not accurately capture true kidney function in cirrhosis, specifically at low GFR. There is an urgent need for a race-neutral equation in liver disease reflecting the complexity of kidney function physiology unique to cirrhosis, given implications for organ allocation and dual organ transplant.

Nephrotic Syndrome Throughout Childhood: Diagnosing Podocytopathies From the Womb to the Dorm

The etiologies of podocyte dysfunction that lead to pediatric nephrotic syndrome (NS) are vast and vary with age at presentation. The discovery of numerous novel genetic podocytopathies and the evolution of diagnostic technologies has transformed the investigation of steroid-resistant NS while simultaneously promoting the replacement of traditional morphology-based disease classifications with a mechanistic approach. Podocytopathies associated with primary and secondary steroid-resistant NS manifest as diffuse mesangial sclerosis, minimal change disease, focal segmental glomerulosclerosis, and collapsing glomerulopathy. Molecular testing, once an ancillary option, has become a vital component of the clinical investigation and when paired with kidney biopsy findings, provides data that can optimize treatment and prognosis. This review focuses on the causes including selected monogenic defects, clinical phenotypes, histopathologic findings, and age-appropriate differential diagnoses of nephrotic syndrome in the pediatric population with an emphasis on podocytopathies.

The Impact of Health Care Algorithms on Racial and Ethnic Disparities : A Systematic Review

BACKGROUND

There is increasing concern for the potential impact of health care algorithms on racial and ethnic disparities.

PURPOSE

To examine the evidence on how health care algorithms and associated mitigation strategies affect racial and ethnic disparities.

DATA SOURCES

Several databases were searched for relevant studies published from 1 January 2011 to 30 September 2023.

STUDY SELECTION

Using predefined criteria and dual review, studies were screened and selected to determine: 1) the effect of algorithms on racial and ethnic disparities in health and health care outcomes and 2) the effect of strategies or approaches to mitigate racial and ethnic bias in the development, validation, dissemination, and implementation of algorithms.

DATA EXTRACTION

Outcomes of interest (that is, access to health care, quality of care, and health outcomes) were extracted with risk-of-bias assessment using the ROBINS-I (Risk Of Bias In Non-randomised Studies - of Interventions) tool and adapted CARE-CPM (Critical Appraisal for Racial and Ethnic Equity in Clinical Prediction Models) equity extension.

DATA SYNTHESIS

Sixty-three studies (51 modeling, 4 retrospective, 2 prospective, 5 prepost studies, and 1 randomized controlled trial) were included. Heterogenous evidence on algorithms was found to: a) reduce disparities (for example, the revised kidney allocation system), b) perpetuate or exacerbate disparities (for example, severity-of-illness scores applied to critical care resource allocation), and/or c) have no statistically significant effect on select outcomes (for example, the HEART Pathway [history, electrocardiogram, age, risk factors, and troponin]). To mitigate disparities, 7 strategies were identified: removing an input variable, replacing a variable, adding race, adding a non-race-based variable, changing the racial and ethnic composition of the population used in model development, creating separate thresholds for subpopulations, and modifying algorithmic analytic techniques.

LIMITATION

Results are mostly based on modeling studies and may be highly context-specific.

CONCLUSION

Algorithms can mitigate, perpetuate, and exacerbate racial and ethnic disparities, regardless of the explicit use of race and ethnicity, but evidence is heterogeneous. Intentionality and implementation of the algorithm can impact the effect on disparities, and there may be tradeoffs in outcomes.

PRIMARY FUNDING SOURCE

Agency for Healthcare Quality and Research.

Evaluation of risk stratification for acute kidney injury: a comparative analysis of EKFC, 2009 and 2021 CKD-EPI glomerular filtration estimating equations

BACKGROUND

The adoption of the 2021 CKD-EPIcr equation for glomerular filtration rate (GFR) estimation provided a race-free eGFR calculation. However, the discriminative performance for AKI risk has been rarely validated. We aimed to evaluate the differences in acute kidney injury (AKI) prediction or reclassification power according to the three eGFR equations.

METHODS

We performed a retrospective observational study within a tertiary hospital from 2011 to 2021. Acute kidney injury was defined according to KDIGO serum creatinine criteria. Glomerular filtration rate estimates were calculated by three GFR estimating equations: 2009 and 2021 CKD-EPIcr, and EKFC. In three equations, AKI prediction performance was evaluated with area under receiver operator curves (AUROC) and reclassification power was evaluated with net reclassification improvement analysis.

RESULTS

A total of 187,139 individuals, including 27,447 (14.7%) AKI and 159,692 (85.3%) controls, were enrolled. In the multivariable regression prediction model, the 2009 CKD-EPIcr model (continuous eGFR model 2, 0.7583 [0.755-0.7617]) showed superior performance in AKI prediction to the 2021 CKD-EPIcr (0.7564 [0.7531-0.7597], < 0.001) or EKFC model in AUROC (0.7577 [0.7543-0.761], < 0.001). Moreover, in reclassification of AKI, the 2021 CKD-EPIcr and EKFC models showed a worse classification performance than the 2009 CKD-EPIcr model. (- 7.24 [- 8.21-- 6.21], - 2.38 [- 2.72-- 1.97]).

CONCLUSION

Regarding AKI risk stratification, the 2009 CKD-EPIcr equation showed better discriminative performance compared to the 2021 CKD-EPIcr equation in the study population.

Impact of the 2021 CKD-EPI eGFR Equation on Kidney Care Referral Criteria in Ontario, Canada: A Population-based Cross-sectional Study

Background

In some jurisdictions, individuals become eligible or recommended for referral for different types of kidney care using criteria based on their estimated glomerular filtration rate (eGFR). Historically, GFR was estimated with an equation developed in 2009, which included a Black race term. An updated, race-free equation was developed in 2021. It is unclear how adoption of the 2021 equation will influence the number of individuals meeting referral criteria to receive different types of kidney care.

Objective

To develop population-based estimates on how the number of individuals meeting the eGFR-based referral criteria to receive three different types of kidney care (nephrologist consultation, care in a multi-care specialty clinic, kidney transplant evaluation) changes when the 2021 versus 2009 equation is used to calculate eGFR.

Design

Population-based, cross-sectional study.

Setting

Ontario, Canada's most populous province with 14.2 million residents as of 2021. Less than 5% of Ontario's residents self-identify as being of Black race.

Patients

Adults with at least one outpatient serum creatinine measurement in the 2 years prior to December 31, 2021.

Measurements

Referral criteria to 3 different types of kidney care: nephrologist consultation, multi-care specialty clinic, and evaluation for a kidney transplant. The eGFR thresholds used to define referral eligibility or recommendation for these kidney health services were based on guidelines from Ontario's provincial renal agency.

Methods

The number of individuals meeting referral criteria for the 3 different healthcare services was compared between the 2009 and 2021 equations, restricted to individuals not yet receiving that level of care. As individual-level race data were not available, estimates were repeated, randomly assigning a Black race status to 1%, 5%, and 10% of the population.

Results

We had an outpatient serum creatinine measurement available for 1 048 110 adults. Using the 2009 equation, 37 345 individuals met the criteria to be referred to a nephrologist, 10 019 met the criteria to receive care in a multi-care specialty clinic, and 10 178 met the criteria to be referred for kidney transplant evaluation. Corresponding numbers with the 2021 equation (and the percent relative to the 2009 equation) were 26 645 (71.3%), 9009 (89.9%), and 8615 (84.6%) individuals, respectively. These numbers were largely unchanged when Black race was assumed in up to 10% of the population.

Limitations

Referral criteria based solely on urine albumin-to-creatinine ratio were not assessed. Self-reported race data were unavailable.

Conclusions

For healthcare planning, in regions where a minority of the population is Black, a substantial number of individuals may no longer meet referral criteria for different types of kidney healthcare following adoption of the new 2021 eGFR equation.

The 2021 Chronic Kidney Disease Epidemiology Collaboration Race-Free Estimated Glomerular Filtration Rate Equations in Kidney Disease: Leading the Way in Ending Disparities

Purpose

In 2020, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) convened a Task Force to recommend an evidence-based race-free approach to estimated glomerular filtration rate (eGFR). After the rigorous review of more than 20 approaches, the NKF/ASN Task Force published the final report that recommended the implementation of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI 2021) equation for eGFR using creatine and expanded utilization of cystatin C testing. The purpose of this manuscript is to provide a comprehensive overview of the evolution of eGFR equations, and an overview of the Task Force deliberations and recommendations. For over two decades, the equation recommended to calculate eGFR included a race coefficient to adjust for data that suggested that American adults with African ancestry had consistently higher serum creatinine levels.

Methods

We will provide a discussion illustrating why the 2021 CKD EPI equations are the most equitable solution to eGFR. We will also provide an overview of the current implementation status and best practices for the new equations. Lastly, we will discuss how deployment of the new equations is an important step toward eliminating significant disparities in CKD care which disproportionately affect communities of color.

Results

Removing race from the algorithm used to assess kidney function is most equitable. Since race is a social construct, its use in clinical algorithms has facilitated health disparities in Black/African American people, Hispanic/Latino people, and other racial and ethnic minority groups-those who are already disproportionately impacted by diabetes, hypertension, and kidney disease. In turn, these same individuals experience significant inequities in kidney health care including reduced access to nephrology care, home dialysis, and kidney transplant.

Conclusions

Adoption of the race-free 2021 CKD-EPI eGFR equations will have life changing implications for kidney health. It will aid in appropriate referral, identification, diagnosis, treatment, and management of kidney disease and transplantation services/options. The outcomes of widespread implementation of the new equations coupled with system change quality improvement interventions such as the kidney profile will lead to more equitable outcomes and begin to address the crippling disparities in early, appropriate testing for CKD.

Mitigating Health Disparities in Transplantation Requires Equity, Not Equality

Despite decades of research and evidence-based mitigation strategies, disparities in access to transplantation persist for all organ types and in all stages of the transplant process. Although some strategies have shown promise for alleviating disparities, others have fallen short of the equity goal by providing the same tools and resources to all rather than tailoring the tools and resources to one's circumstances. Innovative solutions that engage all stakeholders are needed to achieve equity regardless of race, sex, age, socioeconomic status, or geography. Mitigation of disparities is paramount to ensure fair and equitable access for those with end-stage disease and to preserve the trust of the public, upon whom we rely for their willingness to donate organs. In this overview, we present a summary of recent literature demonstrating persistent disparities by stage in the transplant process, along with policies and interventions that have been implemented to combat these disparities and hypotheses for why some strategies have been more effective than others. We conclude with future directions that have been proposed by experts in the field and how these suggested strategies may help us finally arrive at equity in transplantation.

Retaining Race in Chronic Kidney Disease Diagnosis and Treatment

The best overall measure of kidney function is glomerular filtration rate (GFR) as commonly estimated from serum creatinine concentrations (eGFRcr) using formulas that correct for the higher average creatinine concentrations in Blacks. After two decades of use, these formulas have come under scrutiny for estimating GFR differently in Blacks and non-Blacks. Discussions of whether to include race (Black vs. non-Black) in the calculation of eGFRcr fail to acknowledge that the original race-based eGFRcr provided the same CKD treatment recommendations for Blacks and non-Blacks based on directly (exogenously) measured GFR. Nevertheless, the National Kidney Foundation and the American Society of Nephrology Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease removed race in CKD treatment guidelines and pushed for the immediate adoption of a race-free eGFRcr formula by physicians and clinical laboratories. This formula is projected to negate CKD in 5.51 million White and other non-Black adults and reclassify CKD to less severe stages in another 4.59 million non-Blacks, in order to expand treatment eligibility to 434,000 Blacks not previously diagnosed and to 584,000 Blacks previously diagnosed with less severe CKD. This review examines: 1) the validity of the arguments for removing the original race correction, and 2) the performance of the proposed replacement formula. Excluding race in the derivation of eGFRcr changed the statistical bias from +3.7 to -3.6 ml/min/1.73m2 in Blacks and from +0.5 to +3.9 in non-Blacks, i.e., promoting CKD diagnosis in Blacks at the cost of restricting diagnosis in non-Blacks. By doing so, the revised eGFRcr greatly exaggerates the purported racial disparity in CKD burden. Claims that the revised formulas identify heretofore undiagnosed CKD in Blacks are not supported when studies that used kidney failure replacement therapy and mortality are interpreted as proxies for baseline CKD. Alternatively, a race-stratified eGFRcr (i.e., separate equations for Blacks and non-Blacks) would provide the least biased eGFRcr for both Blacks and non-Blacks and the best medical treatment for all patients.

Performance of Nuclear Magnetic Resonance-Based Estimated Glomerular Filtration Rate in a Real-World Setting

An accurate estimate of glomerular filtration rate (eGFR) is essential for proper clinical management, especially in patients with kidney dysfunction. This prospective observational study evaluated the real-world performance of the nuclear magnetic resonance (NMR)-based GFR_NMR equation, which combines creatinine, cystatin C, valine, and myo-inositol with age and sex. We compared GFR_NMR performance to that of the 2021 CKD-EPI creatinine and creatinine-cystatin C equations (CKD-EPI_2021Cr and CKD-EPI_2021CrCys), using 115 fresh routine samples of patients scheduled for urinary iothalamate clearance measurement (mGFR). Median bias to mGFR of the three eGFR equations was comparably low, ranging from 0.4 to 2.0 mL/min/1.73 m². GFR_NMR outperformed the 2021 CKD-EPI equations in terms of precision (interquartile range to mGFR of 10.5 vs. 17.9 mL/min/1.73 m² for GFR_NMR vs. CKD-EPI_2021CrCys; p = 0.01) and accuracy (P15, P20, and P30 of 66.1% vs. 48.7% [p = 0.007], 80.0% vs. 60.0% [p < 0.001] and 95.7% vs. 86.1% [p = 0.006], respectively, for GFR_NMR vs. CKD-EPI_2021CrCys). Clinical parameters such as etiology, comorbidities, or medications did not significantly alter the performance of the three eGFR equations. Altogether, this study confirmed the utility of GFR_NMR for accurate GFR estimation, and its potential value in routine clinical practice for improved medical care.