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

Monitoring of urinary L-type fatty acid-binding protein predicts histological severity of acute kidney injury

The present study aimed to evaluate whether levels of urinary L-type fatty acid-binding protein (L-FABP) could be used to monitor histological injury in acute kidney injury (AKI) induced by cis-platinum (CP) injection and ischemia reperfusion (IR). Different degrees of AKI severity were induced by several renal insults (CP dose and ischemia time) in human L-FABP transgenic mice. Renal histological injury scores increased with both CP dose and ischemic time. In CP-induced AKI, urinary L-FABP levels increased exponentially even in the lowest dose group as early as 2 hours, whereas blood urea nitrogen (BUN) levels increased at 48 hours. In IR-induced AKI, BUN levels increased only in the 30-minute ischemia group 24 hours after reperfusion; however, urinary L-FABP levels increased more than 100-fold, even in the 5-minute ischemia group after 1 hour. In both AKI models, urinary L-FABP levels showed a better correlation with final histological injury scores and glomerular filtration rates measured by fluorescein isothiocyanate-labeled inulin injection than with levels of BUN and urinary N-acetyl-D-glucosaminidase, especially at earlier time points. Receiver operating characteristic curve analysis demonstrated that urinary L-FABP was superior to other biomarkers for the detection of significant histological injuries and functional declines. In conclusion, urinary L-FABP levels are better suited to allow the accurate and earlier detection of both histological and functional insults in ischemic and nephrotoxin-induced AKI compared with conventional renal markers.

Acute kidney injury in critically ill newborns: what do we know? What do we need to learn?

Outcomes in critically ill neonates have improved over the past three decades, yet high residual mortality and morbidity rates exist. Acute kidney injury (AKI) is not just an innocent by-stander in the critically ill patient. Research on incidence and outcomes of AKI in the critically ill neonatal population is scarce. The objective of this publication is to (a) review original articles on the short- and long-term outcomes after neonatal AKI, (b) highlight key articles on adults and children with AKI in order to demonstrate how such insights might be applied to neonates, and (c) suggest clinical research studies to fill the gaps in our understanding of neonatal AKI. To date, observational studies suggest high rates of AKI and poor outcomes in critically ill neonates. Neonates with AKI are at risk of developing chronic kidney disease and hypertension. Large prospective studies are needed to test definitions and to better understand risk factors, incidence, independent outcomes, and mechanisms that lead to poor short- and long-term outcomes. Early biomarkers of AKI need to be explored in critically ill neonates. Infants with AKI need to be followed for sequelae after AKI.

Dialysis and pediatric acute kidney injury: choice of renal support modality

Dialytic intervention for infants and children with acute kidney injury (AKI) can take many forms. Whether patients are treated by intermittent hemodialysis, peritoneal dialysis or continuous renal replacement therapy depends on specific patient characteristics. Modality choice is also determined by a variety of factors, including provider preference, available institutional resources, dialytic goals and the specific advantages or disadvantages of each modality. Our approach to AKI has benefited from the derivation and generally accepted defining criteria put forth by the Acute Dialysis Quality Initiative (ADQI) group. These are known as the risk, injury, failure, loss, and end-stage renal disease (RIFLE) criteria. A modified pediatrics RIFLE (pRIFLE) criteria has recently been validated. Common defining criteria will allow comparative investigation into therapeutic benefits of different dialytic interventions. While this is an extremely important development in our approach to AKI, several fundamental questions remain. Of these, arguably, the most important are "When and what type of dialytic modality should be used in the treatment of pediatric AKI?" This review will provide an overview of the limited data with the aim of providing objective guidelines regarding modality choice for pediatric AKI. Comparisons in terms of cost, availability, safety and target group will be reviewed.

The future of pediatric acute kidney injury management--biomarkers

Acute kidney injury (AKI) represents a common and devastating problem in clinical medicine. A major reason is the lack of early biomarkers for AKI, and hence an unacceptable delay in initiating therapy. Fortunately, the application of innovative technologies has uncovered several novel biomarkers. The most promising of these are included in a putative AKI biomarker panel, consisting of neutrophil gelatinase-associated lipocalin, interleukin-18, and kidney injury molecule-1. These biomarkers have completed initial validation, and have entered the prospective screening stage in the biomarker development process, facilitated by the development of commercial tools for their reproducible measurement across laboratories. The availability of a panel of validated biomarkers will revolutionize renal and critical care, and enable the practice of personalized and predictive medicine at an unprecedented level.

Cardiorenal syndrome

The term cardiorenal syndrome (CRS) increasingly has been used without a consistent or well-accepted definition. To include the vast array of interrelated derangements, and to stress the bidirectional nature of heart-kidney interactions, we present a new classification of the CRS with 5 subtypes that reflect the pathophysiology, the time-frame, and the nature of concomitant cardiac and renal dysfunction. CRS can be generally defined as a pathophysiologic disorder of the heart and kidneys whereby acute or chronic dysfunction of 1 organ may induce acute or chronic dysfunction of the other. Type 1 CRS reflects an abrupt worsening of cardiac function (e.g., acute cardiogenic shock or decompensated congestive heart failure) leading to acute kidney injury. Type 2 CRS comprises chronic abnormalities in cardiac function (e.g., chronic congestive heart failure) causing progressive chronic kidney disease. Type 3 CRS consists of an abrupt worsening of renal function (e.g., acute kidney ischemia or glomerulonephritis) causing acute cardiac dysfunction (e.g., heart failure, arrhythmia, ischemia). Type 4 CRS describes a state of chronic kidney disease (e.g., chronic glomerular disease) contributing to decreased cardiac function, cardiac hypertrophy, and/or increased risk of adverse cardiovascular events. Type 5 CRS reflects a systemic condition (e.g., sepsis) causing both cardiac and renal dysfunction. Biomarkers can contribute to an early diagnosis of CRS and to a timely therapeutic intervention. The use of this classification can help physicians characterize groups of patients, provides the rationale for specific management strategies, and allows the design of future clinical trials with more accurate selection and stratification of the population under investigation.

Screening for kidney diseases: older measures versus novel biomarkers

Biomarkers have been used to screen for kidney disease since creatinine was recognized to be correlated with renal function. The measurement of serum creatinine as a screening test for kidney disease falls short, however, because serum creatinine is not particularly sensitive for the diagnosis of kidney disease. Creatinine reflects renal filtering capacity, which has a lot of reserve and is therefore not sensitive to acute or chronic kidney injury unless the injury is substantial enough to compromise the filtering ability. The sensitivity of serum creatinine is further diminished in certain patient populations that are prone to kidney disease because of the physiology of creatinine. Therefore, researchers are seeking new biomarkers that can aid in the diagnosis of both acute and chronic kidney diseases. The limitations of creatinine in screening for kidney diseases in specific patient populations as well as new potential biomarkers that are actively being researched are discussed in this review.

Year in review 2007: Critical Care--nephrology

We summarize original research in the field of critical care nephrology that was accepted for publication or published in 2007 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Four main topics were identified for a brief overview. The first of these was the definition of acute kidney injury and recent evidence showing the validity of RIFLE (Risk, Injury, Failure, Loss and End-stage kidney disease) criteria and the recent Acute Kidney Injury Network review of the same criteria. Second, we cover the clinical and experimental utilization of novel biomarkers for diagnosis of acute kidney injury, giving special attention to neutrophil gelatinase-associated lipocalin protein. The third area selected for review is outcomes of acute kidney injury during the past 10 years, described by a recent Austrailian epidemiological study. Finally, specific technical features of renal replacement therapies were examined in 2007, specifically regarding anticoagulation and vascular access.

Urinary NGAL in premature infants

Premature infants are at unique risk for developing acute kidney injury (AKI) due to incomplete nephrogenesis, early exposure to nephrotoxic medications, and coexisting conditions such as patent ductus arteriosus (PDA) and respiratory distress syndrome (RDS). Unfortunately, laboratory testing for the diagnosis of AKI in this population is problematic because of the physiology of both the placenta and the extra-uterine premature kidney. Recent research has led to the development of promising biomarkers for the early detection of AKI in children but there are no published reports in neonates. Our goal was to determine whether urine neutrophil gelatinase-associated lipocalin (NGAL) was detectable in premature infants and to correlate levels with gestational age, birth weight (BW), or indomethacin exposure. We enrolled 20 infants in four BW groups: 500-750, 751-1000, 1001-1250, and 1251-1500 g. Urine was collected every day for the first 14 d of life. Neonates born at earlier gestational ages and lower BWs had higher urine NGAL levels (p < 0.01). We conclude that urine NGAL is easily obtained in premature infants and that it correlates significantly with both BW and gestational age. The use of urinary NGAL as a biomarker of AKI in premature infants warrants further investigation.

Biomarkers for the diagnosis of acute kidney injury

The identification of acute kidney injury relies on tests like blood urea nitrogen and serum creatinine that were identified and incorporated into clinical practice several decades ago. This review summarizes clinical studies of newer biomarkers that may permit earlier and more accurate identification of acute kidney injury. The urine may contain sensitive and specific markers of kidney injury that are present due to either impaired tubular reabsorption and catabolism of filtered molecules or release of tubular cell proteins in response to ischemic or nephrotoxic injury. Many potential markers have been studied. Promising injury markers in the urine include N-acetyl-beta-D-glucosaminidase, neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, and interleukin-18. New biomarkers of kidney injury hold the promise of substantially improving the diagnostic approach to acute kidney injury. Adequately powered clinical studies of multiple biomarkers are needed to qualify the biomarkers before they can be fully adopted in clinical practice. Once adopted, more sensitive biomarkers of acute kidney injury hold the potential to transform the care of patients with renal disease.

Progression from acute kidney injury to chronic kidney disease: a pediatric perspective

Although emerging evidence indicates that the incidence of both acute kidney injury (AKI) and chronic kidney disease (CKD) in children is rising and the etiologies are dramatically changing, relatively little is currently known regarding the potential for transition from AKI to CKD. In both situations, early intervention can significantly improve the dismal prognosis. However, the lack of a uniform AKI definition and the paucity of early, predictive biomarkers have impaired our ability diagnose AKI early to institute potentially effective therapies in a timely manner. Fortunately, recent data has validated a multidimensional AKI classification system for children. In addition, the application of innovative technologies has identified candidates that are emerging as early biomarkers of both AKI and CKD. These include neutrophil gelatinase-associated lipocalin, liver-type fatty acid-binding protein, and kidney injury molecule-1. Studies to validate the sensitivity and specificity of these biomarkers in clinical samples from large cohorts and from multiple clinical situations are currently in progress, facilitated by the development of commercial tools for the reproducible measurement of these biomarkers across different laboratories.

Biomarkers of acute kidney injury

The diagnosis of acute kidney injury (AKI) is usually based on measurements of blood urea nitrogen (BUN) and serum creatinine. BUN and serum creatinine are not very sensitive or specific for the diagnosis of AKI because they are affected by many renal and nonrenal factors that are independent of kidney injury or kidney function. Biomarkers of AKI that are made predominantly by the injured kidney have been discovered in preclinical studies. In clinical studies of patients with AKI, some of these biomarkers (eg, interleukin-18, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1) have been shown to increase in the urine before the increase in serum creatinine. These early biomarkers of AKI are being tested in different types of AKI and in larger clinical studies. Biomarkers of AKI may also predict long-term kidney outcomes and mortality.

Biomarkers in acute and chronic kidney disease

PURPOSE OF REVIEW

The paucity of early, predictive, noninvasive biomarkers has impaired our ability to institute potentially effective therapies for acute kidney injury and chronic kidney disease in a timely manner.

RECENT FINDINGS

Promising novel biomarkers for acute kidney injury include a plasma panel (neutrophil gelatinase-associated lipocalin and cystatin C) and a urine panel (neutrophil gelatinase-associated lipocalin, interleukin-18, and kidney injury molecule-1). For chronic kidney disease, these include a similar plasma panel and a urine panel (neutrophil gelatinase-associated lipocalin, asymetric dimethylarginine, and liver-type fatty acid-binding protein). The biomarker panels will probably be useful for assessing the duration and severity of kidney disease, and for predicting progression and adverse clinical outcomes. It is also likely that the biomarker panels will help to distinguish between the various etiologies of acute kidney injury or chronic kidney disease.

SUMMARY

The tools of functional genomics and proteomics have provided us with promising novel biomarkers for acute kidney injury and chronic kidney disease. It will be important in future studies to validate the sensitivity and specificity of these biomarker panels in clinical samples from large cohorts and in multiple clinical situations. Such studies will be facilitated by the availability of commercial tools for reproducible measurement of these panels.

Sensitivity and specificity of a single emergency department measurement of urinary neutrophil gelatinase-associated lipocalin for diagnosing acute kidney injury

BACKGROUND

A single serum creatinine measurement cannot distinguish acute kidney injury from chronic kidney disease or prerenal azotemia.

OBJECTIVE

To test the sensitivity and specificity of a single measurement of urinary neutrophil gelatinase-associated lipocalin (NGAL) and other urinary proteins to detect acute kidney injury in a spectrum of patients.

DESIGN

Prospective cohort study.

SETTING

Emergency department of Columbia University Medical Center, New York, New York.

PARTICIPANTS

635 patients admitted to the hospital with acute kidney injury, prerenal azotemia, chronic kidney disease, or normal kidney function.

MEASUREMENTS

Diagnosis of acute kidney injury was based on the RIFLE (risk, injury, failure, loss, and end-stage) criteria and assigned by researchers who were blinded to experimental measurements. Urinary NGAL was measured by immunoblot, N-acetyl-beta-d-glucosaminidase (NAG) by enzyme measurement, alpha1-microglobulin and alpha(1)-acid glycoprotein by immunonephelometry, and serum creatinine by Jaffe kinetic reaction. Experimental measurements were not available to treating physicians.

RESULTS

Patients with acute kidney injury had a significantly elevated mean urinary NGAL level compared with the other kidney function groups (416 microg/g creatinine [SD, 387]; P = 0.001). At a cutoff value of 130 microg/g creatinine, sensitivity and specificity of NGAL for detecting acute injury were 0.900 (95% CI, 0.73 to 0.98) and 0.995 (CI, 0.990 to 1.00), respectively, and positive and negative likelihood ratios were 181.5 (CI, 58.33 to 564.71) and 0.10 (CI, 0.03 to 0.29); these values were superior to those for NAG, alpha1-microglobulin, alpha1-acid glycoprotein, fractional excretion of sodium, and serum creatinine. In multiple logistic regression, urinary NGAL level was highly predictive of clinical outcomes, including nephrology consultation, dialysis, and admission to the intensive care unit (odds ratio, 24.71 [CI, 7.69 to 79.42]).

LIMITATIONS

All patients came from a single center. Few kidney biopsies were performed.

CONCLUSION

A single measurement of urinary NGAL helps to distinguish acute injury from normal function, prerenal azotemia, and chronic kidney disease and predicts poor inpatient outcomes.

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.

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.

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.

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.

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.

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.

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 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.

Neutrophil gelatinase-associated lipocalin: new paths for an old shuttle

Neutrophil Gelatinase-Associated Lipocalin (NGAL) is a lipocalin that is well known for its functions as a shuttle for iron and siderophores, which comprises a critical component of innate immunity to exogenous bacterial infections. However, several lines of recent evidence have added new dimensions of functionality that have attracted the interest of cancer biologists and oncologists. This review will highlight the exciting new paths and roles that are emerging for NGAL in human cancers, in the tissue response to anticancer therapy, and in the acute kidney injuries that commonly complicate the care of patients with cancer. The evidence for NGAL induction and its role in various human cancers will be explored. The current status of NGAL as a predictive non-invasive biomarker of acute kidney injuries will also be examined.