Cystatin C as a reliable marker of renal function following heart valve replacement surgery with cardiopulmonary bypass

Prognostic Performance of Cystatin C in COVID-19: A Systematic Review and Meta-Analysis

Cystatin C is a specific biomarker of kidney function. We perform this meta-analysis to determine the association of Cystatin C with the COVID-19 severity. In this systematic review and meta-analysis, we searched PubMed, EMBASE, Cochrane library, and Web of Science for studies published until 2nd September 2022 that reported associations between Cystatin C levels and COVID-19 severity. The analysis was performed using a random-effects model to calculate pooled standard mean difference (SMD). Twenty-five studies were included in the meta-analysis. Pooled analysis showed statistically significant differences of Cystatin C levels among survive vs. decreased patients (0.998 ± 0.225 vs. 1.328 ± 0.475 mg/dL, respectively; SMD = -2.14; 95%CI: -3.28 to -1.01; p < 0.001). Cystatin C levels in COVID-19 severe vs. non-severe groups varied and amounted to 1.485 ± 1.191 vs. 1.014 ± 0.601 mg/dL, respectively (SMD = 1.81; 95%CI: 1.29 to 2.32; p < 0.001). Additionally, pooled analysis showed that Cystatin C levels in patients with acute kidney injury (AKI) was 1.562 ± 0.885 mg/dL, compared to 0.811 ± 0.108 mg/dL for patients without AKI (SMD = 4.56; 95%CI: 0.27 to 8.85; p = 0.04). Summing up, Cystatin C is a potentially very good marker to be used in the context of COVID-19 disease due to the prognosis of patients' serious condition, risk of AKI and mortality. In addition, Cystatin C could be used as a marker of renal complications in COVID-19 other than AKI due to the need to monitor patients even longer after leaving the hospital.

Serum Cystatin C as a predictor of acute kidney injury in neonates: a meta-analysis

OBJECTIVES

The objective of this meta-analysis is to evaluate the diagnostic value of serum Cystatin C in acute kidney injury (AKI) in neonates.

SOURCES

PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI), and WanFang Database were searched to retrieve the literature related to the diagnostic value of Cystatin C for neonatal AKI from inception to May 10, 2021. Subsequently, the quality of included studies was determined using the QUADAS-2 tool. Stata 15.0 statistical software was used to calculate the combined sensitivity (SEN), specificity (SPE), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR). Additionally, meta-regression analysis and subgroup analysis contributed to explore the sources of heterogeneity.

SUMMARY OF THE FINDINGS

Twelve articles were included. The pooled sensitivity was 0.84 (95%CI: 0.74-0.91), the pooled specificity was 0.81 (95%CI: 0.75-0.86), the pooled PLR was 4.39 (95%CI: 3.23-5.97), the pooled NLR was 0.19 (95%CI: 0.11-0.34), and the DOR was 22.58 (95%CI: 10.44-48.83). The area under the receiver operating characteristic curve (AUC) was 0.88 (95%CI: 0.85-0.90). No significant publication bias was identified (p > 0.05).

CONCLUSIONS

Serum Cystatin C has a good performance in predicting neonatal AKI; therefore, it can be used as a candidate biomarker after the optimal level is determined by large prospective studies.

Albuminuria Pre-Emptively Identifies Cardiac Patients at Risk of Contrast-Induced Nephropathy

Contrast-induced nephropathy (CIN) is a complication associated with the administration of contrast media (CM). The CIN diagnosis is based on creatinine, a biomarker late and insensitive. The objective proposed was to evaluate the ability of novel biomarkers to detect patients susceptible to suffering CIN before CM administration. The study was carried out with patients undergoing cardiac catheterization involving CM. Patients were divided into two groups: (1) CIN, patients who developed this pathology; (2) control, patients who did not suffer CIN. Prior to the administration of CM, urine samples were collected to measure proteinuria, N-acetyl-β-d-glucosaminidase, neutrophil gelatinase-associated lipocalin and kidney injury molecule-1, albumin, transferrin, t-gelsolin and GM2 ganglioside activator protein (GM2AP). The risk factors advanced age, low body mass index and low estimated glomerular filtration rate; and the urinary biomarkers albumin, transferrin and GM2AP showed significant predictive capacity. Of all of them, albuminuria demonstrated the highest diagnostic power. When a cutoff point was established for albuminuria at values still considered subclinical (10–30 µg/mg Cr_u), it was found that there was a high incidence of CIN (40–75%). Therefore, albuminuria could be applied as a new diagnostic tool to prevent and predict CIN with P4 medicine criteria, independently of risk factors and comorbidities.

Teprasiran, a Small Interfering RNA, for the Prevention of Acute Kidney Injury in High-Risk Patients Undergoing Cardiac Surgery: A Randomized Clinical Study

Supplemental Digital Content is available in the text.

Acute kidney injury (AKI) affects up to 30% of patients undergoing cardiac surgery, leading to increased in-hospital and long-term morbidity and mortality. Teprasiran is a novel small interfering RNA that temporarily inhibits p53-mediated cell death that underlies AKI.

Cystatin C and α-1-Microglobulin Predict Severe Acute Kidney Injury in Patients with Hemorrhagic Fever with Renal Syndrome

Puumala orthohantavirus causes hemorrhagic fever with renal syndrome (HFRS) characterized by acute kidney injury (AKI), an abrupt decrease in renal function. Creatinine is routinely used to detect and quantify AKI; however, early AKI may not be reflected in increased creatinine levels. Therefore, kidney injury markers that can predict AKI are needed. The potential of the kidney injury markers urea, cystatin C, α1-microglobulin (A1M) and neutrophil gelatinase-associated lipocalin (NGAL) to detect early AKI during HFRS was studied by quantifying the levels of these markers in consecutively obtained plasma (P) and urine samples (U) for 44 HFRS patients. P-cystatin C and U-A1M levels were significantly increased during early HFRS compared to follow-up. In a receiver operating characteristic (ROC) curve analysis, P-cystatin C, U-A1M and P-urea predicted severe AKI with area under the curve 0.72, 0.73 and 0.71, respectively, whereas the traditional kidney injury biomarkers creatinine and U-albumin did not predict AKI. Nearly half of the HFRS patients (41%) fulfilled the criteria for shrunken pore syndrome, which was associated with the level of inflammation as measured by P-CRP. P-cystatin C and U-A1M are more sensitive and earlier markers compared to creatinine in predicting kidney injury during HFRS.

Predictive value of cystatin C and neutrophil gelatinase-associated lipocalin in contrast-induced nephropathy: A meta-analysis

Background

There are still limited studies comprehensively examining the diagnostic performance of neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C in contrast-induced nephropathy (CIN). The study aimed to investigate and compare the predictive value of NGAL and cystatin C in the early diagnosis of CIN.

Methods and materials

We searched the PubMed, EMBASE and Cochrane Library databases until November 10, 2019. The methodological quality of the included studies was assessed by the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Bivariate modeling and hierarchical summary receiver operating characteristic (HSROC) modeling were performed to summarize and compare the diagnostic performance of blood/urine NGAL and serum cystatin C in CIN. Subgroup and meta-regression analyses were performed according to the study and patient characteristics.

Results

Thirty-seven studies from thirty-one original studies were included (blood NGAL, 1840 patients in 9 studies; urine NGAL, 1701 patients in 10 studies; serum cystatin C, 5509 patients in 18 studies). Overall, serum cystatin C performed better than serum/urine NGAL (pooled DOR: 43 (95%CI: 12–152); AUROC: 0.93; λ: 3.79); serum and urine NGAL had a similar diagnostic performance (pooled DOR: 25 (95%CI: 6–108)/22(95%CI: 8–64); AUROC: 0.90/0.89; λ: 3.20/3.08). Meta-regression analysis indicated that the sources of heterogeneity might be CIN definition, assays, and nationalities.

Conclusion

Both NGAL and cystatin C can serve as early diagnostic indicators of CIN, while cystatin C may perform better than NGAL.

Counterattacking the tick bite: towards a rational design of anti-tick vaccines targeting pathogen transmission

Hematophagous arthropods are responsible for the transmission of a variety of pathogens that cause disease in humans and animals. Ticks of the Ixodes ricinus complex are vectors for some of the most frequently occurring human tick-borne diseases, particularly Lyme borreliosis and tick-borne encephalitis virus (TBEV). The search for vaccines against these diseases is ongoing. Efforts during the last few decades have primarily focused on understanding the biology of the transmitted viruses, bacteria and protozoans, with the goal of identifying targets for intervention. Successful vaccines have been developed against TBEV and Lyme borreliosis, although the latter is no longer available for humans. More recently, the focus of intervention has shifted back to where it was initially being studied which is the vector. State of the art technologies are being used for the identification of potential vaccine candidates for anti-tick vaccines that could be used either in humans or animals. The study of the interrelationship between ticks and the pathogens they transmit, including mechanisms of acquisition, persistence and transmission have come to the fore, as this knowledge may lead to the identification of critical elements of the pathogens' life-cycle that could be targeted by vaccines. Here, we review the status of our current knowledge on the triangular relationships between ticks, the pathogens they carry and the mammalian hosts, as well as methods that are being used to identify anti-tick vaccine candidates that can prevent the transmission of tick-borne pathogens.

Novel Biomarkers of Acute Kidney Injury After Contrast Coronary Angiography

Acute kidney injury (AKI), defined as a rise in serum creatinine of greater than 25% from baseline measured at 48 hours after renal insult, may follow iodinated contrast coronary angiography. Termed contrast-induced nephropathy, it can result in considerable morbidity and mortality. Measurement of serum creatinine as a functional biomarker of glomerular filtration rate is widely used for detection of AKI, but it lacks sensitivity for the early diagnosis of AKI (typically rising 24 hours after functional loss) and, as a solely functional marker of glomerular filtration rate, is unable to differentiate among the various causes of AKI. These intrinsic limitations to creatinine measurement and the recognition that improved clinical outcomes are linked to a more timely diagnosis of AKI, has led investigators to search for novel biomarkers of "early" kidney injury. Several studies have investigated the utility of renal injury biomarkers in a variety of clinical settings including angiography/percutaneous coronary intervention, coronary artery bypass graft surgery, sepsis in intensive care patients, and pediatric cardiac surgery. In this article, we discuss the use of iodinated contrast for coronary procedures and the risk factors for contrast-induced nephropathy, followed by a review the potential diagnostic utility of several novel biomarkers of early AKI in the clinical settings of coronary angiography/percutaneous coronary intervention. In particular, we discuss neutrophil gelatinase associated lipocalin in depth. If validated, such biomarkers would facilitate earlier AKI diagnosis and improve clinical outcomes.

Association of Peak Changes in Plasma Cystatin C and Creatinine With Death After Cardiac Operations

BACKGROUND

Acute kidney injury is a risk factor for death in cardiac surgical patients. Plasma cystatin C and creatinine have different temporal profiles in the postoperative setting, but the associations of simultaneous changes in both filtration markers compared with change in only one marker with prognosis after hospital discharge are not well described.

METHODS

This is a longitudinal study of 1,199 high-risk adult cardiac surgical patients in the TRIBE-AKI (Translational Research Investigating Biomarker Endpoints for Acute Kidney Injury) Consortium who survived hospitalization. We examined in-hospital peak changes of cystatin C and creatinine in the 3 days after cardiac operations. We evaluated associations of these filtration markers with death, adjusting for demographics, operative characteristics, medical comorbidities, preoperative estimated glomerular filtration rate, preoperative urinary albumin-to-creatinine ratio, and site.

RESULTS

During the first 3 days of hospitalization, nearly twice as many patients had a 25% or higher rise in creatinine (30%) compared with a 25% or higher peak rise in cystatin C (15%). The risk of death was higher in those with elevations in cystatin C (adjusted hazard ratio [HR], 1.83; 95% confidence interval [CI], 1.4 to 2.37) or creatinine (adjusted HR, 1.90; 95% CI, 1.32 to 2.72) compared with patients who experienced a postoperative decrease in either filtration marker. Patients who had simultaneous elevations of 25% or higher in cystatin C and creatinine were at similar adjusted risk for 3-year mortality (HR, 1.79; 95% CI, 1.03 to 3.1) as those with a 25% or higher increase in cystatin C alone (HR, 2.2; 95% CI, 1.09 to 4.47).

CONCLUSIONS

Elevations in creatinine postoperatively are more common than elevations in cystatin C. However, elevations in cystatin C appeared to be associated with a higher risk of death after hospital discharge.

Kidney disease in heart failure: the importance of novel biomarkers for type 1 cardio-renal syndrome detection

Chronic kidney disease (CKD) in heart failure (HF) has been recognized as an independent risk factor for adverse outcome, although the most important clinical trials tend to exclude patients with moderate and severe renal insufficiency. Despite this common association, the precise pathophysiological connection and liaison between heart and kidney is partially understood. Moreover, is it not enough considering how much cardio-renal syndrome type 1 is attributable to previous CKD, and how much to new-onset acute kidney injury (AKI). Neither development of AKI, its progression and time nor duration is related to an adverse outcome. An AKI definition is not universally recognized, and many confounding terms have been used in literature: "worsening renal function", "renal impairment", "renal dysfunction", etc., are all names that contribute to misunderstanding, and do not facilitate an universal classification. Therefore, AKI development should be the consequence of the basal clinical characteristics of patients, different primitive kidney disease and hemodynamic status. AKI could also be the mirror of several underlying associated diseases poorly controlled. Finally, it is not clear which is the optimal laboratory tool for identifying patients with an increased risk of AKI. In the current report, we review the different kidney diseases' impact in HF, and we analyze the modalities for AKI recognition during HF focusing our attention about some new biomarkers with potential application in the current setting.

Cystatin C as a predictive marker of renal dysfunction and mid-term outcomes following off-pump coronary artery bypass grafting

OBJECTIVE

To determine whether plasma cystatin C and creatinine levels after isolated off-pump coronary artery bypass grafting (OPCAB) are predictive of postoperative renal dysfunction and clinical outcomes.

METHODS

Between January 2008 and December 2013, 1033 who underwent isolated OPCAB were recruited. The patients were divided into three groups according to the preoperative level of cystatin C: low (0.83 mg/L>), mid (0.83-1.13 mg/L) and high (1.13 mg/L<). The endpoints of all-cause mortality and major adverse cerebrovascular and cardiovascular events were compared among three groups using the Kaplan-Meier method. The predictive power of cystatin C was compared with creatinine using receiver operating curves.

RESULTS

Follow-up was complete in all of the included patients at a mean of 2.9±1.5 years. Within the follow-up period, 9 early (30-day mortality) and 46 late deaths occurred. The 30-day mortality was zero, four (44%), and five (56%) cases in low, mid and high groups, respectively (p=0.03). The cut-off value of cystatin C for renal dysfunction prediction was approximately 1.04 (mg/L, p<0.001), and cystatin C showed greater predictive power than creatinine for renal dysfunction (area under the curve=0.73 vs 0.65; p=0.01). One-year and five-year overall survival in low, mid and high groups were 99.2%, 98.9% and 94.3%, and 97.9%, 97.3% and 86.3%, respectively (low vs high, p=0.01).

CONCLUSIONS

Cystatin C is a stronger predictor of postoperative renal dysfunction than serum creatinine, and its level is directly correlated with mid-term OPCAB adverse results.

Combined biomarker analysis for risk of acute kidney injury in patients with ST-segment elevation myocardial infarction

BACKGROUND

Acute kidney injury (AKI) complicating ST-segment elevation myocardial infarction (STEMI) increases subsequent morbidity and mortality. We combined the biomarkers of heart failure (HF; B-type natriuretic peptide [BNP] and soluble ST2 [sST2]) and renal injury (NGAL [neutrophil gelatinase-associated lipocalin] and cystatin C) in predicting the development of AKI in patients with STEMI undergoing primary percutaneous coronary intervention (PCI).

METHODS AND RESULTS

From March 2010 to September 2013, 189 STEMI patients were sequentially enrolled and serum samples were collected at presentation for BNP, sST2, NGAL and cystatin C analysis. 37 patients (19.6%) developed AKI of varying severity within 48 hours of presentation. Univariate analysis showed age, Killip class ≥2, hypertension, white blood cell counts, hemoglobin, estimated glomerular filtration rate, blood urea nitrogen, creatinine, and all the four biomarkers were predictive of AKI. Serum levels of the biomarkers were correlated with risk of AKI and the Acute Kidney Injury Network (AKIN) stage and all significantly discriminated AKI (area under the receiver operating characteristic [ROC] curve: BNP: 0.86, sST2: 0.74, NGAL: 0.75, cystatin C: 0.73; all P < 0.05). Elevation of ≥2 of the biomarkers higher than the cutoff values derived from the ROC analysis improved AKI risk stratification, regardless of the creatine level (creatinine < 1.24 mg/dL: odds ratio [OR] 11.25, 95% confidence interval [CI] 1.63-77.92, P = 0.014; creatinine ≥ 1.24: OR 15.0, 95% CI 1.23-183.6, P = 0.034).

CONCLUSIONS

In this study of STEMI patients undergoing primary PCI, the biomarkers of heart failure (BNP and sST2) and renal injury (NGAL and cystatin C) at presentation were predictive of AKI. High serum levels of the biomarkers were associated with an elevated risk and more advanced stage of AKI. Regardless of the creatinine level, elevation of ≥2 of the biomarkers higher than the cutoff values indicated a further rise in AKI risk. Combined biomarker approach may assist in risk stratification of AKI in patients with STEMI.

Early postoperative serum cystatin C predicts severe acute kidney injury following cardiac surgery: a post-hoc analysis of a randomized controlled trial

Objective

Acute kidney injury (AKI) after cardiac surgery procedures is associated with poor patient outcomes. Cystatin C as a marker for renal failure has been shown to be of prognostic value; however, a wide range of its predictive accuracy has been reported. The aim of the study was to evaluate whether the measurement of pre- and postoperative serum cystatin C improves the prediction of AKI.

Methods

In a single-centre, prospective study of 70 patients (74 ± 9ys; range 47-85ys; 77% male), cystatin C was measured six times: (T1 = preoperative, T2 = start cardiopulmonary bypass (CPB), T3 = 20 min after CPB, T4 = end of operation; T5 = 24 h postoperatively; T6 = 7d postoperatively). Predictive property, in terms of the need for renal replacement therapy (RRT), was analysed by receiver operating characteristics (ROC) statistics and described by the area under the curve (AUC).

Results

With respect to RRT (n = 8), serum cystatin C was significantly higher at the end of the operation (T4), 24 h postoperatively at T5 and at T6. The AUCs for preoperative T1 and intraoperative T2/3 cystatin C were <0.7 (95% CI, 0.47-0.85). The earliest significant predictive AUCs were found at the end of the operation (T4: p = 0.03 95% CI 0.58-0.88 AUC 0.73) and 24 h postoperatively (T5: p = 0.003 95% CI 0.74-0.96 AUC 0.85).

Conclusions

Early postoperative serum cystatin C increase appears to be a moderate biomarker in the prediction of AKI, whereas a preoperative and intraoperative cystatin C increase has only a limited diagnostic and predictive value.

Early prediction of acute kidney injury in patients with acute myocardial injury

INTRODUCTION

Previous studies have revealed that acute myocardial infarction (AMI) with acute kidney injury (AKI), about 17%, is strongly related to long-term mortality and heart failure. The dynamic changes in renal function during AMI are strongly related to long-term mortality and heart failure.

OBJECTIVES

Our study used clinical parameters and AKI biomarkers including neutrophil gelatinase-associated lipocalin, interleukin (IL)-6, IL-18, and cystatin C to evaluate prognostic relevance of AKI in the setting of AMI.

METHODS

This prospective study was conducted from November 2009 to January 2011 and enrolled sequential 96 patients with catheter-proven AMI; it was approved by the institutional review board of Chang Gung Memorial Hospital, Taiwan (institutional review board no. 99-0140B) and conformed to the tenets of the Declaration of Helsinki. The definition of AKI is the elevation of serum creatinine of more than 0.3 mg/dL within 48 hours.

RESULTS

Our results show that the incidence of AKI after AMI is 17.7% (17 patients). The following could be statistically related to AKI after AMI: age (P = .012), cardiac functions (Killip stage and echocardiogram; P = .003 each), Thrombolysis in Myocardial Infarction (TIMI) flow grade (P < .001), stenting (P < .001), neutrophil gelatinase-associated lipocalin (P = .005), IL-6 (P = .01), IL-18 (P = .002), and cystatin C (P = .002) in serum. The TIMI flow grade and serum cystatin C were shown to be important predictors by using multivariate analysis. Both TIMI flow lower than grade 2 and serum cystatin C of more than 1364 mg/L could be used to predict AKI (both overall correctness, 0.78). Moreover, IL-6 in serum is also associated with the major cardiovascular events after AMI (P = .02), as demonstrated in our study.

CONCLUSION

In conclusion, the worse TIMI flow and high plasma cystatin C can be used to predict AKI after AMI. Moreover, IL-6 can also be used as a 30-day major cardiovascular event indicator after AMI. A larger prospective and longitudinal study should follow the relationship between AKI predictors after AMI.

Predictive power of serum cystatin C to detect acute kidney injury and pediatric-modified RIFLE class in children undergoing cardiac surgery

OBJECTIVE

Acute kidney injury is a frequent and serious complication of cardiopulmonary bypass. In current clinical practice, serum creatinine is used to detect acute kidney injury. Cystatin C is a novel biomarker for kidney function that has been shown to be superior to serum creatinine in predicting acute kidney injury in adults after cardiopulmonary bypass. The aim of this study was to determine whether early cystatin C levels predict acute kidney injury associated with cardiopulmonary bypass in pediatric patients undergoing cardiac surgery and if cystatin C could predict pediatric-modified RIFLE (Risk, Injury, Failure, Loss, End-stage kidney disease) class and renal injury as determined by estimated glomerular filtration rate. We also investigated whether ultrafiltration during cardiopulmonary bypass affects cystatin C levels.

DESIGN

Prospective, observational cohort study.

SETTING

Cardiac intensive care unit in a tertiary, academic pediatric hospital.

PATIENTS

One hundred pediatric patients who underwent cardiac surgery involving cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Acute kidney injury was defined as a 50% increase in serum creatinine from a preoperative baseline anytime through postoperative day 4. Severity of acute kidney injury was determined by pediatric RIFLE class using estimated glomerular filtration rate criteria only. Renal injury was also determined by an absolute estimated glomerular filtration rate <80 mL/min/1.73 m. Cystatin C levels were measured before and after ultrafiltration. Twenty-eight patients (28%) developed acute kidney injury. Cystatin C predicted acute kidney injury as early as 8 hrs after surgery. When applying pediatric RIFLE criteria to the entire study, 30 patients reached "risk" and five developed "injury." Cystatin C was a good predictor of the development of "injury" (under the receiver operating characteristic curve, 0.834-0.875) and of renal injury by estimated glomerular filtration rate (under the receiver operating characteristic curve, 0.717-0.835) (all p < .05). Cystatin C levels decreased perioperatively and correlated with volume of fluid removed by ultrafiltration.

CONCLUSIONS

Cystatin C is an early predictor of acute kidney injury in children after cardiopulmonary bypass. Cystatin C is a good predictor of pediatric RIFLE classification and of decreased estimated glomerular filtration rate after cardiopulmonary bypass. Serum cystatin C may be cleared by ultrafiltration.

Erythropoietin attenuates cardiopulmonary bypass-induced renal inflammatory injury by inhibiting nuclear factor-κB p65 expression

Acute renal injury is one of the most frequent complications after cardiopulmonary bypass (CPB). This study was designed to evaluate the potential protective effect of erythropoietin (EPO) on CPB-induced renal injury in a rat model. Male Sprague-Dawley rats were randomly divided into three groups, sham-operated group (sham), control CPB group (control), erythropoietin CPB group (EPO). Blood samples were collected at the beginning, at the end of CPB, and at 0.5, 1, 2 and 24 h post-operation, and the kidneys were harvested 24 h postoperatively and observed by optical microscopy. Levels of serum creatinine (Cr) and blood urea nitrogen (BUN) were assayed. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6(IL-6) levels in the renal tissues were evaluated by the method of enzyme linked immunosorbent assay (ELISA). Protein and mRNA levels of nuclear factor kappa B p65 (NF-κB p65), intercellular adhesion molecule-1 (ICAM-1) were also determined using western blot and real-time PCR respectively. Serum Cr and BUN levels as well as TNF-α, IL-1β and IL-6 levels in renal tissues in control group were significantly higher than those in the sham group. However, the levels of above biomarkers were markedly decreased in EPO group when comparing with control group. Furthermore, NF-κB p65, ICAM-1 protein and mRNA expression were significantly down-regulated in EPO group comparing with control group. In addition, microscopic examinations revealed that histological injury was alleviated when treated with EPO. The results indicated that EPO potently protected against CPB-induced acute renal injury and inhibited expression of NF-κB p65 and inflammatory response.

Laboratory parameters of cardiac and kidney dysfunction in cardio-renal syndromes

"Cardio-Renal Syndromes" (CRS) are disorders of the heart and kidneys in which acute or chronic dysfunction in one organ may induce acute or chronic dysfunction of the other. The pathophysiology of CRS is complex, and there is accumulating evidence that various novel biomarkers are useful for diagnosis, prognostication, and risk stratification in patients with heart failure and chronic kidney disease (CRS). When both the heart failure (HF) and CKD occur together, it is important to have biomarkers that are able to risk stratify patients by looking at both their heart and kidney aspects. There are some promising newer renal biomarkers that may contribute to a better evaluation and prediction of prognosis in CRS patients. Most of the renal biomarkers studies in CRS have been performed in the setting of cardiac surgery, acute coronary syndrome (ACS), HF or after exposure to radiocontrast media in diagnostic and/or therapeutic percutaneous coronary procedures. Natriuretic peptides (NPs) have been validated as an important cardiac biomarker for risk stratification and prognostication in HF patients with or without CKD. However, the best cutoff values for each stage of CKD, including those on renal replacement therapy, are yet to be ascertained. In this context, it is likely that panels of multiple biomarkers will be needed for optimal evaluation, risk stratification, timely treatment initiation, and follow-up of patients with CRS.

Cystatin C in prediction of acute kidney injury: a systemic review and meta-analysis

BACKGROUND

Cystatin C (CysC) has been proposed as a filtration marker for the early detection of acute kidney injury (AKI); however, a wide range of its predictive accuracy has been reported.

STUDY DESIGN

Meta-analysis of diagnostic test studies.

SETTING & POPULATION

Various clinical settings of AKI, including patients after cardiac surgery, pediatric patients, and critically ill patients.

SELECTION CRITERIA

Computerized search of PubMed, Current Contents, CINAHL, and EMBASE from inception until November 15, 2010, was performed to identify potentially relevant articles. Inclusion criteria were studies investigating the diagnostic accuracy of CysC level to predict AKI. There were no language restrictions in the search.

INDEX TESTS

Increasing or increased serum CysC level or urinary CysC excretion.

REFERENCE TESTS

The outcome was the development of AKI, primarily based on serum creatinine level (definition varied across studies).

RESULTS

We analyzed data from 19 studies and 11 countries involving 3,336 patients. Of these studies, 13 could be included in the meta-analysis. Across all settings, the diagnostic OR for serum CysC level to predict AKI was 27.7 (95% CI, 12.8-59.8), with sensitivity and specificity of 0.86 and 0.82, respectively. The area under the receiver operating characteristic curve (AUROC) of serum CysC levelto predict AKI was 0.87 (95% CI, 0.81-0.93). In an analysis excluding studies that did not clearly define the measurement time point, early serum CysC (within 24 hours after renal insult or intensive care unit admission) remained of diagnostic value. For the diagnostic value of urinary CysC excretion, the diagnostic OR was 3.10 (95% CI, 2.00-4.81), with sensitivity and specificity of0.61 and 0.67, respectively. TheAUROC of urinary CysC excretion to predict AKI was 0.67 (95% CI, 0.63-0.71) [corrected].

LIMITATIONS

Variation in criteria for definitions of index and reference tests, absence of measured glomerular filtration rate in most studies.

CONCLUSION

Serum CysC appears to be a good biomarker in the prediction of AKI, whereas urinary CysC excretion has only moderate diagnostic value.

Glomerular hyperfiltration and albuminuria in children with sickle cell anemia

Early manifestations of sickle nephropathy include glomerular hyperfiltration and proteinuria, typically microalbuminuria. Over time, a subset of patients develops histologic changes, decreased glomerular filtration, and ultimately renal failure. This study was designed to determine the rate of glomerular hyperfiltration and prevalence of albuminuria in a cross-sectional analysis of untreated children with sickle cell anemia (SCA), and to identify correlates of both complications. Measured glomerular filtration rate (GFR) by plasma clearance of 99-technetium diethylenetriaminepentaacetate was compared to GFR estimates calculated from published formulas. Eighty-five children (mean age 9.4 ± 4.8 years) were studied; 76% had glomerular hyperfiltration with mean GFR = 154 ± 37 ml/min/1.73 m(2). GFR declined in teenage years and was significantly correlated with increased serum cystatin C levels and higher systolic blood pressure. Measured GFR had only modest correlations with GFR estimates (Pearson correlation coefficients ≤0.5). Albuminuria, usually microalbuminuria, occurred in 15.9% and was associated with higher diastolic blood pressure and lower white blood cell and absolute neutrophil counts. Cystatin C levels inversely reflect GFR changes and are associated with albuminuria; serial monitoring may provide a sensitive and accurate marker of nephropathy in children with SCA.

A comparison of alternative serum biomarkers with creatinine for predicting allograft function after kidney transplantation

BACKGROUND

The role of serum cystatin C (Scyc), neutrophil gelatinase-associated lipocalin, and interleukin-18 in predicting early graft function after kidney transplant is poorly defined.

METHODS

We conducted a multicenter prospective cohort study of deceased-donor kidney transplants. We collected serial blood samples for the first 3 days of transplant and monitored need for dialysis within 1 week and graft function at 3 months after transplant.

RESULTS

Among 78 recipients with serum biomarker measurements, 26 had delayed graft function (DGF; hemodialysis within 1 week of transplant). Of those not dialyzed, 29 had slow graft function (serum creatinine [Scr] reduction from transplantation to day 7 <70%), and 23 had immediate graft function (IGF; reduction in Scr ≥70%). Scyc levels were statistically different between groups by the first postoperative day (POD), whereas Scr levels were not. Serum neutrophil gelatinase-associated lipocalin and serum interleukin-18 levels were not different between groups. Scyc on the first POD demonstrated good utility for predicting DGF and non-IGF (DGF or slow graft function) with areas under the receiver-operating characteristic curve of 0.83 and 0.85, respectively. Areas under the receiver-operating characteristic curve for predicting DGF and non-IGF using Scr on the first POD were 0.65 and 0.53, respectively. Substituting Scyc for Scr in a clinical algorithm improved its utility for predicting DGF or non-IGF, with adjusted odds ratios of 2.4 and 3.3 for Scyc levels on the first POD. The change in Scyc during the first POD demonstrated a dose-response relationship with 3-month graft function.

CONCLUSIONS

Scyc outperforms Scr as a predictor of early graft function after deceased-donor kidney transplant.

Urinary biomarkers in prenatally diagnosed unilateral hydronephrosis

The introduction of prenatal ultrasonography as a screening method entails an increasing number of infants diagnosed with prenatal hydronephrosis. Ureteropelvic junction obstruction accounts for 35% of prenatal hydronephrotic cases. Urinary tract obstruction that occurs during early kidney development affects renal morphogenesis, maturation and growth, and in the most severe cases this will ultimately cause renal insufficiency. A major challenge in the clinical management of these patients is to preserve renal function by selection of the 15%-20% who require early surgical intervention, leaving those for whom watchful waiting may be appropriate because of spontaneous resolution/stabilization without significant loss of renal function. Today, this requires medical surveillance, including repetitive invasive diuretic renograms relying on arbitrary threshold values, and therefore there is a need for non-arbitrary, non-invasive urinary biomarkers that may be used as predictors for renal structural changes and/or decreasing renal function, and thereby provide the surgeon with more clear indications for surgical intervention. In this review, we summarize the currently well-known facts about urinary biomarkers in ureteropelvic junction obstruction concerning renal function, and we also suggest potential novel urinary biomarkers.

Plasma cystatin C and acute kidney injury after cardiopulmonary bypass

BACKGROUND AND OBJECTIVES

Little is known about the performance of plasma cystatin C (CysC) in patients undergoing cardiopulmonary bypass (CPB) and its utility in the early diagnosis of acute kidney injury (AKI). In this post hoc analysis, the goal was to determine whether plasma cystatin C, measured 2 hours after the conclusion of CPB, is a reliable marker of AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Plasma CysC was measured in 150 patients undergoing CPB at the following times: preoperatively, 2 hours after the conclusion of CPB, postoperative day 1, and postoperative day 2. Plasma CysC levels were related to the development of AKI as defined by an increase in serum creatinine of >or=50% or >or=0.3 mg/dl from baseline up to 3 days postoperative. Mixed linear models were used to evaluate the relationship of serial plasma CysC values with AKI. The discriminatory capacity of plasma CysC was estimated using receiver operating characteristic curves. Logistic regression was utilized to assess the adjusted relationship between plasma CysC and subsequent AKI.

RESULTS

AKI developed in 47 (31.3%) patients. Plasma CysC was higher at all times among patients who developed AKI compared with those who did not (P < 0.0001). The discriminatory capacity of plasma CysC measured preoperatively and 2 hours after the conclusion of CPB was modest.

CONCLUSIONS

Serial measures of plasma CysC are highly correlated with the development of AKI. However, the discriminatory capacity of plasma CysC as an early marker of AKI remains limited.

Tubular proteinuria in acute kidney injury: a critical evaluation of current status and future promise

The diagnosis and prognosis of acute kidney injury (AKI) by current clinical means is inadequate. Biomarkers of kidney injury that are easily measured and unaffected by physiological variables could revolutionize the management of AKI. Our objective was to systematically review the diagnostic and prognostic utility of urine and serum biomarkers of AKI in humans. We searched MEDLINE, PubMed and EMBASE databases (January 2000–August 2009) for biomarker studies that could be classified into the following categories: (a) confirmation of the diagnosis of established AKI, (b) early prediction of AKI, and (c) prognostication of AKI. We identified 54 manuscripts published since 2000 that met our inclusion and exclusion criteria. Urinary interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and N-acetyl- β-d-glucosaminidase (NAG) are potentially useful biomarkers for the diagnosis of established AKI. Urinary NGAL, IL-18, and liver-type fatty acid binding protein, and serum NGAL and cystatin C represent the most promising biomarkers for early prediction of AKI. Urinary cystatin C, α1-microglobulin, NAG and retinol-binding protein may be useful to predict severity and outcomes of AKI. In conclusion, we identified several studies of promising biomarkers for the diagnosis, prediction and prognostication of AKI. However, we note several limitations, including small sample sizes, inadequate gold standard, exclusion of patients with chronic kidney disease, incomplete statistical analyses, utilization of research-based assays and a paucity of studies examining prediction for clinical outcomes. Future studies will need to address these limitations in order for further progress to be made.

Serum cystatin C in elderly cardiac surgery patients

BACKGROUND

Elderly cardiac surgery patients are more prone to develop postoperative acute kidney injury (AKI). The common clinical glomerular filtration marker, plasma creatinine, is considered to be inadequate to discover AKI in its early stage. The aim of this study was to determine if serum cystatin C can detect mild renal failure earlier than plasma creatinine.

METHODS

From 110 cardiac surgery patients aged 70 or greater years, serum cystatin C and plasma creatinine samples were collected preoperatively and on postoperative days 1 to 5. Their urine output, creatinine, and estimated glomerular filtration rate were calculated and AKI was determined by the risk-injury-failure-loss-end-stage kidney disease criteria (RIFLE). The correlation of plasma creatinine and serum cystatin C to AKI was calculated.

RESULTS

After cardiac surgery, 62 of the 110 patients (56.4%) developed AKI according to the RIFLE classification. In this group, both serum cystatin C and plasma creatinine peaked on postoperative day 3. Cystatin C and creatinine correlated equally with AKI at different time points calculated with receiver operating characteristic curves. On postoperative day 1 the area under the curve (AUC) for creatinine was 0.66 (0.55 to 0.76) and for cystatin C 0.71 (0.61 to 0.81); Delta AUC 0.05 (0.01 to 0.12), p = 0.11. On postoperative day 2 the AUC for creatinine was 0.74 (0.64 to 0.83) and for cystatin was C 0.77 (0.68 to 0.86); Delta AUC -0.03 (-0.09 to 0.03), p = 0.32.

CONCLUSIONS

Elderly cardiac surgery patients have a high incidence of AKI, as defined by the RIFLE criteria. After cardiac surgery serum cystatin C and plasma creatinine detected AKI similarly.

Assessment of glomerular filtration rate by serum cystatin C in patients undergoing coronary artery bypass grafting

BACKGROUND

Assessment of renal function in patients undergoing coronary artery bypass grafting (CABG) is important. Cystatin C has been proposed as an improved indicator of renal function. The aim of this study was to assess cystatin C as an early marker of changes in glomerular filtration rate (GFR) after CABG.

METHODS

Blood samples were collected from 61 CABG patients at different time points. Using (51)Cr-ethylenediaminetetraacetic acid ((51)Cr-EDTA) clearance as a 'gold standard', we compared the correlations and non-parametric receiver operator characteristic curves of serum cystatin C, serum creatinine and 24 h creatinine clearance (Ccr).

RESULTS

The inverse of cystatin C correlated better with (51)Cr-EDTA than those of serum creatinine and Ccr (r = 0.8578, 0.6771 and 0.6929, respectively). Cystatin C exhibited significantly superior diagnostic accuracy for detecting GFR <80 mL/min/1.73 m(2) compared with serum creatinine (P = 0.013) and Ccr (P = 0.025); for detecting GFR <60 mL/min/1.73 m(2), cystatin C had similar diagnostic accuracy to Ccr (P = 0.812) but was superior to creatinine (P = 0.033). At the best cut-off value, cystatin C had sensitivity 89% and specificity 93% for detecting GFR <80 mL/min/1.73 m(2), sensitivity 86% and specificity 96% for detecting GFR <60 mL/min/1.73 m(2).

CONCLUSIONS

Cystatin C is a better marker for detecting small temporary changes of GFR in CABG patients. This may allow better identification of patients with renal impairment.

Novel biomarkers early predict the severity of acute kidney injury after cardiac surgery in adults

BACKGROUND

The purpose of this study was to investigate the ability of neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, and their combination in predicting the duration and severity of acute kidney injury (AKI) after cardiac surgery in adults.

METHODS

Using data from a prospective observational study of 100 adult cardiac surgical patients, we correlated early postoperative concentrations of plasma NGAL and serum cystatin C with the duration (time during which AKI persisted according to the Acute Kidney Injury Network criteria) and severity of AKI (change in serum creatinine) and with length of stay in intensive care.

RESULTS

We found a mean AKI duration of 67.2 +/- 41.0 hours which was associated with prolonged hospitalization (p < 0.001). NGAL, cystatin C, and their combination on arrival in intensive care correlated with subsequent AKI duration (all p < 0.01) and severity (all p < 0.001). The area under the receiver operating characteristic curve for AKI prediction was 0.77 (95% confidence interval: 0.63 to 0.91) for NGAL and 0.76 (95% confidence interval: 0.61 to 0.91) for cystatin C on arrival in intensive care. Both markers also correlated with length of stay in intensive care (p = 0.037; p = 0.001). Neutrophil gelatinase-associated lipocalin and cystatin C were independent predictors of AKI duration and severity and of length of stay in intensive care (all p < 0.05). The value of cystatin C on arrival in intensive care appeared to be due to a carry-over effect from preoperative values.

CONCLUSIONS

Immediately postoperatively, NGAL and cystatin C correlated with and were independent predictors of duration and severity of AKI and duration of intensive care stay after adult cardiac surgery. The combination of both renal biomarkers did not add predictive value.

Novel and conventional serum biomarkers predicting acute kidney injury in adult cardiac surgery--a prospective cohort study

OBJECTIVE

To compare the value of novel with conventional serum biomarkers in the prediction of acute kidney injury (AKI) in adult cardiac surgical patients according to preoperative renal function.

DESIGN

Single-center, prospective observational study.

SETTING

Tertiary hospital.

PATIENTS

One hundred adult cardiac surgical patients.

MEASUREMENTS AND MAIN RESULTS

We measured concentrations of plasma neutrophil gelatinase-associated lipocalin (NGAL), and serum cystatin C, and creatinine and urea at baseline, on arrival in the intensive care unit (ICU) and at 24 hours postoperatively. We assessed such biomarkers in relation to the development of AKI (>50% increase in creatinine from baseline) and to a composite end point (need for renal replacement therapy and in-hospital mortality). We defined an area under the receiver operating characteristic curve of 0.60-0.69 as poor, 0.70-0.79 as fair, 0.80-0.89 as good, and 0.90-1.00 as excellent in terms of predictive value. On arrival in ICU, plasma NGAL and serum cystatin C were of good predictive value, but creatinine and urea were of poor predictive value. After exclusion of patients with preoperative renal impairment (estimated glomerular filtration rate <60 mL/min), the predictive performance for AKI of all renal biomarkers on arrival in ICU remained unchanged except for cystatin C, which was of fair value in such patients. At 24 hours postoperatively, all renal biomarkers were of good predictive value. On arrival in ICU, novel biomarkers were superior to conventional biomarkers (p < 0.05). Plasma NGAL (p = 0.015) and serum cystatin C (p = 0.007) were independent predictors of AKI and of excellent value in the prediction of the composite end point.

CONCLUSIONS

Early postoperative measurement of plasma NGAL was of good value in identifying patients who developed AKI after adult cardiac surgery. Plasma NGAL and serum cystatin C were superior to conventional biomarkers in the prediction of AKI and were also of prognostic value in this setting.

The metabolic and renal effects of adrenaline and milrinone in patients with myocardial dysfunction after coronary artery bypass grafting

INTRODUCTION

Myocardial dysfunction necessitating inotropic support is a typical complication after on-pump cardiac surgery. This prospective, randomized pilot study analyzes the metabolic and renal effects of the inotropes adrenaline and milrinone in patients needing inotropic support after coronary artery bypass grafting (CABG).

METHODS

During an 18-month period, 251 patients were screened for low cardiac output upon intensive care unit (ICU) admission after elective, isolated CABG surgery. Patients presenting with a cardiac index (CI) of less than 2.2 liters/minute per square meter upon ICU admission - despite adequate mean arterial (titrated with noradrenaline or sodium nitroprusside) and filling pressures - were randomly assigned to 14-hour treatment with adrenaline (n = 7) or milrinone (n = 11) to achieve a CI of greater than 3.0 liters/minute per square meter. Twenty patients not needing inotropes served as controls. Hemodynamics, plasma lactate, pyruvate, glucose, acid-base status, insulin requirements, the urinary excretion of alpha-1-microglobuline, and creatinine clearance were determined during the treatment period, and cystatin-C levels were determined up to 48 hours after surgery (follow-up period).

RESULTS

After two to four hours after ICU admission, the target CI was achieved in both intervention groups and maintained during the observation period. Plasma lactate, pyruvate, the lactate/pyruvate ratio, plasma glucose, and insulin doses were higher (p < 0.05) in the adrenaline-treated patients than during milrinone or control conditions. The urinary excretion of alpha-1-microglobuline was higher in the adrenaline than in the control group 6 to 14 hours after admission (p < 0.05). No between-group differences were observed in creatinine clearance, whereas plasma cystatin-C levels were significantly higher in the adrenaline than in the milrinone or the control group after 48 hours (p < 0.05).

CONCLUSION

This suggests that the use of adrenaline for the treatment of postoperative myocardial dysfunction - in contrast to treatment with the PDE-III inhibitor milrinone - is associated with unwarranted metabolic and renal effects.

Biomarkers for the diagnosis and risk stratification of acute kidney injury: a systematic review

The diagnosis of acute kidney injury (AKI) is usually based on changes in serum creatinine, but such measurements are a poor marker of acute deterioration in kidney function. We performed a systematic review of publications that evaluated the accuracy and reliability of serum and urinary biomarkers in human subjects when used for the diagnosis of established AKI or early AKI, or to risk stratify patients with AKI. Two reviewers independently searched the MEDLINE and EMBASE databases (January 2000-March 2007) for studies pertaining to biomarkers for AKI. Studies were assessed for methodologic quality. In total, 31 studies evaluated 21 unique serum and urine biomarkers. Twenty-five of the 31 studies were scored as having 'good' quality. The results of the studies indicated that serum cystatin C, urine interleukin-18 (IL-18), and urine kidney injury molecule-1 (KIM-1) performed best for the differential diagnosis of established AKI. Serum cystatin C and urine neutrophil gelatinase-associated lipocalin, IL-18, glutathione-S-transferase-pi, and gamma-glutathione-S-transferase performed best for early diagnosis of AKI. Urine N-acetyl-beta-D-glucosaminidase, KIM-1, and IL-18 performed the best for mortality risk prediction after AKI. In conclusion, published data from studies of serum and urinary biomarkers suggest that biomarkers may have great potential to advance the fields of nephrology and critical care. These biomarkers need validation in larger studies, and the generalizability of biomarkers to different types of AKI as well as the incremental prognostic value over traditional clinical variables needs to be determined.

How to estimate GFR-serum creatinine, serum cystatin C or equations?

Plasma or serum creatinine is the most commonly used diagnostic marker for the estimation of glomerular filtration rate (GFR) in clinical routine. Due to substantial pre-analytical and analytical interferences and limitations, creatinine cannot be considered accurate. Besides, the diagnostic sensitivity to detect moderate GFR reduction is insufficient. Equations to estimate GFR based on serum creatinine have been introduced, which included anthropometric data to compensate for the limitations of creatinine. Most validated and applied are the MDRD and the Cockcroft-Gault equation for adults, and the Schwartz equation for children. These equations can be calculated at the bedside or issued by the laboratory and provide accurate GFR estimates from 20 to 60 mL/min/1.73 m(2) with good accuracy but moderate to poor bias and precision. Further limiting is the lack of creatinine reference methods and of calibration material. Lately, the low molecular weight protein cystatin C was introduced as a GFR estimate superior to creatinine. In particular, serum cystatin C is sensitive to detect mild GFR reduction between 60 and 90 mL/min/1.73 m(2). However, no reference method and no uniform calibration material exist for cystatin C either. Further limitations are the effect of thyroid dysfunction, of high glucocorticoid doses and potentially the presence of cardiovascular diseases on cystatin C levels. To evade these obstacles and to further improve GFR estimation, cystatin C-based equations have been proposed, which seem to be superior to creatinine-based ones. However, this issue requires further evaluation. We propose a panel of GFR markers to facilitate the detection of reduced GFR at various stages and in different populations; this however needs to be extended and refined in the near future. In principle, clinicians should be aware of the limitations of and cautioned not to overrate estimated GFR by single markers or calculated by equations and should not entirely rely on GFR estimates to make precise clinical decisions.