Should estimates of glomerular filtration rate and creatinine clearance be indexed to body surface area for drug dosing?

Recommended Methods of Drug Dosing Adjustment for Patients With Renal Impairment

Since 2020, there have been changes in Food and Drug Administration guidance and in recommendations by national organizations with a focus on kidney diseases pertaining to the choice of equations used to estimate creatinine clearance and glomerular filtration rate in patients with renal impairment. This includes a recommendation by the National Kidney Foundation to avoid the use of the Cockcroft-Gault equation for drug dosing in patients with renal impairment. This commentary provides an overview of recent recommendations concerning kidney function assessment that have important implications for drug dosing in patients with renal impairment and provides suggestions for implementing these recommendations.

A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease

BACKGROUND

In response to a national call for re-evaluation of the use of race in clinical algorithms, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) established a Task Force to reassess inclusion of race in the estimation of glomerular filtration rate (GFR) in the United States and its implications for diagnosis and management of patients with, or at risk for, kidney diseases.

PROCESS & DELIBERATIONS

The Task Force organized its activities over 10 months in phases to (1) clarify the problem and evidence regarding GFR estimating equations in the United States (described previously in an interim report), and, in this final report, (2) evaluate approaches to address use of race in GFR estimation, and (3) provide recommendations. We identified 26 approaches for the estimation of GFR that did or did not consider race and narrowed our focus, by consensus, to 5 of those approaches. We holistically evaluated each approach considering 6 attributes: assay availability and standardization; implementation; population diversity in equation development; performance compared with measured GFR; consequences to clinical care, population tracking, and research; and patient centeredness. To arrive at a unifying approach to estimate GFR, we integrated information and evidence from many sources in assessing strengths and weaknesses in attributes for each approach, recognizing the number of Black and non-Black adults affected.

RECOMMENDATIONS

(1) For US adults (>85% of whom have normal kidney function), we recommend immediate implementation of the CKD-EPI creatinine equation refit without the race variable in all laboratories in the United States because it does not include race in the calculation and reporting, included diversity in its development, is immediately available to all laboratories in the United States, and has acceptable performance characteristics and potential consequences that do not disproportionately affect any one group of individuals. (2) We recommend national efforts to facilitate increased, routine, and timely use of cystatin C, especially to confirm estimated GFR in adults who are at risk for or have chronic kidney disease, because combining filtration markers (creatinine and cystatin C) is more accurate and would support better clinical decisions than either marker alone. If ongoing evidence supports acceptable performance, the CKD-EPI eGFR-cystatin C (eGFRcys) and eGFR creatinine-cystatin C (eGFRcr-cys_R) refit without the race variables should be adopted to provide another first-line test, in addition to confirmatory testing. (3) Research on GFR estimation with new endogenous filtration markers and on interventions to eliminate race and ethnic disparities should be encouraged and funded. An investment in science is needed for newer approaches that generate accurate, unbiased, and precise GFR measurement and estimation without the inclusion of race, and that promote health equity and do not generate disparate care.

IMPLEMENTATION

This unified approach, without specification of race, should be adopted across the United States. High-priority and multistakeholder efforts should implement this solution.

Peter WL, Warfield C, Powe NR. A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease

BACKGROUND

In response to a national call for re-evaluation of the use of race in clinical algorithms, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) established a Task Force to reassess inclusion of race in the estimation of GFR in the United States and its implications for diagnosis and management of patients with, or at risk for, kidney diseases.

PROCESS DELIBERATIONS

The Task Force organized its activities over 10 months in phases to ( 1 ) clarify the problem and evidence regarding eGFR equations in the United States (described previously in an interim report), and, in this final report, ( 2 ) evaluate approaches to address use of race in GFR estimation, and ( 3 ) provide recommendations. We identified 26 approaches for the estimation of GFR that did or did not consider race and narrowed our focus, by consensus, to five of those approaches. We holistically evaluated each approach considering six attributes: assay availability and standardization; implementation; population diversity in equation development; performance compared with measured GFR; consequences to clinical care, population tracking, and research; and patient centeredness. To arrive at a unifying approach to estimate GFR, we integrated information and evidence from many sources in assessing strengths and weaknesses in attributes for each approach, recognizing the number of Black and non-Black adults affected.

RECOMMENDATIONS

( 1 ) For US adults (>85% of whom have normal kidney function), we recommend immediate implementation of the CKD-EPI creatinine equation refit without the race variable in all laboratories in the United States because it does not include race in the calculation and reporting, included diversity in its development, is immediately available to all laboratories in the United States, and has acceptable performance characteristics and potential consequences that do not disproportionately affect any one group of individuals. ( 2 ) We recommend national efforts to facilitate increased, routine, and timely use of cystatin C, especially to confirm eGFR in adults who are at risk for or have CKD, because combining filtration markers (creatinine and cystatin C) is more accurate and would support better clinical decisions than either marker alone. If ongoing evidence supports acceptable performance, the CKD-EPI eGFR-cystatin C (eGFRcys) and eGFR creatinine-cystatin C (eGFRcr-cys_R) refit without the race variables should be adopted to provide another first-line test, in addition to confirmatory testing. ( 3 ) Research on GFR estimation with new endogenous filtration markers and on interventions to eliminate race and ethnic disparities should be encouraged and funded. An investment in science is needed for newer approaches that generate accurate, unbiased, and precise GFR measurement and estimation without the inclusion of race, and that promote health equity and do not generate disparate care.

IMPLEMENTATION

This unified approach, without specification of race, should be adopted across the United States. High-priority and multistakeholder efforts should implement this solution.

Evaluation and enhancement of standard equations for renal function estimation in individuals with components of metabolic disease

BACKGROUND

The primary objective of this study aims to test patient factors, with a focus on cardiometabolic disease, influencing the performance of the Cockcroft-Gault equation in estimating glomerular filtration rate.

METHODS

A cohort study was performed using data from adult patients with both a 24-h urine creatinine collection and a serum creatinine available. Creatinine clearance was calculated for each patient using the Cockcroft-Gault, Modified Diet in Renal Disease, and Chronic Kidney Disease Epidemiology Collaboration equations and estimates were compared to the measured 24-h urine creatinine clearance. In addition, new prediction equations were developed.

RESULTS

In the overall study population (n = 484), 44.2% of patients were obese, 44.0% had diabetes, and 30.8% had dyslipidemia. A multivariable model which incorporating patient characteristics performed the best in terms of correlation to measured 24-h urine creatinine clearance, accuracy, and error. The modified Cockcroft-Gault equation using lean body weight performed best in the overall population, the obese subgroup, and the dyslipidemia subgroup in terms of strength of correlation, mean bias, and accuracy.

CONCLUSIONS

Regardless of strategy used to calculate creatinine clearance, residual error was present suggesting novel methods for estimating glomerular filtration rate are urgently needed.

Changes of expression levels of serum cystatin C and soluble vascular endothelial growth factor receptor 1 in the treatment of patients with glomerulus nephritis

Expression levels and changes of serum cystatin C (C's C) and soluble vascular endothelial growth factor receptor 1 (sVEGFR1) in treatment of patients with glomerulus nephritis (GN) were investigated. The medical records of 88 patients with GN who were diagnosed in Weifang People's Hospital from March 2014 to June 2017 were collected, and their medical records were considered as a study group. The study group was divided into secondary glomerulonephritis (SGN) group (52 cases) and primary glomerulonephritis (PGN) group (36 cases). Physical examination data of 50 healthy volunteers who were examined in the same hospital during the same period were considered as a control group. The correlation between expression of serum C's C and expression of sVEGFR1 of patients with GN was compared. Expression levels of serum C's C and sVEGFR1 of patients before treatment in the study group were higher than those in the control group (P<0.05). With the extension of the treatment cycle, C's C and sVEGFR1 expression levels in PGN and SGN groups reduced gradually (P<0.05). With the extension of the treatment cycle, the renal function indexes of the study group patients showed a downward trend (P<0.05). Expression of C's C was positively correlated with urea nitrogen and creatinine (P<0.05). In conclusion, C's C and sVEGFR1 are highly expressed in the serum of patients with GN. Expression of C's C and sVEGFR1 decrease as patients are treated. C's C and sVEGFR1 can be used as indicators for monitoring the condition of patients with GN. It is worthwhile to promote C's C and sVEGFR1 in clinical practice.

Assessment of Kidney Function in Patients With Extreme Obesity: A Narrative Review

Objectives:

To discuss the evidence and caveats associated with estimated and measured creatinine clearance (eClCr and mClCr) and glomerular filtration rate (eGFR and mGFR) assessments of kidney function in patients with more extreme forms of obesity.

Data Sources:

PubMed (1976 to mid-May 2020) was used, with bibliographies of retrieved articles searched for additional articles.

Study Selection and Data Extraction:

Articles using gold standard mGFR to evaluate eClCr, mClCr, and eGFR assessments of kidney function in patients with more extreme forms of obesity were included.

Data Synthesis:

The overestimation of GFR by mClCr is well established, but mClCr is an alternative to mGFR assessments for determining medication dosing in patients with extremes of body size or muscle mass, or in patients receiving narrow therapeutic index medications when eGFR is likely to be inaccurate. The vast majority of studies comparing eGFR assessments with gold standard indicators of kidney function were attempts to validate eGFR equations for diagnosing and staging chronic kidney disease (CKD).

Relevance to Patient Care and Clinical Practice:

For dosing medications in patients with stable kidney function and extreme obesity, a deindexed 4-variable Modification of Diet in Renal Disease or CKD Epidemiology Collaboration equation is an alternative to Cockcroft-Gault. Consistent use of the same equation by provider and between providers within any given setting is of paramount importance.

Conclusions:

In patients with extreme obesity and stable kidney function, eClCr or eGFR using deindexed values provides estimates of function for dosing adjustments of medications with elimination by the kidneys, but more research is needed with respect to the best size descriptor to use with estimating equations.

Predictors of Augmented Renal Clearance in a Heterogeneous ICU Population as Defined by Creatinine and Cystatin C

INTRODUCTION

The incidence of augmented renal clearance (ARC) in the intensive care unit (ICU) is highly variable, and identification of these patients remains challenging.

OBJECTIVE

The objective of this study was to define the incidence of ARC in a cohort of critically ill adults, using serum Cr and cystatin C, and to identify factors associated with its development.

METHODS

This is a retrospective cohort study of critically ill patients without stage 2 or 3 acute kidney injury with both serum Cr and cystatin C available. The incidence of ARC was defined as a Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)Cr-cystatin C-estimated glomerular filtration rate >130 mL/min. A multivariable logistic regression model using a penalized Lasso method was fit to identify independent predictors of ARC.

RESULTS

Among the 368 patients included in the study, indication for ICU admission was nonoperative in 55% of patients, and 9% of patients were admitted for major trauma. The overall incidence of ARC was low at 4.1%. In a multivariable logistic regression model, Charlson comorbidity index, major trauma, intracerebral hemorrhage, age, and Sequential Organ Failure Assessment score were found to predict ARC.

CONCLUSION

The incidence of ARC in this study was low, but prediction models identified several factors for early identification of patients with risk factors for or who develop ARC, particularly in a cohort with a low baseline risk of ARC. These factors could be used to help identify patients who may develop ARC.