Method For Measurement Of Glomerular Filtration Rate Research Articles

Chronic Kidney Disease Progression-A Challenge.

Chronic kidney disease (CKD) is a progressive condition characterized by a continuous decline in renal function, independent of the initial cause of damage or external factors such as infection, inflammation, or toxins. The accurate measurement of renal function, typically assessed using the glomerular filtration rate (GFR), is crucial for managing CKD. The most accepted hypothesis for CKD progression is glomerular damage caused by hyperfiltration. Various factors can accelerate CKD progression, and several biomarkers have been identified to monitor this progression. Numerous studies have explored the risk factors associated with CKD progression, and some of these factors can be modified. Additionally, several drugs are now available that can reduce CKD progression. This review summarizes recent publications and highlights potential future research directions in CKD progression. It discusses the evolution of GFR measurement methods, the mechanisms driving CKD progression, and the latest findings on biomarkers and risk factors. Furthermore, it explores therapeutic strategies, including dietary modifications and pharmacological interventions, to slow CKD progression. Understanding these mechanisms and interventions is crucial for developing effective therapeutic strategies to prevent or slow CKD progression.

Updates in Chronic Kidney Disease.

Chronic kidney disease (CKD) affects approximately 14% of adults in the United States and is present in at least 10% of the population worldwide. Blood glucose and blood pressure control are imperative to adequately manage CKD as they are the only primary prevention measures for the condition. Recent changes in CKD evaluation and medication therapies that modify disease progression and aid in managing complications such as anemia of CKD have emerged, including a newly approved mineralocorticoid receptor antagonist and hypoxia-inducible factor-prolyl hydroxylase inhibitor, respectively. This focused update on CKD evaluation and management will review the most recent evidence and approved agents to support patients with CKD, including a review of glomerular filtration rate measurement methods such as CKD-EPI 2021 and utilization of cystatin C, Kidney Disease Improving Global Outcomes (KDIGO) guidelines, American Diabetes Association (ADA) guidelines, and primary literature supporting the use of newer agents in CKD. Checklists for managing blood pressure and blood glucose, CKD-mineral bone disorder, and anemia of CKD targeted for pharmacists are also provided. Additionally, a discussion of Centers for Medicare & Medicaid (CMS) coverage of agents approved for managing complications of CKD is included.

Current clinical application of glomerular filtration rate assessment methods in pediatric populations

Glomerular filtration rate (GFR) is a critical indicator of renal function assessment, which exhibits age-dependency in children and may differ from adults under various disease conditions. In recent years, there has been a growing focus on GFR among scholars, with an increasing number of clinical studies dedicated to refining and optimizing GFR estimation to span all pediatric age groups. However, the methods and assessment equations for estimating GFR may vary under different disease conditions, affecting the accuracy and applicability of assessments. This article reviews the peculiarities of renal function in children, explores GFR measurement methods, and evaluates the application of various GFR assessment equations in pediatric clinical practice, providing a reference for clinical assessment of renal function in children.

Assessing the status of European laboratories in evaluating biomarkers for chronic kidney diseases (CKD) and recommendations for improvement: insights from the 2022 EFLM Task Group on CKD survey.

Chronic kidney disease (CKD) is a global health issue, ranking as the third leading cause of death worldwide. CKD diagnosis and management depend on clinical laboratory tests, necessitating consistency for precise patient care. Global harmonization of CKD testing through clinical practice guidelines (CPGs) is recommended. Prior to CPG development, assessing the current CKD testing landscape is crucial. In 2022, the European Federation of Laboratory Medicine (EFLM) conducted an online survey among European laboratories associated with EFLM, evaluating CKD testing practices, including new glomerular filtration rate (GFR) estimation methods. This report summarizes the 2022 survey findings and offers recommendations for improving CKD test standardization. An online survey was conducted in November 2022 using a questionnaire hosted on LimeSurvey sent to European laboratories affiliated with the EFLM. The survey results were recorded in Excel files and analysed. The results highlight significant discrepancies among countries in unit expression, methods, cystatin C use, and GFR calculation equations. Additionally, limited attention to pediatric renal biology specifics, varied proteinuria and albuminuria result expressions, and limited awareness of GFR measurement methods through iohexol clearance are noted. In an effort to enhance the standardization of crucial biomarkers utilized in nephrology for evaluating renal function and diagnosing kidney injuries, the EFLM Task Group on CKD suggests nine practical recommendations tailored for European laboratories. The group is confident that implementing these measures will minimize result expression discrepancies, ultimately leading to enhanced patient care.

Glomerular Filtration Rate Assessment in Children.

Glomerular filtration rate (GFR) measurement is a key tool for determining the degree of chronic kidney disease. The assessment of GFR is even more challenging in children than in adults with more variables in the equation than race and sex. Monitoring the progress of the kidney disease can therefore be difficult as in the initial stages of a decline in kidney function, there are no clinical signs. Due to children's growth and development, changes in muscle mass and growth impair GFR estimation based solely on serum creatinine values. More invasive methods of GFR measurement are more reliable, but techniques using ionising agents, requiring large volume blood samples or timed voiding, have limited application in children. This paper reviews the methods of measuring and determining glomerular filtration rate and kidney function in children.

2009 CKD-EPI glomerular filtration rate estimation in Black individuals outside the United States: a systematic review and meta-analysis.

The 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is the most used equation to estimate glomerular filtration rate (GFR), with race being a factor thereof, increasing GFR by 16% in self-identified Black persons compared with non-Black persons. However, recent publications indicate that it might overestimate GFR for Black adults outside the USA. In this meta-analysis, we assessed the accuracy, evaluated by the percentage of estimated GFR within 30% of measured GFR (P30), of the 2009 CKD-EPI equation in estimating GFR with and without the race coefficient in Black individuals outside the United States of America (USA). We searched MEDLINE and Embase from inception to 9 July 2022, with no language restriction, supplemented by manual reference searches. Studies that assessed the CKD-EPI P30 accuracy with or without the race coefficient in Black adults outside the USA with an adequate method of GFR measurement were included. Data were extracted by independent pairs of reviewers and were pooled using a random-effects model. We included 11 studies, with a total of 1834 Black adults from South America, Africa and Europe. The race coefficient in the 2009 CKD-EPI equation significantly decreased P30 accuracy {61.9% [95% confidence interval (CI) 53-70%] versus 72.9% [95% CI 66.7-78.3%]; P=.03}. Outside the USA, the 2009 CKD-EPI equation should not be used with the race coefficient, even though the 2009 CKD-EPI equation is not sufficiently accurate either way (<75%). Thus we endorse the Kidney Disease: Improving Global Outcomes guidelines to use exogenous filtration markers when this may impact clinical conduct.

The Xiangya equation could not replace the Asian modified CKD-EPI equation in estimating glomerular filtration rate in Chinese patients with chronic kidney disease.

To evaluate the clinical practicability of the Xiangya equation in estimating glomerular filtration rate (GFR) and compare with the Asian modified Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation, assessing whether the Xiangya equation could replace the Asian modified CKD-EPI equation as the preferred method for predicting GFR in the Chinese CKD patients in an external validation study. The GFR was determined simultaneously by two methods: (a) the Asian modified CKD-EPI equation (GFRCKD-EPI); (b) the Xiangya equation (GFRXiangya); diagnostic performance of the two models was compared by the regression analysis, the Bland-Altman plot, bias, precision and P30 under the background of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) dual plasma sample clearance method as reference method for GFR measurement (mGFR). A total of 158 Chinese CKD patients were included in our external study. The GFRXiangya was highly related with mGFR, with the correlation coefficient of 0.92. The regression equation was GFRXiangya = 0.55*mGFR + 28.25, where the regression coefficient was far away from one and the intercept was wide. Compared with the Asian modified CKD-EPI equation, the performance of the Xiangya equation demonstrated a poorer bias (9.5 vs -3.3ml/min/1.73 m2, P < 0.001), an inferior precision (23.9 vs 13.0ml/min/1.73 m2, P < 0.001), a lower P30 (51.3% vs 73.4%, P < 0.001) and a wider 95% limit of agreement in Bland-Altman analysis (65.0 vs 44.9ml/min/1.73 m2). Due to relatively inferior performance, the Xiangya equation could not replace the Asian modified CKD-EPI equation in estimating GFR in Chinese patients with chronic kidney disease in our external cohort.

The ensemble learning model is not better than the Asian modified CKD-EPI equation for glomerular filtration rate estimation in Chinese CKD patients in the external validation study

ObjectiveTo assess the clinical practicability of the ensemble learning model established by Liu et al. in estimating glomerular filtration rate (GFR) and validate whether it is a better model than the Asian modified Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation in a cohort of Chinese chronic kidney disease (CKD) patients in an external validation study.MethodsAccording to the ensemble learning model and the Asian modified CKD-EPI equation, we calculated estimated GFRensemble and GFRCKD-EPI, separately. Diagnostic performance of the two models was assessed and compared by correlation coefficient, regression equation, Bland–Altman analysis, bias, precision and P30 under the premise of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) dual plasma sample clearance method as reference method for GFR measurement (mGFR).ResultsA total of 158 Chinese CKD patients were included in our external validation study. The GFRensemble was highly related with mGFR, with the correlation coefficient of 0.94. However, regression equation of GFRensemble = 0.66*mGFR + 23.05, the regression coefficient was far away from one, and the intercept was wide. Compared with the Asian modified CKD-EPI equation, the diagnostic performance of the ensemble learning model also demonstrated a wider 95% limit of agreement in Bland-Altman analysis (52.6 vs 42.4 ml/min/1.73 m2), a poorer bias (8.0 vs 1.0 ml/min/1.73 m2, P = 0.02), an inferior precision (18.4 vs 12.7 ml/min/1.73 m2, P < 0.001) and a lower P30 (58.9% vs 74.1%, P < 0.001).ConclusionsOur study showed that the ensemble learning model cannot replace the Asian modified CKD-EPI equation for the first choice for GFR estimation in overall Chinese CKD patients.

A Systematic Review of Renal Functional Reserve in Adult Living Kidney Donors

IntroductionThe kidney’s capacity to increase its glomerular filtration rate (GFR) in response to a higher functional demand is known as the renal functional reserve (RFR). Good short-term outcomes after living kidney donation have led to more acceptance of borderline donors (with hypertension, obesity, older age) due the ongoing shortage of donor organs. Given recent concerns about increased long-term risk in some donor subgroups, better donor stratification is needed. Measurement of RFR could inform assessment of donor risk.MethodsA systematic literature review of studies that assessed RFR in donors pre- and/or post-donation was performed. Given study heterogeneity, descriptive analysis and narrative synthesis was conducted.ResultsSixteen of 3250 identified studies published between 1956 and 2019 met inclusion criteria. Most studies were cross-sectional and conducted before (n = 8) and/or after (n = 16) kidney donation. Methods for measurement of GFR, effective renal plasma flow (ERPF) and RFR were not standardized. Changes in filtration fraction (FF) and ERPF relative to GFR observed after donation varied depending on stimulus used to induce RFR. Overall, RFR fell after donation; however, over the shorter term, RFR was largely preserved in young healthy donors. RFR was more significantly reduced in donors with hypertension, obesity, or older age.ConclusionExisting data suggest possible blunting of RFR post-donation in older, obese, and hypertensive donors, which may represent increased single-nephron GFR at baseline. The long-term implications of these changes deserve further study to determine utility in informing selection of borderline kidney donors.

Correlations between estimating GFR methods and oncological outcomes during cancer chemotherapy

Background: Glomerular filtration rate (GFR) measurements are critical in patients with cancer. A variety of methods are used to calculate the estimated GFR. The aim of this study is to investigate whether there is a correlation between these methods and oncologic outcomes according to the stage and treatment agents. Methods: A total of 153 patients were retrospectively recruited. All GFR measurement methods was determined in all patients, before the first cycle of chemotherapy and before the subsequent administrations. Results: In the study population 40% of whom received platinum-based chemotherapy. In this group, overall survival was statistically significant in patients with a CKD-EPI creatinine value of 65 or greater (p:0.023). When we separated the arms according to the stage, there was no relationship between CKD-EPI Cystatin C and progression-free survival in metastatic patients (p: 0.13). In the non-metastatic group, median DFS was 7 months and OS was 13.9 months in patients with CKD-EPI Cystatine C level above 45 (p:0.005). Conclusions: Both CKD-EPI creatinine and CKD-EPI cystatin C were significantly associated with overall survival and disease-free survival in patients receiving platinum-based chemotherapy. When assessed according to the stage, there was a general survival relationship with CKD-EPI cystatin C in the non-metastatic group and in the other groups there was no significant correlation with the estimated GFR measurements.

Comparison of Glomerular Filtration Rate Measurement Methods between Radionuclide in vivo Scintigraphic Gates' and Plasma Sampling.

AIM:To correlate between the radionuclide in vitro plasma sampling method (using single and dual blood samples) and Gates’ GFR measurement using Tc-99m diethylene triamine penta-acetic acid (Tc-99m DTPA) renal scintigraphy (in vivo method).METHODS:This study included 40 renal donors (group 1) and 40 patients with obstructive uropathy (group 2). Group 1 included 22 males and 18 females with an age range from 22 to 65 years, while group 2 included 24 males and 16 females with age range 27 to 64 years. Both groups subjected to renal Scintigraphy after administration of 5 mCi 99m-Tc DTPA, GFR was calculated using Gates’ method (in vivo method), then plasma sampling was acquired at 60 mins and 180 mins post-injection of the tracer, samples were counted in well counter and GFR was calculated using in vitro technique either using single plasma sample (SPSM 60 mins) or dual sample (DPSM 60 & 180 min). Additionally, GFR was measured by estimated equations based on serum creatinine.RESULTS:In group 1, the mean GFR using in vivo Gates’ method was 115.7 ± 29 ml/min, while using the SPSM was 100.1 ± 16.1 ml/min, and the DPSM was 100.3 ± 20.1 ml/min. In group 2, mean GFR using in vivo method was 74.1 ± 14.5 ml/min, while using in vitro SPSM it was 77.5 ± 24.9 ml/min and DPSM was 76.8 ± 24.8 ml/min. There was no significant difference between mean GFR values using in vivo and in vitro methods (single or dual samples) in group 1 and 2 (p > 0.05). There is high significant correlation between SPSM and DPSM in groups 1 and 2 (r = 0.90, r = 0.91 respectively), moderate significant correlation was found between in vivo Gates’ method and in vitro SPSM in group 1 and 2 (r = 0.46 and 0.57 respectively) and moderate correlation was evident between in vivo and in vitro DPSM in both groups (r = 0.42 and 0.68 respectively). By using the DPSM as the reference standard significant high correlation was found with SPSM and significant-high moderate correlation with in vivo Gates’ scintigraphic method. Conclusion: In vitro plasma sampling considered as a reliable, accurate |method for GFR calculation yet it considered relatively complex, both single and dual sample in vitro techniques showed a very high correlation, and hence SPSM can replace DPSM.CONCLUSION:Renal scintigraphy and GFR estimation using Gates’ in vivo method is considered inaccurate, yet given its simplicity in performance it can still be used if corrected GFR is standardised for Egyptian population-based on studies with large numbers of patients from multiple centres.

Compartmental-modelling-based measurement of murine glomerular filtration rate using 18F-fluoride PET/CT

Accurate measurement of glomerular filtration rate (GFR) is essential for optimal decision making in many clinical settings of renal failure. We aimed to show that GFR can be accurately measured using compartmental tracer kinetic analysis of 18F-fluoride dynamic PET/CT. Twenty-three male Sprague-Dawley rats of three experimental groups (cyclosporine-administered [n = 8], unilaterally nephrectomized [n = 8], and control [n = 7]) underwent simultaneous 18F-fluoride dynamic PET/CT and reference 51Cr-EDTA GFR (GFRCrEDTA) test at day 0 and post-intervention day 3. 18F-fluoride PET GFR (GFRF-PET) was calculated by multiplying the influx rate and functional kidney volume in a single-tissue-compartmental kinetic model. Within-test repeatability and between-test agreement were evaluated by intraclass correlation coefficient (ICC) and Bland-Altman analysis. In the control group, repeatability of GFRF-PET was excellent (ICC = 0.9901, repeatability coefficient = 12.5%). GFRF-PET significantly decreased in the renally impaired rats in accordance with respective GFRCrEDTA changes. In the pooled population, GFRF-PET agreed well with GFRCrEDTA with minimal bias (−2.4%) and narrow 95% limits of agreement (−25.0% to 20.1%). These data suggest that the single-compartmental kinetic analysis of 18F-fluoride dynamic PET/CT is an accurate method for GFR measurement. Further studies in humans are warranted.

Creatinine clearance after cimetidine administration in a new short procedure: comparison with plasma and renal clearances of iohexol.

BackgroundCreatinine clearance after cimetidine administration (Cim-CreatClr) was once proposed as a method of glomerular filtration rate (GFR) measurement, but has been largely abandoned. We investigated whether a new short procedure for Cim-CreatClr determination could be considered an appropriate method for GFR measurement.MethodsA 150-min protocol involving oral cimetidine administration was developed to determine Cim-CreatClr. In total, 168 patients underwent simultaneous assessments of creatinine clearance before and after cimetidine administration [basal creatinine clearance (Basal-CreatClr) and Cim-CreatClr, respectively], renal iohexol clearance and plasma iohexol clearance (R-iohexClr and P-iohexClr, respectively). We compared the agreement between the various methods of GFR measurement, using Bland–Altman plots to determine biases, precisions (standard deviation of the biases) and accuracy (proportions of GFR values falling within 10, 15 and 30% of the mean: P10, P15 and P30, respectively).ResultsAfter cimetidine administration, Basal-CreatClr decreased by 19.8% [95% reference limits of agreement (95% LoA): −2.2 to 41.7%]. The bias between Cim-CreatClr and P-iohexClr was −0.6% (95% LoA −26.8 to 28%); the precision was 14.0%; P10, P15 and P30 were 57.1% [95% confidence interval (95% CI) 49.3 to 64.7%], 73.2% (95% CI 65.8 to 79.7%) and 97.0% (95% CI 93.2 to 99.0%), respectively. Due to the positive bias (16.7%; 95% LoA −3.6 to 36.9%) of Cim-CreatClr relative to R-iohexClr, accuracy of Cim-CreatClr relative to R-iohexClr was poor despite a good precision (10.3%).ConclusionsOur study shows a high level of agreement between Cim-CreatClr and P-iohexClr. These results suggest that this short Cim-CreatClr procedure is a valid method for GFR measurement, which might be useful, in particular, in situations in which P-iohexClr is not suitable or not available.

The Accuracy of Renal Function Measurements in Obstructive Hydronephrosis Using Dynamic Contrast-Enhanced MR Renography.

OBJECTIVE. The objective of our study was to assess the accuracy of glomerular filtration rate (GFR) evaluation in patients with obstructive hydronephrosis using dynamic contrast-enhanced MR renography (DCE-MRR). MATERIALS AND METHODS. A group of 28 adult volunteers were enrolled in this study: 13 without hydronephrosis, eight with low-grade hydronephrosis, and seven with high-grade hydronephrosis. The GFR obtained from DCE-MRR (GFRMRR) and the GFR obtained from renal scintigraphy (GFRRS) were compared with the reference GFR (GFRRef) acquired using the two plasma sample method. The correlation and agreement between GFRMRR and GFRRef, GFRRS and GFRRef, and single-kidney GFRMRR (skGFRMRR) and single-kidney GFRRS (skGFRRS) were assessed. The interrater reliability of DCE-MRR and the interrater reliability of renal scintigraphy (RS) were measured. RESULTS. Both GFRMRR and GFRRS correlated well with GFRRef. In patients with hydronephrosis, DCE-MRR and RS overestimated GFR by 12.8 ± 13.9 mL/min (mean ± SD) and 11.5 ± 12.3 mL/min, respectively. The skGFRRS was higher than skGFRMRR by 5.7 ± 3.8 mL/min in high-grade hydronephrotic kidneys (p = 0.004). Good interrater reliability was observed for skGFRMRR (intraclass correlation coefficient [ICC] = 0.82-0.92) and skGFRRS (ICC = 0.79-0.90) for both nonhydronephrotic kidneys and hydronephrotic kidneys. The overall mean SDs of repeated measurements from three investigators were 4.0 and 3.8 mL/min for skGFRMRR and skGFRRS, respectively. CONCLUSION. Both DCE-MRR and RS tend to overestimate GFR in patients with hydronephrosis. RS-derived skGFR is slightly higher than that of DCE-MRR in kidneys with high-grade hydronephrosis. DCE-MRR is comparable to RS and may serve as an alternative noninvasive method for GFR measurement.

Evaluation of Renal Function in Obese Children and Adolescents Using Serum Cystatin C Levels, Estimated Glomerular Filtration Rate Formulae and Proteinuria: Which is most Useful?

Objective:There is a growing interest in the relationship between obesity and renal damage. The effect of obesity on renal function in children and adolescents has not been adequately investigated. In addition, there is no complete consensus on the reliability of various renal function parameters. The primary goal of this study was to evaluate renal function in obese children and adolescents using glomerular filtration rate (GFR), cystatin C, and creatinine (Cr)-derived formulas. We also compared classical GFR measurement methods with methods based on bioimpedance analysis-derived body cell mass (BCM).Methods:We enrolled 108 obese and 46 healthy subjects aged 6-18 years. Serum cystatin C, serum Cr, 24-hour proteinuria, Cr clearance, and GFR were evaluated in both groups. Estimated GFR was measured with Cr-based, cystatin C-based, combined (cystatin C and Cr) and BCM-based formulae. Both actual and fat-free mass body surface areas (BSA) were used when required. Metabolic parameters (blood glucose, insulin, and lipids) were analyzed in the obese subjects. International Diabetes Federation criteria were used to identify metabolic syndrome (MetS).Results:We did not detect statistically significant differences between the obese and control groups for mean Cr (p=0.658) and mean cystatin C (p=0.126). Mean cystatin C levels of MetS patients were significantly higher than those of non-MetS obese participants (p<0.001). Cr-based GFR measurements, BCM-based measurements and a combined Cr and cystatin C measurement showed a statistically significant increase in the GFR of obese subjects compared to controls (p=0.002 and p<0.001). This increase was negatively correlated with duration of obesity. Estimations based on actual or fat-free mass BSA did not differ either. Only the Filler equation showed a statistically significant decrease in eGFR in MetS patients. There were no statistically significant differences between the obese and control groups for proteinuria (p=0.994) and fat-free mass proteinuria (p=0.476).Conclusion:We conclude that cystatin C could be used as an earlier biomarker than Cr in the detection of impaired renal function in obese children, especially those with MetS. Cr-based formulae reveal hyperfiltration as the first change in renal function. Decreasing eGFR seen in MetS patients with cystatin C-based formulae, but not Cr-based formulae, may represent the early stages of renal damage. Using fat-free mass or BCM for eGFR formulae in obese children seems to provide no additional information.

Elevation of serum creatinine in a renal transplant patient following oral creatine supplementation.

We report the case of a renal transplant recipient presenting with elevated serum creatinine levels whilst taking oral creatine ethyl ester (CEE), but not creatine monohydrate (CM). Standard investigations for allograft dysfunction, including Doppler ultrasound and renal biopsy, were normal. Serum creatinine normalized following cessation of the supplement. CM is poorly absorbed and does not affect creatinine. In contrast, CEE is converted and absorbed as creatinine, elevating serum levels. In such cases, creatinine is not a valid surrogate for glomerular filtration rate (GFR). Alternate methods of GFR measurement should be considered and a rigorous clinical and drug history taken.

Assessment of Agreement between Gates Method and Dual Plasma Sample Method for Measurement of Glomerular Filtration Rate

&lt;p&gt;&lt;strong&gt;Objectives:&lt;/strong&gt; Glomerular filtration rate (GFR) is generally considered to be the best index of renal function in both healthy and diseased kidneys. Calculation of GFR plays a vital role in the management of patients having renal diseases. Clinicians can make their final decision regarding the potential need for kidney transplantation and also selection of a potential kidney donor. Many methods have been developed in order to obtain more accurate GFR values. The most popular radionuclide method is camera based Gates method using 99mTc DTPA (Diethylene triaminepentaacetic acid). This method can provide immediate calculation of individual kidney function as well as of global renal function. But several sources of errors may reduce the reliability of this method. Measurement of multiple blood samples offers almost real values of GFR, which have become the gold standard in clinical research. The aim of this research work was to study the agreement between Gates method and dual plasma sample method for measurement of GFR.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Patients and methods:&lt;/strong&gt; This cross sectional study was carried out in National Institute of Nuclear Medicine &amp;amp; Allied Sciences (NINMAS), during July 2015 to June 2016. A total of 59 patients were included in this study. GFR was estimated by both the camera based Gates method and dual plasma sample method (DPSM).Statistical analyses were carried out by using the Statistical Package for Social Sciences version 20.0 for Windows (SPSS Inc., Chicago, Illinois, USA). The mean values were calculated for continuous variables. Categorical data were expressed in percentage and number. Pearson correlation and Bland &amp;amp; Altman (B &amp;amp; A) analyses were applied for assessing correlation and agreement between Gates method and DPSM. Degree of relation between the variables is expressed by r (Pearson’s correlation coefficient).&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results:&lt;/strong&gt; The mean GFR evaluated by Gates method was found 82.2 ± 27.4 mL/min/1.73m&lt;sup&gt;2&lt;/sup&gt; and mean GFR by DPSM was found 82.8 ± 24.1 mL/min/1.73m&lt;sup&gt;2&lt;/sup&gt;. A strong positive correlation (r = 0.833; p = 0.001) was found between the GFR values measured by Gates method and DPSM. With Bland and Altman analysis, it was observed that mean difference of GFR measured by Gates method and DPSM was – 0.6 ± 15.22 mL/min/1.73m&lt;sup&gt;2&lt;/sup&gt;. The limit of agreement ranged from – 30.44 mL/min/1.73m&lt;sup&gt;2&lt;/sup&gt; to 29.24 mL/min/1.73m&lt;sup&gt;2&lt;/sup&gt;.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion:&lt;/strong&gt; There was strong positive correlation between Gates method and DPSM for measurement of GFR. Mean difference between the methods was small. The bias between the methods was considered not significant. The differences within mean ± 1.96 SD are not clinically important. Hence Gates method and DPSM can reflect GFR almost equally and can be used interchangeably.&lt;/p&gt;&lt;p&gt;Bangladesh J. Nuclear Med. 20(1): 19-23, January 2017&lt;/p&gt;

Performance of glomerular filtration rate estimating equations in a community-based sample of Blacks and Whites: the multiethnic study of atherosclerosis.

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations are recommended for glomerular filtration rate (GFR) estimation in the general population. They have not been evaluated in community-based populations, including Blacks at higher levels of GFR, but are commonly applied in such populations. In an ancillary study of Multi-Ethnic Study of Atherosclerosis conducted at one site, we evaluated the performance of the CKD-EPI equations for creatinine (eGFRcr), cystatin C (eGFRcys) or the combination (eGFRcr-cys) compared with GFR measured as plasma clearance of iohexol. Among 294 participants, the mean age was 71 (SD 9) years, 47% were Black, 48% were women and the mean measured GFR (mGFR) was 72.6 (SD 18.8) mL/min/1.73 m2. The CKD-EPI equations overestimated mGFR with a larger median bias for eGFRcr and eGFRcr-cys than eGFRcys [-8.3 (95% confidence interval -9.7, -6.5), -7.8 (-9.2, -6.2) and -3.7 (-5.0, -1.8) mL/min/1.73 m2, respectively], with smaller bias for those with lower compared with higher eGFR and by race compared with sex. The small differential bias of the CKD-EPI equation between races suggests that they can be used in Blacks as well as Whites in older community-based adults. The large differential bias in women versus men in all equations is in contrast to other studies and is unexplained. Further studies are required in multiracial and multiethnic community-based cohorts, taking into account differences in GFR measurement methods.

A Brain–Kidney Connection: The Delicate Interplay of Brain and Kidney Physiology

The central nervous system (CNS) and kidneys are strongly interconnected. Afferent impulses from the CNS regulate renal blood flow, glomerular filtration rate (GFR), and affect renal sodium handling [1]. Vasopressin hormone is secreted from the posterior pituitary gland and acts on the collecting ducts of the distal nephron to regulate water balance and serum osmolality. However, the kidney is not a target organ that solely responds to impulses from the CNS. Impulses originating from the kidney are carried via unmyelinated and thinly myelinated fibers to the CNS and the contralateral kidney to regulate CNS activity and coordinate renal sodium handling with the contralateral kidney. In animal models with acute kidney injury (AKI), the levels of inflammatory cytokines increase in the brain with evidence of anatomic and functional brain injuries [2]. Both organs also share a common feature—a tight autoregulatory mechanism that maintains constant blood flow over a wide range of blood pressures. It is unclear, however, whether both the renal and brain autoregulatory mechanisms are interconnected in such a way that changes that occur in one organ affect the blood flow in the other. In this issue of Neurocritical Care, two articles by two separate NeuroICU teams report some important observations on the connection between the brain and kidney vascular beds and autoregulatory mechanisms. The first article by Dias et al. [3] reports a retrospective small series of 18 TBI patients in which various laboratory values were analyzed, including serum creatinine. The authors estimated both creatinine clearance (CrCL) and GFR using two creatinine-based equations: the Cockroft–Gault and the four-point Modification of Diet in Renal Diseases (MDRD) equations, respectively. ICP recording with mean arterial pressure (MAP) via a multimodal monitoring (MMM) computer was obtained, and the authors utilized the MMM data to acquire pressure-reactivity index (PRX) as a surrogate for cerebrovascular auto regulation (CVAR) and correlated PRX with CrCL and GFR, as well as other physiological and laboratory parameters. The authors’ data suggest that patients with brain injuries with better CVAR as measured by PRX were statistically associated with renal hyperfiltration, augmented renal clearance (ARC), and potentially better outcomes. While these findings are intriguing, the results should be interpreted with great caution. First, this study was not intended to monitor GFR, and therefore no ‘‘gold standard’’ method for GFR measurement, such as continuous infusion of iothalamate, was utilized. Second, intravenous fluid infusion in critically ill patients and mannitol use in TBI patients will affect serum creatinine concentration without any meaningful change in kidney function [4]. Third, although using creatinine-based equations to calculate CrCl (in the case of CG) and GFR (in the case of MDRD) seems appealing, in reality, serum creatinine is the only variable in these equations that demonstrates day-to-day changes, while the remaining variables in the equation such as age, gender, and race will remain constant. In addition, it is unclear whether ideal body weight, admission weight, or daily weight was utilized in calculating CrCl by CG. MDRD is intended for chronic kidney disease (CKD) patients and is biased in patients without CKD. Because of the way ‘‘hyperfiltration’’ was actually measured and reported, the whole idea of ARC should be taken with a grain of salt. A fourth W. D. Freeman (&) Departments of Neurosurgery, Neurology and Critical Care, Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL 32224, USA e-mail: freeman.william1@mayo.edu

UK audit of glomerular filtration rate measurement from plasma sampling in 2013.

An audit was carried out into UK glomerular filtration rate (GFR) calculation. The results were compared with an identical 2001 audit. Participants used their routine method to calculate GFR for 20 data sets (four plasma samples) in millilitres per minute and also the GFR normalized for body surface area. Some unsound data sets were included to analyse the applied quality control (QC) methods. Variability between centres was assessed for each data set, compared with the national median and a reference value calculated using the method recommended in the British Nuclear Medicine Society guidelines. The influence of the number of samples on variability was studied. Supplementary data were requested on workload and methodology. The 59 returns showed widespread standardization. The applied early exponential clearance correction was the main contributor to the observed variability. These corrections were applied by 97% of centres (50% - 2001) with 80% using the recommended averaged Brochner-Mortenson correction. Approximately 75% applied the recommended Haycock body surface area formula for adults (78% for children). The effect of the number of samples used was not significant. There was wide variability in the applied QC techniques, especially in terms of the use of the volume of distribution. The widespread adoption of the guidelines has harmonized national GFR calculation compared with the previous audit. Further standardization could further reduce variability. This audit has highlighted the need to address the national standardization of QC methods. Radionuclide techniques are confirmed as the preferred method for GFR measurement when an unequivocal result is required.