Neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker for acute renal injury after cardiac surgery

Early diagnosis of pancreatic cancer: neutrophil gelatinase-associated lipocalin as a marker of pancreatic intraepithelial neoplasia

Pancreatic cancer is a highly lethal malignancy with a dismal 5-year survival of less than 5%. The scarcity of early biomarkers has considerably hindered our ability to launch preventive measures for this malignancy in a timely manner. Neutrophil gelatinase-associated lipocalin (NGAL), a 24-kDa glycoprotein, was reported to be upregulated nearly 27-fold in pancreatic cancer cells compared to normal ductal cells in a microarray analysis. Given the need for biomarkers in the early diagnosis of pancreatic cancer, we investigated the expression of NGAL in tissues with the objective of examining if NGAL immunostaining could be used to identify foci of pancreatic intraepithelial neoplasia, premalignant lesions preceding invasive cancer. To examine a possible correlation between NGAL expression and the degree of differentiation, we also analysed NGAL levels in pancreatic cancer cell lines with varying grades of differentiation. Although NGAL expression was strongly upregulated in pancreatic cancer, and moderately in pancreatitis, only a weak expression could be detected in the healthy pancreas. The average composite score for adenocarcinoma (4.26+/-2.44) was significantly higher than that for the normal pancreas (1.0) or pancreatitis (1.0) (P<0.0001). Further, although both well- and moderately differentiated pancreatic cancer were positive for NGAL, poorly differentiated adenocarcinoma was uniformly negative. Importantly, NGAL expression was detected as early as the PanIN-1 stage, suggesting that it could be a marker of the earliest premalignant changes in the pancreas. Further, we examined NGAL levels in serum samples. Serum NGAL levels were above the cutoff for healthy individuals in 94% of pancreatic cancer and 62.5% each of acute and chronic pancreatitis samples. However, the difference between NGAL levels in pancreatitis and pancreatic cancer was not significant. A ROC curve analysis revealed that ELISA for NGAL is fairly accurate in distinguishing pancreatic cancer from non-cancer cases (area under curve=0.75). In conclusion, NGAL is highly expressed in early dysplastic lesions in the pancreas, suggesting a possible role as an early diagnostic marker for pancreatic cancer. Further, serum NGAL measurement could be investigated as a possible biomarker in pancreatitis and pancreatic adenocarcinoma.

Contrast-induced acute kidney injury

Cardiac angiography and coronary/vascular interventions depend on iodinated contrast media and consequently pose the risk of contrast-induced acute kidney injury (AKI). This is an important complication that accounts for a significant number of cases of hospital-acquired renal failure, with adverse effects on prognosis and health care costs. The epidemiology and pathogenesis of contrast-induced AKI, baseline renal function measurement, risk assessment, identification of high-risk patients, contrast medium use, and preventive strategies are discussed in this report. An advanced algorithm is suggested for the risk stratification and management of contrast-induced AKI as it relates to patients undergoing cardiovascular procedures. Contrast-induced AKI is likely to remain a significant challenge for cardiologists in the future because the patient population is aging and chronic kidney disease and diabetes are becoming more common.

Worsening renal function in children hospitalized with decompensated heart failure: evidence for a pediatric cardiorenal syndrome?

OBJECTIVES

The purpose of this study was to determine the incidence of renal insufficiency in children hospitalized with acute decompensated heart failure and whether worsening renal function is associated with adverse cardiovascular outcome.

DESIGN

Prospective observational cohort study.

SETTING

Single-center children's hospital.

PATIENTS

All pediatric patients from birth to age 21 yrs admitted to our institution with acute decompensated heart failure from October 2003 to October 2005.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Acute decompensated heart failure was defined as new-onset or acute exacerbation of heart failure signs or symptoms requiring hospitalization and inpatient treatment. We required that heart failure be attributable to ventricular dysfunction only. Worsening renal function was defined as an increase in serum creatinine by > or = 0.3 mg/dL during hospitalization. Sixty-three patients (35 male, 28 female) comprised 73 patient hospitalizations. Median age at admission was 10 yrs (range 0.1-20.3 yrs). Median serum creatinine at admission was 0.6 mg/dL (range 0.2-3.5 mg/dL), and median creatinine clearance was 103 mL/min/1.73 m2 (range 22-431 mL/min/1.73 m2). Serum creatinine increased during 60 of 73 (82%) patient hospitalizations (median increase 0.2 mg/dL, range 0.1-2.7 mg/dL), and worsening renal function occurred in 35 of 73 (48%) patient hospitalizations. Clinical variables associated with worsening renal function included admission serum creatinine (p = .009) and blood urea nitrogen (p = .04) and, during hospitalization, continuous infusions of dopamine (p = .028) or nesiritide (p = .007). Worsening renal function was independently associated with the combined end point of in-hospital death or need for mechanical circulatory support (adjusted odds ratio 10.2; 95% confidence interval 1.7-61.2, p = .011). Worsening renal function was also associated with longer observed length of stay (33 +/- 30 days vs. 18 +/- 25 days, p < .03).

CONCLUSIONS

These data suggest that an important cardiorenal interaction occurs in children hospitalized for acute decompensated heart failure. Renal function commonly worsens in such patients and is associated with prolonged hospitalization and in-hospital death or the need for mechanical circulatory assistance.

Serum neutrophil gelatinase-associated lipocalin (NGAL) as a marker of acute kidney injury in critically ill children with septic shock

OBJECTIVE

To validate serum neutrophil gelatinase-associated lipocalin (NGAL) as an early biomarker for acute kidney injury in critically ill children with septic shock.

DESIGN

Observational cohort study.

SETTING

Fifteen North American pediatric intensive care units (PICUs).

PATIENTS

A total of 143 critically ill children with systemic inflammatory response syndrome (SIRS) or septic shock and 25 healthy controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Serum NGAL was measured during the first 24 hrs of admission to the PICU. Acute kidney injury was defined as a blood urea nitrogen concentration >100 mg/dL, serum creatinine >2 mg/dL in the absence of preexisting renal disease, or the need for dialysis. There was a significant difference in serum NGAL between healthy children (median 80 ng/mL, interquartile ratio [IQR] 55.5-85.5 ng/mL), critically ill children with SIRS (median 107.5 ng/mL, IQR 89-178.5 ng/mL), and critically ill children with septic shock (median 302 ng/mL, IQR 151-570 ng/mL; p < .001). Acute kidney injury developed in 22 of 143 (15.4%) critically ill children. Serum NGAL was significantly increased in critically ill children with acute kidney injury (median 355 ng/mL, IQR 166-1322 ng/mL) compared with those without acute kidney injury (median 186 ng/mL, IQR 98-365 ng/mL; p = .009).

CONCLUSIONS

Serum NGAL is a highly sensitive but nonspecific predictor of acute kidney injury in critically ill children with septic shock. Further validation of serum NGAL as a biomarker of acute kidney injury in this population is warranted.

Lack of alphavbeta5 integrin receptor or its ligand MFG-E8: distinct effects on retinal function

BACKGROUND/AIMS

Diurnal phagocytosis of spent photoreceptor outer segment fragments by the retinal pigment epithelium (RPE) is critical for vision. We recently identified an important role for alphavbeta5 integrin receptors and their ligand Milk fat globule-EGF factor 8 (MFG-E8) in RPE phagocytosis.

METHODS

We compared RPE phagocytosis and retinal function between mice deficient in alphavbeta5 integrin receptors and mice deficient in the secreted integrin ligand MFG-E8.

RESULTS

Both beta5-/- and MFG-E8-/- mice exhibit the same phagocytic defect: RPE cells retain basal uptake activity but completely lack the burst of phagocytic activity as well as the rhythmic activation of Mer tyrosine kinase that follow circadian photoreceptor shedding in wild-type RPE. Strikingly, electroretinogram photoresponses decline with age only in beta5 -/- but not in MFG-E8-/- retina.

CONCLUSION

These results identify a critical role of alphavbeta5 integrin receptors and their ligand MFG-E8 in synchronizing retinal phagocytosis. Additionally, we show that lack of alphavbeta5 receptors and MFG-E8 ligand have distinct consequences for retinal function. These intriguing results suggest that loss of phagocytic rhythm is not solely responsible for the age-related blindness of beta5-/- mice.

Acute kidney injury

Diagnosis and classification of acute pathology in the kidney are major clinical problems. Azotemia and oliguria represent not only disease but normal responses of the kidney to extracellular volume depletion or decreased renal blood flow. Changes in urine output and glomerular filtration rate are therefore neither necessary nor sufficient for the diagnosis of renal pathology. However, no simple alternative for the diagnosis currently exists. By examining both glomerular and tubular function, clinicians routinely make inferences not only on the presence of renal dysfunction but also on its cause. However, pure prerenal physiology is unusual in hospitalized patients, and its effects are not necessary benign. Sepsis, the most common condition associated with acute renal failure in the intensive care unit, may alter renal function without any characteristic changes in urine indices, and classification of these abnormalities as prerenal will undoubtedly lead to incorrect management decisions. The clinical syndrome known as acute tubular necrosis does not actually manifest the morphologic changes that the name implies. A precise biochemical definition of acute renal failure has never been proposed, and until recently, there has been no consensus on the diagnostic criteria or clinical definition. Depending on the definition used, acute renal failure has been reported to affect from 1% to 25% of intensive care unit patients and has led to mortality rates ranging from 15% to 60%. From this chaos, two principles emerged: first, the need for a standard definition and, second, the need to classify the severity of the syndrome rather than only consider its most severe form. The RIFLE criteria were developed to achieve these goals, and the term acute kidney injury has been proposed to encompass the entire spectrum of the syndrome, from minor changes in renal function to requirement for renal replacement therapy. Thus, acute kidney injury is not acute tubular necrosis, nor is it renal failure. Small changes in kidney function in hospitalized patients are important and are associated with significant changes in short-term and possibly long-term outcomes. The RIFLE criteria provide a uniform definition of acute kidney injury and have now been validated in numerous studies.

N-GAL: diagnosing AKI as soon as possible

Early diagnosis of acute kidney injury (AKI) is often problematic, due to the lack of suitable early biomarkers of renal damage and kidney function. Neutrophil gelatinase-associated lipocalin (NGAL) as an early marker of AKI partially overcomes such limitations and seems to demonstrate that diagnosing AKI in its early stages is possible and useful. Using genomic and protein microarray technology, a series of molecules have been identified as potential markers for AKI; among them NGAL has been demonstrated to rise significantly in patients with AKI but not in the corresponding controls. Furthermore, this rise in NGAL occurs in various studies at 24 to 48 hours before the rise in creatinine is observed. NGAL both in urine and plasma is an excellent early marker of AKI with an area under the receiver operator characteristic curve (AUC) in the range of 0.9. The study of Zappitelli et al. in critically ill children combines for the first time the new RIFLE classification (Risk, Injury, Failure, Loss, End-stage renal disease) of AKI with the validation of NGAL as an early marker of kidney injury. This innovative approach brings a new hope for a timely diagnosis of AKI and thus a timely institution of measures for prevention and protection.

Plasma neutrophil gelatinase-associated lipocalin predicts acute kidney injury, morbidity and mortality after pediatric cardiac surgery: a prospective uncontrolled cohort study

Introduction

Acute kidney injury (AKI) is a frequent complication of cardiopulmonary bypass (CPB). The lack of early biomarkers has impaired our ability to intervene in a timely manner. We previously showed in a small cohort of patients that plasma neutrophil gelatinase-associated lipocalin (NGAL), measured using a research enzyme-linked immunosorbent assay, is an early predictive biomarker of AKI after CPB. In this study we tested whether a point-of-care NGAL device can predict AKI after CPB in a larger cohort.

Methods

First, in a cross-sectional pilot study including 40 plasma samples (NGAL range 60 to 730 ng/ml) and 12 calibration standards (NGAL range 0 to 1,925 ng/ml), NGAL measurements by enzyme-linked immunosorbent assay and by Triage^® NGAL Device (Biosite Inc., San Diego, CA, USA) were highly correlated (r = 0.94). Second, in a subsequent prospective uncontrolled cohort study, 120 children undergoing CPB were enrolled. Plasma was collected at baseline and at frequent intervals for 24 hours after CPB, and analyzed for NGAL using the Triage^® NGAL device. The primary outcome was AKI, which was defined as a 50% or greater increase in serum creatinine.

Results

AKI developed in 45 patients (37%), but the diagnosis using serum creatinine was delayed by 2 to 3 days after CPB. In contrast, mean plasma NGAL levels increased threefold within 2 hours of CPB and remained significantly elevated for the duration of the study. By multivariate analysis, plasma NGAL at 2 hours after CPB was the most powerful independent predictor of AKI (β = 0.004, P < 0.0001). For the 2-hour plasma NGAL measurement, the area under the curve was 0.96, sensitivity was 0.84, and specificity was 0.94 for prediction of AKI using a cut-off value of 150 ng/ml. The 2 hour postoperative plasma NGAL levels strongly correlated with change in creatinine (r = 0.46, P < 0.001), duration of AKI (r = 0.57, P < 0.001), and length of hospital stay (r = 0.44, P < 0.001). The 12-hour plasma NGAL strongly correlated with mortality (r = 0.48, P = 0.004) and all measures of morbidity mentioned above.

Conclusion

Accurate measurements of plasma NGAL are obtained using the point-of-care Triage^® NGAL device. Plasma NGAL is an early predictive biomarker of AKI, morbidity, and mortality after pediatric CPB.

Emerging urinary biomarkers in the diagnosis of acute kidney injury

BACKGROUND: Acute kidney injury (AKI) represents a common and devastating problem in clinical medicine. The lack of early biomarkers for AKI has led to a delay in initiating potentially effective therapies. OBJECTIVE: Identification of novel urinary biomarkers for AKI that have progressed to the clinical phase of the biomarker discovery process. METHODS: A literature review (PubMed, MedLine) from 2000 to the present. RESULTS/CONCLUSIONS;: The most promising AKI biomarkers include neutrophil gelatinase-associated lipocalin, IL-18, kidney injury molecule-1 and liver-type fatty acid binding protein. Studies to validate the sensitivity and specificity of these biomarkers in clinical samples from large cohorts and from multiple clinical situations are in progress, facilitated by the development of commercial tools for their measurement.

Neutrophil gelatinase-associated lipocalin (NGAL) as a marker of kidney damage

Neutrophil gelatinase-associated lipocalin (NGAL) is a protein belonging to the lipocalin superfamily initially found in activated neutrophils, in accordance with its role as an innate antibacterial factor. However, it subsequently was shown that many other types of cells, including in the kidney tubule, may produce NGAL in response to various injuries. The increase in NGAL production and release from tubular cells after harmful stimuli of various kinds may have self-defensive intent based on the activation of specific iron-dependent pathways, which in all probability also represent the mechanism through which NGAL promotes kidney growth and differentiation. NGAL levels predict the future appearance of acute kidney injury after treatments potentially detrimental to the kidney and even the acute worsening of unstable nephropathies. Furthermore, recent evidence also suggests that NGAL somehow may be involved in the pathophysiological process of chronic renal diseases, such as polycystic kidney disease and glomerulonephritis. NGAL levels clearly correlate with severity of renal impairment, probably expressing the degree of active damage underlying the chronic condition. For all these reasons, NGAL may become one of the most promising next-generation biomarkers in clinical nephrology and beyond.

Expression of neutrophil gelatinase-associated lipocalin in calcium-induced keratinocyte differentiation

In a previous search for the differentially expressed genes in keratinocyte differentiation, we identified neutrophil gelatinase-associated lipocalin (NGAL) as a calcium-induced gene. In this study, we further verified the expression of NGAL in cultured keratinocytes as well as in several skin diseases. Reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and ELISA clearly showed that NGAL expression was markedly increased in calcium-induced keratinocyte differentiation in vitro. However, in our previous report, NGAL expression was not detected in normal skin tissue except for hair follicle by in situ hybridization and immunohistochemistry, indicating the difference of cell status between in vitro and in vitro conditions. Interestingly, NGAL expression was highly increased in psoriasis-like inflammatory disorders (lichen planus and pityriasis rubura pilaris) and skin cancers (keratoacanthoma and squamous cell carcinoma), implying that NGAL may be related with the epidermal hyperplasia. Collectively, these results reveal the potential importance of NGAL in the maintenance of skin homeostasis.

Serum neutrophil gelatinase-associated lipocalin as a marker of renal function in hypertensive and normotensive patients with coronary artery disease

AIM

Hypertension is one of the risk factors for cardiovascular diseases. The kidneys could be a victim and/or culprit of hypertension. Recently, the value of neutrophil gelatinase-associated lipocalin (NGAL) was highlighted as a novel marker for early detection of acute renal damage. Therefore, the aim of the study was to assess whether hypertension could affect NGAL and cystatin C levels in patients with normal serum creatinine (lower than 1.5 mg/dL in males and 1.2 mg/dL in females) and stable coronary artery disease.

METHODS

Serum, urinary NGAL, cystatin C and estimated glomerular filtration rate (eGFR; Modification of Diet in Renal Disease study (MDRD) and Cockcroft-Gault formulas) were evaluated in hypertensive, normotensive patients with stable coronary heart disease and healthy volunteers.

RESULTS

Normotensives had significantly lower NGAL than hypertensives. Serum cystatin C was significantly lower in normotensives than in hypertensives. Urinary NGAL did not differ significantly between these groups. Despite similar serum creatinine levels, eGFR (MDRD and Cockcroft-Gault formulas) was significantly higher in normotensives than in hypertensives. Serum NGAL was related, in univariate analysis, to serum creatinine, urea, urinary NGAL, haemoglobin, haematocrit, duration of hypertension, age, eGFR by MDRD and Cockcroft-Gault, and cystatin C.

CONCLUSION

Hypertension is associated with kidney injury as reflected by elevated serum NGAL and cystatin C. It is noteworthy that despite normal serum creatinine, eGFR is relatively low suggesting impaired renal function. Therefore, NGAL needs to be investigated as a potential early marker for impaired kidney function/kidney injury, especially in patients with another risk factor for kidney damage, namely coronary artery disease.

Early detection of acute kidney injury: emerging new biomarkers

Acute kidney injury (AKI) has recently become the preferred term to describe the syndrome of acute renal failure (ARF) with 'failure' or 'ARF' restricted to patients who have AKI and need renal replacement therapy.(1) This allows capture of the broader clinical spectrum of modest reductions in creatinine, which are themselves known to be associated with major increases in both short- and long-term mortality risk.(2-5) It is hoped that this change in nomenclature will facilitate an expansion of our understanding of the underlying pathophysiology and also facilitate definitions of AKI, which allow comparisons among clinical trials of patients with similar duration and severity of illness. This review will cover the need for early detection of AKI and the role of urinary and plasma biomarkers, including enzymuria. The primary message is that use of existing criteria to diagnose AKI, namely elevation of the serum creatinine with or without oliguria, results in identification that is too late to allow successful intervention. New biomarkers are essential to change the dire prognosis of this common condition.

Urine neutrophil gelatinase-associated lipocalin is an early marker of acute kidney injury in critically ill children: a prospective cohort study

Introduction

Serum creatinine is a late marker of acute kidney injury (AKI). Urine neutrophil gelatinase-associated lipocalin (uNGAL) is an early marker of AKI, where the timing of kidney injury is known. It is unknown whether uNGAL predicts AKI in the general critical care setting. We assessed the ability of uNGAL to predict AKI development and severity in critically ill children.

Methods

This was a prospective cohort study of critically ill children. Children aged between 1 month and 21 years who were mechanically ventilated and had a bladder catheter inserted were eligible. Patients with end-stage renal disease or who had just undergone kidney transplantation were excluded. Patients were enrolled within 24 to 48 hours of initiation of mechanical ventilation. Clinical data and serum creatinine were collected daily for up to 14 days from enrollment, and urine was collected once daily for up to 4 days for uNGAL measurement. AKI was graded using pRIFLE (pediatric modified Risk, Injury, Failure, Loss, End Stage Kidney Disease) criteria. Day 0 was defined as the day on which the AKI initially occurred, and pRIFLEmax was defined as the worst pRIFLE AKI grade recorded during the study period. The χ² test was used to compare associations between categorical variables. Mann-Whitney and Kruskal-Wallis tests were used to compare continuous variables between groups. Diagnostic characteristics were evaluated by calculating sensitivity and specificity, and constructing receiver operating characteristic curves.

Results

A total of 140 patients (54% boys, mean ± standard deviation Pediatric Risk of Mortality II score 15.0 ± 8.0, 23% sepsis) were included. Mean and peak uNGAL concentrations increased with worsening pRIFLEmax status (P < 0.05). uNGAL concentrations rose (at least sixfold higher than in controls) in AKI, 2 days before and after a 50% or greater rise in serum creatinine, without change in control uNGAL. The parameter uNGAL was a good diagnostic marker for AKI development (area under the receiver operating characteristic curve [AUC] 0.78, 95% confidence interval [CI] 0.62 to 0.95) and persistent AKI for 48 hours or longer (AUC 0.79, 95% CI 0.61 to 0.98), but not for AKI severity, when it was recorded after a rise in serum creatinine had occurred (AUC 0.63, 95% CI 0.44 to 0.82).

Conclusion

We found uNGAL to be a useful early AKI marker that predicted development of severe AKI in a heterogeneous group of patients with unknown timing of kidney injury.

Biomarkers of nephrotoxic acute kidney injury

Acute kidney injury (AKI) is a common condition with significant associated morbidity and mortality. Epidemiologic data suggest that a significant proportion of AKI cases is at least partially attributable to nephrotoxin exposure. This is not surprising given intrinsic renal susceptibility to toxicant-induced injury, a consequence of the unique physiologic and biochemical properties of the normally functioning kidney. A number of pathophysiologic mechanisms have been identified that mediate toxic effects on the kidney, resulting in a variety of clinical syndromes ranging from subtle changes in tubular function to fulminant renal failure. Unfortunately, standard metrics used to diagnose and monitor kidney injury, such as blood urea nitrogen and serum creatinine, are insensitive and nonspecific, resulting in delayed diagnosis and intervention. Considerable effort has been made to identify biomarkers that will allow the earlier diagnosis of AKI. Further characterization of these candidate biomarkers will clarify their utility in the setting of acute nephrotoxicity, define new diagnostic and prognostic paradigms for kidney injury, facilitate clinical trials, and lead to novel effective therapies.

Kidney function assessment in the critically ill child: is it time to leave creatinine behind?

The accurate diagnosis of acute kidney injury (AKI) is especially problematic in critically ill patients in whom renal function is in an unsteady state, rendering creatinine-based baseline assessment measures of renal function potentially inadequate. Herrero-Morin and colleagues performed a cross-sectional analysis of the ability of cystatin C and β₂ microglobulin to reflect creatinine clearance in pediatric patients with AKI. The aim of this commentary is to review the current state of AKI clinical and translational research in the light of the results presented in that study.

Peeking into the black box: new biomarkers for acute kidney injury

The development of effective therapies for acute kidney injury (AKI) has been hindered by delayed diagnosis in the clinical setting, varying definitions of AKI, and limited prognostic information. In a study by Portilla et al., elevations in liver fatty acid-binding protein (L-FABP) were found to predict AKI in children undergoing cardiac surgery. New biomarkers offer the promise of earlier and more accurate diagnosis of AKI. Before they can be deemed clinically useful, however, they must undergo rigorous validation in multiple cohorts.

Urine NGAL predicts severity of acute kidney injury after cardiac surgery: a prospective study

BACKGROUND AND OBJECTIVES

The authors have previously shown that urine neutrophil gelatinase-associated lipocalin (NGAL), measured by a research ELISA, is an early predictive biomarker of acute kidney injury (AKI) after cardiopulmonary bypass (CPB). In this study, whether an NGAL immunoassay developed for a standardized clinical platform (ARCHITECT analyzer, Abbott Diagnostics Division, Abbott Laboratories, Abbott Park, IL) can predict AKI after CPB was tested.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a pilot study with 136 urine samples (NGAL range, 0.3 to 815 ng/ml) and 6 calibration standards (NGAL range, 0 to 1000 ng/ml), NGAL measurements by research ELISA and by the ARCHITECT assay were highly correlated (r = 0.99). In a subsequent study, 196 children undergoing CPB were prospectively enrolled and serial urine NGAL measurements obtained by ARCHITECT assay. The primary outcome was AKI, defined as a > or = 50% increase in serum creatinine.

RESULTS

AKI developed in 99 patients (51%), but the diagnosis using serum creatinine was delayed by 2 to 3 d after CPB. In contrast, mean urine NGAL levels increased 15-fold within 2 h and by 25-fold at 4 and 6 h after CPB. For the 2-h urine NGAL measurement, the area under the curve was 0.95, sensitivity was 0.82, and the specificity was 0.90 for prediction of AKI using a cutoff value of 100 ng/ml. The 2-h urine NGAL levels correlated with severity and duration of AKI, length of stay, dialysis requirement, and death.

CONCLUSIONS

Accurate measurements of urine NGAL are obtained using the ARCHITECT platform. Urine NGAL is an early predictive biomarker of AKI severity after CPB.

Diagnosis, epidemiology and outcomes of acute kidney injury

Acute kidney injury is an increasingly common and potentially catastrophic complication in hospitalized patients. Early observational studies from the 1980s and 1990s established the general epidemiologic features of acute kidney injury: the incidence, prognostic significance, and predisposing medical and surgical conditions. Recent multicenter observational cohorts and administrative databases have enhanced our understanding of the overall disease burden of acute kidney injury and trends in its epidemiology. An increasing number of clinical studies focusing on specific types of acute kidney injury (e.g., in the setting of intravenous contrast, sepsis, and major surgery) have provided further details into this heterogeneous syndrome. Despite our sophisticated understanding of the epidemiology and pathobiology of acute kidney injury, current prevention strategies are inadequate and current treatment options outside of renal replacement therapy are nonexistent. This failure to innovate may be due in part to a diagnostic approach that has stagnated for decades and continues to rely on markers of glomerular filtration (blood urea nitrogen and creatinine) that are neither sensitive nor specific. There has been increasing interest in the identification and validation of novel biomarkers of acute kidney injury that may permit earlier and more accurate diagnosis. This review summarizes the major epidemiologic studies of acute kidney injury and efforts to modernize the approach to its diagnosis.

Upregulation of neutrophil gelatinase-associated lipocalin, NGAL/Lcn2, in beta-thalassemia patients

BACKGROUND

One of the major consequences in beta- thalassemia is iron overload. Oxidative statuses have been reported in beta-thalassemia patients by several studies. It has been proven that iron plays a critical role in the formation of reactive oxygen species (ROS). More recently, we have found the induction of Lcn2/NGAL expression under oxidative stress condition. In this study, it was assumed that NGAL should be upregulated in beta-thalassemia patients because of oxidative stress condition.

METHODS

Assessment of NGAL expressions in 25 adult beta-thalassemia and 9 pediatric patients was performed by semiquantitative RT-PCR, real-time RT-PCR and ELISA.

RESULTS

Adult beta-thalassemia patients upregulated NGAL expression compared with the normal samples but no upregulation was observed in pediatric patients.

CONCLUSIONS

Upregulation may play an important role in decreasing ROS or iron in beta-thalassemia patients.

Neutrophil gelatinase-associated lipocalin as a biomarker of disease activity in pediatric lupus nephritis

We hypothesized that neutrophil gelatinase-associated lipocalin (NGAL) is an early predictive biomarker of disease activity in lupus nephritis. NGAL in serial plasma (PNGAL) and urine (UNGAL) samples was measured by enzyme-linked immunosorbent assay (ELISA) in 85 participants with pediatric systemic lupus erythematosus (pSLE), healthy children (n = 50), and children with juvenile idiopathic arthritis (JIA) (n = 30). Disease activity was measured by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Plasma and urinary NGAL were significantly increased in subjects with pSLE compared with those with JIA or with healthy controls (all p < 0.03), and unrelated to subjects' age, weight, or height. Plasma and urinary NGAL were stable in pSLE subjects with unchanged disease activity. The pSLE subjects with worsening global or renal disease activity had a mean +/- standard error (SE) increase of UNGAL (in ng/ml) of 11.5 +/- 6.4 or 36.6 +/- 12.1 (p < 0.01), corresponding to a 156% or 380% increase, respectively. PNGAL increased with worsening disease but to a much lesser degree than UNGAL [global disease activity (mean +/- SE): 7.3 +/- 6.2 or 21%; renal disease activity: 20.2 +/- 6.0 or 51%; both p = not significant]. In conclusion, NGAL in urine but not in plasma represents a novel biomarker for renal disease activity in pSLE.

Urinary IL-18 and NGAL as early predictive biomarkers in contrast-induced nephropathy after coronary angiography

BACKGROUND/AIMS

Contrast-induced nephropathy (CIN) is at present the third leading cause of hospital-acquired acute kidney injury (AKI). Traditionally, it is diagnosed by measuring the increase of the serum creatinine concentration. However, in patients with acute changes in their glomerular filtration rate, serum creatinine is an insensitive marker. This clinical study was designed to investigate whether human urinary interleukin-18 (IL-18) and neutrophil gelatinase-associated lipocalin (NGAL) are early predictive markers for AKI after coronary angiography and their correlation with later cardiac events.

METHODS

Patients undergoing coronary angiography using low-osmolar contrast medium were enrolled and then followed up for at least 17 months. Urine samples were collected before and 24 h after coronary angiography and IL-18 and NGAL levels measured by using an ELISA kit.

RESULTS

CIN was diagnosed in 13 of 150 (8.7%) patients (CIN group); 27 patients without CIN served as control group. At 24 h after the procedure, the urinary IL-18 and NGAL levels were significantly increased in the CIN group, but not in the control group (p < 0.05). The predictable time of AKI onset determined by IL-18 was 24 h earlier than determined by serum creatinine (p < 0.01). Receiver operating characteristic curve analysis showed that both IL-18 and NGAL showed a good performance in early diagnosis of CIN as compared with serum creatinine (p < 0.05). We also found that IL-18 is an independent predictive marker for later major cardiac events: relative risk = 2.09 (p < 0.01).

CONCLUSIONS

We conclude that urinary IL-18 or NGAL could be early biomarkers of CIN and that urinary IL-18 is well associated with the later cardiac outcomes in patients after coronary angiography.

A framework and key research questions in AKI diagnosis and staging in different environments

BACKGROUND AND OBJECTIVES

Acute Kidney Injury (AKI) is common worldwide, and associated with significant morbidity, mortality, and resource utilization. The RIFLE system of staging AKI correlates with survival in AKI in several settings. A similar AKI definition and staging system that also incorporates lesser degrees of serum creatinine elevation was proposed at the inaugural Acute Kidney Injury Network (AKIN) meeting in 2005. At the Second AKIN meeting in Vancouver, Canada in September 2006, our group developed a research agenda that would test the utility of these diagnostic and staging criteria to predict patient outcomes in a variety of clinical settings and patient groups.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

Three-day, international, consensus conference. A multidisciplinary stakeholder committee was divided into work groups. Recommendations for clinical practice and for future research were developed by the committee as an iterative process. This procedure consisted of a literature review phase and focus group interactions with presentations to the entire committee.

RESULTS

We first proposed a conceptual framework of disease that describes a series of AKI stages, antecedents and outcomes, and allows a description of research recommendations based on transition between AKI stages. We further proposed methods for testing of the definition and development of research questions to establish the utility of new biomarkers for the diagnosis and staging of AKI and associated illnesses.

CONCLUSIONS

Retrospective studies should be conducted to initiate the process of validating the AKIN definition of AKI, followed by comprehensive prospective studies that incorporate sampling for emerging AKI biomarkers.

Proteomics for biomarker discovery in acute kidney injury

Acute kidney injury (AKI), previously referred to as acute renal failure, represents a common and devastating problem in clinical medicine. Despite significant improvements in therapeutics, the mortality and morbidity associated with AKI remain high. A major reason for this is the lack of early markers for AKI, and hence an unacceptable delay in initiating therapy. Fortunately, the application of innovative technologies such as functional genomics and proteomics to human and animal models of AKI has uncovered several novel biomarkers and therapeutic targets. The most promising of these are chronicled in this review. These include the identification of biomarker panels in plasma (neutrophil gelatinase-associated lipocalin and cystatin C) and urine (neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, interleukin-18, cystatin C, alpha1-microglobulin, Fetuin-A, Gro-alpha, and meprin). It is likely that the AKI panels will be useful for timing the initial insult, and assessing the duration and severity of AKI. It is also probable that the AKI panels will distinguish between the various etiologies of AKI and predict clinical outcomes. It will be important in future studies to validate the sensitivity and specificity of these biomarker panels in clinical samples from large cohorts and from multiple clinical situations. Such studies will be facilitated markedly by the development of commercial tools for the reproducible measurement of biomarkers across different laboratories.

Increased incidence of acute kidney injury with aprotinin use during cardiac surgery detected with urinary NGAL

BACKGROUND

Use of aprotinin has been associated with acute kidney injury after cardiac surgery. Neutrophil gelatinase-associated lipocalin (NGAL) is a novel, very sensitive marker for renal injury. Urinary NGAL may be able to detect renal injury caused by aprotinin. This study determined if the use of aprotinin is associated with an increased incidence of acute kidney injury and increased levels of urinary NGAL.

METHODS

In this prospective, observational study 369 patients undergoing cardiac surgery were enrolled. 205 patients received aprotinin and 164 received epsilon amino-caproic acid intraoperatively. Urinary NGAL was measured before and immediately after cardiac surgery and 3, 18 and 24 h later. The association of aprotinin use with the incidence of acute kidney injury (increase of serum creatinine >0.5 mg/dl) and NGAL levels was determined using logistic and linear regression models.

RESULTS

51 of 205 patients (25%) who received aprotinin developed acute kidney injury compared to 19 of 164 patients (12%) who received epsilon amino-caproic acid (p = 0.0013). Aprotinin use was associated with a two-fold higher risk of acute kidney injury when adjusted for potential confounders (age, Parsonnet score, preoperative serum creatinine, cardiopulmonary bypass and cross-clamp times; multiple logistic regression: OR = 2.164; CI (95%) = 1.102 to 4.249; p = 0.0249. Urinary NGAL was 19 times higher immediately after cardiopulmonary bypass and 18 times higher 3 h later in patients who had received aprotinin (postoperative: 19.23; CI (95%) = 12.60 to 29.33; p < 0.0001; 3 h post-cardiopulmonary bypass 18.67; CI (95%) = 11.45 to 30.43; p < 0.0001).

CONCLUSIONS

Postoperative urinary NGAL - a novel marker for renal injury - is increased in cardiac surgical patients receiving aprotinin compared to patients receiving epsilon amino-caproic acid. These results further support the hypothesis that aprotinin may cause renal injury. The substantial rise of urinary NGAL associated with aprotinin use may in part be due to aprotinin blocking the uptake of NGAL by megalin/gp330 receptors in the proximal tubules.

Effects of acid aspiration-induced acute lung injury on kidney function

Acute lung injury (ALI) in combination with acute kidney injury carries a mortality approaching 80% in the intensive care unit. Recently, attention has focused on the interaction of the lung and kidney in the setting of ALI and mechanical ventilation (MV). Small animal models of ALI and MV have demonstrated changes in inflammatory mediators, water channels, apoptosis, and function in the kidney early in the course of injury. The purpose of this investigation was to test the hypothesis that ALI and injurious MV cause early, measurable changes in kidney structure and function in a canine HCl aspiration model of ALI when hemodynamics and arterial blood gas tensions are carefully controlled. Intratracheal HCl induced profound ALI as demonstrated by increased shunt fraction and airway pressures compared with sham injury. Sham-injured animals had similar mean arterial pressure and arterial Pco(2) and HCO(3) levels compared with injured animals. Measurements of renal function including renal blood flow, urine flow, serum creatinine, glomerular filtration rate, urine albumin-to-creatinine ratio, and kidney histology scores were not different between groups. With maintenance of hemodynamic parameters and alveolar ventilation, ALI and injurious MV do not alter kidney structure and function early in the course of injury in this acid aspiration canine model. Kidney injury in large animal models may be more similar to humans and may differ from results seen in small animal models.

Urinary biomarkers for acute kidney injury: perspectives on translation

Acute kidney injury (previously known as acute renal failure) is a common complication in hospitalized patients, and its incidence has risen significantly in the past 15 yr. Despite significant technical advances in therapeutics, the mortality and morbidity rates associated with acute kidney injury remain dismally high and have not appreciably improved during the past four decades. Although the serum creatinine concentration performs fairly well for estimating kidney function in patients with stable chronic kidney disease, it performs poorly in the setting of acute disease. An ideal biomarker for acute kidney injury would help clinicians and scientists diagnose the most common form of acute kidney injury in hospitalized patients, acute tubular necrosis, early and accurately and may aid to risk-stratify patients with acute kidney injury by predicting the need for renal replacement therapy, the duration of acute kidney injury, the length of stay, and mortality. Herein is reviewed the diagnostic and prognostic performance of several types of urinary biomarkers for the diagnosis and risk stratification of acute kidney injury. The major types of urinary biomarkers fall into three classes: (1) Inflammatory, (2) renal tubular proteins that are excreted into the urine after injury, and (3) surrogate markers of tubular injury. Also discussed are statistical issues in evaluating the accuracy of biomarkers as diagnostic tests. It is likely that a panel of biomarkers, rather than a single biomarker, will be needed to perform extremely well in these three situations.

Cardiorenal syndrome: refining the definition of a complex symbiosis gone wrong

BACKGROUND

The term "cardiorenal syndrome" has generally been reserved for declining renal function in the setting of advanced congestive heart failure. Considering the complex and bi-directional relationship between the heart and the kidneys, we postulate refining the definition to recognize the symbiotic nature of these organs.

DISCUSSION

We divide the cardiorenal syndrome into five subtypes: type I, acute cardiorenal syndrome; type II, chronic cardiorenal syndrome; type III, acute renocardiac syndrome; type IV, chronic renocardiac syndrome; and type V, secondary cardiorenal syndrome.

CONCLUSIONS

As early recognition of dysfunction in one organ may prove important in mitigating the spiral of co-dysfunction in both, the need for early and treatment-guiding biomarkers, along with their characteristics, are also discussed.

Urinary biomarkers as a diagnostic tool for acute kidney injury

Acute kidney injury is a common condition in hospitalized patients with significant associated morbidity and mortality. Although impressive progress has been made in the understanding of the molecular and biochemical mechanisms of kidney injury, the ability to effectively treat and thus impact on the outcomes of acute kidney injury has been disappointing. One of the major reasons for this has been the reliance on current measures of renal dysfunction, such as serum creatinine and blood urea nitrogen, which are insensitive to small changes in renal function and subtle signs of kidney injury. This insensitivity of commonly used biomarkers of renal dysfunction not only prevents timely diagnosis and estimation of injury severity, but also delays administration of putative therapeutic agents. A number of serum and urinary proteins have been identified that may herald acute kidney injury prior to a rise in serum creatinine. Further characterization of these candidate biomarkers will clarify their utility and define new diagnostic and prognostic paradigms for acute kidney injury, facilitate clinical trials and lead to novel effective therapies.

Potential interventions in sepsis-related acute kidney injury

Sepsis is an important cause of morbidity and mortality. Acute kidney injury often complicates sepsis, leading to greater complexity, cost of care, and worsening prognosis. In recent years, a consensus definition of acute kidney injury has been developed, facilitating research into the pathophysiology and epidemiology of this disorder. New and emerging biomarkers to recognize kidney injury before functional abnormalities are manifest may allow early recognition and facilitate prevention or treatment. Furthermore, advances in the clinical management of sepsis may have secondary benefits with respect to renal outcomes. Existing and hybrid extracorporeal therapies are being investigated not only as means to replace lost kidney function but also to modulate the immune response to sepsis. For those who have more advanced forms of kidney injury, strategies to promote renal recovery are being sought to minimize the long-term consequences of impaired kidney function. This review provides an update on the current state of the science and a glimpse toward the future of intervention in sepsis-related acute kidney injury.

The local and systemic inflammatory transcriptome after acute kidney injury

Studies in humans and animal models have demonstrated that acute kidney injury (AKI) has a significant effect on the function of extrarenal organs. The combination of AKI and lung dysfunction is associated with 80% mortality; the lung, because of its extensive capillary network, is a prime target for AKI-induced effects. The study presented here tested the hypothesis that AKI leads to a vigorous inflammatory response and produces distinct genomic signatures in the kidney and lung. In a murine model of ischemic AKI, prominent global transcriptomic changes and histologic injury in both kidney and lung tissues were identified. These changes were evident at both early (6 h) and late (36 h) timepoints after 60-min bilateral kidney ischemia and were more prominent than similar timepoints after sham surgery or 30 min of ischemia. The inflammatory transcriptome (109 genes) of both organs changed with marked similarity, including the innate immunity genes Cd14, Socs3, Saa3, Lcn2, and Il1r2. Functional genomic analysis of these genes suggested that IL-10 and IL-6 signaling was involved in the distant effects of local inflammation, and this was supported by increased serum levels of IL-10 and IL-6 after ischemia-reperfusion. In summary, this is the first comprehensive analysis of concomitant inflammation-associated transcriptional changes in the kidney and a remote organ during AKI. Functional genomic analysis identified potential mediators that connect local and systemic inflammation, suggesting that this type of analysis may be a useful discovery tool for novel biomarkers and therapeutic drug development.

Netrin-1 and kidney injury. II. Netrin-1 is an early biomarker of acute kidney injury

Acute kidney injury is an important complication in hospitalized patients often diagnosed late and associated with high mortality and morbidity. Although biomarkers for nephrotoxicity are available, they often lack sensitivity and specificity for detecting tubular injury. Netrin-1 is a laminin-like molecule highly expressed in many organs including kidney. To determine the value of netrin-1 as a biomarker of renal injury, we analyzed its urinary excretion following ischemia-reperfusion-, cisplatin-, folic acid-, and endotoxin-induced renal injury in mice. Urinary netrin-1 levels increased markedly within 3 h of ischemia-reperfusion (40 +/- 14-fold, P < 0.01 vs. baseline), reached a peak level at 6 h, and decreased thereafter, returning to near baseline by 72 h. Serum creatinine significantly increased only after 24 h of reperfusion. Similarly, in cisplatin-, folic acid-, and lipopolysaccharide-treated mice, urine netrin-1 excretion increased as early as 1 h and reached a peak level at 6 h after injection. However, serum creatinine was raised significantly after 6, 24, and 72 h after folic acid, lipopolysaccharide, and cisplatin administration, respectively. NGAL excretion in folic acid- and lipopolysaccharide-treated mice urine samples could only be detected by 24 h after drug administration. Furthermore, urinary netrin-1 excretion increased dramatically in 13 acute renal failure patients, whereas none was detected in 6 healthy volunteer urine samples. Immunohistochemical localization showed that netrin-1 is highly expressed in tubular epithelial cells in transplanted human kidney. We conclude that urinary netrin-1 is a promising early biomarker of renal injury.

Technology Insight: biomarker development in acute kidney injury--what can we anticipate?

Early diagnosis has been the 'Achilles heel' of acute kidney injury (AKI) that has prevented successful implementation of treatment strategies. To date, pharmacological intervention has been largely unsuccessful or equivocal, and morbidity and mortality associated with AKI have remained unacceptably high. Despite their well-known limitations, the most widely used biomarkers for the early diagnosis of AKI are serum creatinine, blood urea nitrogen and urine output. Development of new biomarkers is imperative. A variety of methods have been employed to discover new biomarkers of AKI, including transcriptomics, proteomics, gene arrays, lipidomics and imaging technologies. Clinical trials are underway to establish the validity of the biomarkers discovered using these techniques. This Review summarizes the importance of biomarkers of AKI, from their discovery to clinical practice, from the current perspective and that of what to expect in the future. Great strides forward are being made in breaking down important barriers to the successful prevention and treatment of this devastating disorder.

Validation of putative genomic biomarkers of nephrotoxicity in rats

Drug-induced renal injury is a common finding in the early preclinical phase of drug development. But the specific genes responding to renal injury remain poorly defined. Identification of drug-induced gene changes is critical to provide insights into molecular mechanisms and detection of renal damage. To identify genes associated with the development of drug-induced nephrotoxicity, a literature survey was conducted and a panel of 48 genes was selected based on gene expression changes in multiple published studies. Male Sprague-Dawley rats were dosed daily for 1, 3 or 5 days to the known nephrotoxicants gentamicin, bacitracin, vancomycin and cisplatin, or the known hepatotoxicants ketoconazole, 1-naphthyl isothiocyanate and 4,4-diaminodiphenylmethane. Histopathological evaluation and clinical chemistry revealed renal proximal tubular necrosis in rats treated with the nephrotoxicants, but not from those treated with the hepatotoxicants. RNA was extracted from the kidney, and RT-PCR was performed to evaluate expression profiles of the selected genes. Among the genes examined, 24 genes are confirmed to be highly induced or repressed in rats treated with nephrotoxicants; further investigation identified that 5 of the 24 genes were also altered by hepatotoxicants. These data led to the identification of a set of genomic biomarker candidates whose expression in kidney is selectively regulated only by nephrotoxicants. Among those genes displaying the highest expression changes specifically in nephrotoxicant-treated rats were kidney injury molecule 1 (Kim1), lipocalin 2 (Lcn2), and osteopontin (Spp1). The establishment of such a genomic marker set offers a new tool in our ongoing quest to monitor nephrotoxicity.

Inflammatory biomarkers associated with obesity and insulin resistance: a focus on lipocalin-2 and adipocyte fatty acid-binding protein

Obesity is an important risk factor for a cluster of metabolic and cardiovascular diseases, including insulin resistance, Type 2 diabetes, nonalcoholic fatty liver disease and atherosclerosis. Systemic low-grade inflammation, characterized by elevated circulating concentrations of proinflammatory factors, has recently been proposed to be a key mediator that links obesity with its medical complications. Adipose tissue is now recognized as the major contributor to systemic inflammation associated with obesity. As obesity develops, adipose tissue is infiltrated with activated macrophages. The 'inflamed' adipose tissue secretes a large number of proinflammatory adipokines and/or cytokines, which can act either in an autocrine manner to perpetuate local inflammation or in an endocrine manner to induce insulin resistance and endothelial dysfunction. In this review, we summarize recent advances in several newly identified adipose tissue-derived inflammatory factors, with the focus on lipocalin-2 and adipocyte fatty acid-binding protein (A-FABP). Both lipocalin-2 and A-FABP possess lipid-binding properties and are important integrators of metabolic and inflammatory pathways. A growing body of evidence from experimental, epidemiological and genetic studies suggests that both lipocalin-2 and A-FABP represent a novel class of serum biomarkers for risk prediction and therapeutic intervention of obesity-related medical complications.

Neutrophil gelatinase-associated lipocalin (NGAL): a new marker of kidney disease

The incidence of both acute kidney injury (AKI, previously referred to as acute renal failure) and chronic kidney disease (CKD) is reaching epidemic proportions. In both situations, early intervention can significantly improve the prognosis. However, the paucity of early, predictive, non-invasive biomarkers has impaired our ability to institute potentially effective therapies for these common clinical conditions in a timely manner. The current status of one of the most promising novel biomarkers, namely neutrophil gelatinase-associated lipocalin (NGAL), is presented in this review. The evidence for the role of NGAL measurements in a variety of clinical situations leading to AKI (cardiac surgery, kidney transplantation, contrast nephropathy, haemolytic uraemic syndrome and in the intensive care setting) or to CKD (lupus nephritis, glomerulonephritides, obstruction, dysplasia, polycystic kidney disease, IgA nephropathy) is explored. The emerging utility of standardized clinical platforms for reliable measurement of NGAL in plasma (Triage NGAL Device; Biosite Incorporated) and urine (ARCHITECT analyzer; Abbott Diagnostics) is also discussed. It will be important in future studies to validate the sensitivity and specificity of NGAL concentration measurements in clinical samples from large cohorts and from multiple clinical situations. Such studies will be facilitated by the anticipated widespread availability of standardized commercial tools in the near future.

Biomarkers for the early detection of acute kidney injury

Acute kidney injury (AKI), previously referred to as acute renal failure (ARF), represents a persistent problem in clinical medicine. Despite significant improvements in therapeutics, the mortality and morbidity associated with AKI remain high. A major reason for this is the lack of early markers for AKI, akin to troponins in acute myocardial disease, and hence an unacceptable delay in initiating therapy. Fortunately, the application of innovative technologies such as functional genomics and proteomics to human and animal models of AKI has uncovered several novel genes and gene products that are emerging as biomarkers. The most promising of these are chronicled in this article. These include a plasma panel [neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C] and a urine panel [NGAL, interleukin 18 (IL-18), and kidney injury molecule 1 (KIM)-1]. As they represent sequentially expressed biomarkers, it is likely that the AKI panels will be useful for timing the initial insult and assessing the duration of AKI. Based on the differential expression of the biomarkers, it is also likely that the AKI panels will distinguish between the various types and etiologies of AKI. It will be important in future studies to validate the sensitivity and specificity of these biomarker panels in clinical samples from large cohorts and from multiple clinical situations.

Influence of volume therapy with a modern hydroxyethylstarch preparation on kidney function in cardiac surgery patients with compromised renal function: a comparison with human albumin

OBJECTIVE

There is continuing concern about the influence of hydroxyethylstarch on renal function in patients with compromised kidney function.

DESIGN

Prospective, randomized, single-center study.

SETTING

University-affiliated hospital.

PATIENTS

Fifty patients undergoing elective, first-time coronary artery bypass grafting using cardiopulmonary bypass with a preoperative serum creatinine between 1.5 and 2.5 mg/dL.

INTERVENTIONS

According to a prospective, randomized sequence, the patients received either hydroxyethylstarch with a low molecular weight (mean molecular weight 130 kD) and a low molar substitution (0.4) (6% hydroxyethylstarch 130/0.4) (n = 25) or 5% human albumin (n = 25). Volume was added to the priming (500 mL) and given perioperatively until the second postoperative day to keep pulmonary artery occlusion pressure or central venous pressure between 12 and 14 mm Hg.

MEASUREMENTS AND MAIN RESULTS

Serum creatinine and cystatin plasma levels were measured from arterial blood samples. From urine specimens, N-acetyl-beta-D-glucosaminidase, glutathione transferase-alpha, and neutrophil gelatinase-associated lipocalin were measured. Measurements were performed after induction of anesthesia, at the end of surgery, 5 hrs after surgery, and on the first and second postoperative days. A follow-up after discharge from the hospital (60 days) was also done. Similar amounts of hydroxyethylstarch and albumin were infused. Serum creatinine, glomerular filtration rate, and cystatin C plasma levels were without significant differences between the groups. Concentrations of kidney-specific proteins were elevated at baseline and increased significantly after surgery without showing group differences. Urinary levels of neutrophil gelatinase-associated lipocalin increased more in the albumin- than in the hydroxyethylstarch-treated patients. None of the patients developed acute renal failure requiring renal replacement therapy during the hospital stay and thereafter.

CONCLUSIONS

A hydroxyethylstarch preparation with a low molecular weight and a low molar substitution given in cardiac surgery patients with preoperative compromised kidney function did not negatively influence kidney integrity compared with a human albumin-based volume replacement strategy.

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.

Liver fatty acid-binding protein as a biomarker of acute kidney injury after cardiac surgery

Acute kidney injury (AKI) is a major complication of cardiac bypass surgery. We examined whether levels of liver fatty acid-binding protein (L-FABP) can be an early biomarker for ischemic injury by measuring this protein in the urine of 40 pediatric patients prior to and following cardiopulmonary bypass surgery. AKI was defined as a 50% increase in the serum creatinine from baseline, which was normally not seen until 24-72 h after surgery. Enzyme-linked immunosorbent assay analysis showed increased L-FABP levels (factored for creatinine excretion) of about 94- and 45-fold at 4 and 12 h, respectively, following surgery in the 21 patients who developed AKI with western blot analysis, confirming L-FABP identity. Univariate logistic regression analyses showed that both bypass time and urinary L-FABP were significant independent risk indicators for AKI. After excluding bypass time from the model and using a stepwise multivariate logistic regression analysis, urinary L-FABP levels at 4 h after surgery were an independent risk indicator with the area under the receiver-operating characteristic curve 0.810, sensitivity 0.714, and specificity 0.684 for a 24-fold increase in urinary L-FABP. Our study shows that urinary L-FABP levels represent a sensitive and predictive early biomarker of AKI after cardiac surgery.