Performance of the 2021 Race-Free CKD-EPI Creatinine- and Cystatin C-Based Estimated GFR Equations Among Kidney Transplant Recipients

Development and validation of a predictive model for atrial fibrillation recurrence post-catheter ablation in patients with nonvalvular atrial fibrillation on the basis of hemodynamic parameters

BACKGROUND

The influence of hemodynamic parameters on the recurrence of atrial fibrillation (AF) after catheter ablation is not well known, and it remains unclear whether a nomogram combining risk factors and hemodynamic parameters improves prediction accuracy.

OBJECTIVE

This study aimed to develop a nomogram on the basis of echocardiographic hemodynamic parameters for predicting AF recurrence after catheter ablation in nonvalvular atrial fibrillation (NVAF).

METHODS

A total of 380 consecutive patients with NVAF undergoing AF catheter ablation treatment were prospectively included. Patients were divided into training and validation cohorts in a 7:3 ratio. The follow-up time averaged 9 months with a median of 12 months, during which 132 patients (34.7%) experienced AF recurrence.

RESULTS

Least absolute shrinkage and selection operator regression and Cox regression analyses identified 4 significant predictors of AF recurrence: persistent AF (hazard ratio [HR] 1.63; 95% confidence interval [CI] 1.02-2.61; P = .041), S/D ratio of pulmonary vein (HR 0.50; 95% CI 0.30-0.84; P = .009), left atrial acceleration factor α (HR 1.31; 95% CI 1.02-1.68; P = .032), and left atrial appendage peak emptying flow velocity (HR 0.98; 95% CI 0.97-0.99; P = .004). On the basis of these 4 variables, a predictive nomogram was constructed. The nomogram demonstrated C indices of 0.664 and 0.728 for predicting 1- and 2-year AF recurrence, respectively, in the validation cohort. The Kaplan-Meier survival analysis indicated that a Nomo score of >128 was associated with a higher risk of AF recurrence.

CONCLUSION

Hemodynamic parameters may offer valuable insight into predicting AF recurrence after catheter ablation. Our study successfully developed a reliable nomogram on the basis of echocardiographic hemodynamic parameters to estimate the risk of AF recurrence after catheter ablation in patients with NVAF.

Performance of Five Estimated Glomerular Filtration Rate Equations in Vietnamese Kidney Transplant Recipients: A Cross-Sectional Study

BACKGROUND

Despite the critical role of glomerular filtration rate (GFR) assessment in monitoring kidney transplants, the most accurate estimate remains uncertain. This study aimed to evaluate the performance of established estimated GFR (eGFR) equations in the Vietnamese population.

METHODS

This cross-sectional study involving 299 Vietnamese kidney transplant recipients (KTRs) compared measured GFR (mGFR), determined using technetium-99m-diethylenetriaminepentaacetate (99mTc-DTPA) renal dynamic scintigraphy, with five eGFR equations (Modification of Diet in Renal Disease [MDRD], Asian modified Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI], CKD-EPI SCysC 2012, CKD-EPI SCr 2021, and CKD-EPI SCr-SCysC 2021). The performances of the five eGFR equations were compared based on bias, P30 accuracy, absolute accuracy, precision, root mean square error (RMSE), concordance correlation coefficient (CCC), and Pearson's correlation coefficient (r), along with their 95% confidence intervals (CIs).

RESULTS

CKD-EPI SCr-SCysC 2021 showed the best performance. The values for median bias, P30 accuracy, absolute accuracy, precision, RMSE, CCC, and r were: 2.57 [1.22; 3.55] mL/min/1.73 m2, 87.6% [83.3; 90.6], 10.0% [8.3; 11.7], 11.29 [9.57; 13.40] mL/min/1.73 m2, 11.54 [10.42; 12.92], 0.787 [0.737; 0.828], and 0.810 [0.759; 0.850], respectively. The MDRD equation did not show significantly lower precision and accuracy than the CKD-EPI SCr-SCysC 2021 equation. All five equations demonstrated improved accuracy in the mGFR ≥ 60 mL/min/1.73 m2 subgroup compared to the mGFR < 60 mL/min/1.73 m2 subgroup.

CONCLUSIONS

CKD-EPI SCr-SCysC 2021 is the most accurate eGFR equation for Vietnamese KTRs. Further studies with larger cohorts and comparisons with gold-standard methods are needed to confirm these findings.

New equation for estimating glomerular filtration rate in Vietnamese kidney transplant recipients

PURPOSE

Accurate assessment of kidney function is essential for post-kidney transplant management. This study aims to develop a new equation tailored to Vietnamese kidney transplant recipients and validate its performance against established equations.

METHODS

A total of 299 kidney transplant recipients underwent glomerular filtration rate (GFR) measurement using technetium-99m-diethylenetriaminepentaacetate renal dynamic scintigraphy, along with demographic, clinical, and laboratory assessments. Participants were divided into a development cohort (n = 150) to generate a new GFR-estimating equation and a validation cohort (n = 149) for internal validation against six equations.

RESULTS

The new equation, G F R = 100.430 × 1 . 080 sex × a g e - 0.097 × S c r - 0.524 × S c y s - 0.435 (sex: 0 = female; 1 = male), showed the smallest median bias (-0.11 [-1.40; 1.11]), highest P30 accuracy (94.0% [88.6; 96.6]), highest precision (interquartile range = 9.82 [7.63; 12.37]), and strongest correlation with measured GFR (r = 0.824 [0.752; 0.880]) among tested equations in the validation cohort. Among creatinine-based equations, the Modification of Diet in Renal Disease equation was the most accurate.

CONCLUSION

The new equation outperformed established equations and is recommended for Vietnamese kidney transplant recipients. The Modification of Diet in Renal Disease equation may serve as an alternative in centers lacking access to serum cystatin C. Further studies with larger cohorts, external validation, and comparisons with gold-standard GFR measurement methods are needed to confirm these results.

Better Prediction of Clinical Outcome with Estimated Glomerular Filtration Rate by CKD-EPI 2021

BACKGROUND

While the real-world impact of estimated glomerular filtration rate (eGFR) equation change on clinical outcome in a longitudinal cohort setting is limited, external valuation of equation performance should be performed in different population cohorts. This study aimed to compare differential impacts of eGFR values, calculated by 5 equations in a Korean patient population, on clinical outcomes.

METHODS

This retrospective longitudinal follow-up cohort study analyzed 23 246 participants with standardized creatinine/cystatin C assay-based laboratory results. The primary exposure was baseline eGFR calculated by 5 different equations including the recently developed 2021 race-free Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. Clinical outcomes including all-cause mortality, renal replacement therapy, and albuminuria were analyzed to estimate the hazard ratio of the eGFR on clinical outcomes.

RESULTS

Among the 5 equations, CKD-EPI 2021 with creatinine and cystatin C (CKD-EPI 2021-CrCys) showed an earlier increase in hazard ratios for all clinical outcomes, while CKD-EPI 2012 with cystatin C showed a higher hazard ratio for all-cause mortality at low eGFR. Replacing CKD-EPI 2012 with CKD-EPI 2021-CrCys, 5.4% of patients with mortality and 3.3% of patients who received renal replacement therapy were reclassified to a lower risk stage.

CONCLUSIONS

The 2021 CKD-EPI equations were acceptable in a Korean population, with better predictive power for clinical outcomes when compared to previous equations. The updated race-free factors for eGFR calculation improved identification of patients at risk for clinical outcomes.

Association of body round index with chronic kidney disease: a population-based cross-sectional study from NHANES 1999-2018

BACKGROUND

Complex nexuses between obesity and chronic kidney disease (CKD) have been reported. Nevertheless, the link between the body roundness index (BRI), an indicator utilized to measure body fat distribution, and CKD risk has been unexplored.

METHODS

We utilized publicly available data from ten survey cycles (1999-2018) of the National Health and Nutrition Examination Survey (NHANES) in the United States. We examined the association between BRI and CKD risk using multivariable logistic regression, subgroup analysis, interaction tests, and smooth curve fitting.

RESULTS

The study ultimately involved 41,953 participants, 3,123 (7.44%) of whom had CKD. Multivariable logistic regression, adjusted for covariates, identified high BRI levels in quartile 4 as a risk factor for CKD (OR = 1.30, 95% CI 1.12-1.50, P = 0.0005). This association remained consistent across subgroups (P for interaction > 0.05). Smoothed curve fitting exhibited a roughly linear positive correlation between BRI and CKD.

CONCLUSION

According to our study, BRI was related to CKD in a roughly linear way, suggesting a novel indicator for improving prevention and treatment for the CKD population. Nevertheless, additional research is needed to identify the association.

The Patient and Treatment Characteristics of Kidney Transplant Recipients with a Clinically Relevant Jaffe/Enzymatic Serum Creatinine Difference

Background: Differences in serum creatinine (SCr) between the Jaffe and enzymatic methods affect the detection and staging of chronic kidney disease in kidney transplant recipients (KTRs). However, there are very limited data on the extent to which the detection of acute kidney injury (AKI) is affected, what impact immunosuppression can have and whether a KTR-specific estimated glomerular filtration rate (eGFR) formula is beneficial. Methods: A total of 12,081 parallel Jaffe/enzymatic SCr (eSCr) measurements of adult outpatient KTRs (61% male, median age 53 years) in the same serum sample at the University Hospital Essen (Germany) between January 2020 and October 2023 were evaluated. AKI and CKD were defined according to current KDIGO guidelines. The GFR was estimated using CKD-EPI and KTR-specific formulas. Results: In about 1% of all measurements and 5% of the KTR patients, the SCr difference between the two methods was ≥ 0.3 mg/dl. A total of 81% of these patients were male; the median age was 52 years. High levels of immunosuppression, including when Belatacept was used, did not seem to have a clinically relevant impact on the difference between Jaffe and eSCr. The KTR-specific eGFR formula generally showed a greater agreement between Jaffe and eSCr than the CKD-EPI eGFR formula, but they showed differences in the classification of CKD stages, especially in less severe stages. Conclusions: Clinically relevant SCr differences between Jaffe and SCr are rare and depend on the type of immunosuppression. A KTR-specific eGFR formula could be beneficial in some cases, but there are limitations in less severe CKD stages.

Ethnic origin in cancer clinical trials: overrated or understated? A comprehensive analysis of cancer clinical trials leading to FDA and EMA approvals between 2020 and 2022

BACKGROUND

Ethnic diversity in cancer clinical trials is essential to ensure that therapeutic advances are equitable and broadly applicable in multicultural societies. Yet, missing consensus on the documentation of ethnic origin, partially based on the complexity of the terminology and fear of discrimination, leads to suboptimal patient management of minority populations. Additionally, eligibility criteria, such as stringent laboratory cut-offs, often fail to account for variations across ethnic groups, potentially excluding patients without evidence-based justification.

PATIENTS AND METHODS

This analysis addresses this issue by investigating ethnic diversity in clinical trials that led to European Medicines Agency (EMA) and Food and Drug Administration (FDA) approvals between 2020 and 2022. Trials were identified from FDA and EMA databases, and available protocols and full-text publications were reviewed for documentation of ethnic background and eligibility criteria for organ function (bone marrow, liver, and renal). Descriptive statistics were applied to summarize the findings.

RESULTS

Of the 56 trials analyzed, only two-thirds of primary result publications included information on ethnic origin. Caucasian and Asian groups were documented in most of those trials and also had the highest percentages of participants across trials, while other ethnic subgroups were less frequently documented and only made up a small proportion of trial participants. Eligibility criteria often set strict organ function cut-offs that did not consider variations among ethnic groups, potentially excluding minorities. The Cockcroft-Gault formula was frequently used to assess kidney function, despite its known limitations for multiethnic cohorts.

CONCLUSIONS

Ethnic homogenous participants and eligibility criteria that favor majority groups limit the applicability of findings in diverse populations, leading to inadequate patient management. While United States guidelines encourage inclusivity, similar recommendations are lacking in Europe. Thus European regulatory authorities, research organizations, and patient advocates should establish guidelines to improve ethnic diversity in cancer clinical trials, aligning research practices with the increasingly multicultural composition of European societies.

Immunosuppression and transplantation-related characteristics affect the difference between eGFR equations based on creatinine compared to cystatin C in kidney transplant recipients

Introduction

Previous studies show heterogeneity when applying estimated glomerular filtration (eGFR) equations to kidney transplant recipients (KTRs). However, research on the impact of transplantation-related characteristics on eGFR equations using creatinine (eGFRcr) compared to cystatin C (eGFRcys) is scarce.

Methods

We conducted a comprehensive analysis with three eGFRcr equations (Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2009, European Kidney Function Consortium (EKFC) 2021, kidney recipient specific-glomerular filtration rate KRS-GFR) 2023), comparing them to two eGFRcys (CKD-EPI 2012 and EKFC 2023) in 596 KTRs. Bland-Altman plots demonstrated relative differences according to different eGFR-stages. Multivariable logistic regression identified transplantation-related characteristics independently associated with smaller or greater differences between eGFRcr and eGFRcys equations.

Results

94.3% of the cohort were White individuals. Median eGFR differed as much as 9 ml/min/1.73 m2 between equations. The median relative differences (Q2) were greater (more negative) when comparing the eGFRcr equations to eGFRcys CKD-EPI 2012, than when comparing them to eGFRcys EKFC 2023 (P < .001). Better average eGFR was associated with smaller mean relative differences in all comparisons but eGFRcr CKD-EPI 2009 with eGFR EKFC 2023 and eGFRcr EKFC 2021 with eGFRcys EKFC 2023. Living kidney donation and belatacept use were independent factors associated with a smaller difference (≥Q3) between eGFRcr and eGFRcys equations, while prednisone use or higher HbA1c were independently associated with a greater difference (≤Q1) between equations.

Conclusion

Different eGFR-stages, donor, or recipient characteristics, along with immunosuppression such as belatacept or prednisone, contribute to differences between eGFRcr and eGFRcys. These effects need to be considered in the clinical management of KTRs.

Comparison of eGFR Equations to Guide Dosing of Medications for Kidney Transplant Recipients

BACKGROUND

Clinicians caring for kidney transplant recipients (KTRs) most commonly use estimated glomerular filtration rate (eGFR) to guide medication dosing as it is the most readily available measure of kidney function. Which eGFR equations provide the most accurate medication dosing guidance for KTRs remains uncertain.

METHODS

We studied 415 stable KTRs in Canada and New Zealand. Participants completed same-day measurements of creatinine and cystatin C and measured GFR (diethylenetriaminepentaacetic acid). Chronic Kidney Disease Epidemiology Collaboration, European Kidney Function Consortium, and transplant-specific eGFR equations were compared with both Cockcroft-Gault creatinine clearance (CrCl) and measured GFR. eGFR equations were assessed both indexed to a standardized body surface area (BSA) of 1.73 m 2 (milliliter per minute per 1.73 m 2 , as is conventional reporting from most clinical laboratories) and nonindexed (milliliter per minute) accounting for actual BSA. The primary outcome was the proportion of medication dosing discordance relative to Cockcroft-Gault CrCl or measured GFR for 8 commonly prescribed medications. Stratified analyses were performed on the basis of obesity status.

RESULTS

Nonindexed eGFR equations (milliliter per minute) resulted in substantially lower medication dosing discordance compared with indexed eGFR equations (milliliter per minute per 1.73 m 2 ). These findings were most pronounced among KTRs with obesity, in whom underdosing was frequent. When compared with Cockcroft-Gault CrCl, the lowest proportion of discordance was found with the nonindexed 2023 transplant-specific equation. When compared with measured GFR, the lowest proportion of discordance was found with the nonindexed 2021 Chronic Kidney Disease Epidemiology Collaboration Cr/CysC equation.

CONCLUSIONS

Nonindexed eGFR values accounting for actual BSA should be used by clinicians for medication dosing in KTRs. These findings may inform KT providers about which eGFR equations provide the safest, most accurate medication dosing guidance for KTRs.

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 electrolyte abnormalities and adverse outcomes in persons with eating disorders: A systematic review protocol

BACKGROUND

Electrolytes (sodium, potassium, calcium, magnesium, chloride, phosphate) are required in specific amounts for proper functioning of the human body. Although the body has different organ systems, such as the kidneys, that regulate electrolyte levels in the blood, electrolyte abnormalities occur frequently in people with eating disorders. The objective of this review will be to examine the association between electrolyte imbalances and adverse outcomes in people with eating disorders.

METHODS

A systematic review of studies on eating and electrolyte disorders shall be conducted. Electronic searches shall be done in the Ovid MEDLINE, EMBASE, and PsycINFO databases. Selected studies shall include randomized control trials (RCTs), non-randomized controlled trials, and cross-sectional studies published in English or French. Quality appraisal of studies and a narrative synthesis of extracted data shall be conducted.

DISCUSSION

This review will synthesize existing evidence on electrolyte abnormalities in people with eating disorders. It will identify the type of electrolyte imbalances, their impact, and outcomes in people with eating disorders. We anticipate that information that will be useful to policy makers and clinicians in designing better policies to prevent eating disorders and or manage people with eating disorders shall be elucidated in this study.

DISSEMINATION

The final manuscript will be submitted for publication in a journal.

REVIEW REGISTRATION

This protocol has been registered with the International Prospective Register of Systematic Reviews (PROSPERO); registration number CRD42023477497.

Short-Term, Mid-Term, and Long-Term Outcomes after Deceased Donor Kidney Transplantation in Patients with AKI: A Systematic Review and Meta-Analysis

Key Points

This study reviews the willingness to use kidneys from donors who have experienced AKI during transplantation and provides a thorough analysis of the existing literature. While delayed graft function is more common, primary nonfunction and acute rejection rates appear comparable, as do allograft function and graft survival compared with non-AKI donor kidneys. Considering the shortage of available organs and the high mortality rate of patients on dialysis, the use of donors with AKI as a source for kidney transplantation is a viable alternative.

Background

AKI is a common complication in hospitalized patients and may occur in potential kidney donors. Observational studies have suggested that kidney transplantation in patients with AKI is feasible and safe, but no systematic evaluation has been performed.

Methods

We performed a systematic review and meta-analysis to evaluate the outcomes of kidney transplantation in patients with AKI. We searched MEDLINE, Embase, Cochrane, Google Scholar, and other databases for studies reporting outcomes of donor kidneys with AKI. We included single-center, multicenter, and registry-based studies and analyzed them according to the definition and severity of AKI. End points were primary and delayed graft function (DGF), primary nonfunction (PNF), length of hospital stay, rejection, graft function, and patient and graft survival at 1, 3, 5, and 8–10 years after transplantation. This study was registered in PROSPERO, number CRD42021260088.

Results

We identified 33 single-center, four multicenter, and seven registry studies with more than 100,000 patients published between 2005 and 2022. Recipients from donors with AKI had a higher risk of DGF (relative risk, 1.51; 95% confidence interval [CI], 1.35 to 1.68). Graft function at discharge was worse in the AKI group (MDCrea [95% CI]: 0.96 mg/dl [0.36 to 1.56, I2=96%], MDGFR [95% CI]: −8.88 ml/min per 1.73 m2 [−15.32 to −2.44, I2=93%]), but improved thereafter and was similar in both groups at 3 months after transplantation (MDCrea [95% CI]: −0.05 mg/dl [−0.18 to 0.07, I2=0%], MDGFR [95% CI]: −1.83 ml/min per 1.73 m2 [−5.29 to 1.63, I2=91%]). Primary nonfunction and patient and graft survival were similar at 1, 3, 5, and 8–10 years after transplantation. There were no differences in rejections regardless of AKI definition and severity.

Conclusions

Transplantation of kidneys with AKI is associated with satisfactory short-term and long-term outcomes and should be pursued to increase the donor pool.

Clinical Impacts of Implementing the 2021 Race-Free Chronic Kidney Disease Epidemiology Collaboration Estimated Glomerular Filtration Rate

BACKGROUND

Estimated glomerular filtration rate (eGFR) has become incorporated into multiple clinical management situations. Historically, equations included a Black race coefficient, which lacked biological plausibility and created potential to exacerbate health disparities. A new equation created in 2021 changed the weighting of age, sex, and creatinine by modeling against a diverse cohort and removing the Black race coefficient.

CONTENT

A variety of clinical outcomes including kidney disease risk stratification, medication dosing, patient eligibility for clinical trials, and kidney donation are impacted by implementation of the new equation. Nearly 2 years after its initial publication, many studies have reported on observed analytical performance of the 2021 eGFR determined as diagnostic concordance and percentage of estimates within 30% of measured GFR. Additionally, the potential clinical impacts following adoption of the new eGFR among different patient populations has also been reported. Here we review these studies with a focus on assessing the data associated with the transition from 2009 to 2021 Chronic Kidney Disease Epidemiology Collaboration equations.

SUMMARY

The reported interindividual variation in eGFR performance is significantly larger than any potential benefit derived from race coefficients. Both the 2021 eGFR and the 2009 eGFR analytical performance fall short of the validation cohort performance in most cohorts. However, the 2021 analytical is similar or better than the 2009 eGFR in most cohorts. Implementing the 2021 eGFR will remove a systematic overestimation of kidney function among Black patients.

FOXP3 full length splice variant is associated with kidney allograft tolerance

Background

Progressive decline of allograft function leads to premature graft loss. Forkhead box P3 (FOXP3), a characteristic gene of T-regulatory cells, is known to be essential for auto-antigen tolerance. We assessed the hypothesis that low FOXP3 mRNA splice variant levels in peripheral blood cells early after transplantation are associated with progressive allograft injury.

Methods

Blood samples were prospectively collected from 333 incident kidney transplant recipients on the first and 29th postoperative day. We used quantitative polymerase chain reaction to determine transcripts of 3 isotypes of FOXP3 splice variants, including pre-mature FOXP3 and full length FOXP3 (FOXP3fl). We investigated the association between FOXP3 splice variant levels and the declines in estimated glomerular filtration rate (eGFR) of more than 5ml/min/1.73m2 within the first-year post-transplant using logistic regression.

Results

We observed lower FOXP3fl levels in recipients with declining eGFR (N = 132) than in recipients with stable eGFR (N = 201), (logarithmic value -4.13 [IQR -4.50 to -3.84] vs -4.00 [4.32 to -3.74], p=0.02). In ad hoc analysis pre-transplant FOXP3fl levels were similar in both groups. The association between FOXP3fl and declining eGFR was confirmed by multivariable analysis adjusted for potential confounding factors (Odds Ratio 0.51, 95% confidence interval 0.28 to 0.91: p=0.02). When stratifying FOXP3fl levels into quartiles, recipients with lower day1 FOXP3fl had the highest rate of declining eGFR (p=0.04).

Conclusion

Low FOXP3fl splice variant levels at the first postoperative day in kidney transplant recipients were associated with severe decline of eGFR, a well-known surrogate for hard endpoints.

A multicenter prospective study to define the natural history of BK viral infections in kidney transplantation

BACKGROUND

BK polyomavirus (BKV) can cause permanent loss of allograft function due to BKV-associated nephropathy (BKVN) in kidney transplant recipients. Besides immunosuppression reduction, there are no consistently effective interventions for BKV infection. Study purpose was to define natural history of BKV infection, identify risk factors for BKV reactivation and BKVN in kidney transplant recipients, and inform the design/conduct of future clinical trials of BKV-targeted therapeutics.

METHODS

We conducted a multicenter prospective observational study of incident kidney transplant recipients at six U.S. transplant centers. Participants were monitored every 4 weeks for BKV reactivation and followed for up to 24 months post-transplant. We used regression models (logistic, survival, mixed models) to study relationships between BK viremia/BKVN, clinical characteristics, and allograft function.

RESULTS

We enrolled 335 participants. Fifty-eight (17%) developed BK viremia, 6 (2%) developed biopsy-proven BKVN, and 29 (9%) developed suspected/presumed BKVN (defined as BKV viral load > 10,000 copies/mL without biopsy). Male donor sex was associated with lower odds for BK viremia, whereas recipient Black race was associated with two-fold increased odds for BK viremia. Recipient female sex was associated with more rapid clearance of BK viremia. Persistent BK viremia/BKVN was associated with poorer allograft function by 24 months post-transplant.

CONCLUSIONS

We identified multiple donor and recipient demographic factors associated with risk for BKV infection and poorer allograft function by 24 months post-transplant. This may help design future clinical trials of therapies to prevent or mitigate the deleterious impact of BKV reactivation on kidney transplant outcomes.

Glucometabolism in Kidney Transplant Recipients with and without Posttransplant Diabetes: Focus on Beta-Cell Function

Posttransplant diabetes mellitus (PTDM) is a common complication after kidney transplantation. Pathophysiologically, whether beta-cell dysfunction rather than insulin resistance may be the predominant defect in PTDM has been a matter of debate. The aim of the present analysis was to compare glucometabolism in kidney transplant recipients with and without PTDM. To this aim, we included 191 patients from a randomized controlled trial who underwent oral glucose tolerance tests (OGTTs) 6 months after transplantation. We derived several basic indices of beta-cell function and insulin resistance as well as variables from mathematical modeling for a more robust beta-cell function assessment. Mean ± standard deviation of the insulin sensitivity parameter PREDIM was 3.65 ± 1.68 in PTDM versus 5.46 ± 2.57 in NON-PTDM. Model-based glucose sensitivity (indicator of beta-cell function) was 68.44 ± 57.82 pmol∙min-1∙m-2∙mM-1 in PTDM versus 143.73 ± 112.91 pmol∙min-1∙m-2∙mM-1 in NON-PTDM, respectively. Both basic indices and model-based parameters of beta-cell function were more than 50% lower in patients with PTDM, indicating severe beta-cell impairment. Nonetheless, some defects in insulin sensitivity were also present, although less marked. We conclude that in PTDM, the prominent defect appears to be beta-cell dysfunction. From a pathophysiological point of view, patients at high risk for developing PTDM may benefit from intensive treatment of hyperglycemia over the insulin secretion axis.

Role of Renal Venous Oxygen Pressure for Renal Function Monitoring After Related Living-Donor Kidney Transplantation: Cohort Study

BACKGROUND

Monitoring of renal function after kidney transplantation (KT) is performed by measuring serum creatinine (SCr), urine volumes (UV), and glomerular filtration rate (GFR). Other methods based on oxygen metabolism, such as the renal venous oxygen pressure (PrvO2), may be useful. The aim of this study was to explore the correlation between PrvO2 and SCr, UV, and GFR 5 days after KT (SCr5, UV5, and GFR5, respectively).

METHODS

We conducted a prospective cohort study in adults scheduled for living donor KT. A venous blood sample was taken from the renal vein after declamping the renal artery, and blood gas determinations were made. Correlation analyses between PrvO2 and SCr5, UV5, and GFR5 were done by calculating Spearman's correlation coefficient with generalized linear models (GLM). A Spearman's correlation analysis was performed between the percentage decrease in SCr (%ΔSCr) and PrvO2. A GLM was also performed to determine the association of PrvO2 with slow graft function (SGF).

RESULTS

The study included 42 patients, of whom 67% were men. The median age was 31 years (IQR, 27-43.5). PrvO2 was negatively correlated with SCr5 (ρ = -0.53, P = .003), and positively correlated with GFR5 (ρ = 0.49, P = .001) and %ΔSCr (ρ = 0.47, P = .002). A higher PrvO2 was associated with an increase in GFR in univariable (β = 1.24, 95% CI, 0.56-1.93, P = .001) and multivariable (β = 1.24, 95% CI, 0.53-1.94, P = .001) analyses. No association was found between PrvO2 and SGF.

CONCLUSION

PrvO2 could be used to monitor renal function in the first 5 days after related living-donor KT, given its good correlation with SCr and GFR.

Challenges in the management of the kidney allograft: from decline to failure: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

In March 2022, Kidney Disease: Improving Global Outcomes (KDIGO) held a virtual Controversies Conference to address the important but rarely examined phase during which the kidney transplant is failing or has failed. In addition to discussing the definition of a failing allograft, 4 broad areas were considered in the context of a declining functioning graft: prognosis and kidney failure trajectory; immunosuppression strategies; management of medical and psychological complications, and patient factors; and choice of kidney replacement therapy or supportive care following graft loss. Identifying and paying special attention to individuals with failing allografts was felt to be important in order to prepare patients psychologically, manage immunosuppression, address complications, prepare for dialysis and/or retransplantation, and transition to supportive care. Accurate prognostication tools, although not yet widely available, were embraced as necessary to define allograft survival trajectories and the likelihood of allograft failure. The decision of whether to withdraw or continue immunosuppression after allograft failure was deemed to be based most appropriately on risk-benefit analysis and likelihood of retransplantation within a few months. Psychological preparation and support was identified as a critical factor in patient adjustment to graft failure, as was early communication. Several models of care were noted that enabled a medically supportive transition back to dialysis or retransplantation. Emphasis was placed on the importance of dialysis-access readiness before initiation of dialysis, in order to avoid use of central venous catheters. The centrality of the patient to all management decisions and discussions was deemed to be paramount. Patient "activation," which can be defined as engaged agency, was seen as the most effective way to achieve success. Unresolved controversies, gaps in knowledge, and areas for research were also stressed in the conference deliberations.

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.

Estimating glomerular filtration rate with new equations: can one size ever fit all?

Glomerular filtration rate (GFR) is thought to be the best overall indicator of kidney health. On an individual patient basis, a working knowledge of GFR is important to understand the future risk for chronic kidney disease (CKD) progression, enhanced risk for cardiovascular disease and death, and for optimal medical management including the dosing of certain drugs. Although GFR can be directly measured using exogenous compounds that are eliminated by the kidney, these methods are not scalable for repeated and routine use in clinical care. Thus, in most circumstances GFR is estimated, termed estimated GFR (eGFR), using serum biomarkers that are eliminated by the kidney. Of these, serum creatinine, and to a lesser extent cystatin C, are most widely employed. However, the resulting number is simply a population average for an individual of that age and sex with a given serum creatinine and/or cystatin C, while the range of potential GFR values is actually quite large. Thus, it is important to consider characteristics of a given patient that might make this estimate better or worse in a particular case. In some circumstances, cystatin C or creatinine might be the better choice. Ultimately it is difficult, if not impossible, to have an eGFR equation that performs equally well in all populations. Thus, in certain cases it might be appropriate to directly measure GFR for high consequence medical decision-making, such as approval for kidney donation or prior to certain chemotherapeutic regimens. In all cases, the eGFR thresholds of CKD stage should not be viewed as absolute numbers. Thus, clinical care should not be determined solely by CKD stage as determined by eGFR alone, but rather by the combination of an individual patient's likely kidney function together with their current clinical situation.

β-Trace Protein and β2-Microglobulin do not Improve Estimation of Glomerular Filtration Rate in Kidney Transplant Recipients Compared With Creatinine and Cystatin C

BACKGROUND

Reliable estimates of glomerular filtration rate (eGFR) are important for detecting changes in graft function in kidney transplant recipients. Current eGFR equations are based on plasma creatinine and/or cystatin C; however, these are associated with significant bias. This study investigated if equations based on β-trace protein (BTP) and β2-microglobulin (B2M) performed better than the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations based on creatinine and cystatin C among kidney transplant recipients.

METHODS

We included samples and data from the clinical trial CONTEXT. Glomerular filtration rate (GFR) was measured by plasma clearance of an exogenous marker. The eGFR was calculated using the CKD-EPI equations for estimating GFR from BTP and/or B2M and the 2021 CKD-EPI creatinine and creatinine-cystatin C equations. The GFR estimates were evaluated 3 (n = 82) and 12 (n = 64) months after transplant using mean bias, precision, and accuracy. Furthermore, we analyzed the ability of the equations to correctly classify the direction of changes in measured GFR from 3 to 12 months.

RESULTS

Among the BTP- and B2M-based equations, the combined eGFR-BTP-B2M performed best with respect to precision (SD = 7.64 mL/min/1.73 m2) and accuracy (±10% from measured GFR = 36%). The eGFR-BTP-B2M and the eGFR-creatinine-cystatin C (2021) performed similarly when comparing precision, accuracy, and residuals (P = .481). The BTP- and/or B2M-based equations did not perform better than the eGFR-creatinine-cystatin C (2021) in correctly classifying the direction of changes in measured GFR from 3 to 12 months.

CONCLUSIONS

β-trace protein and/or B2M do not improve the estimation of GFR when compared with creatinine- and cystatin C-based 2021 CKD-EPI equations.

Relationship Between Plasmatic Metformin Concentration and Renal Replacement Therapy: A Multicenter Cohort Study

BACKGROUND

Metformin is the first-line treatment used for type 2 diabetes mellitus for more than 60 years. Metformin-associated lactic acidosis is the most serious adverse effect of metformin and is most widely defined as metabolic acidosis with elevated lactate levels in the presence of metformin. However, there is no consensus regarding the role of metformin in metformin-associated lactic acidosis onset. This study aimed to determine the metformin toxicity threshold (the metformin plasma concentration that predicts the occurrence of lactic acidosis) and the metformin dialysis threshold (the metformin plasma concentration strongly correlated with dialysis introduction).

METHODS

This was a retrospective multicenter cohort study conducted from January 1, 2013, to December 31, 2020. All consecutive adult patients with at least one metformin-detectable blood concentration measurement were included.

RESULTS

In total, 169 patients (92 men; mean age, 70 ± 11 years) were included in this study. A receiver operating characteristic analysis using Youden index showed that a metformin plasma concentration threshold of 17.9 mg/L was associated with lactic acidosis (sensitivity: 43.8%; specificity: 90.5%). Another receiver operating characteristic analysis using Youden index showed that a metformin plasma concentration threshold of 17.5 mg/L was associated with dialysis (sensitivity, 53.0%; specificity: 94.2%).

CONCLUSIONS

The retrospective study design, lack of clinical data, and selection bias (patients in whom metformin was prescribed owing to pathological conditions) were major limitations, resulting in only preliminary findings. However, this study could serve as a basis for future prospective clinical studies to evaluate the use of these clinical threshold values as therapeutic guides.

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.