Screening for chronic kidney disease of uncertain aetiology in Sri Lanka: usability of surrogate biomarkers over dipstick proteinuria

Background

The use of dipstick proteinuria to screen Chronic Kidney Disease of uncertain aetiology (CKDu) in Sri Lanka is a recently debated matter of dispute. The aim of this study was to assess the suitability of biomarkers: serum creatinine, cystatin C and urine albumin to creatinine ratio (ACR) for screening CKDu in Sri Lanka.

Methods

Forty-four male CKDu patients and 49 healthy males from a CKDu-endemic region were selected. Meanwhile, 25 healthy males from a non-endemic region were selected as an absolute control. The diagnostic accuracy of each marker was compared using the above three study groups.

Results

In receiver operating characteristics (ROC) plots for creatinine, cystatin C and ACR, values of area under the curve (AUC) were 0.926, 0.920 and 0.737 respectively when CKDu was compared to non-endemic control. When CKDu was compared to endemic control, AUCs of above three analytes were distinctly lower as 0.718, 0.808 and 0.678 respectively. Cystatin C exhibited the highest sensitivity for CKDu when analyzed against both control groups where respective sensitivities were 0.75 against endemic control and 0.89 against non-endemic control. ROC-optimal cutoff limits of creatinine, cystatin C and ACR in CKDu vs non-endemic control were 89.0 μmol/L, 1.01 mg/L and 6.06 mg/g-Cr respectively, whereas in CKDu vs endemic control the respective values were 111.5 μmol/L, 1.22 mg/L and 12.66 mg/g-Cr.

Conclusions

Amongst the three biomarkers evaluated in this study, our data suggest that Cystatin C is the most accurate functional marker in detecting CKDu in endemic regions, yet the high cost hinders its usability on general population. Creatinine is favorable over dipstick proteinuria owing to its apparent accuracy and cost efficiency, while having the ability to complement the kidney damage marker (ACR) in screening. ACR may not be favorable as a standalone screening marker in place of dipstick proteinuria due to its significant decline in sensitivity against the CKDu-endemic population. However, creatinine and ACR in a complementary manner could overcome current shortcomings of dipstick proteinuria and such a dual marker tool could be commodious in screening CKDu-type tubulointerstital diseases. Furthermore, use of ACR may also increase the ability to clinically discriminate CKDu from other glomerular nephropathies.

Potential Role of Serum and Urinary Biomarkers in Diagnosis and Prognosis of Diabetic Nephropathy

PURPOSE OF REVIEW

Diabetic nephropathy (DN) is a progressive kidney disease caused by alterations in kidney architecture and function, and constitutes one of the leading causes of end-stage renal disease (ESRD). The purpose of this review is to summarize the state of the art of the DN-biomarker field with a focus on the new strategies that enhance the sensitivity of biomarkers to predict patients who will develop DN or are at risk of progressing to ESRD.

OBJECTIVE

In this review, we provide a description of the pathophysiology of DN and propose a panel of novel putative biomarkers associated with DN pathophysiology that have been increasingly investigated for diagnosis, to predict disease progression or to provide efficient personal treatment.

METHODS

We performed a review of the literature with PubMed and Google Scholar to collect baseline data about the pathophysiology of DN and biomarkers associated. We focused our research on new and emerging biomarkers of DN.

KEY FINDINGS

In this review, we summarized the critical signaling pathways and biological processes involved in DN and highlighted the pathogenic mediators of this disease. We next proposed a large review of the major advances that have been made in identifying new biomarkers which are more sensitive and reliable compared with currently used biomarkers. This includes information about emergent biomarkers such as functional noncoding RNAs, microRNAs, long noncoding RNAs, exosomes, and microparticles.

LIMITATIONS

Despite intensive strategies and constant investigation, no current single treatment has been able to reverse or at least mitigate the progression of DN, or reduce the morbidity and mortality associated with this disease. Major difficulties probably come from the renal disease being heterogeneous among the patients.

IMPLICATIONS

Expanding the proteomics screening, including oxidative stress and inflammatory markers, along with metabolomics approaches may further improve the prognostic value and help in identifying the patients with diabetes who are at high risk of developing kidney diseases.

Evaluation and comparison of Abbott Jaffe and enzymatic creatinine methods: Could the old method meet the new requirements?

BACKGROUND

The aim of this study is to evaluate and compare the analytical performance characteristics of the two creatinine methods based on the Jaffe and enzymatic methods.

METHODS

Two original creatinine methods, Jaffe and enzymatic, were evaluated on Architect c16000 automated analyzer via limit of detection (LOD) and limit of quantitation (LOQ), linearity, intra-assay and inter-assay precision, and comparability in serum and urine samples. The method comparison and bias estimation using patient samples according to CLSI guideline were performed on 230 serum and 141 urine samples by analyzing on the same auto-analyzer.

RESULTS

The LODs were determined as 0.1 mg/dL for both serum methods and as 0.25 and 0.07 mg/dL for the Jaffe and the enzymatic urine method respectively. The LOQs were similar with 0.05 mg/dL value for both serum methods, and enzymatic urine method had a lower LOQ than Jaffe urine method, values at 0.5 and 2 mg/dL respectively. Both methods were linear up to 65 mg/dL for serum and 260 mg/dL for urine. The intra-assay and inter-assay precision data were under desirable levels in both methods. The higher correlations were determined between two methods in serum and urine (r=.9994, r=.9998 respectively). On the other hand, Jaffe method gave the higher creatinine results than enzymatic method, especially at the low concentrations in both serum and urine.

CONCLUSIONS

Both Jaffe and enzymatic methods were found to meet the analytical performance requirements in routine use. However, enzymatic method was found to have better performance in low creatinine levels.

Cystatin-C is associated with partial recovery of kidney function and progression to chronic kidney disease in living kidney donors: Observational study

Donor nephrectomy in living-donor kidney transplantation may result in hyperfiltration injury in remnant kidney; however, its clinical implication in partial recovery of kidney function (PRKF) in remnant kidney and chronic kidney disease (CKD) progression remains unclear. Thus, we investigated the effect of PRKF on CKD development in the residual kidney and the utility of cystatin-C (Cys-C) in evaluating renal function in living-donor kidney transplantation donors.The electronic medical records and laboratory results of 1648 kidney transplant (KT) donors and 13,834 healthy nondonors between January 2006 and November 2014 were reviewed. The predictors of PRKF and CKD diagnosed by Kidney Disease: Improving Global Outcomes (KDIGO) criteria were evaluated by multivariate analysis. CKD risk was compared between KT donors and healthy nondonors using Cox proportional hazard regression analysis following propensity score matching (PSM).The incidence of PRKF for KT donors was 49.3% (813). CKD incidence was 24.8% (408) in KT donors and 2.0% (277) in healthy nondonors. The predictors of PRKF were, male sex (odds ratio [OR], 17.32; 95% confidence interval [CI] 9.16-32.77), age (OR, 1.02; 95% CI, 1.00-1.04; P < 0.001), Cys-C concentration (OR, 1.02; 95% CI, 1.00-1.04; P = 0.02), and preoperative albumin level (OR, 0.49; 95% CI, 0.27-0.89; P = 0.02). The predictors of CKD were age (hazards ratio [HR], 1.04; 95% CI, 1.02-1.05; P < 0.001), Cys-C concentration (HR, 1.024; 95% CI, 1.012-1.037; P < 0.001), and PRKF (HR, 1.41; 95% CI, 1.04-1.92; P = 0.03). After PSM, the risk of progression to CKD was higher in KT donors than in healthy nondonors (HR, 58.4; 95% CI, 34.2-99.8; P < 0.001).Donor nephrectomy is associated with PRKF and progression to CKD. Cys-C is a useful early marker for detecting PRKF and CKD.

Application of Biomarkers for Risk Stratification in Patients with Atrial Fibrillation

BACKGROUND

Atrial fibrillation is the most common sustained arrhythmia and an important contributor to cardiovascular morbidity and mortality. Several strategies have been proposed for prediction of outcomes and individualization of treatments to better balance the benefits of stroke prevention and risks of bleeding during anticoagulation.

CONTENT

The availability of analytically more specific and sensitive methods to measure circulating biomarkers of cellular and organ stress and dysfunction has led to testing of their utility in several cardiovascular conditions. In patients with atrial fibrillation, biomarkers of myocardial injury (troponin) and cardiovascular stress and dysfunction (natriuretic peptides, growth differentiation factor 15), myocardial fibrosis (galectin-3), renal dysfunction (creatinine, cystatin C), inflammation (C-reactive protein, cytokines) and coagulation activity (d-dimer) have been found associated with underlying pathophysiology, clinical outcomes and effects of treatment. Measurements of these markers might therefore expand the understanding of the pathophysiology, improve risk assessment and optimize treatment in individual patients with atrial fibrillation.

SUMMARY

Biomarkers for risk stratification have potential roles as tools for evaluation of patients with atrial fibrillation and for selection of the best treatment strategies to prevent stroke, major bleeding, and mortality.

Serum cystatin C for acute kidney injury evaluation in children treated with aminoglycosides

BACKGROUND

Serum cystatin C (CysC) is a more accurate glomerular filtration rate marker than serum creatinine (SCr) and may rise more quickly with acute kidney injury (AKI).

METHODS

We performed a prospective cohort study of 81 non-critically ill children during 110 aminoglycoside (AG) treatments. We calculated area under the curve (AUC) for CysC to diagnose SCr-defined AKI and predict persistent AKI. SCr-AKI definition was based on the Kidney Disease: Improving Global Outcomes (≥stage 1: ≥50 % or 26.5 μmol/l SCr rise from baseline; stage 2: SCr doubling); CysC-AKI was based on a modified version using CysC rise.

RESULTS

SCr-AKI and CysC-AKI developed in 45 and 48 % treatments, respectively. CysC rise predicted stage 1 (AUC = 0.75, 95 % CI 0.60-0.90) and 2 (AUC = 0.85, 95 % CI 0.75-0.95) SCr-AKI 2 days before SCr-AKI attainment. The best combined sensitivity/specificity for percent CysC rise to predict stage 1 SCr-AKI was with a 44 % CysC rise (sensitivity = 65 %, specificity = 83 %). CysC rise on day of SCr-AKI development was associated with SCr-AKI ≥48 h (AUC = 0.73, 95 % CI 0.56-0.90) and ≥50 % persistent SCr rise at treatment end (AUC = 0.76, 95 % CI 0.61-0.90).

CONCLUSIONS

CysC is as an early AKI biomarker and predictive of persistent AKI on aminoglycoside treatment.

Cystatin C Levels in Middle-Aged Patients with Obstructive Sleep Apnea Syndrome

Background. Obstructive sleep apnea syndrome (OSAS) is associated with systemic inflammation and increased risk of cardiovascular and chronic kidney disease. Cystatin C (Cyst C) is a novel biomarker of both latent renal damage and cardiovascular disease. Aim of the study was to measure serum levels of Cyst C, as well as IL-8 and CRP, in otherwise healthy OSAS patients. Methods. 84 individuals examined with polysomnography for OSAS symptoms without known comorbidities were prospectively recruited. Results. According to apnea hypopnea index (AHI) subjects were divided in two groups: OSAS group (AHI > 5/hour, n = 64) and controls (AHI < 5/hour, n = 20), which were age- and BMI-matched. Cyst C levels were higher in OSAS patients versus controls (1176.13 ± 351.33 versus 938.60 ± 245.83 ng/mL, resp.; p = 0.017) while serum IL-8 and CRP levels did not differ significantly. Positive correlation was found between Cyst C levels and respiratory disturbance index (RDI) (r = 0.240, p = 0.039) and percentage of time with oxygen saturation <90% (r = 0.290, p = 0.02) and negative correlation was found between Cyst C levels and average oxygen saturation during sleep (r = -0.291, p = 0.012). After adjustment for age and BMI, RDI was the only independent predictor of Cyst C levels (β = 0.256, p = 0.039). Conclusion. Cyst C serum levels are increased in OSAS patients without comorbidities, suggesting an increased renal and cardiovascular disease risk.

Creatinine-Based and Cystatin C-Based GFR Estimating Equations and Their Non-GFR Determinants in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

eGFR equations have been evaluated in kidney transplant recipients with variable performance. We assessed the performance of the Modification of Diet in Renal Disease equation and the Chronic Kidney Disease Epidemiology Collaboration equations on the basis of creatinine, cystatin C, and both (eGFR creatinine-cystatin C) compared with measured GFR by iothalamate clearance and evaluated their non-GFR determinants and associations across 15 cardiovascular risk factors.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A cross-sectional cohort of 1139 kidney transplant recipients >1 year after transplant was analyzed. eGFR bias, precision, and accuracy (percentage of estimates within 30% of measured GFR) were assessed. Interaction of each cardiovascular risk factor with eGFR relative to measured GFR was determined.

RESULTS

Median measured GFR was 55.0 ml/min per 1.73 m(2). eGFR creatinine overestimated measured GFR by 3.1% (percentage of estimates within 30% of measured GFR of 80.4%), and eGFR Modification of Diet in Renal Disease underestimated measured GFR by 2.2% (percentage of estimates within 30% of measured GFR of 80.4%). eGFR cystatin C underestimated measured GFR by -13.7% (percentage of estimates within 30% of measured GFR of 77.1%), and eGFR creatinine-cystatin C underestimated measured GFR by -8.1% (percentage of estimates within 30% of measured GFR of 86.5%). Lower measured GFR associated with older age, women, obesity, longer time after transplant, lower HDL, lower hemoglobin, lower albumin, higher triglycerides, higher proteinuria, and an elevated cardiac troponin T level but did not associate with diabetes, smoking, cardiovascular events, pretransplant dialysis, or hemoglobin A1c. These risk factor associations differed for five risk factors with eGFR creatinine, six risk factors for eGFR Modification of Diet in Renal Disease, ten risk factors for eGFR cystatin C, and four risk factors for eGFR creatinine-cystatin C.

CONCLUSIONS

Thus, eGFR creatinine and eGFR creatinine-cystatin C are preferred over eGFR cystatin C in kidney transplant recipients because they are less biased, more accurate, and more consistently reflect the same risk factor associations seen with measured GFR.

Short-term Lipid-Lowering Treatment with Atorvastatin Improves Renal Function But Not Renal Blood Flow Indices in Patients with Peripheral Arterial Disease

Some studies have suggested that lipid lowering with statins exerts favorable effects on the progression of chronic kidney disease. Therefore, the authors assessed the effects of short-term atorvastatin treatment on biochemical markers of renal function and evaluated duplex indices of renal blood flow (RBF) in patients with peripheral arterial disease. Hyperlipidemic claudicants (n=18), aged 44-85 years, were treated for 8 weeks with 20 mg/day atorvastatin. Blood tests at baseline and after 8 weeks included serum fasting lipids, creatinine, urate, and cystatin C (a sensitive indicator of renal function) levels. RBF was also assessed (n=9) by measuring pulsatile and resistance duplex indices. As expected, there was a significant improvement in total cholesterol, low-density lipoprotein cholesterol, and triglycerides. There was also a significant (p<0.0001) fall in serum creatinine from 89 (58-125) to 79 µmol/L (54-119) and an increase in calculated creatinine clearance (CrCl) from 72 (40-129) to 80 mL/minute (47-138; p<0.0001). Serum cystatin C values decreased significantly (p=0.0002) from 1.04 (0.57-1.56) to 0.90 mg/L (0.47-1.47). There were no detectable changes in the RBF duplex indices. Treatment of stable claudicants with atorvastatin for 8 weeks was associated with improved renal function (as assessed by serum creatinine, cystatin C, and calculated CrCl) without changes in RBF. Further studies are required to identify the mechanisms involved in this phenomenon.

Prevalence of Reduced Kidney Function by Estimated Glomerular Filtration Rate Using an Equation Based on Creatinine and Cystatin C in Metabolic Syndrome and Its Components in Korean Adults

BACKGROUND

It is known that metabolic syndrome (MetS) is associated with chronic kidney disease. We evaluated and compared the prevalence of reduced kidney function in MetS and its components by estimated glomerular filtration rate (eGFR) using an equation based on creatinine (eGFRcr), cystatin C (eGFRcys), and combined creatinine-cystatin C (eGFRcr-cys) in Korean adults.

METHODS

We analyzed data from 3,649 adults who participated in a comprehensive health examination.

RESULTS

Mean values of eGFRcys were higher compared with mean values of eGFRcr (96.1±18.2 mL/min/1.73 m² vs. 91.2±13.6 mL/min/1.73 m²) in total subjects. The prevalence of reduced kidney function increased with age (9.6% for eGFRcys vs. 5.8% for eGFRcr-cys vs. 4.9% for eGFRcr, in subjects aged ≥60 years), and significantly increased with MetS, abdominal obesity, hypertension, high triglyceride, low high density lipoprotein (HDL), and high insulin resistance. The prevalence of MetS, abdominal obesity, hypertension, high insulin resistance, low HDL, and hepatic steatosis was significantly increased in subjects with reduced kidney function. This increased prevalence and the odds ratio of reduced kidney function for prevalence of MetS was highest for eGFRcys, followed by those of eGFRcr-cys, and eGFRcr.

CONCLUSION

The prevalence of reduced kidney function by eGFR was significantly increased in subjects with MetS and its related components. eGFRcys and eGFRcr-cys were superior to eGFRcr in detecting reduced kidney function.

Renal tubular damage is associated with poor clinical outcome in patients with peripheral artery disease who underwent endovascular therapy

BACKGROUND

Kidney dysfunction is associated with adverse outcome in patients with peripheral artery disease (PAD). Renal tubulointerstitial damage (RTD) is another type of kidney dysfunction from glomerular damage. RTD is reported to be a risk for future cardiac event in patients with heart disease. However, it remains to be determined whether RTD is predictive of poor clinical outcome in patients with PAD.

METHODS AND RESULTS

RTD markers (urinary N-acetyl-β-D-glucosamidase; NAG and urinary β-2 microglobulin to creatinine ratio) and Glomerular damage markers (cystatin C-based estimated glomerular filtration rate, proteinuria, and microalbuminuria) were measured in 265 consecutive PAD patients who underwent endovascular therapy. Patients were prospectively followed for a median length of 804days, with end points of major adverse cardiovascular and cerebrovascular events (MACCE). Overall, 73% of patients exhibited excess urinary NAG excretion, and values were higher in patients with critical limb ischemia. A multivariate Cox proportional hazard analysis revealed that NAG was an independent predictor of MACCE. When patients were divided according to NAG level, Kaplan-Meier analysis demonstrated that the third tertile was associated with the greatest risk for MACCE. The C index in NAG was the greatest among kidney dysfunction markers. Moreover, the net reclassification index was improved by the addition of NAG to basic predictors including glomerular damage markers.

CONCLUSION

RTD is common and associated with disease severity and clinical outcome in patients with PAD, indicating that it could be the additional clinical information to glomerular damage in patients with PAD.

Update on atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia with a substantial effect on individual morbidity and mortality as well as healthcare expenditure. The management of AF is complex and fraught with many uncertain and contentious issues. We have seen substantial progress in AF management in the last two decades including better understanding of the epidemiology, genomics, monitoring, drug and non-pharmacological treatment of the arrhythmia, its complications and stroke risk reduction. In this review, we present a comprehensive discussion on AF with emphasis on most recent updates.

Acute kidney injury following liver transplantation: a systematic review of published predictive models

Acute kidney injury is a frequent postoperative complication amongst liver transplant recipients and is associated with increased morbidity and mortality. This systematic review analysed the existing predictive models, in order to solidify current understanding. Articles were selected for inclusion if they described the primary development of a clinical prediction model (either an algorithm or risk score) to predict AKI post liver transplantation. The database search yielded a total of seven studies describing the primary development of a prediction model or risk score for the development of AKI following liver transplantation. The models span thirteen years of clinical research and highlight a gradual change in the definitions of AKI, emphasising the need to employ standardised definitions for subsequent studies. Collectively, the models identify a diverse range of predictive factors with several common trends. They emphasise the impact of preoperative renal dysfunction, liver disease severity and aetiology, metabolic risk factors as well as intraoperative variables including measures of haemodynamic instability and graft quality. Although several of the models address postoperative parameters, their utility in predictive modelling seems to be of questionable relevance. The common risk factors identified within this systematic review provide a minimum list of variables, which future studies should address. Research in this area would benefit from prospective, multi-site studies with larger cohorts as well as the subsequent internal and external validation of predictive models. Ultimately, the ability to identify patients at high risk of post-transplant AKI may enable early intervention and perhaps prevention.

The correct renal function evaluation in patients with thyroid dysfunction

Thyroid dysfunction induces several renal derangements involving all nephron portions. Furthermore, dysthyroidism is a recognized risk factor associated with the development of chronic kidney disease. Current data, in fact, demonstrate that either subclinical or overt thyroid disease is associated with significant changes in creatinine, estimated glomerular filtration rate, measured glomerular filtration rate and Cystatin C. Herein, we systematically reviewed several relevant studies aiming at the identification of the most sensitive and specific parameter for the correct renal function evaluation in patients with thyroid dysfunction, that are usually treated as outpatients. Our systematic review indicates that estimated glomerular filtration rate, preferably with CKD-EPI equation, appears to be the most reliable and wieldy renal function parameter. Instead, Cystatin C should be better used in the grading of thyroid dysfunction severity.

Cystatin C-based glomerular filtration rate associates more closely with mortality than creatinine-based or combined glomerular filtration rate equations in unselected patients

BACKGROUND

Decreased glomerular filtration rate (GFR) is an important cardiovascular risk factor, but estimated GFR (eGFR) may differ depending on whether it is based on creatinine or cystatin C. A combined creatinine/cystatin C equation has recently been shown to best estimate GFR; however, the benefits of using the combined equation for risk prediction in routine clinical care have been less studied. This study compares mortality risk prediction by eGFR using the combined creatinine/cystatin C equation (CKD-EPI), a sole creatinine equation (CKD-EPI) and a sole cystatin C equation (CAPA), respectively, using assays that are traceable to international calibrators.

METHODS AND RESULTS

All patients analysed for both creatinine and cystatin C from the same blood sample tube (n = 13,054) during 2005-2007 in Uppsala University Hospital Laboratory were divided into eGFR risk categories>60, 30-60 and <30 mL/min/1.73 m(2) by each eGFR equation. During follow-up (median 4.6 years), 4398 participants died, of which 1396 deaths were due to cardiovascular causes. Reduced eGFR was significantly associated with death as assessed by all eGFR equations. The net reclassification improvement (NRI) for the combination equation compared with the sole creatinine equation was 0.10 (p < 0.001) for all-cause mortality and 0.08 (p < 0.001) for cardiovascular mortality, indicating improved reclassification. In contrast, NRI for the combination equation, compared with the sole cystatin C equation, was -0.06 (p < 0.001) for all-cause mortality and -0.02 (p = 0.032) for cardiovascular mortality, indicating a worsened reclassification.

CONCLUSIONS

In routine clinical care, cystatin C-based eGFR was more closely associated with mortality compared with both creatinine-based eGFR and creatinine/cystatin C-based eGFR.

Effects of serelaxin in acute heart failure patients with renal impairment: results from RELAX-AHF

BACKGROUND

Serelaxin showed beneficial effects on clinical outcome and trajectories of renal markers in patients with acute heart failure. We aimed to study the interaction between renal function and the treatment effect of serelaxin.

METHODS

In the current post hoc analysis of the RELAX-AHF trial, we included all patients with available estimated glomerular filtration rate (eGFR) at baseline (n = 1132). Renal impairment was defined as an eGFR <60 ml/min/1.73 m(2) estimated by creatinine.

RESULTS

817 (72.2 %) patients had a baseline eGFR <60 ml/min/1.73 m(2). In placebo-treated patients, baseline renal impairment was related to a higher 180 day cardiovascular (HR 3.12, 95 % CI 1.33-7.30) and all-cause mortality (HR 2.81, 95 % CI 1.34-5.89). However, in serelaxin-treated patients, the risk of cardiovascular and all-cause mortality was less pronounced (HR 1.19, 95 % CI 0.54 -2.64; p for interaction = 0.106, and HR 1.15 95 % CI 0.56-2.34 respectively; p for interaction = 0.088). In patients with renal impairment, treatment with serelaxin resulted in a more pronounced all-cause mortality reduction (HR 0.53, 95 % CI 0.34-0.83), compared with patients without renal impairment (HR 1.30, 95 % CI 0.51-3.29).

CONCLUSION

Renal dysfunction was associated with higher cardiovascular and all-cause mortality in placebo-treated patients, but not in serelaxin-treated patients. The observed reduction in (cardiovascular) mortality in RELAX-AHF was more pronounced in patients with renal dysfunction. These observations need to be confirmed in the ongoing RELAX-AHF-2 trial.

Correlation of cystatin C and creatinine based estimates of renal function in children with hydronephrosis

INTRODUCTION

The use of a simple and accurate glomerular filtration rate (GFR) estimating method aiming minute assessment of renal function can be of great clinical importance.

OBJECTIVES

This study aimed to determine the association of a GFR estimating by equation that includes only cystatin C (Gentian equation) to equation that include only creatinine (Schwartz equation) among children.

PATIENTS AND METHODS

A total of 31 children aged from 1 day to 5 years with the final diagnosis of unilateral or bilateral hydronephrosis referred to Besat hospital in Hamadan, between March 2010 and February 2011 were consecutively enrolled. Schwartz and Gentian equations were employed to determine GFR based on plasma creatinine and cystatin C levels, respectively.

RESULTS

The proportion of GFR based on Schwartz equation was 70.19± 24.86 ml/min/1.73 m(2), while the level of this parameter based on Gentian method and using cystatin C was 86.97 ± 21.57 ml/min/1.73 m(2). The Pearson correlation coefficient analysis showed a strong direct association between the two levels of GFR measured by Schwartz equation based on serum creatinine level and Gentian method and using cystatin C (r = 0.594, P < 0.001). The linear association between GFR values measured with the two methods included cystatin C based GFR = 50.8+ 0.515 × Schwartz GFR. The correlation between GFR values measured by using serum creatinine and serum cystatin C measurements remained meaningful even after adjustment for patients' gender and age (r = 0.724, P < 0.001).

CONCLUSION

The equation developed based on cystatin C level is comparable with another equation, based on serum creatinine (Schwartz formula) to estimate GFR in children.

Relationship between High Serum Cystatin C Levels and the Risk of Gestational Diabetes Mellitus

Aims

Serum cystatin C (CysC) has recently been shown to be associated with the incidence of type 2 diabetes mellitus (T2DM) and progression to the pre-diabetic state. The aim of this study was to explore the relationship between serum CysC and the risk of gestational diabetes mellitus (GDM) in Chinese pregnant women.

Methods

This cross-sectional study consisted of 400 pregnant women including111 with GDM and 289 with normal glucose tolerance at 24–28 weeks of gestation. The subjects were further divided into four groups according to the CysC quartiles, and their clinical characteristics were compared. The serum CysC concentration was measured using immunoturbidimetry and the degree of insulin resistance was assessed by the homeostasis model assessment of insulin resistance (HOMA-IR).

Results

Serum CysC levels were significantly higher in pregnant women with GDM than in the healthy pregnant women[1.0(0.8–1.8) vs 0.7(0.6–1.0), P<0.01). The Spearman’s correlation analysis showed that serum CysC was positively associated with HOMA-IR(r = 0.118, P<0.05) and the occurrence of GDM(r = 0.348, P<0.01). The pregnant women were divided into quartiles according to their serum CysC concentrations. Compared to the first quartile, pregnant women in Q2 (OR, 2.441; P = 0.025), Q3 (OR, 3.383; P = 0.001) and Q4 (OR, 5.516; P<0.001) had higher risk of GDM after adjusted for age, BMI, HbA1c and HOMA-IR. Further, with a rise in the serum CysC, there was an increasing trend in the HOMA-IR levels (P<0.05). A binary logistic regression analysis after adjusting for other confounding variables revealed a significant and independent association between serum CysC and GDM [OR = 14.269; 95% confidence interval, 4.977–40.908, P<0.01].The receiver operating characteristic curve analysis revealed that the optimal cutoff point for serum CysC to indicate GDM was 0.95mg/L.

Conclusions

Serum CysC is significantly and independently associated with insulin resistance and GDM. It may be a helpful biomarker to identify the risk of GDM in Chinese pregnant women.

Prediction of urine volume soon after birth using serum cystatin C

BACKGROUND

Urine volume is an important clinical finding particularly during the early neonatal period. Oliguria is not a sign of impaired renal function but also a predictive factor for various complications and prognoses. It has been postulated that serum cystatin C (S-CysC) is a more sensitive biomarker for renal function than serum creatinine (S-Cr) in both adults and children. The objective of the current study was to investigate whether urine volume during 24 h after birth can be predicted using S-CysC.

METHODS

The subjects were 87 infants. The average gestational age was 34.7 ± 2.9 weeks and the average birth weight was 2135 ± 614 g. Blood samples were obtained from either the umbilical cord or the peripheral veins or artery of the newborn at birth. Data regarding the amount of urine volume and fluid intake during the first 24 h of life, maternal S-Cr and S-CysC levels within 48 h before delivery, and neonatal S-Cr and S-CysC levels at birth were collected from the medical records.

RESULTS

A significantly positive correlation was observed between maternal and neonatal S-Cr levels (r = 0.84, p < 0.0001) but not between maternal S-Cr levels and neonatal S-CysC levels (r = -0.069, p = 0.52). A significant negative correlation was seen between neonatal S-CysC levels and urine volume (r = -0.47, p < 0.0001).

CONCLUSION

The present study findings indicate that it may be possible to use S-CysC levels at birth to predict urine volume during the first 24 h of life.

Usefulness of serum cystatin C to determine the dose of vancomycin in neonate

Purpose

The vancomycin dosage regimen is regularly modified according to the patient's glomerular filtration rate (GFR). In the present study, we aimed to assess the usefulness of serum cystatin C (Cys-C) concentration, compared with serum creatinine (SCr) concentration, for predicting vancomycin clearance (CLvcm) in neonates.

Methods

We retrospectively analyzed the laboratory data of 50 term neonates who were admitted to the neonatal intensive care unit and received intravenous vancomycin, and assessed the pharmacokinetic profiles. Creatinine clearance (CLcr) and GFR based on Cys-C (GFRcys-c) were estimated using the Schwartz and Larsson formulas, respectively.

Results

The mean CLvcm (±standard deviation) was 74.52±31.17 L/hr, the volume of distribution of vancomycin was 0.67±0.14 L, and vancomycin half-life was 9.16±17.42 hours. The SCr was 0.46±0.25 mg/dL and serum Cys-C was 1.43±0.34 mg/L. The peak and trough concentrations of vancomycin were 24.65±14.84 and 8.10±5.35 mcg/mL, respectively. The calculated GFR based on serum creatinine concentration (GFR-Cr) and GFRcys-c were 70.2±9.45 and 63.6±30.18 mL/min, respectively. The correlation constant for CLvcm and the reciprocal of Cys-C (0.479, P=0.001) was significantly higher than that for CLvcm and the reciprocal of SCr (0.286, P=0.044). GFRcys-c was strongly correlated with CLvcm (P=0.001), and the correlation constant was significantly higher than that for CLvcm and CLcr (0.496, P=0.001). Linear regression analysis showed that only GFRcys-c was independently and positively correlated with CLvcm (F=41.9, P<0.001).

Conclusion

The use of serum Cys-C as a marker of CLvcm could be beneficial for more reliable predictions of serum vancomycin concentrations, particularly in neonates.

Angiotensin-Converting Enzyme Inhibitor Prevents the Worsening of Renal Function in the Late Phase after Percutaneous Coronary Intervention

AIM

The amount of contrast media and renal atheroemboli are risk factors for acute kidney injury after percutaneous coronary intervention (PCI). However, the chronic kidney injury after PCI has not been fully characterized. The purpose of this study was to investigate factors affecting renal function in the late phase after PCI by measuring serum Cystatin C (CysC).

METHODS

In 143 consecutive patients who underwent elective PCI, CysC was evaluated at baseline and at 9 months after PCI, and the percent change in CysC (%CysC) was calculated. The association between %CysC and baseline characteristics, including medication use, was assessed.

RESULTS

Of 143 patients, 86 had worsening renal function (WRF; %CysC ≥0), and 57 did not (non-WRF; %CysC <0). Only the use of angiotensin-converting enzyme inhibitor (ACEI) and baseline CysC were significantly different between WRF and non-WRF patients (15 vs. 40%, p=0.001 and 1.02±0.26 vs. 1.13±0.26 mg/L, p=0.015). In univariate analysis, the use of ACEI and CysC were negatively associated with WRF [Odds ratio (OR)=0.26, 95% confidence interval (CI)=0.12-0.57, p<0.001 and OR=0.20, 95% CI=0.05-0.73, p=0.015]. Furthermore, multivariate analysis revealed that the use of ACEI and CysC significantly correlated with WRF (OR=0.26, 95% CI=0.11-0.57, p<0.001 and OR=0.20, 95% CI=0.05-0.74, p=0.016). The %CysC in 36 patients with ACEI was significantly lower than that in 107 patients without ACEI [median: -3.8%; interquartile range (IQR), -11.0 to 4.2%; vs. median: 3.3%; IQR -2.9 to 11.0%, p=0.001].

CONCLUSION

The use of ACEI was associated with lower CysC after PCI, suggesting that ACEI prevents worsening of renal function in late phase after PCI.

Incremental value of cystatin C over conventional renal metrics for predicting clinical response and outcomes in cardiac resynchronization therapy: The BIOCRT study

BACKGROUND

Despite the benefit of CRT in select patients with heart failure (HF), there remains significant need for predicting those at risk for adverse outcomes for this effective but costly therapy. CysC, an emerging marker of renal function, is predictive of worsening symptoms and mortality in patients with HF. This study assessed the utility of baseline and serial measures of cystatin C (CysC), compared to conventional creatinine-based measures of renal function (estimated glomerular filtration rate, eGFR), in predicting clinical outcomes following cardiac resynchronization therapy (CRT).

METHODS

In 133 patients, we measured peripheral venous (PV) and coronary sinus (CS) CysC concentrations and peripheral creatinine levels at the time of CRT implant. Study endpoints included clinical response to CRT at 6 months and major adverse cardiac events (MACE) at 2 years.

RESULTS

While all 3 renal metrics were predictive of MACE (all adjusted p ≤ 0.02), only CysC was associated with CRT non-response at 6 months (adjusted odds ratio 3.6, p = 0.02). CysC improved prediction of CRT non-response (p ≤ 0.003) in net reclassification index analysis compared to models utilizing standard renal metrics. Serial CysC > 1mg/L was associated with 6-month CRT non-response and reduced 6-minute walk distance as well as 2-year MACE (all p ≤ 0.04).

CONCLUSION

In patients undergoing CRT, CysC demonstrated incremental benefit in the prediction of CRT non-response when compared to standard metrics of renal function. Baseline and serial measures of elevated CysC were predictive of CRT non-response and functional status at 6 months as well as long-term clinical outcomes.

Cystatin C: A prognostic marker after myocardial infarction in patients without chronic kidney disease

Aims

Cystatin C is an endogenous marker of renal function. It is a well established better marker of glomerular filtration rate than serum creatinine. There is also evidence that cystatin C is associated with atherosclerotic disease. The present prospective study evaluated the prognostic value of cystatin C after myocardial infarction in patients without chronic kidney disease.

Methods and results

A total of 127 patients who underwent coronary angiography after an acute coronary syndrome (ACS) were included. Cystatin C was associated with the severity of coronary artery disease (CAD). Cystatin C levels were significantly higher in patients with 3-vessels disease and severe CAD according to GENSINI score (p = 0.01 and p < 0.001 respectively). Among the patients admitted for ST elevation myocardial infarction, Cystatin C concentration was correlated with the initial TIMI flow in the culprit artery (p < 0.001). Mean duration of the follow-up period was 10.76 ± 2.1 months. High Cystatin C concentrations were associated to the occurrence of unfavourable outcomes and cardiovascular mortality during follow-up (1.19 ± 0.4 vs. 1.01 ± 0.35 mg/L, p = 0.01 and 1.21 ± 0.36 vs. 0.96 ± 0.27 mg/L, p = 0.03). Among different laboratory parameters, cystatin C was the best marker to predict the occurrence of major adverse cardiovascular events during the follow-up (Area under the receiveroperating characteristic curve = 0.743).

Conclusion

High cystatin C levels are associated with the severity of coronary artery disease in patients presenting an acute coronary syndrome and a normal renal function. Cystatin C is also associated to unfavourable cardiovascular outcomes during follow-up and appears as a strong predictor for risk of cardiovascular events and death.

Kidney Failure and Liver Allocation: Current Practices and Potential Improvements

In February 2002, the United Network for Organ Sharing implemented a system for prioritizing candidates for liver transplantation that was based on the risk of 90-day mortality as determined by the Model for End-Stage Liver Disease (MELD) score. As the MELD score is driven in part by serum creatinine as a marker of kidney function, the prevalence of kidney dysfunction and failure in patients with end-stage liver disease at the time of listing and at transplantation has steadily risen. In this review, we discuss current practices in liver transplantation in patients with kidney dysfunction focusing briefly on the decision to perform simultaneous liver-kidney transplantation. We then discuss pitfalls to the current practices of liver transplantation in patients with kidney dysfunction. We conclude by discussing potential improvements to current practices including the use of the MELD-Na score, alternatives to creatinine and creatinine-based equation for estimating kidney function, and the use of intraoperative kidney replacement therapy during liver transplantation.

Relationship of Changes in Cystatin-C With Serum Creatinine and Estimated Glomerular Filtration Rate in Kidney Transplantation

BACKGROUND

Serum creatinine (S-Cr) is the most commonly used marker for the assessment of renal function in kidney transplantation (KTx). Cystatin-C (Cys-C) has been proposed as an alternative marker of renal function for the estimated glomerular filtration rate (eGFR), which seems to be more accurate than S-Cr. The aim of this study was to investigate the relationship between changes in S-Cr, Cys-C, and eGFR measurements in KT patients during the early post-transplantation (post-Tx) period.

METHODS

Fifty consecutive patients, aged 15 to 70 years, were subjected to KT. Blood samples were collected at stable time-points on pre-Tx and post-Tx days 2, 6, and 14 and in the third month. Cys-C and S-Cr levels were measured, and GFR was estimated at all time-points using the Cockcroft-Gault and Le Bricon equations.

RESULTS

S-Cr and Cys-C levels decreased significantly post-Tx in all time-point determinations compared with pre-Tx levels. Both markers showed a parallel decrease, reaching normal levels in the third month. Estimated GFR post-Tx by S-Cr and Cys-C exhibited a parallel progressive increase without significant difference between the calculations. Correlation between S-Cr and Cys-C in all time-point determinations was positive and of high significance using Pearson's correlation (r = 0.969, P < .01; r = 0.951, P < .01; r = 0.969, P < .01; r = 0.701, P < .01). Also, the correlation between the eGFR by Cys-C and S-Cr was positive and of high significance in all post-Tx calculations (r = 0.896, P < .01; r = 0.935, P < .01; r = 0.929, P < .01; r = 0.861, P < .01). Ten recipients had acute rejection and were treated successfully with antirejection therapy. Their S-Cr, cys-C, and eGFR results were analyzed separately and showed a significant difference from no-rejection patients, with Cys-C being more sensitive to earlier eGFR changes.

CONCLUSION

Cystatin-C is an alternative and accurate marker of renal function in KT patients showing similar diagnostic characteristics to S-Cr. However, Cys-C appears superior to S-Cr in reflecting early GFR temporary changes, which is critical for the early detection of acute rejection.

Cystatin C: why clinical laboratories should be measuring it

Cystatin C is a 13-kDa cysteine protease inhibitor that satisfies many of the criteria required of a marker of glomerular filtration rate. It can be readily measured in laboratories using automated, standardised immunoassays. Hitherto there has been reluctance to adopt cystatin C measurement in the assessment of kidney function, despite demonstrated superiority compared to the current standard of practice, serum creatinine. This may be due to increased direct reagent costs. Recent strong evidence has confirmed the superior ability of cystatin C compared to creatinine to predict risk of a range of poor outcomes (including kidney failure, cardiovascular events and mortality) among patients with chronic kidney disease. On the back of this, national and international guidelines including those of the National Institute for Health and Clinical Excellence have recommended the use of cystatin C to risk stratify individuals with mild to moderately reduced glomerular filtration rate and no albuminuria. Cystatin C presents an opportunity for laboratories to engage with their users in developing clinical pathways which will usefully focus chronic kidney disease management on those most likely to benefit while reassuring patients at low risk.

Cystatin C as a potential biomarker for dosing of renally excreted drugs

The objective of the present study was to review the available pharmacokinetic evidence for the utility of cystatin C (CysC) as a marker of renal function to predict the dose of renally excreted drugs.The bibliographic search used PubMed and EMBASE databases, from its inception through to January 2014, with the following keywords 'pharmacokinetics' and 'cystatin C'.Sixteen pharmacokinetic publications were identified and seven drugs primarily excreted by the kidney were studied. Among them, only one study was performed in children, the others were performed in adults and/or elderly subjects, either healthy volunteers or patients with variable clinical conditions, such as cystic fibrosis and cancer. Most of studies (n = 13/16) demonstrated that CysC was better correlated with clearance/trough concentration of evaluated drugs compared with creatinine.Our review supports that CysC is a good marker of renal function to predict dose of renally excreted drugs. Efforts should be made to evaluate the impact of CysC in special populations in order to define its clinical value in dosing optimization.

Biomarkers for risk prediction in acute decompensated heart failure

Risk prediction in patients admitted with acute decompensated heart failure (ADHF) remains a challenge. Biomarkers may improve risk prediction, which in turn may help to better inform patients regarding short-term and long-term prognosis, therapy and care. Most data on biomarkers have been derived from patient cohorts with chronic heart failure. In ADHF, currently, risk tools largely rely on common clinical and biochemical parameters. However, ADHF is not a single disease. It presents in various manners and different etiologies may underlie ADHF, which are reflected by different biomarkers. In the last decade, many studies have reported the prognostic value of these biomarkers. These studies have attempted to describe a value for statistical modeling, e.g., reclassification indices, in an effort to report incremental value over a clinical model or the "gold standard". However, the overall incremental predictive value of biomarkers has been modest compared to already existing clinical models. Natriuretic peptides, e.g., (NTpro-)BNP, are the benchmark, but head-to-head comparisons show that there are novel biomarkers with comparable prognostic value. Multimarker strategies may provide superior risk stratification. Future studies should elucidate cost-effectiveness of single or combined biomarker testing. The purpose of this review was to provide an update on current biomarkers and to identify new promising biomarkers than can be used in prognostication of acute heart failure.

Cystatin C, Beta2 Microglobulin, N-Acetyl-beta-D-glucosaminidase, Retinol-Binding Protein, and Endothelin 1 Levels in the Evaluation of Sickle Cell Disease Nephropathy

OBJECTIVES

Renal involvement is common in sickle cell disease (SCD). Early demonstration of renal injury and commencement of appropriate treatment will increase survival and quality of life in these patients. We investigated renal manifestations in our pediatric and adult SCD patients and evaluated the role of cystatin C, Beta2 microglobulin (B2M), retinol-binding protein (RBP), N-acetyl-beta-D-glucosaminidase (NAG), and endothelin-1 (ET-1) to indicate renal damage.

METHODS

The study involved 45 pediatric and 10 adult patients with SCD and 20 healthy children and 10 healthy adults as a control. All the patients were questioned for possible renal manifestations. 24-hour urine samples were collected and glomerular filtration rates (GFRs) were calculated by using creatinine (GFR(creatinine)), Schwartz formula (GFR(Schwartz)), and cystatin C (GFR(cystatin C)). Blood and urine samples were collected and serum cystatin C, urine B2M, RBP, NAG, and ET-1 levels were measured.

RESULTS

Nocturnal enuresis and proteinuria were the most common renal manifestations in SCD patients. When the groups were compared in terms of GFR, GFR(creatinine) and GFR(Schwartz) levels were higher in group 1 and 2 patients than in control 1 and 2 patients (P < .05). Cystatin C, B2M, RBP, NAG, and ET-1 values were normal in both the patient and the control groups. However, B2M/creatinine levels were higher than 160 μg/mg creatinine levels in 10 patients.

CONCLUSIONS

Serum cystatin C, urine NAG, RBP, and ET-1 levels were found to be insufficient for the evaluation of SCD nephropathy. Increased B2M/creatinie levels can be valuable in estimating possible glomerular and tubular damage in SCD.

Cystatin C in acute kidney injury diagnosis: early biomarker or alternative to serum creatinine?

BACKGROUND

Early acute kidney injury (AKI) diagnosis is needed to pursue treatment trials. We evaluated cystatin C (CysC) as an early biomarker of serum creatinine (SCr)-AKI and an alternative to define AKI.

METHODS

We studied 160 non-cardiac children in the intensive care unit (ICU). We measured daily CysC and SCr. AKI was staged by KDIGO (Kidney Disease: Improving Global Outcomes) guidelines using SCr and CysC (CysC-AKI). We calculated area under the curve (AUC) for (1) neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1) and urine CysC to diagnose SCr- and CysC-AKI; and (2) for CysC to diagnose SCr-AKI. We evaluated AKI associations with length of stay and ventilation duration.

RESULTS

We found that 44 % of patients developed SCr-AKI; 32 % developed CysC-AKI. Early ICU NGAL was most diagnostic of CysC-AKI (AUC 0.69, 95% CI 0.54-0.84); IL-18 was most diagnostic for SCr-AKI (AUC 0.69 95% CI 0.55-0.82). Combining SCr and CysC-AKI definition led to higher biomarker diagnostic AUC's. CysC-AKI was not more strongly associated with clinical outcomes. Early ICU CysC predicted SCr-AKI development (AUC 0.70, 95 % CI 0.53-0.89).

CONCLUSIONS

Our findings do not support replacing SCr by CysC to define AKI. Early ICU CysC predicts SCr-AKI development and combined SCr-CysC-AKI definition leads to stronger AKI biomarker associations.

Estimating glomerular filtration rate in acute coronary syndromes: Different equations, different mortality risk prediction

AIMS

Renal dysfunction is a powerful predictor of adverse outcomes in patients hospitalized for acute coronary syndrome. Three new glomerular filtration rate (GFR) estimating equations recently emerged, based on serum creatinine (CKD-EPIcreat), serum cystatin C (CKD-EPIcyst) or a combination of both (CKD-EPIcreat/cyst), and they are currently recommended to confirm the presence of renal dysfunction. Our aim was to analyse the predictive value of these new estimated GFR (eGFR) equations regarding mid-term mortality in patients with acute coronary syndrome, and compare them with the traditional Modification of Diet in Renal Disease (MDRD-4) formula.

METHODS AND RESULTS

801 patients admitted for acute coronary syndrome (age 67.3±13.3 years, 68.5% male) and followed for 23.6±9.8 months were included. For each equation, patient risk stratification was performed based on eGFR values: high-risk group (eGFR<60ml/min per 1.73m(2)) and low-risk group (eGFR⩾60ml/min per 1.73m(2)). The predictive performances of these equations were compared using area under each receiver operating characteristic curves (AUCs). Overall risk stratification improvement was assessed by the net reclassification improvement index. The incidence of the primary endpoint was 18.1%. The CKD-EPIcyst equation had the highest overall discriminate performance regarding mid-term mortality (AUC 0.782±0.20) and outperformed all other equations (ρ<0.001 in all comparisons). When compared with the MDRD-4 formula, the CKD-EPIcyst equation accurately reclassified a significant percentage of patients into more appropriate risk categories (net reclassification improvement index of 11.9% (p=0.003)). The CKD-EPIcyst equation added prognostic power to the Global Registry of Acute Coronary Events (GRACE) score in the prediction of mid-term mortality.

CONCLUSION

The CKD-EPIcyst equation provides a novel and improved method for assessing the mid-term mortality risk in patients admitted for acute coronary syndrome, outperforming the most widely used formula (MDRD-4), and improving the predictive value of the GRACE score. These results reinforce the added value of cystatin C as a risk marker in these patients.

Biomarkers in electrophysiology: role in arrhythmias and resynchronization therapy

Circulating biomarkers related to inflammation, neurohormones, myocardial stress, and necrosis have been associated with commonly encountered arrhythmic disorders such as atrial fibrillation (AF) and more malignant processes including ventricular arrhythmias (VA) and sudden cardiac death (SCD). Both direct and indirect biomarkers implicated in the heart failure cascade have potential prognostic value in patients undergoing cardiac resynchronization therapy (CRT). This review will focus on the role of biomarkers in AF, history of SCD, and CRT with an emphasis to improve clinical risk assessment for arrhythmias and patient selection for device therapy. Notably, information obtained from biomarkers may supplement traditional diagnostic and imaging techniques, thus providing an additional benefit in the management of patients.

A comparison of the effects of ketamine and remifentanil on renal functions in coronary artery bypass graft surgery

We have investigated the effects of ketamine-based and remifentanil-based anesthetic protocol on perioperative serum cystatin-C levels, and creatinine and/or cystatin-C-based eGFR equations in terms of acute kidney injury in coronary artery bypass graft (CABG) surgery. Using a simple randomization method (coin tossing), patients were divided into the two groups and not-blinded to the anesthetist. Remifentanil-midazolam-propofol or ketamine-midazolam-propofol-based anesthetic regimen was chosen. Different eGFR formulas using creatinine (MDRD, CKD-EPI, Cockrauft Gault); cystatin-C (eGFR1, eGFR2) or a combination of creatinine and cystatin-C (eGFR 3) were used to calculate estimated glomerular filtration rates (eGFRs). High-sensitive troponin T was used to determine if ketamine use in coronary surgery contributed to myocardial cell damage. Thirty-seven patients were included in the study (remifentanil group = 19, ketamine Group = 18). Urea, creatinine, cystatin-C levels were comparable between the groups in all the measurement times and also postoperative day 2 samples showed statistically higher results compared to baseline (p < 0.001). Effects of ketamine and remifentanil on renal functions were found similar. Creatinine and cystatin-C-based eGFR equations resulted similar in our study. Reversible stage 1 acute kidney injury (AKI) was observed on postoperative day 2 in seven patients from the remifentanil group and six patients from the ketamine group. Hs-troponin T was found to be higher in postoperative day 1 samples; there were no significant difference between the groups. Our results indicated that patients who have normal renal functions undergoing on-pump coronary bypass surgery, effects of ketamine and remifentanil on renal functions in terms of AKI were found to be similar.

Renal effects of the angiotensin receptor neprilysin inhibitor LCZ696 in patients with heart failure and preserved ejection fraction

BACKGROUND

Increases in serum creatinine with renin-angiotensin-aldosterone system (RAAS) inhibitors can lead to unnecessary discontinuation of these agents. The dual-acting angiotensin receptor neprilysin inhibitor LCZ696 improves clinical outcome patients with heart failure with reduced ejection fraction, and pilot data suggest potential benefit in heart failure with preserved ejection fraction (HFpEF). The effects of LCZ696 on renal function have not been assessed.

METHODS AND RESULTS

A total of 301 HFpEF patients were randomly assigned to LCZ696 or valsartan in the PARAMOUNT trial. We studied renal function [creatinine, estimated glomerular filtration rate (eGFR), cystatin C, and urinary albumin to creatinine ratio (UACR)] at baseline, 12 weeks, and after 36 weeks of treatment. Worsening renal function (WRF) was determined as an serum creatinine increase of >0.3 mg/dL and/or >25% between two time-points. Mean eGFR at baseline was 65.4 ± 20.4 mL/min per 1.73 m(2) . The eGFR declined less in the LCZ696 group than in the valsartan group (-1.5 vs. -5.2 mL/min per 1.73 m(2) ; P = 0.002). The incidence of WRF was lower in the LCZ696 group (12%) than in the valsartan group (18%) at any time-point, but this difference was not statistically significant (P = 0.18). Over 36 weeks, the geometric mean of UACR increased in the LCZ696 group (2.4-2.9 mg/mmol), whereas it remained stable in the valsartan group (2.1-2.0 mg/mmol; P for difference between groups = 0.016).

CONCLUSION

In patients with HFpEF, therapy with LCZ696 for 36 weeks was associated with preservation of eGFR compared with valsartan therapy, but an increase in UACR.

Evaluation of renal function by cystatin C in renal transplant recipients

OBJECTIVES

We evaluated cystatin C concentration as a marker of glomerular filtration rate in renal transplant recipients, and its correlation with creatinine-based glomerular filtration rate by urinary creatinine clearance, and the Cockroft-Gault and Modification of Diet in Renal Disease formulas.

MATERIALS AND METHODS

In this cross-sectional study, we measured serum cystatin C levels and its correlation with serum creatinine, creatinine clearance, and glomerular filtration rate using the Cockroft-Gault formula and Modification of Diet in Renal Disease formulas.

RESULTS

One hundred two recipients between June and December 2012, were examined. The mean subject age was 31.87 ± 8.37 years; the male:female ratio was 4.3:1. Mean serum creatinine concentration was 141.44 ± 43.31 mol/L (1.60 ± 0.49 mg/dL) and serum cystatin C 122.09 ± 38.95 nmol/L (1.63 ± 0.52 mg/L). Serum cystatin C was significantly correlated with serum creatinine (r=0.90; P<.001), creatinine clearance (r=0.77; P<.001), and the Cockroft-Gault (r=0.73; P<.001) and the Modification of Diet in Renal Disease formulas (r=0.82; P<.001). We assessed the correlation among serum cystatin C with serum creatinine, creatinine clearance, the Cockroft-Gault and Modification of Diet in Renal Disease at 1, 2-3, 4-5, and more than 5 years after transplant. The correlation between serum cystatin C and serum creatinine ranged from 0.8 to 1.0; cystatin C and creatinine clearance ranged from 0.8 to 0.85; serum cystatin C and the Cockroft-Gault Formula ranged from 0.7 to 0.8; and serum cystatin C and the Modification of Diet in Renal Disease formulas ranged from 0.8 to 0.84.

CONCLUSIONS

Our results show that serum cystatin C is a reliable marker for estimating glomerular filtration rate among renal transplant recipients. This test can determine the glomerular filtration rate of renal transplant recipients on follow-up. Further studies are required to establish serum cystatin C as a standard test for monitoring glomerular filtration rate in transplanted patients.

Cystatin C: a kidney function biomarker

Renal function is essential for homeostasis. The kidneys play important pleiotropic roles including removal of metabolic waste products and maintenance of water-electrolyte balance and blood pressure. Early diagnosis of renal dysfunction and institution of appropriate therapy are vital to survival. Unfortunately, common indicators of renal function lack necessary sensitivity and specificity. Recent evidence has, however, suggested that cystatin C (cysC) may be useful as a marker for glomerular filtration. CysC is a protein belonging to a group of cysteine proteases inhibitors produced primarily by nucleated cells. Due to low molecular weight and positive pI, it is easily filtered. Moreover, its serum concentration is independent of gender, age, or muscle mass, i.e., typical confounders in assessing glomerular filtration rate (GFR). This chapter discusses the structure and biologic function of cysC, its role as an indicator of GFR, and the most frequently used methods for its determination.