Measurement of renal function in chronic renal disease

Development of a high-sensitivity double kinetic assay for creatinine using the enzymatic cycling method and its application to serum samples

Estimated glomerular filtration rate (eGFR) is often used as a measure of renal function in clinical practice owing to its simplicity. Serum creatinine levels are essential for eGFR calculation. Although the Jaffé method is widely used for creatinine measurement, it exhibits low specificity and sensitivity. Development of various enzyme methods has increased its specificity; however, its sensitivity is still insufficient for accurate eGFR calculation. To overcome this issue, we developed a highly sensitive assay for creatinine detection using enzymatic cycling reaction in this study. Our method consisted of two steps: Endogenous ammonia elimination and creatinine analysis. NADH derived from creatinine changed the water-soluble tetrazolium salt-8 color in the presence of the electron carrier, 1-methoxy-5-methylphenazinium methylsulfate. The cycling oxidation-reduction of 1-methoxy-5-methylphenazinium methylsulfate to NADH facilitated the coloration of water-soluble tetrazolium salt-8, aiding in creatinine measurement with high sensitivity. The within-run reproducibility of the developed method was good (<1.76 % at each concentration tested), with a detection limit of 1.00 μmol/L, making it approximately 9 times more sensitive than the Jaffé method. Notably, its correlation with the high-performance liquid chromatography method was excellent (r = 0.976). Overall, this study successfully developed a new, rapid, simple, and highly sensitive method for creatinine analysis.

Kidney function estimation equations: a narrative review

Glomerular filtration rate (GFR) as a marker of kidney function is important in health and disease management because decreased kidney function is associated with all-cause and cardiovascular mortality, progression of kidney disease, predisposition to acute kidney injury (AKI), and for drug dosage modification. While measured glomerular filtration rate (mGFR) is acknowledged as the most accurate method for evaluating kidney function, it is at present not feasible to be applied in the clinical arena. Estimated glomerular filtration rate (eGFR) is preferred due to its convenience, cost-effectiveness, and seamless integration into standard clinical practice for kidney function evaluation. The presence of multiple equations for eGFR with applications to differing populations makes their use challenging for clinicians. We reviewed available estimated glomerular filtration rate (GFR) equations and their application in different clinical settings both in normal and chronic kidney disease (CKD) patients. These formulae incorporate serum creatinine and/or serum cystatin C levels and correlate them with measured kidney function. Among the many available equations, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is the most recommended due to its robustness and accuracy across diverse patient populations. Strengths and limitations of different eGFR equations are discussed emphasizing the importance of selecting the appropriate equation based on specific patient demographics and clinical scenarios. There is need for regional validation studies to ensure the global applicability of these equations, considering the variations in population characteristics.

Impaired creatinine-based estimated glomerular filtration rate in Thai individuals switching to dolutegravir: illustrating the role of cystatin C testing to aid clinical decision making

INTRODUCTION

Data about impact of switch to dolutegravir (DTG)-based antiretroviral therapy (ART) on estimated glomerular filtration rate (eGFR) in Asians are scarce. RV254/SEARCH010 is a prospective observational cohort in Bangkok, Thailand with ART initiation during acute HIV infection (AHI) where participants switched to DTG-based ART.

METHODS

Participants started Efavirenz (EFV)-based ART during AHI (n = 214) and switched to DTG-based ART after a median of 97 weeks (IQR 61-145). GFR was estimated by serum creatinine (eGFRcre) every 24 weeks before and after switch. Estimated GFR by cystatin C (eGFRcystC) was ordered at clinician's discretion for decreased eGFRcre after switch. Random-effect linear regression model was used to assess changes in eGFRcre over 96 weeks from starting ART, and from switching to DTG.

RESULTS

At study entry, 20 participants (9.3%) had eGFRcre < 90 ml/min/1.73 m2. During EFV-based ART, an additional 17 (8%) developed eGFRcre < 90 ml/min/1.73 m2, nearly all transient, while mean eGFRcre remained stable and within normal range. At switch to DTG, 21 (9.8%) had eGFRcre < 90 ml/min/1.73 m2 but an additional 116 (54%) developed eGFRcre < 90 ml/min/1.73 m2 during follow-up with eGFRcre decrease being mostly persistent. Mean eGFRcre decreased 20.8% from 117.0 to 92.4 ml/min/1.73 m2 (p < 0.001). Among 20 post-switch participants with eGFRcystC measured within 4 weeks of eGFRcre < 90 mL/min/1.73 m2, 13 (65%) had normal kidney function by eGFRcystC.

CONCLUSIONS

Persistent eGFRcre decrease to < 90 ml/min/1.73 m2 after switch to DTG was common in this Thai population. eGFRcystC was helpful to identify individuals with clinically significant decrease in kidney function and obviate unnecessary ART modifications. Trial registration Clinical Trials Registry Number: ClininicalTrials.gov NCT00796146.

Accuracy of estimating equations for the assessment of glomerular filtration rate in critically ill patients versus outpatients

BACKGROUND

Estimating equations for the assessment of glomerular filtration rate (GFR) have been poorly investigated in the critical care setting. We evaluated the agreement between the GFR measured with 51CrEDTA/iohexol (mGFR) and four estimating equations based on serum concentrations of creatine and/or cystatin C (eGFR) in two cohorts: critically ill patients and outpatients with normal-to-moderately reduced GFR.

METHODS

Forty-three patients in the critical care group and 48 patients in the outpatient group were included. GFR was measured (mGFR) by plasma infusion clearance of 51Cr-EDTA/iohexol (critical care group) and the single injection, one-sample plasma 51Cr-EDTA clearance technique (outpatients). The following estimating equations (eGFR) were used: the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for creatinine (CKD-EPICr), cystatin C (CKD-EPICys C), creatinine+cystatin C (CKD-EPICr + Cys C) and the Lund-Malmö creatinine+cystatin C equation (LMCr + Cys C). Agreement between mGFR and eGFR was assessed by the Bland-Altman method and accuracy by calculating P30 and P10.

RESULTS

In the critically ill group, the bias between the estimating equations and mGFR was -3.6 to 2.8 mL/min/1.73 m2, while the error was 121%-127% and the accuracy (P30) 33%-40%. In the outpatients, the bias between the estimating equations and mGFR was -13.0 to 7.6 mL/min/1.73 m2, while the error was 31%-41% and the accuracy (P30), 67%-96%.

CONCLUSIONS

All four equations performed poorly in assessing GFR in the critically ill cohort with an unacceptably high error and low accuracy in contrast to the outpatient group. To accurately assess GFR in critically ill patients, GFR must be measured not estimated.

EDITORIAL COMMENT

For the assessment of glomerular filtration rate (GFR), it can be measured directly, but is frequently estimated using a point measure of serum creatinine concentration. In this study, ICU case GFR estimations, by different adjusted equations, done also for a cohort of outpatients, showed that these serum creatinine-based estimations for ICU cases are not highly precise or reliable.

Past, present, and future biomarkers of kidney function and injury: The relationship with antibiotics

Routinely used kidney biomarkers of injury and function such as serum creatinine and urine albumin to creatinine ratio, are neither sensitive nor specific. Future biomarkers are being developed for clinical use and have already been included in guidance from groups such as the U.S. Food and Drug Administration and the Predictive Safety Testing Consortium. These biomarkers have important implications for early identification of kidney injury and more accurate measurement of kidney function. Many antibiotics are either eliminated by the kidney or can cause clinically significant nephrotoxicity. As a result, clinicians should be familiar with new biomarkers of kidney function and injury, their place in clinical practice, and applications for antibiotic dosing.

Reframing acute kidney injury as a pathophysiological continuum of disrupted renal excretory function

Surrogate measures of glomerular filtration rate (GFR) continue to serve as pivotal determinants of the incidence, severity, and management of acute kidney injury (AKI), as well as the primary reference point underpinning knowledge of its pathophysiology. However, several clinically important deficits in aspects of renal excretory function during AKI other than GFR decline, including acid-base regulation, electrolyte and water balance, and urinary concentrating capacity, can evade detection when diagnostic criteria are built around purely GFR-based assessments. The use of putative markers of tubular injury to detect "sub-clinical" AKI has been proposed to expand the definition and diagnostic criteria for AKI, but their diagnostic performance is curtailed by ambiguity with respect to their biological meaning and context specificity. Efforts to devise new holistic assessments of overall renal functional compromise in AKI would foster the capacity to better personalize patient care by replacing biomarker threshold-based diagnostic criteria with a shift to assessment of compromise along a pathophysiological continuum. The term AKI refers to a syndrome of sudden renal deterioration, the severity of which is classified by precise diagnostic criteria that have unquestionable utility in patient management as well as blatant limitations. Particularly, the absence of an explicit pathophysiological definition of AKI curtails further scientific development and clinical handling, entrapping the field within its present narrow GFR-based view. A refreshed approach based on a more holistic consideration of renal functional impairment in AKI as the basis for a new diagnostic concept that reaches beyond the boundaries imposed by the current GFR threshold-based classification of AKI, capturing broader aspects of pathogenesis, could enhance AKI prevention strategies and improve AKI patient outcome and prognosis.

Comparison of estimated GFR using cystatin C versus creatinine in pediatric kidney transplant recipients

BACKGROUND

An accurate, rapid estimate of glomerular filtration rate (GFR) in kidney transplant patients affords early detection of transplant deterioration and timely intervention. This study compared the performance of serum creatinine (Cr) and cystatin C (CysC)-based GFR equations to measured GFR (mGFR) using iohexol among pediatric kidney transplant recipients.

METHODS

CysC, Cr, and mGFR were obtained from 45 kidney transplant patients, 1-18 years old. Cr- and CysC-estimated GFR (eGFR) was compared against mGFR using the Cr-based (Bedside Schwartz, U25-Cr), CysC-based (Gentian CysC, CAPA, U25-CysC), and Cr-CysC combination (CKiD Cr-CysC, U25 Cr-CysC) equations in terms of bias, precision, and accuracy. Bland-Altman plots assessed the agreement between eGFR and mGFR. Secondary analyses evaluated the formulas in patients with biopsy-proven histological changes, and K/DOQI CKD staging.

RESULTS

Bias was small with Gentian CysC (0.1 ml/min/1.73 m2); 88.9% and 37.8% of U25-CysC estimations were within 30% and 10% of mGFR, respectively. In subjects with histological changes on biopsy, Gentian CysC had a small bias and U25-CysC were more accurate-both with 83.3% of and 41.7% of estimates within 30% and 10% mGFR, respectively. Precision was better with U25-CysC, CKiD Cr-CysC, and U25 Cr-CysC. Bland-Altman plots showed the Bedside Schwartz, Gentian CysC, CAPA, and U25-CysC tend to overestimate GFR when > 100 ml/min/1.72 m2. CAPA misclassified CKD stage the least (whole cohort 24.4%, histological changes on biopsy 33.3%).

CONCLUSIONS

In this small cohort, CysC-based equations with or without Cr may have better bias, precision, and accuracy in predicting GFR.

Doppler-Derived Renal Functional Reserve in the Prediction of Postoperative Acute Kidney Injury in Patients Undergoing Robotic Surgery

BACKGROUND

Postoperative acute kidney injury (PO-AKI) is a frequent complication after surgery. Various tools have been proposed to identify patients at high risk for AKI, including preoperative serum creatinine or estimated glomerular filtration rate (eGFR), urinary cell cycle arrest, and tubular damage biomarkers; however, none of these can appropriately assess AKI risk before surgery. Renal functional reserve (RFR) screened by the Doppler-derived intraparenchymal renal resistive index variation (IRRIV) test has been proposed to identify patients at risk for AKI before a kidney insult. IRRIV test has been developed in healthy individuals and previously investigated in cardiac surgery patients. This study aims to evaluate the value of the IRRIV test in identifying PO-AKI among patients undergoing robotic abdominal surgery in the Trendelenburg position for pelvic oncological disease.

METHODS

We performed a prospective, double-blinded, observational study. Preoperative baseline renal function and RFR were assessed in 53 patients with baseline eGFR >60 mL/min/1.73 m2, undergoing robotic surgery in the Trendelenburg position for pelvic oncological disease. The capability of Doppler-derived RFR in predicting PO-AKI was investigated with the area under the receiver operating characteristic curve (ROC-AUC).

RESULTS

Approximately 15.1% of patients developed AKI within the first 3 postoperative days. Thirty-one (58.5%) patients had a physiologic delta-RRI (ie, ≥0.05), while 22 (41.5%) patients did not. The ROC-AUC for PO-AKI was 0.85 (95% confidence interval [CI], 0.74-0.97; P = .007) for serum creatinine, 0.84 (95% CI, 0.71-0.96; P = .006) for eGFR, and 0.84 (95% CI, 0.78-0.91; P = .017) for delta-RRI. When combined with eGFR, the ROC-AUC for delta-RRI was 0.95 (95% CI, 0.9-1).

CONCLUSIONS

Our findings show that the preoperative assessment of Doppler-derived RFR combined with baseline renal function improves the capability of identifying patients at high risk for PO-AKI with eGFR >60 mL/min/1.73 m2 after robotic abdominal surgery in Trendelenburg position for pelvic oncological disease.

Serum creatinine is an unreliable marker of renal function in patients undergoing heart transplantation

BACKGROUND

Renal dysfunction is a common complication after heart transplantation (Htx). Glomerular filtration rate (GFR) can be assessed by various estimating equations (eGFR). We evaluated the correlation, agreement, and accuracy between eGFR and mGFR and the ability of eGFR to track changes in mGFR early after Htx.

METHODS

A single-center prospective observational study on 55 patients undergoing Htx. Serum creatinine and mGFR (plasma clearance of Cr51-EDTA or iohexol) were measured preoperatively and on the fourth postoperative day. The accuracy of eGFR to predict true mGFR was calculated as the percentage of patients with an eGFR within 30% of mGFR (P30). The agreement between eGFR and mGFR was assessed according to Bland and Altman. A four-quadrant plot was made to evaluate the ability of eGFR to track changes in mGFR.

RESULTS

The accuracy of eGFR to assess mGFR was 52%. The bias was 11.2 ± 17.4 mL/min/1.72 m2. The limits of agreement were -23.0 to 45.4 mL/min/1.72 m2 and the error 58%. The concordance rate between eGFR and mGFR was 72%.

CONCLUSIONS

eGFR underestimated mGFR and the agreement between eGFR and mGFR was low with an unacceptably large between-group error and low accuracy. Furthermore, the ability of eGFR to assess changes in mGFR, postoperatively, was poor. Thus, the use of estimating equations from serum creatinine will not adequately assess renal function early after major heart surgery. To gain adequate information on renal function early after Htx, GFR needs to be measured, not estimated.

Persistent Acute Kidney Injury is Associated with Poor Outcomes and Increased Hospital Cost in Vascular Surgery

BACKGROUND

Postoperative acute kidney injury (AKI) is common after major surgery and is associated with increased morbidity, mortality, and cost. Additionally, there are recent studies demonstrating that time to renal recovery may have a substantial impact on clinical outcomes. We hypothesized that patients with delayed renal recovery after major vascular surgery will have increased complications, mortality, and hospital cost.

METHODS

A single-center retrospective cohort of patients undergoing nonemergent major vascular surgery between 6/1/2014 and 10/1/2020 was analyzed. Development of postoperative AKI (defined using Kidney Disease Improving Global Outcomes (KDIGO) criteria: >50% or > 0.3 mg/dl absolute increase in serum creatinine relative to reference after surgery and before discharge) was evaluated. Patients were divided into 3 groups: no AKI, rapidly reversed AKI (<48 hours), and persistent AKI (≥48 hours). Multivariable generalized linear models were used to evaluate the association between AKI groups and postoperative complications, 90-day mortality, and hospital cost.

RESULTS

A total of 1,881 patients undergoing 1,980 vascular procedures were included. Thirty five percent of patients developed postoperative AKI. Patients with persistent AKI had longer intensive care unit and hospital stays, as well as more mechanical ventilation days. In multivariable logistic regression analysis, persistent AKI was a major predictor of 90-day mortality (odds ratio 4.1, 95% confidence interval 2.4-7.1). Adjusted average cost was higher for patients with any type of AKI. The incremental cost of having any AKI ranged from $3,700 to $9,100, even after adjustment for comorbidities and other postoperative complications. The adjusted average cost for patients stratified by type of AKI was higher among patients with persistent AKI compared to those with no or rapidly reversed AKI.

CONCLUSIONS

Persistent AKI after vascular surgery is associated with increased complications, mortality, and cost. Strategies to prevent and aggressively treat AKI, specifically persistent AKI, in the perioperative setting are imperative to optimize care for this population.

Discrepancies between Cystatin C-Based and Creatinine-Based eGFR

BACKGROUND

Recent guidance suggests clinicians increase use of cystatin C for the estimation of GFR. Discrepant levels of creatinine- versus cystatin C-based eGFR (eGFRcr versus eGFRcys) can occur and might signify inaccurate estimation of GFR using creatinine alone. This study sought to enhance the knowledge of the risk factors and clinical implications of having a large eGFR discrepancy.

METHODS

Participants in the Atherosclerosis Risk in Communities Study, a prospective cohort study of US adults, were followed over 25 years. eGFR discrepancy was measured at five clinical visits and defined as eGFRcys either 30% lower or higher than eGFRcr, the current clinical standard of care. The associations between eGFR discrepancies and kidney-related laboratory parameters were assessed using linear and logistic regression and long-term adverse outcomes, including kidney failure, AKI, heart failure, and death, using Cox proportional hazards models.

RESULTS

Among 13,197 individuals (mean age 57 [SD 6] years, 56% women, 25% Black race), 7% had eGFRcys 30% lower than eGFRcr at visit 2 (1990-1992), and this proportion increased over time to 23% by visit 6 (2016-2017). By contrast, the percent with eGFRcys 30% higher than eGFRcr was relatively stable (3%-1%). Independent risk factors for having eGFRcys 30% lower than eGFRcr included older age, female sex, non-Black race, higher eGFRcr, higher body mass index, weight loss, and current smoking. Those with eGFRcys 30% lower than eGFRcr had more anemia and higher uric acid, fibroblast growth factor 23, and phosphate levels as well as higher risk of subsequent mortality, kidney failure, AKI, and heart failure compared with those with similar eGFRcr and eGFRcys values.

CONCLUSIONS

Having eGFRcys lower than eGFRcr was associated with worse kidney-related laboratory derangements and a higher risk of adverse health outcomes.

PODCAST

This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2023_09_08_CJN0000000000000217.mp3.

Cystatin C is glucocorticoid responsive, directs recruitment of Trem2+ macrophages, and predicts failure of cancer immunotherapy

Cystatin C (CyC), a secreted cysteine protease inhibitor, has unclear biological functions. Many patients exhibit elevated plasma CyC levels, particularly during glucocorticoid (GC) treatment. This study links GCs with CyC's systemic regulation by utilizing genome-wide association and structural equation modeling to determine CyC production genetics in the UK Biobank. Both CyC production and a polygenic score (PGS) capturing predisposition to CyC production were associated with increased all-cause and cancer-specific mortality. We found that the GC receptor directly targets CyC, leading to GC-responsive CyC secretion in macrophages and cancer cells. CyC-knockout tumors displayed significantly reduced growth and diminished recruitment of TREM2+ macrophages, which have been connected to cancer immunotherapy failure. Furthermore, the CyC-production PGS predicted checkpoint immunotherapy failure in 685 patients with metastatic cancer from combined clinical trial cohorts. In conclusion, CyC may act as a GC effector pathway via TREM2+ macrophage recruitment and may be a potential target for combination cancer immunotherapy.

The estimation of glomerular filtration in acute and critical illness: Challenges and opportunities

Recent events have made it apparent that the creatinine based estimating equations for glomerular filtration have their flaws. Some flaws have been known for some time; others have prompted radical modification of the equations themselves. These issues persist in part owing to the behaviour of the creatinine molecule itself, particularly in acute and critical illness. There are significant implications for patient treatment decisions, including drug and fluid therapies and choice of imaging modality (contrast vs. non-contrast CT scan for example). An alternative biomarker, Cystatin C, has been used with some success both alone and in combination with creatinine to help improve the accuracy of particular estimating equations. Problems remain in certain circumstances and costs may limit the more widespread use of the alternative assay. This review will explore both the historical and more recent evidence for glomerular filtration estimation, including options to directly measure glomerular filtration (rather than estimate), perhaps the holy grail for both Biochemistry and Nephrology.

Pharmacokinetics in Critically Ill Children with Acute Kidney Injury

Acute kidney injury (AKI) is a commonly encountered comorbidity in critically ill children. The coexistence of AKI disturbs drug pharmacokinetics and pharmacodynamics, leading to clinically significant consequences. This can complicate an already critical clinical scenario by causing potential underdosing or overdosing giving way to possible therapeutic failures and adverse reactions. Current available studies offer little guidance to help maneuver such complex dosing regimens and decision-making in pediatric patients as most of them are done on heterogeneous groups of adult populations. Though there are some studies on drug dosing during continuous renal replacement therapy (CRRT), their utility is in question because of the recent advances in CRRT technology. Our review aims to discuss the principles of pharmacokinetics pertinent for honing the existing practices of drug dosing in critically ill children with AKI, and the various complexities and intricate challenges involved. This in turn will provide a framework to help enable caretakers to tailor dosing regimens in complex clinical setups with further ease and precision.

Renal function estimating equations performance during pregnancy and postpartum

STUDY OBJECTIVES

The objectives of this study were to evaluate the performance of renal function estimating equations compared to measured creatinine clearance (CrCl) during pregnancy and postpartum and to evaluate which body weight (pre-pregnancy weight (PPW), actual body weight (ABW), and ideal body weight (IBW)) provides the best performance.

DESIGN

A retrospective study.

SETTING

Collections tookplace in the University of Washington clinical research unit.

PATIENTS

Women (n = 166) who completed ≥1 pharmacokinetic (PK) study with a 6-24 h measured CrCl during pregnancy and/or ≥3 months postpartum were included.

INTERVENTION

CrCl was estimated utilizing estimated glomerular filtration rate (eGFR) and CrCl equations with common weight descriptors. Analyses included Bland-Altman, relative accuracies within 10% and 25%, and root mean squared error (RMSE). Overall performance was determined by summation of rank for evaluation parameters.

MEASUREMENTS AND MAIN RESULTS

During pregnancy, correlations between measured CrCl and estimated CrCl were between 0.5-0.8; equations with slopes closest to one were Modification of Diet in Renal Disease (MDRD2; PPW and ABW) and Cockcroft-Gault (CG) (PPW); and y-intercept closest to zero was Preeclampsia Glomerular Filtration Rate (PGFR). The lowest bias was seen with CG (ABW), and the highest accuracy within 25% was CG (ABW). CG (PPW) had the lowest RMSE. Postpartum, the best correlation was found with MDRD2 (PPW), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI (ABW)), and CKD-EPI 2021 (PPW). For slopes closest to one, MDRD2 (ABW) was best, whereas the equation with y-intercept closest to zero was CKD-EPI (ABW). CG (PPW) had the highest accuracy within 25%, and 100/serum creatinine (SCr) had the lowest bias. Based on overall performance, CG (PPW) was the best followed by CG (ABW) and PGFR during pregnancy and 100/SCr followed by CG (PPW) and CG (ABW) postpartum.

CONCLUSION

The new CKD-EPI 2021 equation did not perform well during pregnancy. When 24-h CrCls are not available during pregnancy, CG (PPW or ABW) performed the best overall, whereas at 3 months postpartum, 100/SCr performed the best overall.

A low BUN/creatinine ratio predicts histologically confirmed acute interstitial nephritis

INTRODUCTION

In hospitalized patients with acute renal injury (AKI), acute tubulointerstitial nephritis (AIN) constitutes one of the leading etiologies. The objective of this study was to identify clinical and biochemical variables in patients with AKI associated with kidney biopsy-confirmed AIN.

METHODS

For our prospective study, we recruited hospitalized patients aged 18 years and older who were diagnosed with AKI based on biochemical criteria. Prior to enrollment, each patient was assessed with a complete metabolic panel and a kidney biopsy.

RESULTS

The study consisted of 42 patients (with a mean age of 45 years) and equal numbers of male and female patients. Diabetes and hypertension were the main comorbidities. Nineteen patients had histological findings consistent with AIN. There was a correlation between histology and the BUN/creatinine ratio (BCR) (r = -0.57, p = 0.001). The optimal Youden point for classifying AIN via a receiver operating characteristic (ROC) curve analysis was a BCR ≤ 12 (AUC = 0.73, p = 0.024). Additionally, in diagnosing AIN, BCR had a sensitivity of 76%, a specificity of 81%, a positive predictive value of 81%, a negative predictive value of 76%, and OR of 14 (95% CI = 2.6 to 75.7, p = 0.021). In the multivariable analysis, BCR was the sole variable associated with AIN.

CONCLUSION

A BCR ≤ 12 identifies AIN in patients with AKI. This study is the first to prospectively assess the relationship between renal biopsy results and BCR.

Implementation of a new definition for acute kidney injury in the National Surgical Quality Improvement Project: What is the impact?

BACKGROUND

The National Surgical Quality Improvement Project is the preeminent surgical quality database, but it undercaptures acute kidney injury. Recently, the National Surgical Quality Improvement Project lowered the thresholds for acute kidney injury for the first time, so we assessed the impact of implementing the definition change on the rate of acute kidney injuries.

METHODS

For this interrupted time series analysis, we assembled 2 institutional National Surgical Quality Improvement Project files to identify adults undergoing inpatient noncardiac nonvascular surgery. The acute kidney injury definition changed on July 1, 2021, so patients were stratified by their operative date into 12-month pre and post groups. Weighted covariate propensity score matching and logistic regression were used to balance the periods and compare outcomes.

RESULTS

In total, 4,784 adults were eligible (55% pre and 45% post change). The overall rate of postoperative outcomes was similar, aside for acute kidney injury (pre 0.3%, post 5.6%, P < .0001). Regardless of the period, patients with acute kidney injuries had significantly longer lengths of stay and morbidity and mortality rates compared to those without an acute kidney injury. After the definition change, 81% of acute kidney injuries were stage I, and none were identified by urine output alone. After matching, surgery after the definition change was associated with an increased weighted odds of an acute kidney injury compared to surgery before the change (odds ratio 26.2; 95% confidence interval, 12.1-56.8).

CONCLUSION

In the year after the definition change, there was a 1,700% relative increase in the rate of reported acute kidney injuries. Newly identified acute kidney injuries are associated with high complication rates, and this definition change has implications for patient counseling, research, and quality reporting.

Serum Metabolites Characterization Produced by Cats CKD Affected, at the 1 and 2 Stages, before and after Renal Diet

Utilizing metabolomics, a tool for measuring and characterizing low-molecular-weight substances (LMWs), to identify eventual changes in response to dietary intervention is novel in cats with chronic kidney disease (CKD), a condition characterized by retention of uremic solutes. This study aims to assess the serum metabolomic profile of cats in early stages of CKD and to compare the serum metabolomic of CKD cats after 60 days of a renal diet to evaluate the effect of dietary intervention on these metabolites. Twenty-five domestic cats were included in the study. Fifteen cats with CKD stages 1 (n = 6) and 2 (n = 9) according to the International Renal Interest Society (IRIS) were included in the renal groups, and a control group consisting of 10 cats was included. All animals were enrolled on a maintenance diet for 30 days before the experimental period. The metabolomics analysis was performed by gas chromatography-mass spectrometry (GC-MS). Partial least squares discriminant analysis (PLS-DA) was performed on Metaboanalyst 4.0 software. Forty-three metabolites were identified. Citric acid and monostearin were altered in the CKD2 group when compared to CKD1 and the control group at T0. A total of seven serum metabolites differed after 60 days of the renal diet: glycine, fructose, glutamic acid, arachidonic acid, stearic acid, creatinine, and urea. Changes were seen in the serum metabolomic profile after 60 days of the renal diet, and some of the metabolites that changed in response to the diet have beneficial effects on health. Overall, metabolomics markers have the potential to identify early stages of CKD, providing insights into the possible pathophysiologic processes that contribute to the development and progression of CKD.

Advantages, Limitations, and Clinical Considerations in Using Cystatin C to Estimate GFR

Cystatin C has been shown to be a reliable and accurate marker of kidney function across diverse populations. The 2012 Kidney Disease Improving Global Outcomes (KDIGO) guidelines recommended using cystatin C to confirm the diagnosis of chronic kidney disease (CKD) determined by creatinine-based estimated glomerular filtration rate (eGFR) and to estimate kidney function when accurate eGFR estimates are needed for clinical decision-making. In the efforts to remove race from eGFR calculations in the United States, the National Kidney Foundation (NKF) and American Society of Nephrology (ASN) Joint Task Force recommended increasing availability and clinical adoption of cystatin C to assess kidney function. This review summarizes the key advantages and limitations of cystatin C use in clinical practice. Our goals were to review and discuss the literature on cystatin C; understand the evidence behind the recommendations for its use as a marker of kidney function to diagnose CKD and risk stratify patients for adverse outcomes; discuss the challenges of its use in clinical practice; and guide clinicians on its interpretation.

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

BACKGROUND

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.

METHODS

The GFR was determined simultaneously by two methods: (a) the Asian modified CKD-EPI equation (GFR_CKD-EPI); (b) the Xiangya equation (GFR_Xiangya); 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).

RESULTS

A total of 158 Chinese CKD patients were included in our external study. The GFR_Xiangya was highly related with mGFR, with the correlation coefficient of 0.92. The regression equation was GFR_Xiangya = 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 - 3.3 ml/min/1.73 m², P < 0.001), an inferior precision (23.9 vs 13.0 ml/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 44.9 ml/min/1.73 m²).

CONCLUSION

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.

Kidney Function Assessment in African American Patients: A Narrative Review for Pharmacists

Recent recognitions of longstanding societal inequity in kidney function assessments have prompted the call to eliminate race as part of the algorithm to assess estimated glomerular filtration rate (eGFR). Previous equations for eGFR estimation adopted race as part of the calculation. Incorporating race within eGFR equations results in overestimating and underestimating Black and nonblack patients, respectively. The inclusion of race is controversial. In September 2021, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) combined task force recommended estimating the kidney function without using a race variable. The task force endorsed race-free creatinine-cystatin C equations to be more accurate than the creatinine-only equations. Before the application of NKF-ASN revised recommendations, major healthcare disparities influenced daily clinical practice. Those disparities include the delay in initiating medications that have reanl or cardio-protective effects, such as sodium-glucose cotransporter–2 inhibitors (SGLT-2i) and angiotensin-converting enzyme inhibitors (ACEIs). Clinical judgment should be employed when dose adjusting medications. Combining the eGFR with other clinical assessment tools such as urinary output, the expanded use of confirmatory tests, and the eGFR trend is suggested for a better kidney function assessment. Additionally, creatinine-cystatin C is recommended when feasible, and when institutions have the laboratory abilities.

Kidney Function According to Different Equations in Patients Admitted to a Cardiology Unit and Impact on Outcome

Background: This paper aims to evaluate the concordance between the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula and alternative equations and to assess their predictive power for all-cause mortality in unselected patients discharged alive from a cardiology ward. Methods: We retrospectively included patients admitted to our Cardiology Division independently of their diagnosis. The total population was classified according to Kidney Disease: Improving Global Outcomes (KDIGO) categories, as follows: G1 (estimated glomerular filtration rate (eGFR) ≥90 mL/min/1.73 m²); G2 (eGFR 89–60 mL/min/1.73 m²); G3a (eGFR 59–45 mL/min/1.73 m²); G3b (eGFR 44–30 mL/min/1.73 m²); G4 (eGFR 29–15 mL/min/1.73 m²); G5 (eGFR <15 mL/min/1.73 m²). Cockcroft-Gault (CG), CG adjusted for body surface area (CG-BSA), Modification of Diet in Renal Disease (MDRD), Berlin Initiative Study (BIS-1), and Full Age Spectrum (FAS) equations were also assessed. Results: A total of 806 patients were included. Good agreement was found between the CKD-EPI formula and CG-BSA, MDRD, BIS-1, and FAS equations. In subjects younger than 65 years or aged ≥85 years, CKD-EPI and MDRD showed the highest agreement (Cohen’s kappa (K) 0.881 and 0.588, respectively) while CG showed the lowest. After a median follow-up of 407 days, overall mortality was 8.2%. The risk of death was higher in lower eGFR classes (G3b HR4.35; 95%CI 1.05–17.80; G4 HR7.13; 95%CI 1.63–31.23; G5 HR25.91; 95%CI 6.63–101.21). The discriminant capability of death prediction tested with ROC curves showed the best results for BIS-1 and FAS equations. Conclusion: In our cohort, the concordance between CKD-EPI and other equations decreased with age, with the MDRD formula showing the best agreement in both younger and older patients. Overall, mortality rates increased with the renal function decreasing. In patients aged ≥75 years, the best discriminant capability for death prediction was found for BIS-1 and FAS equations.

Estimated Glomerular Filtration Rate in Chronic Kidney Disease: A Critical Review of Estimate-Based Predictions of Individual Outcomes in Kidney Disease

Chronic kidney disease (CKD) is generally regarded as a final common pathway of several renal diseases, often leading to end-stage kidney disease (ESKD) and a need for renal replacement therapy. Estimated GFR (eGFR) has been used to predict this outcome recognizing its robust association with renal disease progression and the eventual need for dialysis in large, mainly cross-sectional epidemiological studies. However, GFR is implicitly limited as follows: (1) GFR reflects only one of the many physiological functions of the kidney; (2) it is dependent on several non-renal factors; (3) it has intrinsic variability that is a function of dietary intake, fluid and cardiovascular status, and blood pressure especially with impaired autoregulation or medication use; (4) it has been shown to change with age with a unique non-linear pattern; and (5) eGFR may not correlate with GFR in certain conditions and disease states. Yet, many clinicians, especially our non-nephrologist colleagues, tend to regard eGFR obtained from a simple laboratory test as both a valid reflection of renal function and a reliable diagnostic tool in establishing the diagnosis of CKD. What is the validity of these beliefs? This review will critically reassess the limitations of such single-focused attention, with a particular focus on inter-individual variability. What does science actually tell us about the usefulness of eGFR in diagnosing CKD?

Assessing Renal Function for Kidney Donation. How Low Is Too Low?

Kidney transplantation (KT) is the treatment of choice for patients with end-stage kidney disease (ESKD) with decreased morbi-mortality, improved life quality, and reduced cost. However, the shortage of organs from deceased donors led to an increase in KT from living donors. Some stipulate that living donors have a higher risk of ESKD after donation compared with healthy non-donors. The reason for this is not clear. It is possible that ESKD is due to the nephrectomy-related reduction in glomerular filtration rate (GFR), followed by an age-related decline that may be more rapid in related donors. It is essential to assess donors properly to avoid rejecting suitable ones and not accepting those with a higher risk of ESKD. GFR is a central aspect of the evaluation of potential donors since there is an association between low GFR and ESKD. The methods for assessing GFR are in continuous debate, and the kidney function thresholds for accepting a donor may vary according to the guidelines. While direct measurements of GFR (mGFR) provide the most accurate evaluation of kidney function, guidelines do not systematically use this measurement as a reference. Also, some studies have shown that the GFR decreases with age and may vary with gender and race, therefore, the lower limit of GFR in patients eligible to donate may vary based on these demographic factors. Finally, it is known that CrCl overestimates mGFR while eGFR underestimates it, therefore, another way to have a reliable GFR could be the combination of two measurement methods.

Healthy and Chronic Kidney Disease (CKD) Dogs Have Differences in Serum Metabolomics and Renal Diet May Have Slowed Disease Progression

Chronic kidney disease (CKD) is highly prevalent in dogs, and metabolomics investigation has been recently introduced for a better understanding of the role of diet in CKD. This study aimed to compare the serum metabolomic profile of healthy dogs (CG) and dogs with CKD (CKD-T0 and CKD-T6) to evaluate whether the diet would affect metabolites. Six dogs (5 females; 1 male; 7.47 ± 2.31 years old) with CKD stage 3 or 4 (IRIS) were included. CG consisted of 10 healthy female dogs (5.89 ± 2.57 years old) fed a maintenance diet. Serum metabolites were analyzed by ¹H nuclear magnetic resonance (¹H NMR) spectra. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed to assess differences in metabolomic profiles between groups and before (CKD-T0) and after renal diet (CKD-T6). Data analysis was performed on SIMCA-P software. Dogs with CKD showed an altered metabolic profile with increased urea, creatinine, creatine, citrate, and lipids. Lactate, branched-chain amino acids (BCAAs), and glutamine were decreased in the CKD group. However, after 6 months of diet, the metabolite profiles of CKD-T0 and CKD-T6 were similar. Metabolomics profile may be useful to evaluate and recognize metabolic dysfunction and progression of CKD, and the diet may have helped maintain and retard the progression of CKD.

Diet-dependent acid load associates with mean arterial pressure in a cohort of non-obese, non-black, post-menopausal women

Higher sodium (Na+) intakes are associated with higher blood pressure (BP). Whether this relationship is stronger with diet-dependent acid load (DAL) and in patients with diagnosed hypertension or normal BP is not well determined. We studied 170 postmenopausal women randomized to potassium bicarbonate or placebo till 36 months where 24-hour urine and arterialized blood were collected. We investigated the association of DAL estimated as urinary potential renal acid load (UPRAL) and mean arterial pressure (MAP) using mixed-effects model, adjusting for age, anthropometrics, creatinine clearance, and treatment. Adjusted regression estimates for change in Na+ and UPRAL on MAP after 12 months follow-up were calculated, and further adjustments were made for change in potassium (K+) and body mass index (BMI). MAP was inversely associated with UPRAL (β [95% CI]:-0.11[-0.25,-0.001]). There was effect modification by hypertension (p-interaction=0.04); MAP decreased significantly in normotensives but the association was not significant in hypertensives. A decrease of 0.70 mmHg in MAP (0.13,1.69) per 50 mmol/24 hr reduction in Na+ was noted when the model was adjusted for change in K+. Our results with UPRAL exhibited stronger dose-response for MAP, which remained significant after adjustment for BMI. UPRAL was independently associated with MAP even after adjustment for potential confounders, and the data showed this association to be more pronounced in normotensives. Novelty: • First longitudinal study on the association of UPRAL and MAP • Association was a more robust relationship than between U[Na/K] ratio and MAP • UPRAL may play a significant role in the pathogenesis of primary hypertension.

Comparison of inulin clearance with 2-h creatinine clearance in Japanese pediatric patients with renal disease: open-label phase 3 study of inulin

Background

There is no approved dosage and administration of inulin for children. Therefore, we measured inulin clearance (Cin) in pediatric patients with renal disease using the pediatric dosage and administration formulated by the Japanese Society for Pediatric Nephrology, and compared Cin with creatinine clearance (Ccr) measured at the same time. We examined to what degree Ccr overestimates Cin, using the clearance ratio (Ccr/Cin), and confirmed the safety of inulin in pediatric patients.

Methods

Pediatric renal disease patients aged 18 years or younger were enrolled. Inulin (1.0 g/dL) was administered intravenously at a priming rate of 8 mL/kg/hr (max 300 mL/hr) for 30 min. Next, patients received inulin at a maintenance rate of 0.7 × eGFR mL/min/1.73 m² × body surface area (max 100 mL/hr) for 120 min. With the time the maintenance rate was initiated as a starting point, blood was collected at 30 and 90 min, while urine was collected twice at 60-min intervals. The primary endpoint was the ratio of Ccr to Cin (Ccr/Cin).

Results

Inulin was administered to 60 pediatric patients with renal disease; 1 patient was discontinued and 59 completed. The primary endpoint, Ccr/Cin, was 1.78 ± 0.52 (mean ± standard deviation). Regarding safety, five adverse events were observed in four patients (6.7%); all were non-serious. No adverse reactions were observed in this study.

Conclusions

The results in this study on the dosage and administration of inulin showed that inulin can safely and accurately determine GFR in pediatric patients with renal disease.

ClinicalTrials.gov identifier

NCT03345316.

Ultrasonographic Intraparenchymal Renal Resistive Index Variation for Assessing Renal Functional Reserve in Patients Scheduled for Cardiac Surgery: A Pilot Study

INTRODUCTION

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common complication in patients undergoing cardiac surgery. Preoperative renal functional reserve (RFR) has been demonstrated to be highly predictive of CSA-AKI. We have previously demonstrated that intraparenchymal renal resistive index variation (IRRIV) measured by ultrasound (US) can identify the presence of RFR in healthy individuals. This study aimed (1) to examine the correlation between the US IRRIV test and RFR measured through the protein loading test in patients undergoing elective cardiac surgery and (2) to determine the value of the 2 methods for predicting occurrence of AKI or subclinical AKI after cardiac surgery.

METHODS

Consecutive patients scheduled for cardiac surgery were enrolled for this pilot study. The protein loading test and the IRRIV test were performed in all patients 2 days before cardiac surgery. Correlation between IRRIV and RFR was tested using Pearson correlation analysis. Association between presence of RFR and positive IRRIV test, presence of RFR and AKI and subclinical AKI, and positive IRRIV test and AKI and subclinical AKI was evaluated using logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the values of IRRIV for predicting RFR, RFR for predicting AKI and subclinical AKI, and IRRIV for predicting AKI and subclinical AKI.

RESULTS

Among the 31 patients enrolled, significant association was found between IRRIV and RFR (r = 0.81; 95% CI: 0.63-0.90; p < 0.01). The association between RFR and IRRIV was described in 27/31 (87.1%) patients. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the IRRIV test were 100, 84, 60, and 100%, respectively. In ROC curve analysis, the area under the curve (AUC) was 0.80 (95% CI: 0.64-0.96). After cardiac surgery, 1/31 (3.2%) patient had AKI and 12/31 (38.7%) had subclinical AKI. RFR predicted subclinical AKI (odds ratio [OR] = 0.93; 95% CI: 0.87-0.98; p = 0.02). The sensitivity, specificity, PPV, and NPV of the RFR were 61, 88.8, 80, and 76%, respectively; the AUC was 0.75 (95% CI: 0.59-0.91). IRRIV predicts subclinical AKI (OR = 0.79; 95% CI: 0.67-0.93; p = 0.005). The sensitivity, specificity, PPV, and NPV of the IRRIV test were 46.1, 100, 100, and 72%, respectively; the AUC was 0.73 (95% CI: 0.58-0.87).

CONCLUSION

This pilot study suggests that a positive IRRIV test can significantly predict the presence of RFR in patients scheduled for cardiac surgery. RFR measured by the protein loading test or by the US IRRIV test can predict the occurrence of subclinical postoperative AKI. The findings of this study need to be confirmed in large patient cohorts.

Iohexol plasma clearance simplified by Dried Blood Spot (DBS) sampling to measure renal function in conscious mice

There is no simple method to measure glomerular filtration rate (GFR) in mice, which limits the use of mice in models of renal diseases. We aimed at simplifying the plasma clearance of iohexol in mice, using dried blood spot (DBS) sampling in order to reduce the amount of blood taken for analysis. GFR was measured simultaneously by a reference method in total blood-as described before-and tested method using DBS in fifteen male and six female C57BL/6J mice. Total blood extraction was 50 μL for the reference methods and 25μL for the tested methods, distributed in 5 samples. The agreement of GFR values between both methods was analyzed with the concordance correlation coefficient (CCC), total deviation index (TDI) and coverage probability (CP). The agreement between both methods was excellent, showing a TDI = 8.1%, which indicates that 90% of the GFR values obtained with DBS showed an error ranging from - 8 to + 8% of the reference method; a CCC of 0.996 (CI: 0.992), reflecting high precision and accuracy and a CP of 94 (CI: 83), indicating that 6% of the GFR values obtained with DBS had an error greater than 10% of the method in blood. So, both methods are interchangeable. DBS represent a major simplification of GFR measurement in mice. Also, DBS improves animal welfare by reducing the total blood required and refining the procedure.

Midazolam and hydroxymidazolam plasma concentrations can be monitored with selected biochemical and physiological parameters of palliative care patients

RATIONALE & OBJECTIVE

Midazolam is one of top three drugs used in palliative care. Its use increases in the last days of hospice patients' lives while safe dosage can be challenging. Equations currently used to estimate glomerular filtration rate, e.g: the Cockroft-Gault (eGFR_CR) and the Modification of Diet in Renal Disease (eGFR_MDRD) ones, do not generate precise calculations, especially in palliative patients exhibiting variations in body parameters. Our aim was to seek new relationships between mean midazolam (M_avg) and alfahydroxymidazolam (OH-M_avg) concentrations in plasma, and selected biochemical and physiological parameters of palliative patients, to enable optimal midazolam pharmacotherapy.

STUDY DESIGN, PARTICIPANTS AND INTERVENTIONS

The pilot study included 11 Caucasians, aged 42-95, with advanced cancer disease, receiving midazolam in a hospice in-patient unit. We tested correlations among M_avg, BMI, eGFR_MDRD, midazolam clearance (CL), OH-M_avg, bilirubin (Bil) and blood creatinine concentration (Cr). F test and leave-one out (LOO) validation was applied to verify the correlations' significance and predictive ability.

RESULTS

We found ten statistically significant (p < 0.05) correlations related to midazolam pharmacokinetics and physiological factors. We formulated two equations with high degree of predictive ability, based on the eGFR_MDRD→CL and the (Bil + BMI × Ln(Cr))→M_avg-(OH-M_avg) correlations. The limitations of the study mainly revolve around its pilot nature and the need to continue testing the results on a bigger population. No funding to disclose.

CONCLUSIONS

The significance of correlations corresponding to the arithmetic expressions confirms that Bil, BMI, Ln(Cr) analyzed simultaneously report a series of processes on which midazolam metabolism depends. Two of ten correlations proposed came close to meet all LOO validation criteria. Current findings can help optimize midazolam treatment in palliative therapy.

Polyamine biomarkers as indicators of human disease

The significant increase of periodontitis, chronic kidney disease (CKD), Alzheimer's disease and cancer can be attributed to an ageing population. Each disease produces a range of biomarkers that can be indicative of disease onset and progression. Biomarkers are defined as cellular (intra/extracellular components and whole cells), biochemical (metabolites, ions and toxins) or molecular (nucleic acids, proteins and lipids) alterations which are measurable in biological media such as human tissues, cells or fluids. An interesting group of biomarkers that merit further investigation are the polyamines. Polyamines are a group of molecules consisting of cadaverine, putrescine, spermine and spermidine and have been implicated in the development of a range of systemic diseases, in part due to their production in periodontitis. Cadaverine and putrescine within the periodontal environment have demonstrated cell signalling interfering abilities, by way of leukocyte migration disruption. The polyamines spermine and spermidine in tumour cells have been shown to inhibit cellular apoptosis, effectively prolonging tumorigenesis and continuation of cancer within the host. Polyamine degradation products such as acrolein have been shown to exacerbate renal damage in CKD patients. Thus, the use of such molecules has merit to be utilized in the early indication of such diseases in patients.

Risk factors associated with disturbances of calcium homeostasis after initiation of a phosphate-restricted diet in cats with chronic kidney disease

BACKGROUND

Dietary phosphate restriction improves survival in cats with chronic kidney disease (CKD). However, feeding a phosphate-restricted diet may disrupt calcium homeostasis leading to hypercalcemia in some cats.

OBJECTIVES

To identify risk factors associated with increasing plasma total calcium (tCa) concentration after transition to a phosphate-restricted diet and to explore its role in CKD-mineral and bone disorder (CKD-MBD) in cats.

ANIMALS

Seventy-one geriatric (≥9 years) euthyroid client-owned cats with International Renal Interest Society (IRIS) stage 2 to 3 azotemic CKD.

METHODS

Retrospective cross-sectional cohort study. Changes in plasma tCa concentration in the first 200 days of diet transition were assessed using linear regression. Binary logistic regressions were performed to identify risk factors for increasing calcium concentration. Changes in clinicopathological variables associated with CKD-MBD over time were explored using linear mixed model and generalized linear mixed model analyses.

RESULTS

Lower baseline plasma potassium (odds ratio [OR] = 1.19 per 0.1 mmol/L decrease; P = .003) and phosphate (OR = 1.15 per 0.1 mmol/L decrease; P = .01) concentrations remained independent risk factors for increasing plasma tCa concentration. Plasma creatinine (β = .069 ± .029 mg/dL; P = .02), symmetric dimethylarginine (β = .64 ± .29 μg/dL; P = .03), phosphate (β = .129 ± .062 mg/dL; P = .04), and ln[FGF23] (β = .103 ± .035 pg/mL; P = .004) concentrations had significantly increased rates of change in cats with increasing plasma tCa concentration over time.

CONCLUSION AND CLINICAL IMPORTANCE

Lower plasma potassium or phosphate concentrations or both at the time of transition of cats with CKD to a phosphate-restricted diet are independently associated with increased risk of an increase in plasma tCa concentration. Increasing plasma tCa concentration is associated with progression of CKD.

Protective role of apple cider vinegar (APCV) in CCl4-induced renal damage in wistar rats

Background

Apple Cider Vinegar, (APCV) has been locally associated with a number of health benefits, including protection against oxidative stress and related ailments. It is on this background the present study assessed its protective effects against carbon tetrachloride (CCl₄)-induced oxidative damage in kidneys of rats.

Methods

Twenty four adult rats of Wistar strain were randomly assigned to four groups (n = 6). While group I animals served as control; kidney oxidative damage was induced in groups II and III animals using a single intraperitoneal injection of CCl₄ (100%, 1.73 mL/kg body weight, BW). Group II animals were left untreated and groups III and IV counterparts were administered APCV (1.56 mL/kg BW) once daily for a period of 7 days. Thereafter, the animals were fasted over night, and sacrificed by cervical dislocation, and samples (blood and kidney tissues) were collected for biochemical/histopathological examinations. Kidney function markers including urea, creatinine, sodium ion (Na⁺) and potassium ion (k⁺) were determined in the serum while thin sections of kidneys were processed for histopathological screening.

Results

Compared to the control animals, CCl₄ administration caused kidney damage as evidenced by significant (P < 0.05) increase in the evaluated indices (urea, creatinine, Na⁺ and K⁺). Interestingly, treatment of CCl₄-exposed rats with APCV markedly reversed the above alterations to near normal. Besides, APCV treatment ameliorated the histological derangements (hemorrhagic lesions) caused by CCl₄ in the kidney of the experimental rats.

Conclusion

These observations apparently suggest that Apple cider vinegar has the therapeutic potential to protect against renal impairment and attendant malfunction.

Synthesis and characterization of V2 O5 /urease for a biosensor of urea

Vanadium pentoxide (V₂ O₅ ) was used as support material to immobilize the urease enzyme. V₂ O₅ was prepared from a sol-gel process, and the immobilization of urease was done onto the surface of the PET/ITO/V₂ O₅ film. Different concentrations of urea were tested to study the sensitivity of the biosensor. Tests with pH variation were carried out, and it was noticed that the total charge in the cyclic voltammograms decreases due to the increase in pH that influences the catalytic activity of the enzyme. From cyclic voltammograms, with a different scan rate, for linear correlation testing, it was observed that the anodic currents varied as a function of the scan rate. Based on the variation in the urea concentration, the current increased with the increase in the urea concentration, indicating the sensitivity of the material. The use of V₂ O₅ /urease showed favorable electrochemical responses for application in biosensors as well as being sensitive to the variation in the urea concentration and easy to obtain and prepare.

Simultaneous glomerular filtration rate determination using inulin, iohexol, and 99mTc-DTPA demonstrates the need for customized measurement protocols

Urinary inulin clearance is considered the gold standard of glomerular filtration rate (GFR) measurement but plasma clearance of less expensive and more accessible tracers is more commonly performed. Many plasma sampling protocols exist but little is known about their accuracy. Here, the study objectives were to compare plasma iohexol and ^99mTc-DTPA GFR with varying sampling strategies to the GFR measured by urinary inulin and to identify protocols with the greatest accuracy according to clinical characteristics. GFR was measured simultaneously using urinary inulin, plasma iohexol, and plasma ^99mTc DTPA clearance. Blood was sampled from 2 to 10 hours after injection. For each method, bias, precision, and accuracy (P30 and mean absolute error) were calculated for the entire cohort and for eGFR-EPI creatinine subgroups (<30, 30-59, and ≥60 ml/min/1.73m²) and the edema stage using urinary inulin clearance as the gold standard. The mean inulin GFR of the 77 participants was 33 ml/min/1.73m². Delay of both the initial and the final samples in plasma iohexol protocols yielded the highest accuracy in the setting of low GFR (<30 ml/min/1.73m²). Early initial and final samples yielded the highest accuracy in the setting of high GFRs (≥60 ml/min/1.73m²). No sampling strategy was accurate in edematous patients. Thus, our study demonstrates that customization of GFR protocols according to the anticipated level of GFR are required to optimize protocol accuracy.

Detection of renal biomarkers in chronic kidney disease using microfluidics: progress, challenges and opportunities

Chronic kidney disease (CKD) typically evolves over many years in a latent period without clinical signs, posing key challenges to detection at relatively early stages of the disease. Accurate and timely diagnosis of CKD enable effective management of the disease and may prevent further progression. However, long turn-around times of current testing methods combined with their relatively high cost due to the need for established laboratory infrastructure, specialized instrumentation and trained personnel are drawbacks for efficient assessment and monitoring of CKD, especially in underserved and resource-poor locations. Among the emerging clinical laboratory approaches, microfluidic technology has gained increasing attention over the last two decades due to the possibility of miniaturizing bioanalytical assays and instrumentation, thus potentially improving diagnostic performance. In this article, we review current developments related to the detection of CKD biomarkers using microfluidics. A general trend in this emerging area is the search for novel, sensitive biomarkers for early detection of CKD using technology that is improved by means of microfluidics. It is anticipated that these innovative approaches will be soon adopted and utilized in both clinical and point-of-care settings, leading to improvements in life quality of patients.

Evaluation of Systematic Blood Testing at the Time of Recruitment to the Armed Forces: Retrospective Monocentric Study Among 726 French Army Soldiers

INTRODUCTION

In the French armed forces, the biological checkup required during the recruitment process comprises a urinalysis (urinary dipstick), a complete blood count (CBC), and measurement of serum levels of aspartate aminotransferase, alanine aminotransferase, fasting blood glucose, and creatinine. This study aimed to evaluate the benefits of this biological checkup and to determine the most relevant parameters.

MATERIALS AND METHODS

We conducted a monocentric retrospective study of all standardized and systematically conducted blood tests (CBC and measurement of aspartate aminotransferase, alanine aminotransferase, fasting blood glucose, and creatinine) over a 15-month period among 726 French Army recruits.

RESULTS

The population included mainly young males (85.4%, mean age 21.6 years). More than half (54.1%) of the blood tests had at least one abnormal parameter, most often concerning the CBC. Anemia occurred in 5.3% of the population and was mostly normocytic. Microcytosis was mostly not associated with anemia (72.3% of cases). Lymphopenia occurred in 20.1% of the population and was mostly mild. Eosinophilia was present in 5.1% of the population and was never severe. Thrombocytopenia occurred in 0.7% of the population and was never severe. Serum levels of aminotransferases were elevated in 8.1% of the population. Fasting plasma glucose averaged 84 mg/dL (SD: 0.07) ranging from 64 to 123 mg/dL, was abnormal in 0.4% of the population, and one case of diabetes was diagnosed. Serum creatinine concentration was elevated in 0.7% of the population.

CONCLUSION

CBCs gave useful information but iron deficiency was common and insufficiently detected by this single analysis. Assessing aminotransferase levels without screening for viral hepatitis and systematic measurement of fasting plasma glucose levels did not appear to be efficient. In addition, the only interest in systematic measurement of creatinine serum levels was to obtain a reference level for long-term follow-up. In addition to the urinary dipstick, the systematic biological checkup at recruitment could be limited to a CBC with measurement of plasma ferritin levels and Hepatitis B virus serology, providing that any CBC abnormalities, in particular cytopenia, eosinophilia, and microcytosis, are systematically investigated. For a public health approach, systematic screening for other sexually transmitted infections could be proposed.

Use of Intravenous Iodinated Contrast Media in Patients with Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation

Intravenous iodinated contrast media are commonly used with CT to evaluate disease and to determine treatment response. The risk of acute kidney injury (AKI) developing in patients with reduced kidney function following exposure to intravenous iodinated contrast media has been overstated. This is due primarily to historic lack of control groups sufficient to separate contrast-induced AKI (CI-AKI; ie, AKI caused by contrast media administration) from contrast-associated AKI (CA-AKI; ie, AKI coincident to contrast media administration). Although the true risk of CI-AKI remains uncertain for patients with severe kidney disease, prophylaxis with intravenous normal saline is indicated for patients who have AKI or an estimated glomerular filtration rate less than 30 mL/min/1.73 m² who are not undergoing maintenance dialysis. In individual high-risk circumstances, prophylaxis may be considered in patients with an estimated glomerular filtration rate of 30-44 mL/min/1.73 m² at the discretion of the ordering clinician. This article is a simultaneous joint publication in Radiology and Kidney Medicine. The articles are identical except for stylistic changes in keeping with each journal's style. Either version may be used in citing this article.

GFR Measurement and Chemotherapy Dosing in Patients with Kidney Disease and Cancer

Chemotherapeutic agents require precise dosing to ensure optimal efficacy and minimize complications. For those agents that are removed from the body by the kidney, accurate knowledge of GFR is critical. In addition, GFR needs to be determined rapidly, easily, and, if possible, with little additional cost. The ability to easily measure GFR also allows for rapid detection of nephrotoxicity. Current methodologies include direct clearance measurement of an indicator substance or estimation of creatinine clearance or GFR through regression equations that use a serum marker, such as creatinine or cystatin C. These methodologies all have shortfalls and limitations, some of which are specific to the patient with cancer. Newer methodologies that directly measure GFR are in clinical trials and offer the ability to rapidly and noninvasively provide accurate estimates of drug clearance as well as detection of nephrotoxicity. These methods offer the opportunity to refine drug dosing and improve outcomes.

Use of Intravenous Iodinated Contrast Media in Patients With Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation

Intravenous iodinated contrast media are commonly used with CT to evaluate disease and to determine treatment response. The risk of acute kidney injury (AKI) developing in patients with reduced kidney function following exposure to intravenous iodinated contrast media has been overstated. This is due primarily to historic lack of control groups sufficient to separate contrast-induced AKI (CI-AKI; ie, AKI caused by contrast media administration) from contrast-associated AKI (CA-AKI; ie, AKI coincident to contrast media administration). Although the true risk of CI-AKI remains uncertain for patients with severe kidney disease, prophylaxis with intravenous normal saline is indicated for patients who have AKI or an estimated glomerular filtration rate less than 30 mL/min/1.73 m² who are not undergoing maintenance dialysis. In individual high-risk circumstances, prophylaxis may be considered in patients with an estimated glomerular filtration rate of 30-44 mL/min/1.73 m² at the discretion of the ordering clinician.

Blood and urine biomarkers in chronic kidney disease: An update

INTRODUCTION

Chronic kidney disease (CKD) is a silent disease. Most CKD patients are unaware of their condition during the early stages of the disease which poses a challenge for healthcare professionals to institute treatment or start prevention. The trouble with the diagnosis of CKD is that in most parts of the world, it is still diagnosed based on measurements of serum creatinine and corresponding calculations of eGFR. There are controversies with the current staging system, especially in the methodology to diagnose and prognosticate CKD.

OBJECTIVE

The aim of this review is to examine studies that focused on the different types of samples which may serve as a good and promising biomarker for early diagnosis of CKD or to detect rapidly declining renal function among CKD patient.

METHOD

The review of international literature was made on paper and electronic databases Nature, PubMed, Springer Link and Science Direct. The Scopus index was used to verify the scientific relevance of the papers. Publications were selected based on the inclusion and exclusion criteria.

RESULT

63 publications were found to be compatible with the study objectives. Several biomarkers of interest with different sample types were taken for comparison.

CONCLUSION

Biomarkers from urine samples yield more significant outcome as compare to biomarkers from blood samples. But, validation and confirmation with a different type of study designed on a larger population is needed. More comparison studies on different types of samples are needed to further illuminate which biomarker is the better tool for the diagnosis and prognosis of CKD.

Beta-thalassemia: renal complications and mechanisms: a narrative review

OBJECTIVES

Beta-thalassemias are a group of recessively autosomal inherited disorders of hemoglobin synthesis, which, due to mutations of the beta-globin gene, lead to various degrees of defective beta-chain production, an imbalance in alpha/beta-globin chain synthesis, ineffective erythropoiesis, and anemia. Improved survival in thalassemic patients has led to the emergence of previously unrecognized complications, such as renal disease.

METHODS

A comprehensive literature review through PubMed was undertaken to summarize the published evidence on the epidemiology and pathophysiology of renal disease in thalassemia. Literature sources published in English since 1990 were searched, using the terms beta-thalassemia, renal disease.

RESULTS

Renal disease is considered to be the 4th cause of morbidity among patients with transfusion dependent thalassemia. Chronic anemia, hypoxia and iron overload are the main mechanisms implicated in development of renal injury, whereas several studies also suggested a contributive role of iron chelators.

DISCUSSION AND CONCLUSION

Kidney disease may develop through progressive renal tubular and glomerular damage; thus, its early recognition is important in order to prevent and/or reverse deterioration. This review will provide an insight on the involved mechanisms implicated in kidney disease in thalassemic patients and will discuss the updates on diagnosis and prevention of renal complications in thalassemia.

Association between Lipid Profiles and Renal Functions among Adults with Type 2 Diabetes

<b><i>Introduction:</i></b> Type 2 diabetes mellitus (T2DM) affects renal functions and lipid profiles of patients. <b><i>Objectives:</i></b> In this study, 100 patients (65 females, 35 males) with T2DM were evaluated to determine whether renal function characteristics and lipid profiles are associated with T2DM. <b><i>Methods:</i></b> Blood samples were collected from all patients with T2DM, and the levels of hemoglobin A_1c (HbA_1c), blood urea, serum creatinine, cholesterol, triglyceride (TGR), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and very low-density lipoprotein (VLDL) were analyzed. <b><i>Results:</i></b> A direct correlation of blood sugar and HbA_1c was observed with blood urea, serum creatinine, serum cholesterol, serum TGR, HDL, LDL, and VLDL. The results revealed elevated TGR levels in patients administered medications for hyperglycemia. Furthermore, serum TGR levels were significantly correlated with blood sugar levels (<i>p</i> = 0.035). Blood urea levels were significantly correlated with glycated hemoglobin (<i>p</i> = 0.008). Blood urea, serum creatinine, and serum cholesterol levels were highly significantly correlated with HbA_1c (<i>p</i> = 0.008, 0.017, and 0.005, respectively), while HDL, LDL, and VLDL were not significantly correlated with HbA_1c. <b><i>Conclusion:</i></b> This study highlights the importance of serum TGR and serum creatinine measurement for guiding the treatment of T2DM.

Lower glomerular filtration rate predicts increased hepatic and mucosal toxicity in myeloma patients treated with high-dose melphalan

High-dose melphalan followed by autologous hematopoietic stem cell transplantation (ASCT) is a standard treatment for younger myeloma patients. However, the correlation between its toxicity and renal impairment is not clear. We analyzed this relationship, focusing on estimated glomerular filtration rate (eGFR) as an index of renal function. We evaluated 78 multiple myeloma patients who underwent ASCT following high-dose melphalan at our center. Patients were divided into a higher eGFR group (eGFR ≥ 60) and a lower eGFR group (eGFR < 60). Multivariate analyses revealed that lower eGFR was independently associated with alkaline phosphatase elevation (OR 10.2, P = 0.038), mucositis (OR 10.5, P = 0.032), grade 2-4 co-elevation of both aspartate aminotransferase and alanine aminotransferase (OR 21.3, P = 0.016), delay of reticulocyte engraftment (HR 0.524, P = 0.034), and delay of platelet engraftment (HR 0.535, P = 0.0016). However, lower eGFR was not correlated with overall survival or time-to-next treatment. In summary, renal dysfunction secondary to administration of high-dose melphalan was associated with increased hepatic and mucosal toxicity and delay of hematological recovery, but did not affect survival outcomes.

Serum BTP concentrations are not affected by hepatic dysfunction

Background

Beta Trace Protein (BTP) is a promising marker of glomerular filtration rate (GFR). Equations to estimate GFR using BTP have been proposed. Very little is known about BTP’s production and metabolism. It has been hypothesized that the liver metabolizes certain BTP isoforms. As such, hepatic dysfunction may influence serum levels independently of GFR. This would impact on the accuracy and precision of GFR estimates using BTP. The purpose of this study was to assess the impact of cirrhosis on serum BTP concentrations.

Methods

BTP, cystatin C (cysC) and creatinine (Cr) were measured in 99 cirrhotic subjects and in matched controls. BTP/cysC and Cr/cysC ratios were compared between cases and controls. This was repeated after stratification by Child Pugh category. Comparisons of ratios between Child Pugh category A and combined B and C case subjects were also performed.

Results

There were no differences in BTP/cysC ratios between cases and controls for the entire cohort (0.80 vs 0.79) or for any of the Child Pugh categories (p > 0.10). There were significant differences between cases (1.09) and controls (0.73) for the BTP/Cr ratios (p < 0.001). The BTP/Cr ratio was higher in those with more advanced cirrhosis as compared to those with less severe cirrhosis (1.20 vs 1.03, p < 0.01). There were no differences in BTP/cysC ratios between those with less severe and more advanced cirrhosis (p = 0.25).

Conclusions

This study suggests that hepatic dysfunction does not influence serum BTP levels and argues against a significant role for the liver in BTP metabolism. Confirmation in a larger group of patients with advanced cirrhosis is required.