The applicability of eGFR equations to different populations

Diagnostic standard: assessing glomerular filtration rate

Creatinine-based estimated glomerular filtration rate (eGFR) is imprecise at individual level, due to non-GFR-related serum creatinine determinants, including atypical muscle mass. Cystatin C has the advantage of being independent of muscle mass, a feature that led to the development of race- and sex-free equations. Yet, cystatin C-based equations do not perform better than creatinine-based equations for estimating GFR unless both variables are included together. The new race-free Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation had slight opposite biases between Black and non-Black subjects in the USA, but has poorer performance than that the previous version in European populations. The European Kidney Function Consortium (EKFC) equation developed in 2021 can be used in both children and adults, is more accurate in young and old adults, and is applicable to non-white European populations, by rescaling the Q factor, i.e. population median creatinine, in a potentially universal way. A sex- and race-free cystatin C-based EKFC, with the same mathematical design, has also be defined. New developments in the field of GFR estimation would be standardization of cystatin C assays, development of creatinine-based eGFR equations that incorporate muscle mass data, implementation of new endogenous biomarkers and the use of artificial intelligence. Standardization of different GFR measurement methods would also be a future challenge, as well as new technologies for measuring GFR. Future research is also needed into discrepancies between cystatin C and creatinine, which is associated with high risk of adverse events: we need to standardize the definition of discrepancy and understand its determinants.

Comparative Determination of Glomerular Filtration Rate Estimation Formulae in Type 2 Diabetic Patients: An Observational Study

Assessing glomerular filtration rate (GFR) involves collecting timed urine samples for 24 hours, requiring significant time and resources in the clinical setting. Using predictive GFR formulae to assess renal function may be a better alternative. Our goal was to determine which predictive GFR formula had the highest level of concordance with the GFR that has been measured in a resource-poor setting. This is an observational study. We selected fifty (50) individuals diagnosed with type 2 diabetes (T2DM) in Kumasi, Ghana. The sociodemographic and clinical characteristics were obtained using a structured questionnaire. Urine was obtained from each subject over 24 hours. The levels of glucose (FBG) and creatinine in patients' blood, as well as the levels of creatinine in their urine, were measured after the patients had fasted overnight. Participants had a mean age of 57.4 ± 10.7 (years), BMI of 27.8 ± 4.1 (kg/m2), FBG of 9.0 ± 3.1 (mmol/L), and creatinine concentrations of 95.6 ± 29.1 (μmol/L). A Krouwer plot was used to compare the measured GFR with three formulae: Chronic Kidney Disease Epidemiology (CKD-EPI), Modification of Diet in Renal Disease (MDRD), and Cockroft-Gault (CG) for GFR prediction. Among the 3 estimates, CG showed nonsignificance (p > 0.05) with the measured GFR. The primary finding was that the GFR calculated using the CG formula was not different from the GFR measured, suggesting that CG is the most appropriate alternative GFR estimate among a cross-section of T2DM patients in Ghana.

Associations among plasma, MRI, and amyloid PET biomarkers of Alzheimer's disease and related dementias and the impact of health-related comorbidities in a community-dwelling cohort

INTRODUCTION

We evaluated associations between plasma and neuroimaging-derived biomarkers of Alzheimer's disease and related dementias and the impact of health-related comorbidities.

METHODS

We examined plasma biomarkers (neurofilament light chain, glial fibrillary acidic protein, amyloid beta [Aβ] 42/40, phosphorylated tau 181) and neuroimaging measures of amyloid deposition (Aβ-positron emission tomography [PET]), total brain volume, white matter hyperintensity volume, diffusion-weighted fractional anisotropy, and neurite orientation dispersion and density imaging free water. Participants were adjudicated as cognitively unimpaired (CU; N = 299), mild cognitive impairment (MCI; N = 192), or dementia (DEM; N = 65). Biomarkers were compared across groups stratified by diagnosis, sex, race, and APOE ε4 carrier status. General linear models examined plasma-imaging associations before and after adjusting for demographics (age, sex, race, education), APOE ε4 status, medications, diagnosis, and other factors (estimated glomerular filtration rate [eGFR], body mass index [BMI]).

RESULTS

Plasma biomarkers differed across diagnostic groups (DEM > MCI > CU), were altered in Aβ-PET-positive individuals, and were associated with poorer brain health and kidney function.

DISCUSSION

eGFR and BMI did not substantially impact associations between plasma and neuroimaging biomarkers.

HIGHLIGHTS

Plasma biomarkers differ across diagnostic groups (DEM > MCI > CU) and are altered in Aβ-PET-positive individuals. Altered plasma biomarker levels are associated with poorer brain health and kidney function. Plasma and neuroimaging biomarker associations are largely independent of comorbidities.

Significance of Organic Anion Transporter 2 and Organic Cation Transporter 2 in Creatinine Clearance: Mechanistic Evaluation Using Freshly Prepared Human Primary Renal Proximal Tubule Cells

Creatinine, a clinical marker for kidney function, is predominantly cleared by glomerular filtration, with active tubular secretion contributing to about 30% of its renal clearance. Recent studies suggested the potential involvement of organic anion transporter (OAT)2, in addition to the previously known organic cation transporter (OCT)2-mediated basolateral uptake, in creatinine active secretion. Here we characterized the transport mechanisms of creatinine using transfected human embryonic kidney (HEK)293 cells and freshly prepared human primary renal proximal tubule epithelial cells (hPTCs). Creatinine showed transport by OAT2 in transfected HEK293 cells. In addition, both creatinine and metformin showed transport by OCT2 and multidrug and toxin extrusion pump (MATE)1 and MATE2K, while penciclovir was selective for OAT2. Time-dependent cell accumulation was observed for creatinine and metformin in hPTCs. Their accumulation was increased by pyrimethamine but inhibited by decynium-22, likely due to differential inhibition of OCT2 versus MATEs. Additionally, indomethacin (an OAT2 inhibitor) reduced penciclovir uptake (∼75%) in hPTCs illustrating functional OAT2 activity. However, no modulation of creatinine and metformin cell accumulation was apparent with indomethacin. Creatinine transport characteristics in the presence of inhibitors approached those of metformin, an OCT2/MATE substrate, but were distinct from those of penciclovir, an OAT2-selective substrate. Moreover, indomethacin showed no significant effect on the basolateral-to-apical transport and net secretion of creatinine across hPTC monolayers. Collectively, the functional studies suggest OCT2 as the primary basolateral uptake mechanism and that OAT2 has a minimal role, in creatinine renal secretion. Our results highlight the utility of hPTCs to enable the functional assessment of renal transport mechanisms. SIGNIFICANCE STATEMENT: Our results obtained with primary hPTCs indicate that OCT2/MATE (vs. OAT2) play a major role in the active renal secretion of creatinine. Quantitative pharmacokinetic models should therefore focus on OCT2/MATE when describing serum creatinine and creatinine clearance modulation by inhibitor drugs and genotype- or disease-related activity changes. The present study highlights the utility of freshly isolated hPTCs to support solute carrier phenotyping to enable the functional assessment of renal transport mechanisms.

A magnetic solid phase chemiluminescent immunoassay for quantification of Cystatin C in human serum

A chemiluminescent immunoassay for human serum Cystatin C (Cys C) was established using a direct-antibody sandwich model. The immunoassay kit uses magnetic separation technology, using magnetic particles as the reaction solid phase, alkaline phosphatase as the marker enzyme, and a new chemiluminescent substrate APLS as the substrate. It has the characteristics of high sensitivity and short reaction time. This product uses high-affinity antibodies, resulting in a high specificity. The established method showed good accuracy, uniformity, and stability. The limit of detection was 2.39 ng/mL. The intra-assay coefficient of variation (CV) was 3.36%-6.00%, the interassay CV was 4.12%-5.35%, and the recovery rate was 99.07%. The correlation coefficient (r) of Cys-C kit was 0.999388 ≥ 0.9900. The accuracy of the developed method was tested by automatic chemiluminescence instrument (P > 0.05). The lowest titer was 0.92500, and the highest was 1.10000. The developed method showed a good correlation with the product from Roche by comparing these two kits in 240 clinical samples from China. In total, 1392 clinical patient from China samples were measured using the reagent kit developed in this study.

Effects of low versus high inspired oxygen fraction on myocardial injury after transcatheter aortic valve implantation: A randomized clinical trial

BACKGROUND

Oxygen therapy is used in various clinical situation, but its clinical outcomes are inconsistent. The relationship between the fraction of inspired oxygen (FIO2) during transcatheter aortic valve implantation (TAVI) and clinical outcomes has not been well studied. We investigated the association of FIO2 (low vs. high) and myocardial injury in patients undergoing TAVI.

METHODS

Adults undergoing transfemoral TAVI under general anesthesia were randomly assigned to receive FIO2 0.3 or 0.8 during procedure. The primary outcome was the area under the curve (AUC) for high-sensitivity cardiac troponin I (hs-cTnI) during the first 72 h following TAVI. Secondary outcomes included the AUC for postprocedural creatine kinase-myocardial band (CK-MB), acute kidney injury and recovery, conduction abnormalities, pacemaker implantation, stroke, myocardial infarction, and in-hospital mortality.

RESULTS

Between October 2017 and April 2022, 72 patients were randomized and 62 were included in the final analysis (n = 31 per group). The median (IQR) AUC for hs-cTnI in the first 72 h was 42.66 (24.82-65.44) and 71.96 (35.38-116.34) h·ng/mL in the FIO2 0.3 and 0.8 groups, respectively (p = 0.066). The AUC for CK-MB in the first 72 h was 257.6 (155.6-322.0) and 342.2 (195.4-485.2) h·ng/mL in the FIO2 0.3 and 0.8 groups, respectively (p = 0.132). Acute kidney recovery, defined as an increase in the estimated glomerular filtration rate ≥ 25% of baseline in 48 h, was more common in the FIO2 0.3 group (65% vs. 39%, p = 0.042). Other clinical outcomes were comparable between the groups.

CONCLUSIONS

The FIO2 level did not have a significant effect on periprocedural myocardial injury following TAVI. However, considering the marginal results, a benefit of low FIO2 during TAVI could not be ruled out.

Adipose tissue is associated with kidney function parameters

Obesity is characterized by the accumulation of adipose tissue in different body compartments. Whether adipose tissue directly affects kidney function is still unknown. We aimed to investigate the role of the adipose tissue and circulating creatinine, cystatin C and kidney function in subjects free of cardio-renal diseases. In the KORA-MRI population-based study, 377 subjects (mean age 56.2 ± 9.2 years; 41.6% female) underwent whole-body 3T-MRI examination. Adipose tissue defined as visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were quantified from T1-DIXON sequence using a semi-automatic algorithm. Serum creatinine and cystatin C were measured using standard laboratory and estimated glomerular filtration rate (e-GFR) was performed based on creatinine (e-GFR_crea), cystatin C (e-GFR_cys) and creatinine-cystatin C (e-GFR_cc). Linear regression analysis, adjusted for risk factors, was used to investigate the relationship between adipose tissue and circulating creatinine, cystatin C, and kidney function. In multivariate analyses VAT was inversely associated with eGFR_cys (ß = - 4.88, p =  < 0.001), and positively associated with serum cystatin C (ß = 0.05, p =  < 0.001), respectively. No association was found between other adipose parameters such as total adipose tissue (TAT) and subcutaneous adipose tissue (SAT) and serum creatinine, urine microalbumin and eGFR_crea. Stratified analyses according to BMI revealed confirmatory results for category of BMI > 30. VAT is positively associated with serum cystatin C and inversely with eGFR based on cystatin C, suggesting a direct involvement of visceral adipose tissue in increased metabolism of cystatin C and consequently decreased kidney function.

Cardiorespiratory Optimisation By Arteriovenous fistula Ligation after renal Transplantation (COBALT): study protocol for a multicentre randomised interventional feasibility trial

INTRODUCTION

Cardiovascular events are a major cause of mortality following successful kidney transplantation.Arteriovenous fistulas (AVFs) are considered the best option for haemodialysis, but may contribute to this excess mortality because they promote adverse cardiac remodelling and ventricular hypertrophy. This raises the question whether recipients with a well-functioning kidney transplant should undergo elective AVF ligation.

METHODS AND ANALYSIS

The COBALT feasibility study is a multicentre interventional randomised controlled trial (RCT) that will randomise renal transplant patients with stable graft function and a working AVF on a 1:1 basis to standard care (continued conservative management) or to AVF ligation. All patients will perform cardiopulmonary exercise testing (CPET) on recruitment and 6 months later. Daily functioning and quality of life will be additionally assessed by questionnaire completion and objective measure of physical activity. The primary outcome-the proportion of approached patients who complete the study (incorporating rates of consent, receipt of allocated intervention and completion of both CPETs without withdrawal)-will determine progression to a full-scale RCT. Design of the proposed RCT will be informed by an embedded qualitative assessment of participant and healthcare professional involvement.

ETHICS AND DISSEMINATION

This study has been approved by the East Midlands-Derby Research Ethics Committee (22/EM/0002) and the Health Research Authority. The results of this work will be disseminated academically through presentation at national and international renal meetings and via open access, peer-reviewed outputs. Existing networks of renal patient groups will also be used to disseminate the study findings to other key stakeholders.

TRIAL REGISTRATION NUMBER

ISRCTN49033491.

Comparison of creatinine-based equations for estimating renal function for digoxin dose adjustment in patients with atrial fibrillation and heart failure

The aim of this study was to determine an appropriate equation for estimating renal function to dose regulate the serum digoxin trough concentration to a target of <0.9 ng/ml in patients with atrial fibrillation (AF) and heart failure (HF). All patients received 0.125 mg oral digoxin daily. The estimated glomerular filtration rate by the Modification of Diet in Renal Disease (eGFRMDRD ) equation deindexed based on body surface area had the highest correlation with digoxin trough concentrations (r = -0.450) compared to the Cockcroft-Gault equation (r = -0.415) or deindexed eGFR based on the Chronic Kidney Disease Epidemiology Collaboration (eGFRCKD-EPI ) equation (r = -0.416). The median digoxin trough concentrations were 0.60, 0.77, 0.97 and 1.30 ng/ml in patients with a deindexed eGFRMDRD  ≥ 60, 45-59, 30-44 and < 30 ml/min, respectively. The deindexed eGFRMDRD is an appropriate equation for digoxin dose adjustment in patients with AF and HF.

Improved equations to estimate GFR in Chinese children with chronic kidney disease

BACKGROUND

There is currently no specific equation for estimating glomerular filtration rate (GFR) in Chinese children with chronic kidney disease (CKD). The commonly used equations are less robust than expected; we therefore sought to derive more appropriate equations for GFR estimation.

METHODS

A total of 751 Chinese children with CKD were divided into 2 groups, training group (n = 501) and validation group (n = 250). In the training group, a univariate linear regression model was used to calculate predictability of variables associated with GFR. Residuals were compared to determine multivariate predictability of GFR in the equation. Standard regression techniques for Gaussian data were used to determine coefficients of GFR-estimating equations after logarithmic transformation of measured GFR (iGFR), height/serum creatinine (height/Scr), cystatin C, blood urea nitrogen (BUN), and height. These were compared with other well-known equations using the validation group.

RESULTS

Median ^99mTc-DTPA GFR was 90.1 (interquartile range: 67.3-108.6) mL/min/1.73 m² in training dataset. Our CKD equation, eGFR (mL/min/1.73 m²) = 91.021 [height(m)/Scr(mg/dL)/2.7]^0.443 [1.2/Cystatin C(mg/L)]^0.335 [13.7/BUN (mg/dL)]^-0.095 [ 0.991^male] [height(m)/1.4]^0.275, was derived. This was further tested in the validation group, with percentages of eGFR values within 30% and 15% of iGFR (P30 and P15) of 76.00% and 48.40%, respectively. For centres with no access to cystatin C, a creatinine-based equation, eGFR (mL/min/1.73 m²) = 89.674 [height(m)/Scr(mg/dL)/2.7]^0.579 [ 1.007^male] [height(m)/1.4]^0.187, was derived, with P30 and P15 73.60% and 49.20%, respectively. These were significantly higher compared to other well-known equations (p < 0.05).

CONCLUSION

We developed equations for GFR estimation in Chinese children with CKD based on Scr, BUN and cystatin C. These are more accurate than commonly used equations in this population.

Standardization of serum creatinine is essential for accurate use of unbiased estimated GFR equations: evidence from three cohorts matched on renal function

BACKGROUND

Differences in the performance of estimated glomerular filtration rate (eGFR) equations have been attributed to the mathematical form of the equations and to differences between patient demographics and measurement methods. We evaluated differences in serum creatinine (SCr) and eGFR in cohorts matched for age, sex, body mass index (BMI) and measured GFR (mGFR).

METHODS

White North Americans from Minnesota (n = 1093) and the Chronic Renal Insufficiency Cohort (CRIC) (n = 1548) and White subjects from the European Kidney Function Consortium (EKFC) cohort (n = 7727) were matched for demographic patient characteristics (sex, age ± 3 years, BMI ± 2.5 kg/m2) and renal function (mGFR ± 3 ml/min/1.73 m2). SCr was measured with isotope dilution mass spectrometry (IDMS)-traceable assays in the Minnesota and EKFC cohorts and with non-standardized SCr assays recalculated to IDMS in the CRIC. The Minnesota cohort and CRIC shared a common method to measure GFR (renal clearance of iothalamate), while the EKFC cohort used a variety of exogenous markers and methods, all with recognized sufficient accuracy. We compared the SCr levels and eGFR predictions [for Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and EKFC equations] of patients fulfilling these matching criteria.

RESULTS

For 305 matched individuals, mean SCr (mg/dL) was not different between the Minnesota and EKFC cohorts (females 0.83 ± 0.20 versus 0.86 ± 0.23, males 1.06 ± 0.23 versus 1.12 ± 0.37; P > .05) but significantly different from the CRIC [females 1.13 ± 0.23 (P < .0001), males 1.42 ± 0.31 (P < .0001)]. The CKD-EPI equations performed better than the EKFC equation in the CRIC, while the opposite was true in the Minnesota and EKFC cohorts.

CONCLUSION

Significant differences in SCr concentrations between the Minnesota and EKFC cohorts versus CRIC were observed in subjects with the same level of mGFR and equal demographic characteristics and can be explained by the difference in SCr calibration.

Predicting acute kidney injury risk in acute myocardial infarction patients: An artificial intelligence model using medical information mart for intensive care databases

Background

Predictive models based on machine learning have been widely used in clinical practice. Patients with acute myocardial infarction (AMI) are prone to the risk of acute kidney injury (AKI), which results in a poor prognosis for the patient. The aim of this study was to develop a machine learning predictive model for the identification of AKI in AMI patients.

Methods

Patients with AMI who had been registered in the Medical Information Mart for Intensive Care (MIMIC) III and IV database were enrolled. The primary outcome was the occurrence of AKI during hospitalization. We developed Random Forests (RF) model, Naive Bayes (NB) model, Support Vector Machine (SVM) model, eXtreme Gradient Boosting (xGBoost) model, Decision Trees (DT) model, and Logistic Regression (LR) models with AMI patients in MIMIC-IV database. The importance ranking of all variables was obtained by the SHapley Additive exPlanations (SHAP) method. AMI patients in MIMIC-III databases were used for model evaluation. The area under the receiver operating characteristic curve (AUC) was used to compare the performance of each model.

Results

A total of 3,882 subjects with AMI were enrolled through screening of the MIMIC database, of which 1,098 patients (28.2%) developed AKI. We randomly assigned 70% of the patients in the MIMIC-IV data to the training cohort, which is used to develop models in the training cohort. The remaining 30% is allocated to the testing cohort. Meanwhile, MIMIC-III patient data performs the external validation function of the model. 3,882 patients and 37 predictors were included in the analysis for model construction. The top 5 predictors were serum creatinine, activated partial prothrombin time, blood glucose concentration, platelets, and atrial fibrillation, (SHAP values are 0.670, 0.444, 0.398, 0.389, and 0.381, respectively). In the testing cohort, using top 20 important features, the models of RF, NB, SVM, xGBoost, DT model, and LR obtained AUC of 0.733, 0.739, 0.687, 0.689, 0.663, and 0.677, respectively. Placing RF models of number of different variables on the external validation cohort yielded their AUC of 0.711, 0.754, 0.778, 0.781, and 0.777, respectively.

Conclusion

Machine learning algorithms, particularly the random forest algorithm, have improved the accuracy of risk stratification for AKI in AMI patients and are applied to accurately identify the risk of AKI in AMI patients.

Negative interference from immunoglobulin M paraproteinaemia on the Roche enzymatic creatinine method

Although enzymatic creatinine methods are subject to fewer interferences than traditional Jaffe creatinine methods, every method in clinical chemistry has limitations. We report, for the first time in the literature, a case of an immunoglobulin M (IgM) paraproteinaemia causing an undetectably low creatinine result on the Roche enzymatic assay. This interference did not occur with other enzymatic creatinine methods produced by Abbott and Siemens or the Roche Jaffe, VITROS dry slide and liquid chromatography with tandem mass spectrometry (LC-MS/MS) creatinine methods. IgM interference was confirmed as patient serum precipitated with polyethylene glycol (PEG) and anti-IgM antiserum yielded detectable Roche enzymatic creatinine results comparable to unaffected methods. The patient's serum formed an obvious precipitate when mixed with reagent one of the Roche enzymatic creatinine method. This is in contrast to a report of positive interference from IgM paraproteinaemia in a different enzymatic creatinine method, which showed that a precipitate formed when mixing blood with reagent two. As each patient's paraprotein has a unique structure, it is possible that there are variations in the chemical characteristics of IgM paraproteins between patients. This, as well as IgM-class antibodies' tendency to form multimers and aggregates, can lead to unpredictable assay interferences and precipitation tendencies between different manufacturers of enzymatic creatinine reagents and their incubation steps. This case highlights the importance of continuing to question and investigates results that do not fit the clinical picture, especially as more laboratories switch from primarily using traditional Jaffe creatinine methods to enzymatic creatinine methods.

Determinants of serum half-lives for linear and branched perfluoroalkyl substances after long-term high exposure-A study in Ronneby, Sweden

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are persistent substances with surfactant and repellent properties. Municipal drinking water contaminated with PFAS had been distributed for decades to one third of households in Ronneby, Sweden. The source was firefighting foam used in a nearby airfield since the mid-1980s. Clean water was provided from December 16, 2013.

AIMS

The purpose was to estimate serum half-lives and their determinants in the study population for different PFAS.

METHODS

Up to ten blood samples were collected between 2014 and 2018 from 114 participants (age 4-84 years at entry, 53% female). 19 PFAS were analysed. Linear mixed models were used to estimate the half-lives.

RESULTS

Eight PFAS were increased in Ronneby: perfluorooctanoic acid (PFOA), perfluoropentane sulfonate (PFPeS), perfluorohexane sulfonate (PFHxS), perfluoroheptane sulfonate (PFHpS), linear perfluorooctane sulfonate (L-PFOS) and three branched perfluorooctane sulfonates (1 m-PFOS, 3/4/5m-PFOS and 2/6m-PFOS). The mean estimated half-lives (in years) were 0.94 (95 %CI 0.86-1.02) for PFPeS, 2.47 (2.27-2.7) for PFOA, 2.67 (2.51-2.85) for 2/6m-PFOS, 2.73 (2.55-2.92) for L-PFOS, 3.43 (3.19-3.71) for 3/4/5m-PFOS, 4.52 (4.14-4.99) for PFHxS, 4.55 (4.14-5.06) for PFHpS, and 5.01 (4.56-5.55) for 1 m-PFOS. The most important determinants of a shorter half-life were young age, and better kidney function measured by estimated glomerular filtration rate and ratio of paired urine and serum PFAS levels, followed by female sex during their fertile period aged 15-50. Markers of gut inflammation and reduced permeability i.e. zonulin and calprotectin were also possibly associated with shorter half-life. The results also suggested a time-dependent PFAS elimination process, with more rapid elimination in the first year after the end of exposure.

CONCLUSION

The half-life estimates are in line with past estimates for some PFAS such as PFOA, and the novel results for different PFOS isomers. These results provide observational support for elimination routes - renal, fecal and maternal.

Managing Patients with Failing Kidney Allograft: Many Questions Remain

Patients who receive a kidney transplant commonly experience failure of their allograft. Transplant failure often comes with complex management decisions, such as when and how to wean immunosuppression and start the transition to a second transplant or to dialysis. These decisions are made in the context of important concerns about competing risks, including sensitization and infection. Unfortunately, the management of the failed allograft is, at present, guided by relatively poor-quality data and, as a result, practice patterns are variable and suboptimal given that patients with failed allografts experience excess morbidity and mortality compared with their transplant-naive counterparts. In this review, we summarize the management strategies through the often-precarious transition from transplant to dialysis, highlighting the paucity of data and the critical gaps in our knowledge that are necessary to inform the optimal care of the patient with a failing kidney transplant.

Evaluation of novel glomerular filtration rate estimation equations in adolescents and young adults with type 1 diabetes

AIMS

Individuals with type 1 diabetes (T1D) are at an increased risk of chronic kidney disease making estimation of glomerular filtration rate (eGFR) an important component of diabetes care. Which eGFR equation is most appropriate to use in patients with T1D during the transition to adult care is unclear. We, therefore, sought to evaluate the performance of five eGFR equations in adolescents and young adults with T1D.

METHODS

Measured iohexol-based glomerular filtration rate was compared to the Chronic Kidney Disease and Epidemiology Collaboration (CKD-EPI) eGFR, Chronic Kidney Disease in Children (CKiD) eGFR, and three recently developed age-adjusted versions of these in 53 patients with T1D and preserved GFR using bias, precision, and accuracy.

RESULTS

The best performance was found in the sex-dependent CKiD equation (bias: -0.8, accuracy: 11.8 ml/min/1.73 m²). Bias and accuracy (26.4 and 26.8 ml/min/1.73 m²) were worst in the CKD-EPI equation. Age-dependent adjustment improved performance for this equation (bias: 5.3, accuracy: 13.4 ml/min/1.73 m²), but not for the CKiD equation (bias: 15.5, accuracy: 18.8 ml/min/1.73 m²).

CONCLUSION

Age-adjustment improved performance for the CKD-EPI equation, but not for the CKiD equation. The sex-adjusted CKiD equation performed best out of all equations.

Mortality risk stratification in isolated severe traumatic brain injury using the revised cardiac risk index

PURPOSE

Traumatic brain injury (TBI) continues to be a significant cause of mortality and morbidity worldwide. As cardiovascular events are among the most common extracranial causes of death after a severe TBI, the Revised Cardiac Risk Index (RCRI) could potentially aid in the risk stratification of this patient population. This investigation aimed to determine the association between the RCRI and in-hospital deaths among isolated severe TBI patients.

METHODS

All adult patients registered in the TQIP database between 2013 and 2017 who suffered an isolated severe TBI, defined as a head AIS ≥ 3 with an AIS ≤ 1 in all other body regions, were included. Patients were excluded if they had a head AIS of 6. The association between different RCRI scores (0, 1, 2, 3, ≥ 4) and in-hospital mortality was analyzed using a Poisson regression model with robust standard errors while adjusting for potential confounders, with RCRI 0 as the reference.

RESULTS

259,399 patients met the study's inclusion criteria. RCRI 2 was associated with a 6% increase in mortality risk [adjusted IRR (95% CI) 1.06 (1.01-1.12), p = 0.027], RCRI 3 was associated with a 17% increased risk of mortality [adjusted IRR (95% CI) 1.17 (1.05-1.31), p = 0.004], and RCRI ≥ 4 was associated with a 46% increased risk of in-hospital mortality [adjusted IRR(95% CI) 1.46 (1.11-1.90), p = 0.006], compared to RCRI 0.

CONCLUSION

An elevated RCRI ≥ 2 is significantly associated with an increased risk of in-hospital mortality among patients with an isolated severe traumatic brain injury. The simplicity and bedside applicability of the index makes it an attractive choice for risk stratification in this patient population.

The « race » correction in estimating glomerular filtration rate: an European point of view

PURPOSE OF REVIEW

There is currently a heated debate ongoing whether or not to use the race coefficient for black people in the Modification of Diet in Renal Diseases and Chronic Kidney Disease Epidemiology-equation. The use of the race coefficient is thought by several American authors as a source of discrimination.

RECENT FINDINGS

It has recently been shown that the race coefficient is inaccurate in European and African black people. Therefore, it seems that the race correction is more a correction for black Americans, rather than for black in general. This 'correction' at the glomerular filtration rate (GFR)-level has been criticized, as it is misleading, and should be abandoned, as it has not been shown that GFR is different between black and white people. However, as differences in creatinine generation between black and white people might exist, a correction or adjustment, different for black and white people, at the creatinine level might be required, very similar to the different scaling of creatinine for males and females.

SUMMARY

The current debate on the race coefficient is particularly difficult because of the absence of good scientific data in black subjects and there lies the real discrimination in our opinion. We therefore call for future dedicated studies, both in Europe and USA.

Noninvasive assessment of kidney dysfunction in children by using blood oxygenation level-dependent MRI and intravoxel incoherent motion diffusion-weighted imaging

Objectives

To explore whether multiparametric approach including blood oxygenation level-dependent MRI (BOLD-MRI) and intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) can be applied in the assessment of renal function in children with chronic kidney disease (CKD).

Materials and methods

This prospective study included 74 children (CKD stage 1–3, 51; CKD stage 4–5, 12; healthy volunteers, 11) for renal MRI examinations including coronal T2WI, axial T1WI and T2WI, BOLD-MRI, and DWI sequences. We measured the renal cortex and medulla T2*, ADC, D_t, D_p, and f_p values on BOLD and DWI images. Appropriate statistical methods were applied for comparing MRI-derived parameters among the three groups and calculating the correlation coefficients between MRI-derived parameters and clinical data. Receiver operating characteristic (ROC) curves were used to assess the diagnostic performance of MRI-derived parameters.

Results

There were significant differences in cortex T2*, ADC, D_t, f_p and medulla T2*, ADC, D_t among the three groups. Cortex T2*, ADC, D_t, f_p and medulla T2*, ADC, D_t had a trend: CKD stage 4–5 < CKD stage 1–3 < healthy volunteers. Cortex and medulla T2*, ADC, D_t were significantly correlated with eGFR, serum creatinine (Scr), cystatin C. In addition, cortex T2* and eGFR showed the highest correlation coefficient (r = 0.824, p < 0.001). Cortex D_t and medulla T2* were optimal parameters for differentiating healthy volunteers and CKD stage 1–3 or CKD stage 4–5 and CKD stage 1–3, respectively.

Conclusions

BOLD-MRI and IVIM-DWI might be used as a feasible method for noninvasive assessment of renal function in children with CKD.

Assessment of Pre-Donation Glomerular Filtration Rate: Going Back To Basics A Position Paper from the DESCARTES Working Group of the ERA-EDTA

The 2017 version of the KDIGO (Kidney Disease: Improving Global Outcomes) guidelines is the most recent international framework for the evaluation and care of living kidneys donors. Along with the call for an integrative approach evaluating the long-term end-stage kidney disease risk for the future potential donor, several recommendations are formulated regarding the predonation glomerular filtration rate (GFR) adequacy with no or little consideration for the donor candidate's age and for the importance of using reference methods of GFR measurements. Herein, we question the position of the KDIGO guidelines and discuss the rationale and modalities for a more basic, but not less demanding GFR evaluation susceptible to enable a more efficient selection of the potential kidney donor.

Serum electrolytes and renal alterations in HIV-seropositive Mexican subjects

To examine potential risk factors associated with biochemical alterations in renal function in a population diagnosed with HIV/AIDS undergoing antiretroviral treatment.This is an observational, transversal, and relational design study that included 179 HIV-seropositive subjects. Glucose serum, cholesterol, triglycerides, total proteins, albumin, creatine, urea, blood urea nitrogen (BUN), and electrolytes levels were determined for each individual. Renal function was evaluated through the glomerular filtration rate (GFR), using the CKD-EPI equation. Chronic kidney disease (CKD) was defined as estimated glomerular filtration rate  < 60 mL/min/1.73 m2. Univariate model significant variables, with a 95% confidence interval (CI), were included in a multivariate logistic regression analysis.CKD prevalence in patients was 7.3%, with comorbidities of 7.8% for type 2 diabetes mellitus, 7.3% for arterial hypertension, and 35.2% for dyslipidemia. Additionally, both hypernatremia and hypophosphatemia were detected in 57% (n = 102) of the patients. Multivariate logistic regression suggested that CD4+ T cell count < 200 (P = .02; OR 0.2; CI 95% 0.08-0.8) was associated to hyponatremia; similarly, detectable viral load was associated to hypokalemia (P = .02; OR 5.1; CI 95% 1.2-21.3), hypocalcemia (P = .01; OR 4.1; CI 95% 1.3-12.3), and hypermagnesemia (OR 3.9; CI 95% 1.1-13.6). Patient age was associated to both hypophosphatemia (P = .01; OR 2.4; CI 95% 1.1-5.0) and hypermagnesemia (P = .01; OR 2.8; IC 95% 1.1-7.0), and high creatinine levels were associated to nucleoside reverse transcriptase inhibitor treatment (P = .001; OR 42.5; CI 95% 2.2-806.9). Lastly, high BUN levels were associated to age (P = .03; OR 3.8; CI 95% 1.0-14.4), while GFR 60 to 89 mL/min/1.73 m2 was associated to dyslipidemia (P = .02; OR 2.2; CI 95% 1.1-4.5).CD4+ T cell and viral load were the main factors associated with renal biochemical alterations.

Association Between Renal Dysfunction and Low HDL Cholesterol Among the Elderly in China

Objective: Chronic kidney disease (CKD) and cardiovascular disease (CVD) have a high morbidity and mortality among the elderly. Low levels of high-density lipoprotein cholesterol (HDL-C), a traditional risk marker for CVD, are common in CKD patients. Little is known about the association of low HDL-C with renal dysfunction in the community dwelling population. Methods: This was a population-based cross-sectional study included 4,753 participants enrolled in a prospective study, the Shanghai Elderly Cardiovascular Health (SHECH) study. Estimated glomerular filtration rate (eGFR), calculated by the Chinese Modification of Diet in Renal Disease (C-MDRD equation), was used to assess renal dysfunction. Associations between renal dysfunction and low HDL-C were evaluated using multiple logistic regression models and restricted cubic splines. Results: Of 4,649 individuals who met inclusion criteria, 620 (13.34%) had low HDL-C at <40 mg/dl. In the fully adjusted model, lower eGFR of <60 ml/min/1.73 m² (OR, 2.03; 95% CI, 1.21-3.43) and marginal eGFR of 60 to 90 ml/min/1.73 m² (OR, 1.26; 95% CI, 1.01-1.58) were significantly associated with low HDL-C, compared with normal eGFR of ≥90 ml/min/1.73 m². Moreover, consistent findings were obtained in subsidiary analyses using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Fully adjusted cubic spline models indicated a significant dose-response relationship between eGFR and low HDL-C (P for non-linearity, 0.356). Conclusion: In this general elderly population, renal dysfunction was independently and significantly associated with low HDL-C, and the prevalence of low HDL-C increased with decreasing eGFR, such that even slight changes in renal function may be associated with altered lipid levels.

Direct Oral Anticoagulants in Patients with Atrial Fibrillation and Renal Dysfunction

Atrial fibrillation and renal dysfunction often coexist, each disorder may predispose to the other and contribute to worsening prognosis. Both atrial fibrillation and chronic kidney disease are associated with increased risk of stroke and thromboembolic complications. Oral anticoagulation for stroke prevention is therefore recommended in patients with atrial fibrillation and decreased renal function. Each direct oral anticoagulant has unique pharmacologic properties of which clinician should be aware to optimally manage patients. The doses of direct oral anticoagulants require adjustment for renal function. There is debate regarding which equation, the Chronic Kidney Disease Epidemiology (CKD-EPI) equation vs. the Cockcroft-Gault equation, should be used to estimate glomerular filtration rate in patients with atrial fibrillation treated with direct oral anticoagulants. Our review tries to find arguments for benefit of direct oral anticoagulants in patients with renal dysfunction.

Factors Related to Survival in Low-Glomerular Filtration Rate Cohorts Undergoing Lung Transplant

BACKGROUND

Historically, a glomerular filtration rate (GFR) of less than 50 mL/min per 1.73 m² has been considered a contraindication to lung transplantation. Combined or sequential lung-kidney transplantation is an option for those with a GFR less than 30 mL/min per 1.73 m². Patients with a GFR of 30 to 50 mL/min per 1.73 m² are provided with no options for transplantation. This study explores factors associated with improved survival in patients who undergo isolated lung transplantation with a GFR of 30 to 50 mL/min per 1.73 m².

METHODS

The United Network for Organ Sharing database was queried for adult patients undergoing primary isolated lung transplantation between January 2007 and March 2018. Regression models were used to identify factors associated with improved survival in lung recipients with a preoperative GFR of 30 to 50 mL/min per 1.73 m². The propensity score method was used to match highly performing patients (outpatient recipients aged less than 60 years) with a GFR of 30 to 50 mL/min per 1.73 m² with patients who had a GFR greater than 50 mL/min per 1.73 m². Kaplan-Meier, Cox, and logistic regression analyses compared outcomes in matched populations.

RESULTS

A total of 21,282 lung transplantations were performed during the study period. Compared with patients with a GFR greater than 50 mL/min per 1.73 m², survival was significantly worse for patients with a GFR of 30 to 50 mL/min per 1.73 m². Multivariate analysis of patients with a GFR of 30 to 50 mL/min per 1.73 m² demonstrated outpatient status and age less than 60 years to be predictive of superior survival. After propensity matching, survival of this highly performing subset with a GFR of 30 to 50 mL/min per 1.73 m² was no different from that of patients with a normal GFR.

CONCLUSIONS

Outpatient recipients aged less than 60 years represent an optimal subset of patients with a GFR of 30 to 50 mL/min per 1.73 m². Lung transplant listing should not be declined based only on a GFR less than 50 mL/min per 1.73 m².

Drug dosing in cancer patients with decreased kidney function: A practical approach

Correct drug dosing of anticancer agents is essential to obtain optimal outcomes. Overdosing will result in increased toxicity, treatment interruption and possible cessation of anticancer treatment. Underdosing may result in suboptimal anti-cancer effects and may increase the risk of cancer-related mortality. As it is practical nor feasible to perform therapeutic drug monitoring for all anti-cancer drugs, kidney function is used to guide drug dosing for those drugs whose primary mode of excretion is through the kidney. However, it is not well-established what method should be utilized to measure or estimate kidney function and the choice of method does influence treatment decisions regarding eligibility for anti-cancer drugs and their dose. In this review, we will provide an overview regarding the importance of drug dosing, the preferred method to determine kidney function and a practical approach to drug dosing of anticancer drugs.

Relationship between decline in estimated or measured glomerular filtration rate and 16-year postrenal transplant outcome

Background

Glomerular filtration rate (GFR) decline ≥30% over 2 years can substitute for the conventional ‘doubling of serum creatinine’ to predict end-stage renal disease in patients with native kidneys. While chronic kidney disease trajectory is less predictable in transplanted patients, recent data have suggested that similar GFR decline might be an acceptable surrogate for long-term transplant outcome. We sought (i) to confirm the prognostic value of an early GFR decline in kidney transplant recipients and (ii) to determine whether using direct measurement of GFR with inulin improves the performance of this surrogate.

Methods

We retrospectively analysed all recipients transplanted between 1989 and 2000 in our centre, with inulin-measured and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)-estimated GFR at 1 and 5 years post-transplant, and evaluated the performance [time-dependent area under the receiver operating characteristic curve (ROC AUC) and subdistribution hazard ratio (sdHR) with competing risk model] of GFR change to predict graft failure and all-cause mortality.

Results

Out of 417 kidney transplant recipients, 116 patients had lost their graft and 77 had died 16 years after transplantation. While being significantly associated with graft failure [sdHR = 2.37 (95% confidence interval 1.47–3.83)], CKD-EPI-GFR decline ≥30% failed to appropriately predict long-term graft survival (C-statistics of 0.63). Concordance between inulin-GFR and CKD-EPI-GFR to detect similar GFR change was only 53%. Inulin-GFR change was, however, not a better predictor (C-statistics of 0.59). Comparable results were observed for mortality.

Conclusions

Our data suggest that early GFR decline is a poor surrogate for long-term transplant outcome, even when change in GFR is directly measured by a reference method.

Changing How Race Is Portrayed in Medical Education: Recommendations From Medical Students

The medical community has been complicit in legitimizing claims of racial difference throughout the history of the United States. Unfortunately, a rigorous examination of the role medicine plays in perpetuating inequity across racial lines is often missing in medical school curricula due to time constraints and other challenges inherent to medical education. The imprecise use of race-a social construct-as a proxy for pathology in medical education is a vestige of institutionalized racism. Recent examples are presented that illustrate how attributing outcomes to race may contribute to bias and unequal care. This paper proposes the following recommendations for guiding efforts to mitigate the adverse effects associated with the use of race in medical education: emphasize the need for incoming students to be familiar with how race can influence health outcomes; provide opportunities to hold open conversations about race in medicine among medical school faculty, students, and staff; craft and implement protocols that address and correct the inappropriate use of race in medical school classes and course materials; and encourage a large cultural shift within the field of medicine. Adoption of an interdisciplinary approach that taps into many fields, including ethics, history, sociology, evolutionary genetics, and public health is a necessary step for cultivating more thoughtful physicians who will be better prepared to care for patients of all racial and ethnic backgrounds.

KDIGO Controversies Conference on onco-nephrology: understanding kidney impairment and solid-organ malignancies, and managing kidney cancer

The association between kidney disease and cancer is multifaceted and complex. Persons with chronic kidney disease (CKD) have an increased incidence of cancer, and both cancer and cancer treatments can cause impaired kidney function. Renal issues in the setting of malignancy can worsen patient outcomes and diminish the adequacy of anticancer treatments. In addition, the oncology treatment landscape is changing rapidly, and data on tolerability of novel therapies in patients with CKD are often lacking. Caring for oncology patients has become more specialized and interdisciplinary, currently requiring collaboration among specialists in nephrology, medical oncology, critical care, clinical pharmacology/pharmacy, and palliative care, in addition to surgeons and urologists. To identify key management issues in nephrology relevant to patients with malignancy, KDIGO (Kidney Disease: Improving Global Outcomes) assembled a global panel of multidisciplinary clinical and scientific expertise for a controversies conference on onco-nephrology in December 2018. This report covers issues related to kidney impairment and solid organ malignancies as well as management and treatment of kidney cancer. Knowledge gaps, areas of controversy, and research priorities are described.

Comparison of bias and accuracy using cystatin C and creatinine in CKD-EPI equations for GFR estimation

BACKGROUND

The directly measured glomerular filtrate rate (mGFR) is the gold standard for kidney function, but it is invasive and costly. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations have been widely used to estimate GFR, however, the comparative accuracy of estimated GFR (eGFR) using creatinine and cystatin C in CKD-EPI equations remains unclear. We performed this meta-analysis to assess the bias and accuracy of eGFR using equations of CKD-EPI_crea, CKD-EPI_cys, and CKD-EPI_crea/cys in adult populations relevant to primary health care.

METHODS

Pubmed, Web of Science, EMBASE, and the Cochrane Library were searched from inception until December 2019 for related studies.

RESULTS

A total of 35 studies with 23,667 participants, which reported the data on the bias, and/or P30, and/or R were included. The difference in the bias of eGFR using CKD-EPI_cys was 4.84 mL/min/1.73 m² (95% CI, 1.88~7.80) lower than using CKD-EPI_crea, and 1.50 mL/min/1.73 m² (95% CI, 0.05~2.95) lower than using CKD-EPI_crea/cys. These gaps increased in subgroups of low mGFR (<60 mL/min/1.73 m²). CKD-EPI_crea/cys eGFR achieved the highest accuracy, 7.50% higher than CKD-EPI_crea (95% CI, 4.81~10.18), and 3.21% higher than CKD-EPI_cys (95% CI, -0.43~6.85); and the best correlation with mGFR, with Fisher's z transformed R of 1.20 (95% CI, 0.89-1.50).

CONCLUSIONS

CKD-EPI_crea/cys and CKD-EPI_cys gave less bias and more accurate estimates of mGFR than CKD-EPI_crea. More variables and coefficients could be added in CKD-EPI equations to achieve less bias and more accuracy in future research.

Uromodulin and microRNAs in Kidney Transplantation-Association with Kidney Graft Function

Uromodulin and microRNAs (miRNAs) have recently been investigated as potential biomarkers for kidney graft associated pathology and outcome, with a special focus on biomarkers indicating specific disease processes and kidney graft survival. The study's aim was to determine whether expression of serum uromodulin concentration and selected miRNAs might be related to renal function in kidney transplant recipients (KTRs). The uromodulin concentration and expression of six selected miRNAs (miR-29c, miR-126, miR-146a, miR-150, miR-155, and miR-223) were determined in the serum of 100 KTRs with stable graft function and chronic kidney disease of all five stages. Kidney graft function was estimated with routine parameters (creatinine, urea, cystatin C, and Chronic Kidney Disease Epidemiology Collaboration study equations) and precisely measured using chromium-51 labelled ethylenediaminetetraacetic-acid clearance. The selected miRNAs were shown to be independent of kidney graft function, indicating their potential as biomarkers of associated kidney graft disease processes. In contrast, the serum uromodulin level depended entirely on kidney graft function and thus reflected functioning tubules rather than any specific kidney graft injury. However, decreased concentrations of serum uromodulin can be observed in the early course of tubulointerstitial injury, thereby suggesting its useful role as an accurate, noninvasive biomarker of early (subclinical) kidney graft injury.

The urinary β2 microglobulin-creatinine ratio is inversely associated with lumbar spine bone mineral density in the elderly Chinese males

Renal tubule cells play a pivotal role in maintaining bone homeostasis. Hence, renal tubular function may be associated with bone mineral density. Our study found that urinary β₂ microglobulin-creatinine ratio (UBCR) levels correlated negatively with lumbar spine bone mineral density (BMD) and T and Z values, and may be a marker for osteoporosis in Chinese elderly male adults.

PURPOSE

To study the association of UBCR levels with BMD and the predictive value of UBCR for osteoporosis in elderly Chinese male adults.

METHODS

A cross-sectional study of 149 (65 to 85 years, 69.7 ± 4.6) Chinese male adults who underwent health checkups in Huadong Hospital in Shanghai China was conducted. BMD was measured by dual-energy X-ray absorptiometry. The clinical variables and BMD of the participants in the low UBCR group (B1, UBCR < 300 μg/g) and the high UBCR group (B2, UBCR ≥ 300 μg/g) were compared. Associations between UBCR with clinical variables and BMD were analyzed by Pearson's correlation coefficient and multiple regression analysis. BMD and T and Z values were compared between the B1 and B2 groups. The odds ratios (ORs) for dose-dependent increases in osteoporosis between B1 and B2 were analyzed by binary logistic regression analysis. The area under the receiver operating characteristic (ROC) curve was used to analyze the capacity of UBCR to predict osteoporosis.

RESULTS

UBCR was significantly higher in the osteoporosis group. After adjusting for multiple confounders, UBCR levels correlated negatively with BMD and T and Z values of the lumbar spine. Lumbar spine BMD and T and Z values were significantly lower in the B2 UBCR group than in the B1 UBCR group. Compared with the B1 participants, the ORs for "osteoporosis" were 12.401 times higher in B2 participants (P = 0.005) by binary logistic regression analysis after adjusting for potential confounders. The UBCR index (cutoff = 362.48 μg/g) had a sensitivity of 78.6% and a specificity of 68.7% for identifying osteoporosis, with an area under the ROC curve of 0.760.

CONCLUSIONS

These results suggest that UBCR levels correlate negatively with lumbar spine BMD and T and Z values and may serve as a marker for osteoporosis in Chinese elderly male adults.

Renal and Cardiovascular Outcomes After Weight Loss From Gastric Bypass Surgery in Type 2 Diabetes: Cardiorenal Risk Reductions Exceed Atherosclerotic Benefits

OBJECTIVE

We examined detailed renal and cardiovascular (CV) outcomes after gastric bypass (GBP) surgery in people with obesity and type 2 diabetes mellitus (T2DM), across several renal function categories, in a nationwide cohort study.

RESEARCH DESIGN AND METHODS

We linked data from the National Diabetes Register and the Scandinavian Obesity Surgery Register with four national databases holding information on socioeconomic variables, medications, hospitalizations, and causes of death and matched 5,321 individuals with T2DM who had undergone GBP with 5,321 who had not (age 18-65 years, mean BMI >40 kg/m², mean follow-up >4.5 years). The risks of postoperative outcomes were assessed with Cox regression models.

RESULTS

During the first years postsurgery, there were small reductions in creatinine and albuminuria and stable estimated glomerular filtration rate (eGFR) in the GBP group. The incidence rates of most outcomes relating to renal function, CV disease, and mortality were lower after GBP, being particularly marked for heart failure (hazard ratio [HR] 0.33 [95% CI 0.24, 0.46]) and CV mortality (HR 0.36 [(95% CI 0.22, 0.58]). The risk of a composite of severe renal disease or halved eGFR was 0.56 (95% CI 0.44, 0.71), whereas nonfatal CV risk was lowered less (HR 0.82 [95% CI 0.70, 0.97]) after GBP. Risks for key outcomes were generally lower after GBP in all eGFR strata, including in individuals with eGFR <30 mL/min/1.73 m².

CONCLUSIONS

Our data suggest robust benefits for renal outcomes, heart failure, and CV mortality after GBP in individuals with obesity and T2DM. These results suggest that marked weight loss yields important benefits, particularly on the cardiorenal axis (including slowing progression to end-stage renal disease), whatever the baseline renal function status.

Glomerular filtration rate: when to measure and in which patients?

Of the glomerular, tubular and endocrine functions of the kidney, nephrologists have mostly focused their attention on the glomerular functions-albuminuria and glomerular filtration rate (GFR)-to grade the severity of chronic kidney disease (CKD). Although both albuminuria and GFR are associated with renal and cardiovascular morbidity and mortality, the utility of measured GFR (mGFR) has been questioned. GFR when measured adequately is the most precise measure of glomerular function and can be useful to individualize therapy among patients with CKD. In situations where estimated GFR is known to provide imprecise estimates of glomerular function, for example, sarcopenia and advanced cirrhosis, the measurement of GFR may be especially important. We discuss several clinical situations where mGFR can potentially influence the quality of life or complications of therapy because of interventions based on imperfect knowledge of GFR. We reason that although large databases may not detect the benefits of mGFR at the population level, precision medicine requires that therapy be individualized based on the best estimate of GFR that can be obtained particularly when the risk of harm is increased. The recent standardization of mGFRs is a step in the right direction and may help in treating the individual patient with CKD with a lower risk of complications and a better quality of life. We call for research in these subgroups of patients where it is clinically felt that mGFR is useful for clinical decision-making.

How to determine kidney function in cancer patients?

A precise and efficient method for estimating kidney function in cancer patients is important to determine their eligibility for clinical trials and surgery and to allow for appropriate dose adjustment of anti-cancer drugs, especially toxic drugs with a narrow therapeutic index. Since direct measurement of glomerular filtration rate (GFR) is cumbersome, several formulae have been developed to estimate kidney function. Most of these are based on serum creatinine concentration. Though the CKD-EPI formula is recognised as being the most accurate, there is an ongoing debate on which is the optimal formula for cancer patients. In this review, we provide an overview of different GFR estimating equations for kidney function and the advantages and disadvantages of each method and compare their performance in cancer patients. We discuss the importance of body surface area-indexing and propose a framework for evaluating kidney function in cancer patients.

20-year longitudinal follow-up of measured and estimated glomerular filtration rate in kidney transplant patients

Background

The slopes of estimated glomerular filtration rate (eGFR) equations are used in the longitudinal follow-up of transplant patients. A 30% reduction in eGFR over 2 years is often used to predict the subsequent risk of mortality or end-stage renal disease. Whether, at the individual level, such changes in eGFR correspond to changes in measured GFR (mGFR) is actually unknown.

Methods

The performance of serum creatinine–based eGFR equations was compared with mGFR during the longitudinal follow-up of 20 years in a monocentric study of 417 transplanted patients.

Results

The accuracy within 30% for the eGFR equations varied between 70 and 75%. All eGFR equations showed a similar pattern, very like the mGFR time profiles. Individual changes (slopes) of mGFR or eGFR were predictive of graft loss in the next months or years, following the decline in GFR, with no evidence for a difference. However, although the tendency is the same as for mGFR, the percentage of transplant patients with a >30% GFR decrease in the last period before graft loss is significantly lower for eGFR than for mGFR, with discordant results from mGFR in ~25% of the cases.

Conclusions

All eGFR equations showed similar trends as mGFR, but eGFR predictions may not be very useful at the individual patient level.

Single- versus multiple-sample method to measure glomerular filtration rate

Background

There are many different ways to measure glomerular filtration rate (GFR) using various exogenous filtration markers, each having their own strengths and limitations. However, not only the marker, but also the methodology may vary in many ways, including the use of urinary or plasma clearance, and, in the case of plasma clearance, the number of time points used to calculate the area under the concentration-time curve, ranging from only one (Jacobsson method) to eight (or more) blood samples.

Methods

We collected the results obtained from 5106 plasma clearances (iohexol or 51Cr-ethylenediaminetetraacetic acid (EDTA)) using three to four time points, allowing GFR calculation using the slope-intercept method and the Bröchner-Mortensen correction. For each time point, the Jacobsson formula was applied to obtain the single-sample GFR. We used Bland-Altman plots to determine the accuracy of the Jacobsson method at each time point.

Results

The single-sample method showed within 10% concordances with the multiple-sample method of 66.4%, 83.6%, 91.4% and 96.0% at the time points 120, 180, 240 and ≥300 min, respectively. Concordance was poorer at lower GFR levels, and this trend is in parallel with increasing age. Results were similar in males and females. Some discordance was found in the obese subjects.

Conclusion

Single-sample GFR is highly concordant with a multiple-sample strategy, except in the low GFR range (<30 mL/min).

Impact of MELD score and cardiopulmonary bypass duration on post-operative hypoxic hepatitis in patients with liver cirrhosis undergoing open heart surgery

BACKGROUND

The outcome of open-heart surgery for patients with liver cirrhosis (LC) varies widely, indicating multifactorial influences on liver injury after cardiopulmonary bypass (CPB).

METHODS

This observational single center study evaluated adult LC patients receiving open heart surgery with CPB during 2007 and 2017. The primary endpoint was post-operative hypoxic hepatitis (POHH), defined by post-operative serum glutamate oxaloacetate transaminase and glutamate pyruvate transaminase more than 10 times the pre-operative value.

RESULTS

In total, 61 patients were included in the study, of whom 14 (18.7%) developed POHH. Hospital mortality of non-POHH group (4.3%) was similar to that estimated using Euroscore II (4.0%), but that of the POHH group (21.4%) was 2.7 times as that estimated using Euroscore II (8.0%). Model for End-Stage Liver Disease (MELD) score and CPB duration were found as independent risk factors for POHH by multivariate logistic regression. POHH incidence was 0.0% if MELD <5 and 80.0% of MELD >20 regardless of CPB duration. For those with MELD between 5 and 20, POHH incidence increases as CPB duration increases.

CONCLUSION

For LC patients undergoing cardiac surgery with CPB, the incidence of POHH is highly associated with MELD score and CPB duration. To prevent POHH, the CPB duration should be shortened for those with MELD score between 5 and 20, and CPB be avoid for those with MELD >20.

Measured (and estimated) glomerular filtration rate: reference values in West Africa

Background

Establishment of normal reference values for glomerular filtration rate (GFR) is mandatory in nephrology. However, no data are available for measured GFR (mGFR) in Africa.

Methods

GFR was measured in 237 healthy adult subjects (103 women and 134 men, mean age 34 ± 10 years) by iohexol plasma clearance.

Results

The mean mGFR was 103 ± 17 mL/min/1.73 m2 and the median value was 103 mL/min/1.73 m2 (2.5th and 97.5th percentiles are 76 and 137 mL/min/1.73 m2, respectively). No significant difference in mGFR results was observed in patients < 40 years of age, whereas a significant decline in mGFR was observed after 40 years of age. There was no significant difference between mGFR in men and women.

Conclusions

Normal GFR values and descriptions of percentiles are now available for West Africa. As in Caucasians, no significant difference was observed between men and women. Moreover, the same age-associated decline in mGFR is also observed after 40 years of age, as in Caucasians.

Validating the Performance of 5 Risk Scores for Major Adverse Cardiac Events in Patients Who Achieved Complete Revascularization After Percutaneous Coronary Intervention

BACKGROUND

Risk scores, like the Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) score (SS), clinical SS, logistic SS (core model and extended model [LSS_extended]), Age, Creatinine, and Ejection Fraction (ACEF) score, and modified ACEF score, are predictive for major adverse cardiac events (MACE; including all-cause mortality, myocardial infarction [MI], and revascularization) in patients who have undergone percutaneous coronary intervention (PCI). However, few studies have validated the performance of these scores in complete revascularization (CR) patients. We aimed to compare the performance of previous risk scores in patients who achieved CR after PCI.

METHODS

All patients (N = 10,724) who underwent PCI at Fuwai Hospital in 2013 were screened, and those who achieved CR after PCI were enrolled. Risk scores were calculated by experienced cardiologists blinded to the clinical outcomes. Discrimination of risk scores was assessed according to the area under the receiver operating characteristic curve (AUC).

RESULTS

Fifty-one percent (5375/10,724) of patients who underwent PCI achieved CR. At a mean follow-up of 2.4 years, the mortality, MI, revascularization, and MACE rates were 1.2%, 1.0%, 6.3%, and 7.7%, respectively. SS was not predictive for mortality (AUC, 0.51; 95% confidence interval [CI], 0.44-0.59). All scores involving clinical variables, especially modified ACEF score (AUC, 0.73; 95% CI, 0.66-0.79), could predict mortality. LSS_extended was the most accurate for MI (AUC, 0.68; 95% CI, 0.61-0.75). SS and LSS_extended were predictive for revascularization, with marginally significant AUCs (SS, 0.54; LSS_extended, 0.55). No score was particularly accurate for predicting MACE, with AUCs ranging from 0.51 (ACEF score) to 0.58 (LSS_extended).

CONCLUSIONS

In CR patients, risk scores involving clinical variables might help to predict mortality; however, no risk scores showed helpful discrimination for MACE.

Estimated glomerular filtration rate and functional status among older people: A systematic review

BACKGROUND

The association between chronic kidney disease (CKD) and functional status may change as a function of the equation used to estimate glomerular filtration rate (eGFR). We reviewed the predictive value of different eGFR equations in regard to frailty and disability outcomes.

METHODS

We searched Pubmed from inception to March 2018 for studies investigating the association between eGFR and self-reported and/or objective measures of frailty or disability. Cross-sectional and longitudinal studies were separately analysed.

RESULTS

We included 16 studies, one of which reporting both cross-sectional and longitudinal data. Three out of 7 cross-sectional studies compared different eGFR equations in regard to their association with functional status: two studies showed that cystatin C-based, but not creatinine-based eGFR may be associated with hand-grip strength or frailty; another study showed that two different creatinine-based eGFR equations may be similarly associated with disability. Four out of 10 longitudinal studies provided comparative data: two studies reported similar association with disability for different creatinine-based eGFR equations; one study showed that creatinine-based eGFR was not associated with frailty, but a not significant trend for association was observed with cystatin C-based eGFR; one study showed that cystatin C-based but not creatinine-based eGFR may predict incident mobility disability, while both methods may predict gait speed decline. High heterogeneity was observed in regard to confounders included in reviewed studies. None of them included the most recently published equations.

CONCLUSION

Available data do not support the superiority of one of the eGFR equations in terms of measuring or predicting functional decline.

Creatinine Versus Cystatin C: Differing Estimates of Renal Function in Hospitalized Veterans Receiving Anticoagulants

BACKGROUND

Current practice in anticoagulation dosing relies on kidney function estimated by serum creatinine using the Cockcroft-Gault equation. However, creatinine can be unreliable in patients with low or high muscle mass. Cystatin C provides an alternative estimation of glomerular filtration rate (eGFR) that is independent of muscle.

OBJECTIVE

We compared cystatin C-based eGFR (eGFR_cys) with multiple creatinine-based estimates of kidney function in hospitalized patients receiving anticoagulants, to assess for discordant results that could impact medication dosing.

DESIGN

Retrospective chart review of hospitalized patients over 1 year who received non-vitamin K antagonist anticoagulation, and who had same-day measurements of cystatin C and creatinine.

PARTICIPANTS

Seventy-five inpatient veterans (median age 68) at the San Francisco VA Medical Center (SFVAMC).

MAIN MEASURES

We compared the median difference between eGFR by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) study equation using cystatin C (eGFR_cys) and eGFRs using three creatinine-based equations: CKD-EPI (eGFR_EPI), Modified Diet in Renal Disease (eGFR_MDRD), and Cockcroft-Gault (eGFR_CG). We categorized patients into standard KDIGO kidney stages and into drug-dosing categories based on each creatinine equation and calculated proportions of patients reclassified across these categories based on cystatin C.

KEY RESULTS

Cystatin C predicted overall lower eGFR compared to creatinine-based equations, with a median difference of - 7.1 (IQR - 17.2, 2.6) mL/min/1.73 m² versus eGFR_EPI, - 21.2 (IQR - 43.7, - 8.1) mL/min/1.73 m² versus eGFR_MDRD, and - 25.9 (IQR - 46.8, - 8.7) mL/min/1.73 m² versus eGFR_CG. Thirty-one to 52% of patients were reclassified into lower drug-dosing categories using cystatin C compared to creatinine-based estimates.

CONCLUSIONS

We found substantial discordance in eGFR comparing cystatin C with creatinine in this group of anticoagulated inpatients. Our sample size was limited and included few women. Further investigation is needed to confirm these findings and evaluate implications for bleeding and other clinical outcomes.

NIH TRIAL REGISTRY NUMBER

Not applicable.

Utility of cystatin C-based equations in patients undergoing dialysis

Serum cystatin C (CysC) measurement is regarded as a simple and practical alternative to measure residual renal function for dialysis patients. Recent studies have shown that CysC has better diagnostic accuracy or at least equivalence to creatinine in predicting the early stages of renal damage, and is closely related to clinical outcomes of dialysis patients. Thus, the applicability of CysC-derived equations in patients undergoing dialysis should be paid attention. Here, we review the role of CysC in diagnosis, renal function evaluation, and prognosis outcomes for dialysis patients, so as to provide them with useful suggestions on evaluating renal function and predicting adverse outcomes in clinical practice.

One-year mortality of patients with ST-Elevation myocardial infarction: Prognostic impact of creatinine-based equations to estimate glomerular filtration rate

BACKGROUND

Renal dysfunction is associated with worse outcomes after primary percutaneous coronary intervention (PCI). However, whether glomerular filtration rate (GFR) estimated with various equations can equally predict outcomes after ST-Elevation Myocardial Infarction (STEMI) is still debated.

METHODS

We compared the clinical impact of 3 different creatinine-based equations (Cockcroft and Gault (CG), CKD-epidemiology (CKD-EPI) and Full Age Spectrum (FAS)) to predict 1-year mortality in STEMI patients.

RESULTS

Among 1755 consecutive STEMI patients who had undergone primary PCI included between 2006 and 2011, median estimated GFR was 79 (61;96) with the CG, 81 (65;95) with CKD-EPI and 75 (60;91) mL/min/1.73 m2 with FAS equation. Reduced GFR values were independently associated with 1-year mortality risk with the 3 equations. Receiver operating curves (ROC) of CG and FAS equations were significantly superior to the CKD-EPI equation, p = 0.03 and p = 0.01, respectively. Better prediction with FAS and CG equations was confirmed by net reclassification index.

CONCLUSIONS

Our results suggest that in STEMI patients who have undergone primary PCI, 1-year mortality is better predicted by CG or FAS equations compared to CKD-EPI.

Baseline Renal Function and Albumin are Powerful Predictors for Allogeneic Transplantation-Related Mortality

Biomarkers measured in blood chemistry before allogeneic hematopoietic stem cell transplantation (HSCT) may reflect patients' physiological status. We hypothesized that selected markers are predictive for nonrelapse mortality (NRM) following transplantation and could contribute to risk assessment. We investigated the value of pre-HSCT albumin, estimated glomerular filtration rate (eGFR), and alkaline phosphatase (AlkP) in predicting NRM. We retrospectively analyzed clinical and laboratory data from 1217 patients receiving a first HSCT in 2 European centers between 2003 and 2015. Transplantation indications and conditioning regimens were diverse. Patients had a median age of 55 years and hematopoietic cell transplantation comorbidity index (HCT-CI) scores of 0 (24%), 1 to 2 (39%), and ≥3 (37%). Cutoffs of eGFR <60 mL/min, albumin <3.5 g/dL, and AlkP >180 IU/L corresponded with 8.8%, 8.3%, and 6.5% of the patients, respectively. eGFR and albumin were associated with increased risk and higher cumulative incidence of day-100, 1-year, and 2-year NRM, both as continuous or categorized variables. A similar pattern was observed for AlkP, except for day-100 NRM. In multivariable analyses, eGFR and albumin were consistently among the top risk factors for early and late-term NRM, abrogating the role of age. Prediction models for day-100, 1-year, and 2-year NRM based only on HCT-CI resulted in c-statistics of .565, .575, and .577, respectively. Addition of both biomarkers increased c-statistics for day-100, 1-year, and 2-year NRM to .651, .633, and .624, respectively. Albumin and eGFR are prognostic biomarkers for NRM after HSCT and improve the discriminative power of the HCT-CI.

Reliability of serum creatinine-based formulae estimating renal function in non-critically ill surgery patients: Focus on augmented renal clearance

WHAT IS KNOWN AND OBJECTIVES

Formulae estimating glomerular filtration rate (GFR) are frequently used to guide drug dosing. The objectives of this prospective single-center study were to evaluate agreement between these equations and measured creatinine clearance (CrCl) in non-critically ill surgery patients with normal kidney function and augmented renal clearance (ARC, CrCl ≥ 130 mL/min/1.73 m²), to determine predictors for disagreement, define a GFR estimator cut-off value identifying ARC and determine the ARC prevalence and duration in non-critically ill surgical patients.

METHODS

Hospitalized adult non-critically ill abdominal and trauma surgery patients were eligible for inclusion. Measured CrCl based on an 8-hour urinary collection (CrCl_8h ) was used as the primary method for determining kidney function. Agreement between equations and measured CrCl_8h was assessed in terms of precision, defined as a bias within ±10 mL/min/1.73 m². Predictors for disagreement were identified for the most precise estimator using an ordinal logistic regression model with negative bias, agreement and positive bias as outcome variables. A receiver operating characteristic (ROC) analysis was performed to identify an estimator cut-off predicting ARC, which was subsequently applied for the daily proportion of patients displaying ARC and ARC duration.

RESULTS AND DISCUSSION

During the study period (14/11/2013 - 13/05/2014), in 232 adult non-critically ill abdominal and trauma surgery patients, all estimators tend to underestimate CrCl_8h (mean bias ranging from 17 to 22 mL/min/1.73 m²), especially in patients displaying ARC (mean bias ranging from 44 to 56 mL/min/1.73 m²). eGFR_CKD-EPI performed the best. Younger age and low ASA score independently predicted underestimation of CrCl_8h . Three different eGFR_CKD-EPI cut-offs with decreasing sensitivity and increasing specificity (84, 95 and 112 mL/min/1.73 m²) identified, respectively, 65%, 44% and 14% patients displaying ARC. The median ARC duration was 4, 4 and 3 days, respectively.

WHAT IS NEW AND CONCLUSION

In surgical patients, eGFR frequently underestimates measured CrCl, especially in young patients with low ASA score. eGFR cut-offs predicting ARC were identified.