Measured GFR in Routine Clinical Practice-The Promise of Dried Blood Spots

Risk Factor-Based Screening for Early Detection of Chronic Kidney Disease in Primary Care Settings: A Systematic Review

Rationale & Objective

Kidney failure can be prevented or delayed if chronic kidney disease (CKD) is detected and treated early. Targeted screening has been shown effective in detecting CKD worldwide, but a recently updated summary of evidence is lacking. We synthesized up-to-date evidence of the effectiveness of risk factor-based screening for the early detection of CKD among adults in primary care.

Study Design

We retrieved articles from Medline, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, and Scopus. Relevant gray literature and hand-searching bibliographies of key articles were also performed.

Setting & Study Populations

Adult patients (age ≥ 18 years) with at least 1 known CKD risk factor in primary care.

Selection Criteria for Studies

Prospective studies applying CKD screening in adults based on at least 1 CKD risk factor.

Data Extraction

Data were abstracted from full texts and the risk of bias was assessed using the Joanna Briggs Institute critical appraisal tools.

Analytical Approach

No meta-analysis was conducted.

Results

In total, 24 studies from 11 countries fulfilled the inclusion criteria. Diverse screening tests, CKD definitions, formulas for estimating kidney function, and positive screening test cutoffs were used. Most studies (n = 22) employed estimated glomerular filtration rate (eGFR), albumin-creatinine ratio (ACR) (n = 14), and dipstick urinalysis (n = 9) for screening. The prevalence of reduced kidney function and/or kidney damage was between 2.9% and 56%, and confirmed CKD varied from 4.4% to 17.1%. Increased patient referrals and physician visits, higher patient satisfaction, and some form of patient willingness to pay for the services were reported because of screening.

Limitations

Meta-analysis was not conducted, and the findings might not be generalized to resource-limited settings.

Conclusions

Risk factor-based screening effectively identifies a substantial proportion of people with undiagnosed CKD, but there is still scope for improvement. We recommend future studies have robust designs and multidimensional interventions to establish the effectiveness of targeted CKD screening in primary care.

Comparison of estimated glomerular filtration rate using five equations to predict acute kidney injury following hip fracture surgery

BACKGROUND

Decreased estimated glomerular filtration rate (eGFR) is associated with acute kidney injury (AKI) following hip fracture surgery. Delaying surgery for preoperative treatment of comorbidities is controversial in this patient population. The purpose of this study was 1) to assess differences in demographics and comorbidities between AKI and non-AKI groups, 2) to analyze equations used in calculating eGFR, and 3) to identify the equation which best predicts the development of AKI following hip fracture surgery. We hypothesize that one of the equations used to calculate eGFR will be superior to the others.

PATIENTS AND METHODS

124,002 cases of hip fracture surgery were performed from 2012 to 2019, based upon a query of the National Surgical Quality Improvement Program (NSQIP). Preoperative eGFR was calculated using the following: Modification of Diet in Renal Disease (MDRD) II, re-expressed MDRD II, Chronic Kidney Disease Epidemiology Collaboration, Mayo quadratic, and Cockcroft-Gault equations. Independent associations between preoperative eGFR and postoperative renal failure were evaluated using multivariate regression analysis. The predictive ability of each equation was determined using the Akaike information criterion (AIC).

RESULTS

AKI was diagnosed in 584 (0.71%) out of the 82,326 patients following hip fracture surgery. The AKI and no AKI cohorts differed significantly by patient sex (p = <0.001), race (p = <0.001), BMI (p = < 0.001), preoperative hematocrit (p = <0.001), preoperative albumin (p = <0.001), diabetes mellitus (p = <0.001), hypertension (p = <0.001), and congestive heart failure (p = <0.001). The Mayo equation (84.0 ± 23.7) was the equation with the highest calculated mean eGFR, followed by the CKD-EPI equation (83.6 ± 20.0), MDRD II equation (83.0 ± 38.9), CG equation (74.7 ± 35.5), and finally the re-expressed MDRD II equation (68.5 ± 36.0) which had the lowest calculated mean eGFR.. All five equations detected that a decrease in preoperative eGFR was associated with an increased risk of postoperative AKI. Lower preoperative eGFR, as calculated by each of the five equations, was significantly associated with an increased risk of AKI following surgical fixation of hip fracture. The AIC was the lowest in the Mayo equation, demonstrating the best fit of the equations to predict postoperative AKI CONCLUSIONS: We propose that using the equation that best identifies those at risk of developing postoperative AKI may help with perioperative decision making and treatment to improve outcomes, which we found to be the Mayo equation. The risk of postoperative AKI was independently associated with decreased preoperative eGFR. The results of this study may warrant further investigation utilizing prospective studies.

LEVEL OF EVIDENCE

III; retrospective cohort study.

Withaferin A ameliorates ovarian cancer-induced renal damage through the regulation of expression of inflammatory cytokines

BACKGROUND

Cachexia a multifactorial syndrome is a common sequala in patients with cancer. It varies from 42 to 80% depending upon the oncological stage and is directly responsible for 30% of deaths in these patients. Previous research from our laboratory demonstrated that peritoneal ovarian cancer generated in NSG mice resulted in skeletal and cardiac muscle atrophy - leading to loss of skeletal muscle mass and strength, and cardiac dysfunction (cachexia). Treatment of mice bearing i.p. tumors with withaferin A (WFA) showed reversal of skeletal muscle and cardiac cachexia. The present study is focused on determining effects of peritoneal ovarian tumors on kidney damage and effects of WFA treatment on ameliorating kidney damage.

METHODS

We generated intraperitoneal ovarian cancer by injecting female NSG mice with ovarian cancer cell line (A2780). After one week of injecting cancer cells, mice were treated with WFA (4 mg/kg) every third day, for three weeks. After 4 weeks of injection of cancer cells, the mice were sacrificed and various tissues including kidney and blood were collected, snap-frozen in liquid nitrogen, and stored at -800C. The presence of kidney biomarker creatinine, was measured in the plasma by an ELISA. The mRNA was isolated from mouse kidneys and was used to examine the expression levels of signaling proteins, inflammatory cytokines, and genes responsible for inducing cachexia (IL-1β, IL-6, TNF-α, TGF-β, GDF-15, and MYD88).

RESULTS

Our results showed a significant increase in levels of expression of inflammatory cytokine IL-1 β (p < 0.01), IL-6 (p < 0.001), TNF-α (p < 0.001), and other related genes including TRAF6 (p < 0.01), MYD88 (p < 0.01), and GDF-15 (p = 0.005) in tumor-bearing mice compared to controls. Treatment of mice bearing tumors with WFA attenuated the increase in expression of each gene. In addition, our results showed a significant increase in creatinine levels in circulation in tumor-bearing mice compared to control mice. Treatment of tumor-bearing mice with WFA resulted in a significant decrease in plasma creatinine levels compared to tumor-bearing mice.

CONCLUSIONS

Our results conclude that ovarian tumors in NSG mice caused kidney damage and renal dysfunction, which was effectively ameliorated by WFA treatment, suggesting a protective effect of WFA on kidney injury induced by ovarian cancer.

High Protein Diets and Glomerular Hyperfiltration in Athletes and Bodybuilders: Is Chronic Kidney Disease the Real Finish Line?

Several observational and experimental studies in humans have suggested that high protein intake (PI) causes intraglomerular hypertension leading to hyperfiltration. This phenomenon results in progressive loss of renal function with long-term exposure to high-protein diets (HPDs), even in healthy people. The recommended daily allowance for PI is 0.83 g/kg per day, which meets the protein requirement for approximately 98% of the population. A HPD is defined as a protein consumption > 1.5 g/kg per day. Athletes and bodybuilders are encouraged to follow HPDs to optimize muscle protein balance, increase lean body mass, and enhance performance. A series of studies in resistance-trained athletes looking at HPD has been published concluding that there are no harmful effects of HPD on renal health. However, the aim of these studies was to evaluate body composition changes and they were not designed to assess safety or kidney outcomes. Here we review the effects of HPD on kidney health in athletes and healthy individuals with normal kidney function.

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.

Bias and Accuracy of Glomerular Filtration Rate Estimating Equations in the US: A Systematic Review and Meta-Analysis

Importance

There is increasing concern that continued use of a glomerular filtration rate (GFR) estimating equation adjusted for a single racial group could exacerbate chronic kidney disease-related disparities and inequalities.

Objective

To assess the performance of GFR estimating equations across varied patient populations.

Data Sources

PubMed, Embase, Web of Science, ClinicalTrials.gov, and Scopus databases were systematically searched from January 2012 to February 2023.

Study Selection

Inclusion criteria were studies that compared measured GFR with estimated GFR in adults using established reference standards and methods. A total of 6663 studies were initially identified for screening and review.

Data Extraction and Synthesis

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 2 authors independently extracted data on studies that examined the bias and accuracy of GFR estimating equations. For each outcome, a random-effects model was used to calculate pooled estimates. Data analysis was conducted from March to December 2023.

Main Outcomes and Measures

The primary outcomes were bias and accuracy of estimated GFRs in Black vs non-Black patients, as well as in individuals with chronic conditions. Bias was defined as the median difference between the measured GFR and the estimated GFR. Accuracy was assessed with P30 (the proportion of persons in a data set whose estimated GFR values were within 30% of measured GFR values) and measures of heterogeneity.

Results

A total of 12 studies with a combined 44 721 patients were included. Significant heterogeneity was found in the bias of various GFR estimation equations. Race-corrected equations and creatinine-based equations tended to overestimate GFR in Black populations and showed mixed results in non-Black populations. For creatinine-based equations, the mean bias in subgroup analysis was 2.1 mL/min/1.73 m2 (95% CI, -0.2 mL/min/1.73 m2 to 4.4 mL/min/1.73 m2) in Black persons and 1.3 mL/min/1.73 m2 (95% CI, 0.0 mL/min/1.73 m2 to 2.5 mL/min/1.73 m2) in non-Black persons. Equations using only cystatin C had small biases. Regarding accuracy, heterogeneity was high in both groups. The overall P30 was 84.5% in Black persons and 87.8% in non-Black persons. Creatinine-based equations were more accurate in non-Black persons than in Black persons. For creatinine-cystatin C equations, the P30 was higher in non-Black persons. There was no significant P30 difference in cystatin C-only equations between the 2 groups. In patients with chronic conditions, P30 values were generally less than 85%, and the biases varied widely.

Conclusions and Relevance

This systematic review and meta-analysis of GFR estimating equations suggests that there is bias in race-based GFR estimating equations, which exacerbates kidney disease disparities. Development of a GFR equation independent of race is a crucial starting point, but not the sole solution. Addressing the disproportionate burden of kidney failure on Black individuals in the US requires an enduring, multifaceted approach that should include improving diagnostics, tackling social determinants of health, confronting systemic racism, and using effective disease prevention and management strategies.

Combined Heart Kidney Transplantation Versus Heart Transplant in Patients with Renal Failure: Contemporary Insights and Future Perspectives

PURPOSE OF REVIEW

In this review, we aim to outline the criteria regarding the evaluation of patients with chronic renal disease (CKD) awaiting heart transplantation and discuss the outcomes of combined heart/kidney transplantation. Herein, we also review pathophysiology and risk factors that predispose to chronic kidney disease (CKD) and acute kidney injury (AKI) in patients with HF and after OHT.

RECENT FINDINGS

In patients with end-stage systolic heart failure (HF) and an estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m2, orthotopic heart transplantation (OHT) alone is a relative contraindication, with a consensus that these patients are better served with heart-kidney transplant (HKT). However, there is significant variation between institutions regarding timing and indication for heart/kidney transplantation, with little data available to predict post-transplant outcomes. A Scientific Statement from American Heart Association was published detailing the indications, evaluation, and outcomes for Heart-Kidney Transplantation, and noted a steady rise in the incidence of heart/kidney dual organ transplants. Recently, the Organ Procurement and Transplantation Network (OPTN) Multi-Organ Transplantation Committee implemented a safety net policy for heart transplant recipients who do need meet criteria for simultaneous heart-kidney transplant in 2023 but with a likely need for sequential kidney transplantation. Optimization of organ distribution and patient outcomes after cardiac transplantation requires appropriate recipient selection. This review also outlines the criteria regarding the evaluation of patients with CKD awaiting heart transplantation and outcomes of combined HKT.

Evaluating and Improving the Performance and Racial Fairness of Algorithms for GFR Estimation

Data-driven clinical prediction algorithms are used widely by clinicians. Understanding what factors can impact the performance and fairness of data-driven algorithms is an important step towards achieving equitable healthcare. To investigate the impact of modeling choices on the algorithmic performance and fairness, we make use of a case study to build a prediction algorithm for estimating glomerular filtration rate (GFR) based on the patient's electronic health record (EHR). We compare three distinct approaches for estimating GFR: CKD-EPI equations, epidemiological models, and EHR-based models. For epidemiological models and EHR-based models, four machine learning models of varying computational complexity (i.e., linear regression, support vector machine, random forest regression, and neural network) were compared. Performance metrics included root mean squared error (RMSE), median difference, and the proportion of GFR estimates within 30% of the measured GFR value (P30). Differential performance between non-African American and African American group was used to assess algorithmic fairness with respect to race. Our study showed that the variable race had a negligible effect on error, accuracy, and differential performance. Furthermore, including more relevant clinical features (e.g., common comorbidities of chronic kidney disease) and using more complex machine learning models, namely random forest regression, significantly lowered the estimation error of GFR. However, the difference in performance between African American and non-African American patients did not decrease, where the estimation error for African American patients remained consistently higher than non-African American patients, indicating that more objective patient characteristics should be discovered and included to improve algorithm performance.

Diagnostic challenges of diabetic kidney disease

Diabetic kidney disease (DKD) is one of the most common microvascular complications of both type 1 and type 2 diabetes and the most common cause of the end-stage renal disease (ESRD). It has been evidenced that targeted interventions at an early stage of DKD can efficiently prevent or delay the progression of kidney failure and improve patient outcomes. Therefore, regular screening for DKD has become one of the fundamental principles of diabetes care. Long-established biomarkers such as serum-creatinine-based estimates of glomerular filtration rate and albuminuria are currently the cornerstone of diagnosis and risk stratification in routine clinical practice. However, their immanent biological limitations and analytical variations may influence the clinical interpretation of the results. Recently proposed new predictive equations without the variable of race, together with the evidence on better accuracy of combined serum creatinine and cystatin C equations, and both race- and sex-free cystatin C-based equation, have enabled an improvement in the detection of DKD, but also require the harmonization of the recommended laboratory tests, wider availability of cystatin C testing and specific approach in various populations. Considering the complex pathophysiology of DKD, particularly in type 2 diabetes, a panel of biomarkers is needed to classify patients in terms of the rate of disease progression and/or response to specific interventions. With a personalized approach to diagnosis and treatment, in the future, it will be possible to respond to DKD better and enable improved outcomes for numerous patients worldwide.

Association between estimated glomerular filtration rate slope and cardiovascular disease among individuals with and without diabetes: a prospective cohort study

BACKGROUND

Previous studies have reported an association between a significant decline in estimated glomerular filtration rate (eGFR) over time and an increased risk of cardiovascular disease (CVD). This study aimed to investigate the association between the eGFR slope and CVD among individuals with and without diabetes.

METHODS

This prospective cohort study was conducted within the Tehran Lipid and Glucose Study (TLGS) framework. We studied 6919 adults aged 20-70 years, including 985 with diabetes and 5934 without diabetes. The eGFR slope was determined based on repeated measurements of eGFR through linear mixed-effects models. A multivariable Cox proportional hazard model was employed to evaluate the association between eGFR slope, both in continuous and categorical form, and the risk of CVD.

RESULTS

The slopes of eGFR exhibited a bell-shaped distribution, with a mean (standard deviation (SD)) of -0.63 (0.13) and - 0.70 (0.14) ml/min per 1.73 m2 per year in individuals with and without diabetes, respectively. During a median follow-up of 8.22 years, following the 9-year eGFR slope ascertainment period, a total of 551 CVD events (195 in patients with diabetes) were observed. Among individuals with diabetes, a steeper decline in eGFR slope was significantly associated with a higher risk of CVD events, even after adjusting for baseline eGFR, demographic factors, and traditional risk factors for CVD; slopes of (-1.05 to -0.74) and (-0.60 to -0.52) were associated with 2.12 and %64 higher risks for CVD, respectively, compared with a slope of (-0.51 to 0.16). Among individuals without diabetes, the annual eGFR slope did not show a significant association with the risk of CVD.

CONCLUSION

Monitoring the eGFR slope may serve as a potential predictor of CVD risk in individuals with diabetes.

Biomarkers of the End-Stage Renal Disease Progression: Beyond the GFR

Chronic kidney disease can progress to the end-stage renal disease (ESRD) characterized by a high risk of morbidity and mortality. ESRD requires immediate therapy or even dialysis or kidney transplantation, therefore, its timely diagnostics is critical for many patients. ESRD is associated with pathological changes, such as inflammation, fibrosis, endocrine disorders, and epigenetic changes in various cells, which could serve as ESRD markers. The review summarizes information on conventional and new ESRD biomarkers that can be assessed in kidney tissue, blood, and urine. Some biomarkers are specific to a particular pathology, while others are more universal. Here, we suggest several universal inflammatory, fibrotic, hormonal, and epigenetic markers indicative of severe deterioration of renal function and ESRD progression for improvement of ESRD diagnostics.

Clustering-based spatial analysis (CluSA) framework through graph neural network for chronic kidney disease prediction using histopathology images

Machine learning applied to digital pathology has been increasingly used to assess kidney function and diagnose the underlying cause of chronic kidney disease (CKD). We developed a novel computational framework, clustering-based spatial analysis (CluSA), that leverages unsupervised learning to learn spatial relationships between local visual patterns in kidney tissue. This framework minimizes the need for time-consuming and impractical expert annotations. 107,471 histopathology images obtained from 172 biopsy cores were used in the clustering and in the deep learning model. To incorporate spatial information over the clustered image patterns on the biopsy sample, we spatially encoded clustered patterns with colors and performed spatial analysis through graph neural network. A random forest classifier with various groups of features were used to predict CKD. For predicting eGFR at the biopsy, we achieved a sensitivity of 0.97, specificity of 0.90, and accuracy of 0.95. AUC was 0.96. For predicting eGFR changes in one-year, we achieved a sensitivity of 0.83, specificity of 0.85, and accuracy of 0.84. AUC was 0.85. This study presents the first spatial analysis based on unsupervised machine learning algorithms. Without expert annotation, CluSA framework can not only accurately classify and predict the degree of kidney function at the biopsy and in one year, but also identify novel predictors of kidney function and renal prognosis.

Estimating the Glomerular Filtration Rate in Pediatric Patients With Neurogenic Bladder: A Comparison Between Creatinine- and Cystatin C-Equations

Background and objective Patients with neurogenic bladder (NB) are at a higher risk of developing chronic kidney disease (CKD). Due to their lower muscle mass, the estimated glomerular filtration rate (eGFR) based on creatinine (Cr) may be overestimated and delay the diagnosis of renal failure. This study compared eGFR calculated with different equations based on Cr and/or cystatin C (CysC) in children with NB, and the differences between patients with lower muscle mass (underdeveloped lower limbs) and those with independent gait (less muscle depletion). Methods We calculated the eGFR in pediatric patients with NB and CKD stages 1 and 2 by using the following equations: Chronic Kidney Disease in Children equation for serum creatinine (CKiD-Cr), CKiD-CysC, CKiD combined-Cr/CysC, Zappitelli-CysC, and Zappitelli combined-Cr/CysC. Results We evaluated a total of 47 patients, 74.5% with CKD stage 1, with a median age of 14.1 years. Of these participants, 59.6% had lipo/myelomeningocele. The CKiD-Cr and CysC-based equations led to significantly lower calculated eGFR ​​(p<0.05), specifically CKiD-CysC (p<0.001), Zappitelli-CysC (p<0.001), CKiD-Cr/CysC (p<0.001), and Zappitelli combined-Cr/CysC (p<0.05). When CKiD-CysC was used, 68% of the patients moved to a more advanced CKD stage. In patients without independent gait, with lower muscle mass (55.3%), the median eGFR calculated using the CKiD-Cr and CKiD combined-Cr/CysC equations was significantly higher (p<0.05). However, there were no differences between the two groups when using the other CysC-based equations. Conclusion In patients with NB and poor muscle mass, the CKiD-Cr equation may overestimate renal function. CysC-based equations seem more reliable in these patients, especially in those with greater muscular atrophy.

Comparing five equations to calculate estimated glomerular filtration rate to predict acute kidney injury following total joint arthroplasty

BACKGROUND

Acute kidney injury (AKI) following total joint arthroplasty (TJA) is associated with increased morbidity and mortality. Estimated glomerular filtration rate (eGFR) is used as an indicator of renal function. The purpose of this study was (1) to assess each of the five equations that are used in calculating eGFR, and (2) to evaluate which equation may best predict AKI in patients following TJA.

METHODS

The National Surgical Quality Improvement Program (NSQIP) was queried for all 497,261 cases of TJA performed from 2012 to 2019 with complete data. The Modification of Diet in Renal Disease (MDRD) II, re-expressed MDRD II, Cockcroft-Gault, Mayo quadratic, and Chronic Kidney Disease Epidemiology Collaboration equations were used to calculate preoperative eGFR. Two cohorts were created based on the development of postoperative AKI and were compared based on demographic and preoperative factors. Multivariate regression analysis was used to assess for independent associations between preoperative eGFR and postoperative renal failure for each equation. The Akaike information criterion (AIC) was used to evaluate predictive ability of the five equations.

RESULTS

Seven hundred seventy-seven (0.16%) patients experienced AKI after TJA. The Cockcroft-Gault equation yielded the highest mean eGFR (98.6 ± 32.7), while the Re-expressed MDRD II equation yielded the lowest mean eGFR (75.1 ± 28.8). Multivariate regression analysis demonstrated that a decrease in preoperative eGFR was independently associated with an increased risk of developing postoperative AKI in all five equations. The AIC was the lowest in the Mayo equation.

CONCLUSIONS

Preoperative decrease in eGFR was independently associated with increased risk of postoperative AKI in all five equations. The Mayo equation was most predictive of the development of postoperative AKI following TJA. The mayo equation best identified patients with the highest risk of postoperative AKI, which may help providers make decisions on perioperative management in these patients.

Renal hemodynamic changes in patients with type 2 diabetes and their clinical impact

The dysfunction of the internal mechanics within the kidney's filtering units, known as glomeruli, has been linked to the emergence and progression of diabetic kidney disease (DKD). To better understand this crucial aspect of kidney function and the pathology of DKD, a variety of methods are employed in research, from the introduction of external compounds, such as inulin, iohexol, iothalamate and p-aminohippurate, to cutting-edge imaging techniques and computational analysis. Given the significance of intraglomerular hemodynamic dysfunction in the pathogenesis and treatment of DKD, it is essential to thoroughly examine the available data on this topic. Accordingly, the aim of this review is to provide a comprehensive appraisal of the role of intraglomerular hemodynamic dysfunction in the development of DKD and the effects of current therapies used to mitigate DKD. Through this analysis, we can gain a deeper understanding of the complex pathogenesis of DKD and potentially discover new avenues for tailored therapeutic management of patients with DKD.

Use of Estimated Glomerular Filtration Rate and Urine Albumin-to-Creatinine Ratio Based on KDIGO 2012 Guideline in a Thai Community Hospital: Prevalence of Chronic Kidney Disease and its Risk Factors

BACKGROUND Kidney disease is hard to detect at its early stage; therefore, the Kidney Disease: Improving Global Outcomes (KDIGO) 2012 guideline was developed for improving care and outcomes of patients with kidney disease. This study aimed to determine clinical outcomes from applying this guideline in a community hospital service. MATERIAL AND METHODS The patients' data were extracted from their medical records and analyzed for outcomes of using the estimated glomerular filtration rate (eGFR) and urine albumin-creatinine ratio (UACR) for detecting kidney disease. RESULTS The eGFR was utilized in 36 172 patients aged ≥18 years, and 76.86% of them had normal kidney function. The prevalence of chronic kidney disease (CKD) was 8.20%; most patients (68%) with CKD were in stages 3a and 3b. The most common causes of CKD were diabetes and hypertension. The UACR was mainly used in patients with diabetes. The percentage of patients with UACR ≥3 mg/mmol creatinine alone was significantly higher than that of patients with eGFR.

Time to Rethink the Current Paradigm for Assessing Kidney Function in Drug Development and Beyond

Chronic kidney disease (CKD) is an important health issue that affects ~ 9.1% of the world adult population. Serum creatinine is the most commonly used biomarker for assessing kidney function and is utilized in different equations for estimating creatinine clearance or glomerular filtration rate (GFR). The Cockcroft-Gault formula for adults and "original" Schwartz formula for children have been the most commonly used equations for estimating kidney function during the last 3-4 decades. Introduction of standardized serum creatinine bioanalytical methodology has reduced interlaboratory variability but is not intended to be used with Cockcroft-Gault or original Schwartz equations. More accurate equations (for instance, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) for adults and bedside Schwartz or Chronic Kidney Disease in Children Schwartz equation for children) based on standardized serum creatinine values (and another biomarker-cystatin C) have been introduced and validated in recent years. Recently, the CKD-EPI equation refitted without a race variable was introduced. Clinical practice guidance in nephrology advocates a shift to these equations for managing health care of patients with CKD. The guidance also recommends use of albuminuria in addition to GFR for CKD diagnosis and management. Significant research with large data sets would be necessary to evaluate whether this paradigm would also be valuable in drug dose adjustments. This article attempts to highlight some important advancements in the field from a clinical pharmacology perspective and is a call to action to industry, regulators, and academia to rethink the current paradigm for assessing kidney function to enable dose recommendation in patients with CKD.

Future of kidney imaging: Functional magnetic resonance imaging and kidney disease progression

INTRODUCTION

Chronic kidney disease (CKD) which is a common cause of death has an increasing trend, but there is no established approach for predicting CKD progression yet. Functional magnetic resonance imaging (fMRI) studies such as blood oxygenation level-dependent MRI (BOLD-MRI), diffusion-weighted MRI (DWI-MRI), diffusion-tensor MRI (DTI-MRI) and arterial spin labelling MRI (ASL-MRI) are rising methods for the assessment of kidney functions in native and transplanted kidneys as well as the estimation of CKD progression.

METHODS

Systematic literature review was performed through the Embase (Elsevier), Cochrane Central Register of Controlled Trials (Wiley), PubMed/Medline and Web of Science databases, and studies investigating the role of fMRI methods assessing kidney functions in native and transplanted kidneys, as well as the value of fMRI methods to predict CKD progression, were included. Working mechanisms, advantages and limitations of the fMRI modalities were reviewed, and three studies investigating the role of fMRI studies in kidney functions were analysed.

RESULTS AND CONCLUSION

BOLD-MRI signal was found to be inversely correlated with annual eGFR change, and DWI/ADC (apparent diffusion coefficient map) values were shown to be correlated with annual eGFR decline. fMRI methods which are currently used for other systems can be utilized to provide more detailed information about kidney functions, and doctors should be ready to interpret kidney MRIs.

Estimating Renal Function Following Lung Transplantation

Background: Patients undergoing lung transplantation (LTx) experience a rapid decline in glomerular filtration rate (GFR) in the acute postoperative period. However, no prospective longitudinal studies directly comparing the performance of equations for estimating GFR in this patient population currently exist. Methods: In total, 32 patients undergoing LTx met the study criteria. At pre-LTx and 1-, 3-, and 12-weeks post-LTx, GFR was determined by ⁵¹Cr-EDTA and by equations for estimating GFR based on plasma (P)-Creatinine, P-Cystatin C, or a combination of both. Results: Measured GFR declined from 98.0 mL/min/1.73 m² at pre-LTx to 54.1 mL/min/1.73 m² at 12-weeks post-LTx. Equations based on P-Creatinine underestimated GFR decline after LTx, whereas equations based on P-Cystatin C overestimated this decline. Overall, the 2021 CKD-EPI combination equation had the lowest bias and highest precision at both pre-LTx and post-LTx. Conclusions: Caution must be applied when interpreting renal function based on equations for estimating GFR in the acute postoperative period following LTx. Simplified methods for measuring GFR may allow for more widespread use of measured GFR in this vulnerable patient population.

Current development of bioanalytical sample preparation techniques in pharmaceuticals

Sample preparation is considered as the bottleneck step in bioanalysis because each biological matrix has its own unique challenges and complexity. Competent sample preparation to extract the desired analytes and remove redundant components is a crucial step in each bioanalytical approach. The matrix effect is a key hurdle in bioanalytical sample preparation, which has gained extensive consideration. Novel sample preparation techniques have advantages over classical techniques in terms of accuracy, automation, ease of sample preparation, storage, and shipment and have become increasingly popular over the past decade. Our objective is to provide a broad outline of current developments in various bioanalytical sample preparation techniques in chromatographic and spectroscopic examinations. In addition, how these techniques have gained considerable attention over the past decade in bioanalytical research is mentioned with preferred examples. Modern trends in bioanalytical sample preparation techniques, including sorbent-based microextraction techniques, are primarily emphasized.

•

Bioanalytical sampling techniques are described with suitable applications in pharmaceuticals.

•

The pros and cons of each bioanalytical sampling techniques are described.

•

Relevant biological matrices are outlined.

Hypertensive Diseases in Pregnancy and Kidney Function Later in Life: The Genetic Epidemiology Network of Arteriopathy (GENOA) Study

OBJECTIVE

To evaluate the relationship between hypertensive diseases in pregnancy and kidney function later in life.

METHODS

We evaluated measured glomerular filtration rate (mGFR) using iothalamate urinary clearance in 725 women of the Genetic Epidemiology Network of Arteriopathy (GENOA) study. Women were classified by self-report as nulliparous (n=62), a history of normotensive pregnancies (n=544), a history of hypertensive pregnancies (n=102), or a history of pre-eclampsia (n=17). We compared adjusted associations among these four groups with mGFR using generalized estimating equations to account for familial clustering. Chronic kidney disease (CKD) was defined as mGFR of less than 60 mL/min per 1.73 m² or urinary albumin-creatinine ratio (UACR) greater than or equal to 30 mg/g.

RESULTS

Among women with kidney function measurements (mean age, 59±9 years, 52.9% African American), those with a history of hypertensive pregnancy had lower mGFR (-4.66 ml/min per 1.73 m²; 95% CI, -9.12 to -0.20) compared with women with a history of normotensive pregnancies. Compared with women with a history of normotensive pregnancies, women with a history of hypertensive pregnancy also had higher odds of mGFR less than 60 ml/min per 1.73 m² (odds ratio, 2.09; 95% CI, 1.21 to 3.60). Additionally, women with a history of hypertensive pregnancy had greater odds for chronic kidney disease (odds ratio, 4.89; 95% CI, 1.55 to 15.44), after adjusting for age, race, education, smoking history, hypertension, body mass index, and diabetes.

CONCLUSION

A history of hypertension in pregnancy is an important prognostic risk factor for kidney disease. To our knowledge, this is the first and largest investigation showing the association between hypertensive diseases in pregnancy and subsequent kidney disease using mGFR in a large biracial cohort.

Quantification of Fetal Renal Function Using Fetal Urine Production Rate and Its Reflection on the Amniotic and Fetal Creatinine Levels During Pregnancy

Adequate prediction of fetal exposure of drugs excreted by the kidney requires the incorporation of time-varying renal function parameters into a pharmacokinetic model. Published data on measurements of fetal urinary production rate (FUPR) and creatinine at various gestational ages were collected and integrated for prediction of the fetal glomerular filtration rate (GFR). The predicted GFR values were then compared to neonatal values recorded at birth. Collected data for FUPR across different gestational ages using both 3D (N = 517) and 2D (N = 845) ultrasound methods showed that 2D techniques yield significantly lower estimates of FUPR than 3D (p < 0.0001). A power law function was shown to best capture the change in FUPR with fetal age (FA) for both 2D ( F U P R 2 D ( m L min ) = 0 . 000169     FA 2 . 19 ); and 3D ( F U P R 3 D   ( m L min ) =   3 . 21 × 1 0 - 7   FA 4 . 21 ) data. The predicted FUPR based on the observed 3D data was shown to be strongly linearly related (R ² = 0.95) to measured values of amniotic creatinine concentration (N = 664). The FUPR_3D data together with creatinine levels in the fetal urine and serum resulted in median predicted fetal GFR values of 0.47, 1.2, 2.5, and 4.9 ml/min at 23, 28, 33, and 38 weeks of fetal age (50% CV), respectively. These values are in good agreement with neonatal values observed immediately at birth. The derived FUPR and creatinine functions can be utilized to assess fetal renal maturation and predict fetal renal clearance.

Measured Glomerular Filtration Rate: The Query for a Workable Golden Standard Technique

Inulin clearance has, for a long time, been considered as the reference method to determine measured glomerular filtration rates (mGFRs). However, given the known limitations of the standard marker, serum creatinine, and of inulin itself, and the frequent need for accurate GFR estimations, several other non-radioactive (iohexol and iothalamate) and radioactive (51Cr-EDTA, 99mTc-DTPA, 125I iothalamate) exogenous mGFR filtration markers are nowadays considered the most accurate options to evaluate GFR. The availability of 51Cr-EDTA is limited, and all methods using radioactive tracers necessitate specific safety precautions. Serum- or plasma-based certified reference materials for iohexol and iothalamate and evidence-based protocols to accurately and robustly measure GFR (plasma vs. urinary clearance, single-sample vs. multiple-sample strategy, effect of sampling time delay) are lacking. This leads to substantial variation in reported mGFR results across studies and questions the scientific reliability of the alternative mGFR methods as the gold standard to evaluate kidney function. On top of the scientific discussion, regulatory issues are further narrowing the clinical use of mGFR methods. Therefore, this review is a call for standardization of mGFR in terms of three aspects: the marker, the analytical method to assess concentrations of that marker, and the procedure to determine GFR in practice. Moreover, there is also a need for an endogenous filtration marker or a panel of filtration markers from a single blood draw that would allow estimation of GFR as accurately as mGFR, and without the need for application of anthropometric, clinical, and demographic characteristics.

The use of dried blood spots for characterizing children's exposure to organic environmental chemicals

Biomonitoring is a commonly used tool for exposure assessment of organic environmental chemicals with urine and blood samples being the most commonly used matrices. However, for children's studies, blood samples are often difficult to obtain. Dried blood spots (DBS) represent a potential matrix for blood collection in children that may be used for biomonitoring. DBS are typically collected at birth to screen for several congenital disorders and diseases; many of the states that are required to collect DBS archive these spots for years. If the archived DBS can be accessed by environmental health researchers, they potentially could be analyzed to retrospectively assess exposure in these children. Furthermore, DBS can be collected prospectively in the field from children ranging in age from newborn to school-aged with little concern from parents and minimal risk to the child. Here, we review studies that have evaluated the measurement of organic environmental toxicants in both archived and prospectively collected DBS, and where available, the validation procedures that have been performed to ensure these measurements are comparable to traditional biomonitoring measurements. Among studies thus far, the amount of validation has varied considerably with no studies systematically evaluating all parameters from field collection, shipping and storage contamination and stability to laboratory analysis feasibility. These validation studies are requisite to ensure reliability of the measurement and comparability to more traditional matrices. Thus, we offer some recommendations for validation studies and other considerations before DBS should be adopted as a routine matrix for biomonitoring.

Volumetric absorptive microsampling as alternative sampling technique for renal function assessment in the paediatric population using iohexol

The glomerular filtration rate (GFR) is considered the best overall index for the renal function. Currently, one of the most promising exogenous markers for GFR assessment is iohexol. In this study, the suitability of volumetric absorptive microsampling (VAMS) as alternative for the conventional blood sampling and quantification of iohexol in paediatric plasma was assessed. Therefore, a new, fully validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed. Subsequently, the clinical suitability was evaluated in 20 paediatric patients by comparing plasma iohexol concentrations and associated GFR values obtained by the VAMS method with those obtained by conventional blood sampling and quantification of iohexol in plasma. The developed, simple and cost-effective LC-MS/MS-method fulfilled all pre-set validation acceptance criteria. Iohexol could be accurately quantified within a haematocrit range of 20-60% and long-term stability of iohexol in VAMS was demonstrated up to 245 days under different storage temperatures. Both iohexol plasma concentrations (r = 0.98, mean bias: -4.20%) and derived GFR values (r = 0.99; mean bias: 1.31%), obtained by a conventional plasma and the VAMS method, demonstrated good correlation and acceptable bias. The agreement between the two methods was especially good for GFR values higher than 60 mL/min/1.73 m². Nevertheless, for GFR values <60 mL/min/1.73 m² the accuracy compared to the plasma method was lower. However, small adjustments to the sampling protocol could probably solve this problem.

A plasma creatinine- and urea-based equation to estimate glomerular filtration rate in rats

Monitoring renal function is a vital part of kidney research involving rats. The laborious measurement of glomerular filtration rate (GFR) with administration of exogenous filtration markers does not easily allow serial measurements. Using an in-house database of inulin clearances, we developed and validated a plasma creatinine- and plasma urea-based equation to estimate GFR in a large cohort of male rats [development cohort n = 325, R² = 0.816, percentage of predictions that fell within 30% of the true value (P30) = 76%] that had high accuracy in the validation cohort (n = 116 rats, R² = 0.935, P30 = 79%). The equation was less accurate in rats with nonsteady-state creatinine, in which the equation should therefore not be used. In conclusion, applying this equation facilitates easy and repeatable estimates of GFR in rats.NEW & NOTEWORTHY This is the first equation, that we know of, which estimates glomerular filtration rate in rats based on a single measurement of body weight, plasma creatinine, and plasma urea.

Renal functional reserve: from physiological phenomenon to clinical biomarker and beyond

Glomerular filtration rate (GFR) is acutely increased following a high-protein meal or systemic infusion of amino acids. The mechanisms underlying this renal functional response remain to be fully elucidated. Nevertheless, they appear to culminate in preglomerular vasodilation. Inhibition of the tubuloglomerular feedback signal appears critical. However, nitric oxide, vasodilator prostaglandins, and glucagon also appear important. The increase in GFR during amino acid infusion reveals a "renal reserve," which can be utilized when the physiological demand for single nephron GFR increases. This has led to the concept that in subclinical renal disease, before basal GFR begins to reduce, renal functional reserve can be recruited in a manner that preserves renal function. The extension of this concept is that once a decline in basal GFR can be detected, renal disease is already well progressed. This concept likely applies both in the contexts of chronic kidney disease and acute kidney injury. Critically, its corollary is that deficits in renal functional reserve have the potential to provide early detection of renal dysfunction before basal GFR is reduced. There is growing evidence that the renal response to infusion of amino acids can be used to identify patients at risk of developing either chronic kidney disease or acute kidney injury and as a treatment target for acute kidney injury. However, large multicenter clinical trials are required to test these propositions. A renewed effort to understand the renal physiology underlying the response to amino acid infusion is also warranted.

Determination of iohexol by capillary blood microsampling and UHPLC-MS/MS

One of the most important tools used to evaluate kidney function in the context of chronic kidney disease or other renal function related pathologies is the exploration of glomerular filtration rate (GFR). Iohexol is up to this moment a good candidate molecule for the GFR assessment since it exhibits minimum protein binding rates and minimum extra-renal clearance, being neither secreted nor reabsorbed at the tubular level. This study proposes and evaluates a new LC-MS/MS method for the iohexol determination from capillary blood, prelevated using volumetric absorbative microsampling (VAMS) systems. As an alternative to VAMS, a brand new HemaPEN^® device for micro-prelevation was also tested. A new high throughput sample preparation protocol adapted for iohexol quantification from whole blood VAMS samples was developed. The medium term stability study of iohexol in dried whole blood VAMS samples that was conducted showed a good stability of this molecule for up to 12 days. By collecting only 10 μL of blood, iohexol can be analyzed from dried whole blood VAMS samples for concentration ranges between 1 and 250 μg/mL. Due to the analyte stability in VAMS for up to 12 days, this approach might be successfully applied for GFR assessment for clinical cases allowing minimum invasiveness and even delayed analysis.

•

Successful VAMS-based bioanalytical method for iohexol analysis in whole human blood.

•

Proven medium term stability of iohexol in VAMS samples.

•

HemaPens as a promising alternative for iohexol analysis using only 2.74 μL of blood.