The New 2021 CKD-EPI Equation Without Race in a European Cohort of Renal Transplanted Patients

De-indexed estimated glomerular filtration rates for the dosing of oral antidiabetic drugs in patients with chronic kidney disease

Introduction: Adjusting drug dose levels based on equations that standardize the estimated glomerular filtration rate (eGFR) to a body surface area (BSA) of 1.73 m2 can pose challenges, especially for patients with extremely high or low body mass index (BMI). The objective of the present study of patients with CKD and diabetes was to assess the impact of deindexing creatinine-based equations on estimates of kidney function and on the frequency of inappropriate prescriptions of oral antidiabetic drugs (OADs). Methods: The prospective CKD-REIN cohort is comprised of patients with eGFR <60 mL/min/1.73 m2. The inclusion criteria for this study were the use of OADs and the availability of data on weight, height and serum creatinine. We compared data for three BMI subgroups (group 1 <30 kg/m2; group 2 30-34.9 kg/m2; group 3 ≥35 kg/m2). Inappropriate prescriptions (contraindicated or over-dosed drugs) were assessed with regard to the summary of product characteristics and the patient's kidney function estimated with the 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, the 2021 CKD-EPI equation, the Modification of Diet in Renal Disease (MDRD) equation, the European Kidney Function Consortium (EKFC) equation, their deindexed estimates, and the Cockcroft-Gault (CG) formula. The impact of deindexing the equations was evaluated by assessing 1) the difference between the indexed and deindexed eGFRs, and 2) the difference in the proportion of patients with at least one inappropriate OAD prescription between the indexed and deindexed estimates. Results: At baseline, 694 patients were receiving OADs. The median BMI was 30.7 kg/m2, the mean BSA was 1.98 m2, and 90% of patients had a BSA >1.73 m2. Deindexing the kidney function estimates led to higher eGFRs, especially in BMI group 3. The proportion of patients with at least one inappropriate prescription differed greatly when comparing indexed and deindexed estimates. The magnitude of the difference increased with the BMI: when comparing BMI group 1 with BMI group 3, the difference was respectively -4% and -10% between deindexed 2021 CKD-EPI and indexed CKD-EPI. Metformin and sitagliptin were the most frequent inappropriately prescribed OADs. Conclusion: We highlight significant differences between the BSA-indexed and deindexed versions of equations used to estimate kidney function, emphasizing the importance of using deindexed estimates to adjust drug dose levels - especially in patients with an extreme BMI.

The EKFC equation outperforms the CKD-EPI and CKiD equations for GFR estimation in adolescent and young adult kidney transplant patients

AIM

This study evaluated the bias and accuracy of the CKD-EPI/CKiD and EKFC equations compared with the reference exogenous tracer-based assessment of glomerular filtration rate (GFR) in adult and pediatric patients according to their renal transplant status.

METHODS

We assessed the bias and P30 accuracy of the CKD-EPI/CKiD and EKFC equations compared with iohexol-based GFR measurement.

RESULTS

In the overall population (n = 59), the median age was 29 years (IQR, 16.0-46.0) and the median measured GFR was 73.9 mL/min/1.73m2 (IQR, 57.3-84.6). Among non-kidney transplant patients, the median was 77.7 mL/min/1.73m2 (IQR, 59.3-86.5), while among kidney transplant patients, it was 60.5 mL/min/1.73m2 (IQR, 54.2-66.8). The bias associated with the EKFC and CKD-EPI/CKiD equations was significantly higher among kidney transplant patients than among non-kidney transplant patients, with a difference between medians (Hodges-Lehmann) of +10.4 mL/min/1.73m2 (95% CI, 2.2-18.9; p = .02) for the EKFC and +12.1 mL/min/1.73m2 (95% CI, 4.2-21.4; p = .006) for the CKD-EPI/CKiD equations. In multivariable analysis, kidney transplant status emerged as an independent factor associated with a bias of >3.4 mL/min/1.73m2 (odds ratio, 7.7; 95% CI, 1.4-43.3; p = .02) for the EKFC equation and a bias of >13.4 mL/min/1.73m2 (odds ratio, 15.0; 95% CI, 2.6-85.7; p = .002) for the CKD-EPI/CKiD equations.

CONCLUSION

In our study, which included adolescent and young adult kidney transplant patients, both the CKD-EPI/CKiD and EKFC equations tended to overestimate the measured glomerular filtration rate, with the EKFC equation exhibiting less bias. Renal transplant status significantly influenced the degree of estimation bias.

Early progression of chronic histologic lesions in kidney transplant biopsies is not associated with HLA histocompatibility

BACKGROUND

Early progression of chronic histologic lesions in kidney allografts represents the main finding in graft attrition. The objective of this retrospective cohort study was to elucidate whether HLA histocompatibility is associated with progression of chronic histologic lesions in the first year post-transplant. Established associations of de novo donor-specific antibody (dnDSA) formation with HLA mismatch and microvascular inflammation (MVI) were calculated to allow for comparability with other study cohorts.

METHODS

We included 117 adult kidney transplant recipients, transplanted between 2016 and 2020 from predominantly deceased donors, who had surveillance biopsies at 3 and 12 months. Histologic lesion scores were assessed according to the Banff classification. HLA mismatch scores [i.e. eplet, predicted indirectly recognizable HLA-epitopes algorithm (PIRCHE-II), HLA epitope mismatch algorithm (HLA-EMMA), HLA whole antigen A/B/DR] were calculated for all transplant pairs. Formation of dnDSAs was quantified by single antigen beads.

RESULTS

More than one-third of patients exhibited a progression of chronic lesion scores by at least one Banff grade in tubular atrophy (ct), interstitial fibrosis (ci), arteriolar hyalinosis (ah) and inflammation in the area of interstitial fibrosis and tubular atrophy (i-IFTA) from the 3- to the 12-month biopsy. Multivariable proportional odds logistic regression models revealed no association of HLA mismatch scores with progression of histologic lesions, except for ah and especially HLA-EMMA DRB1 [odds ratio (OR) = 1.10, 95% confidence interval (CI) 1.03-1.18]. Furthermore, the established associations of dnDSA formation with HLA mismatch and MVI (OR = 5.31, 95% CI 1.19-22.57) could be confirmed in our cohort.

CONCLUSIONS

These data support the association of HLA mismatch and alloimmune response, while suggesting that other factors contribute to early progression of chronic histologic lesions.

Performance of the race-free CKD-EPI creatinine-based eGFR equation in a Danish cohort with measured GFR

Background

In 2021, an updated Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for estimated glomerular filtration rate (eGFR) without a coefficient for race (CKD-EPI21) was developed. The performance of this new equation has yet to be examined among specific patient groups.

Methods

We compared the performances of the new CKD-EPI21 equation and the 2009 equation assuming non-Black race (CKD-EPI09-NB) in patients with GFR measured by chromium-51-EDTA plasma clearance at Aarhus University Hospital in Denmark during 2010-18. We examined bias, accuracy, precision and correct classification of chronic kidney disease (CKD) stage using chromium-51-EDTA clearance as the reference standard. We assessed the performance in the total cohort, cancer patients and potential living kidney donors. We also assessed the performance stratified by CKD stage in the total cohort.

Results

In this predominantly white population, the CKD-EPI21 equation performed slightly better than the CKD-EPI09-NB equation in both the total cohort (N = 4668), and in cancer patients (N = 3313) and potential living kidney donors (N = 239). In the total cohort, the CKD-EPI21 equation demonstrated a slightly lower median absolute bias (-0.2 versus -4.4 mL/min/1.73 m2), and a similar accuracy, precision and correct classification of CKD stage compared with the CKD-EPI09-NB equation. When stratified by CKD stage, the CKD-EPI09-NB equation performed slightly better than the CKD-EPI21 equation among patients with a measured GFR (mGFR) <60 mL/min/1.73 m2.

Conclusions

In a selected cohort of Danish patients with mGFR, the CKD-EPI21 equation performed slightly better than the CKD-EPI09-NB equation except for patients with a mGFR <60 mL/min/1.73 m2, where CKD-EPI09-NB performed slightly better although the differences were considered clinically insignificant.

Association of serum uric acid levels with bone mineral density and the presence of osteoporosis in Chinese patients with Parkinson's disease: a cross-sectional study

INTRODUCTION

As the population ages, the incidence of osteoporosis among patients suffering from Parkinson's disease (PD) will surge continually, and the ensuing disability from falls is becoming a serious social burden. Due to its antioxidant properties, much literature has indicated the possible ability of serum uric acid (UA) to prevent ageing-related diseases caused by oxidative stress, including osteoporosis and PD. Therefore, this study was for exploring the connection of serum UA levels with bone mineral density (BMD) and the osteoporosis presence in Chinese PD patients.

MATERIALS AND METHODS

A cross-sectional design was used to statistically analyze 42 clinical parameters obtained from 135 patients with PD treated in Wuhan Tongji Hospital during 2020-2022. Multiple stepwise linear regression and multiple logistic regression analyses were constructed for identifying the association of serum UA levels with BMD as well as osteoporosis in PD patients, respectively. With receiver operative characteristic (ROC) curves, the optimal cutoff value was acquired for serum UA in the diagnosis of osteoporosis.

RESULTS

According to the regression analysis adjusted for confounders, serum UA levels in PD patients had positive correlation with BMD at each site and negative correlation with the presence of osteoporosis (P < 0.05 for all). ROC curves determined that the optimal cutoff value for UA to perform well in diagnosing osteoporosis in PD patients was 284.27 μmol/L (P < 0.001).

CONCLUSION

Relatively higher serum UA levels in the physiological range can work as a biomarker of higher BMD, and were strongly linked to lower prevalence of osteoporosis in Chinese PD patients.

Association between multiple metal(loid)s exposure and renal function: a cross-sectional study from southeastern China

In the real world, humans are exposed to multiple metal(loid)s (designated hereafter metals) that contain essential metals as well as toxic metals. Exposure to the metal mixture was assumed to be associated with renal function impairment; however, there is no consensus on available studies. Therefore, we here explored the association between multiple metals exposure and indicators of renal function in the general population from southeastern China. A total of 11 metals with 6 human essential metals and 5 toxic metals were determined in the selected 720 subjects. In addition, serum uric acid (SUA), serum creatinine (SCR), and the estimated glomerular filtration rate (eGFR) were measured or calculated as indicators of renal function. Using multiple flexible statistical models of generalized linear model, elastic net regression, and Bayesian kernel machine regression, the joint as well as the individual effect of metals within the mixture, and the interactions between metals were explored. When exposed to the metal mixture, the statistically non-significantly increased SUA, the significantly increased SCR, and the significantly declined eGFR were observed. In addition, the declined renal function may be primarily attributed to lead (Pb), arsenic (As), and nickel (Ni) exposure. Finally, interactions, such as the synergistic effect between Pb and Mo on SUA, whereas the antagonistic effect between Ni and Cd on SCR and eGFR were identified. Our finding suggests that combined exposure to multiple metals would impair renal function. Therefore, reducing exposure to toxic heavy metals of Pb, As, and Cd and limiting exposure to the human essential metal of Ni would protect renal function.

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.

Is the use of the new Chronic Kidney Disease Epidemiology Consortium (CKD-EPI 2021) formula appropriate for the Spanish population?

INTRODUCTION

United States nephrology societies recommend changing from the CKD-EPI 2009 equation to the new CKD-EPI 2021 equation, which does not include the race coefficient, for calculating estimated glomerular filtration rate (eGFR). It is unknown how this change might affect the distribution of kidney disease in the predominantly Caucasian Spanish population.

METHODS

Two databases of adults from the province of Cádiz, DB-SIDICA (N=264,217) and DB-PANDEMIA (N=64,217), that had plasma creatinine measurements recorded between 2017 and 2021 were studied. Changes in eGFR and the consequent reclassification into different categories of the KDIGO 2012 classification resulting from substituting the CKD-EPI 2009 equation for the 2021 equation were calculated.

RESULTS

Compared to the 2009 equation, CKD-EPI 2021 yielded a higher eGFR, with a median of 3.8mL/min/1.73m² (IQR 2.98-4.48) in DB-SIDICA and 3.89mL/min/1.73m² (IQR 3.05-4.55) in DB-PANDEMIA. The first consequence was that 15.3% of the total population in DB-SIDICA and 15.1% of the total population in DB-PANDEMIA were reclassified into a higher category of eGFR, as were 28.1% and 27.3%, respectively, of the population with CKD (G3-G5); no subjects were classified into the more severe category. The second consequence was that the prevalence of kidney disease decreased from 9% to 7.5% in both cohorts.

CONCLUSIONS

Implementing the CKD-EPI 2021 equation in the Spanish population, which is predominantly Caucasian, would increase eGFR by a modest amount (greater in men and those who are older or have a higher GFR). A significant proportion of the population would be classified into a higher eGFR category, with a consequent decrease in the prevalence of kidney disease.

The new, race-free, Chronic Kidney Disease Epidemiology Consortium (CKD-EPI) equation to estimate glomerular filtration rate: is it applicable in Europe? A position statement by the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM)

The EFLM recommends not to implement the race-free Chronic Kidney Disease Epidemiology Consortium (CKD-EPI) equation in European laboratories and to keep the 2009 version of the CKD-EPI equation, without applying a race correction factor. This recommendation is completely in line with a recent Editorial published by the European Renal Association who has also proposed to change to a novel equation only when it has considerably better performance, trying to reach global consensus before implementing such a new glomerular filtration rate (GFR) estimation equation. In Europe, this equation could be for instance the new European Kidney Function Consortium (EKFC) equation, which is population-specific, developed from European cohorts and accurate from infants to the older old. Beyond serum creatinine, the estimating equations based on cystatin C will probably gain in popularity, especially because cystatin C seems independent of race. Finally, we must keep in mind that all GFR equations remain an estimation of GFR, especially rough at the individual level. Measuring GFR with a reference method, such as iohexol clearance, remains indicated in specific patients and/or specific situations, and here also, the role of the clinical laboratories is central and should still evolve positively in the future.

Cystatin C-Based Equation to Estimate GFR without the Inclusion of Race and Sex

BACKGROUND

The accuracy of estimation of kidney function with the use of routine metabolic tests, such as measurement of the serum creatinine level, has been controversial. The European Kidney Function Consortium (EKFC) developed a creatinine-based equation (EKFC eGFRcr) to estimate the glomerular filtration rate (GFR) with a rescaled serum creatinine level (i.e., the serum creatinine level is divided by the median serum creatinine level among healthy persons to control for variation related to differences in age, sex, or race). Whether a cystatin C-based EKFC equation would increase the accuracy of estimated GFR is unknown.

METHODS

We used data from patients in Sweden to estimate the rescaling factor for the cystatin C level in adults. We then replaced rescaled serum creatinine in the EKFC eGFRcr equation with rescaled cystatin C, and we validated the resulting EKFC eGFRcys equation in cohorts of White patients and Black patients in Europe, the United States, and Africa, according to measured GFR, levels of serum creatinine and cystatin C, age, and sex.

RESULTS

On the basis of data from 227,643 patients in Sweden, the rescaling factor for cystatin C was estimated at 0.83 for men and women younger than 50 years of age and 0.83 + 0.005 × (age - 50) for those 50 years of age or older. The EKFC eGFRcys equation was unbiased, had accuracy that was similar to that of the EKFC eGFRcr equation in both White patients and Black patients (11,231 patients from Europe, 1093 from the United States, and 508 from Africa), and was more accurate than the Chronic Kidney Disease Epidemiology Collaboration eGFRcys equation recommended by Kidney Disease: Improving Global Outcomes. The arithmetic mean of EKFC eGFRcr and EKFC eGFRcys further improved the accuracy of estimated GFR over estimates from either biomarker equation alone.

CONCLUSIONS

The EKFC eGFRcys equation had the same mathematical form as the EKFC eGFRcr equation, but it had a scaling factor for cystatin C that did not differ according to race or sex. In cohorts from Europe, the United States, and Africa, this equation improved the accuracy of GFR assessment over that of commonly used equations. (Funded by the Swedish Research Council.).

Removing race and body surface area indexation for estimated kidney function based drug dosing: Aminoglycosides as justification of these principles

STUDY OBJECTIVE

The use of race in medicine can contribute to health inequity. Updated equations for estimated glomerular filtration rate (eGFR) without race have been published. Likewise, de-indexation of eGFR to body surface area (BSA) has been recommended by regulatory guidance for drug dosing in renal impairment. Clinical data justifying these recommendations for drug dosing are sparse. We examined the gain or loss of precision in drug dosing with estimated creatinine clearance (eCLcr) and eGFR using serum creatinine (eGFRcr) with and without race and BSA indexation by evaluating the population pharmacokinetics of the aminoglycosides as a classic drug class to probe kidney function.

DESIGN

Medical records from adult patients treated with gentamicin or tobramycin over a 13-year period were queried. Population pharmacokinetic analyses were performed using a 1-compartment base structural model. Models compared body size descriptors as covariates of the volume of distribution (V). Estimated creatinine clearance and eGFRcr using multiple contemporary equations with and without BSA indexation were tested as covariates of clearance (CL).

MAIN RESULTS

The final data set included 2968 patients treated with either gentamicin (20.2%) or tobramycin (79.8%). Patients self-identified as Caucasian (82%), African-American (10%), or other. The median [5th, 95th percentile] weight and BSA were 80.5 [49.4, 136] kg and 1.94 [1.48, 2.56] m² , respectively. Models of eCLcr and eGFRcr without indexation to BSA had a better model fit than eGFRcr indexed to BSA for aminoglycoside CL. The 2021 Chronic Kidney Disease Epidemiology collaboration (CKD-EPI) eGFRcr equation (no race, no BSA indexation) provided a comparable model fit to the 2009 CKD-EPI eGFRcr equation (with race, no BSA indexation) for aminoglycoside CL.

CONCLUSIONS

Race is not a relevant covariate of aminoglycoside CL. The 2021 CKD-EPI eGFR equation without race and BSA indexation is a better method for gentamicin and tobramycin CL estimation. Confirmation of these results for other drugs can support the harmonization of dosing by kidney function.

Alterations in Glomerular Filtration Rates Using Different Algorithms in the Korean Population Visiting Local Clinics and Hospitals

We retrospectively reviewed the estimated glomerular filtration rates (eGFR) calculated by three equations: (1) Modification of Diet in Renal Disease Study (MDRD), (2) Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) using serum creatinine in 2009 (CKD-EPI 2009), and (3) CKD-EPI suggested in 2021 (CKD-EPI 2021), in an adult Korean population visiting local clinics and hospitals for health check-ups between 2019 and 2021 to investigate the effect of changes in the prevalence of chronic kidney diseases using those equations. During the study period, serum creatinine tests were performed on 442,566 subjects (205,236 men and 237,330 women). The overall prevalence rates of decreased eGFR (<60 mL/min/1.73 m2) at baseline measurement were as follows: 3.4% using MDRD, 2.8% using CKD-EPI 2009, and 2.1% using CKD-EPI 2021. The prevalence of decreased eGFR increased with age. Among 442,566 tests, specimens having simultaneously measured random urine dipstick tests for proteinuria represented 6.0% of the population, and the albumin-creatinine ratio (ACR) was 0.3%. The prevalence of specimens having both decreased eGFR and proteinuria was significantly different among equations (p < 0.05). Among the three equations, MDRD and CKD-EPI 2009 had a similar specimen prevalence of decreased eGFR and proteinuria (≥1+) using a dipstick test or albuminuria (urine ACR > 30 mg/g creatinine), while those based on CKD-EPI 2021 were about half of those based on MDRD and CKD-EPI 2009. Future studies are needed to clarify the clinical impact of the changes in the calculations for eGFR.