NGAL is an early predictive biomarker of contrast-induced nephropathy in children

Hypertensive nephropathy in children - do we diagnose early enough?

BACKGROUND/AIMS

The aim was to evaluate the level of neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18) and retinol binding protein (RBP) in children with primary hypertension and no features of hypertensive nephropathy.

METHODS

The study group consisted of 19 children (15 males) aged 14.8 ± 2.18 years with primary hypertension. Estimated glomerular filtration rate (eGFR) and albumin/creatinine ratio (ACR) were within the normal range. Mean blood pressure (BP) was 141/79 mmHg (mean systolic BP percentile was 98, mean diastolic BP percentile was 80). Ambulatory BP measurement (ABPM), blood and urine biochemical measurements and features of end organ damage were assessed. The control group consisted of 20 healthy children.

RESULTS

Hypertensive children showed significantly increased serum and urine NGAL concentration vs controls. Urine RBP was significantly higher in the study group vs controls. A positive correlation was found between urine NGAL and the index of mean systolic BP measured in ABPM, between urine IL-18 and the index of office diastolic BP, between serum NGAL and ACR, and between urine NGAL concentration and serum HDL.

CONCLUSION

In children with primary hypertension, increased serum and urine NGAL may reflect kidney injury earlier than typical markers of hypertensive nephropathy.

Neutrophil gelatinase-associated lipocalin (NGAL) as biomarker of acute kidney injury: a review of the laboratory characteristics and clinical evidences

Acute kidney injury (AKI) is a common and serious condition, currently diagnosed by functional biomarkers, such as serum creatinine measurements. Unfortunately, creatinine increase is a delayed and unreliable indicator of AKI. The lack of early biomarkers of structural kidney injury has hampered our ability to translate promising experimental therapies to human AKI. The recent discovery, translation and validation of neutrophil gelatinase-associated lipocalin (NGAL), possibly the most promising novel AKI biomarker, is reviewed here. NGAL may be measured by several methods both in plasma and urine for the early diagnosis of AKI and for the prediction of clinical outcomes, such as dialysis requirement and mortality, in several common clinical scenarios, including in the intensive care unit, cardiac surgery and renal damage due the exposition to toxic agent and drugs, and renal transplantation. Furthermore, the predictive properties of NGAL, may play a critical role in expediting the drug development process. A systematic review of literature data indicates that further studies are necessary to establish accurate reference population values according to age, gender and ethnicity, as well as reliable and specific decisional values concerning the more common clinical settings related to AKI. Furthermore, proper randomized clinical trials on renal and systemic outcomes comparing the use of NGAL vs. standard clinical practice are still lacking and accurate cost-benefit and/or cost-utility analyses for NGAL as biomarker of AKI are also needed. However, it is important to note that NGAL, in the absence of diagnostic increases in serum creatinine, is able to detect some patients affected by subclinical AKI who have an increased risk of adverse outcomes. These results also suggest that the concept and definition of AKI might need to be reassessed.

A combined cardiorenal assessment for the prediction of acute kidney injury in lower respiratory tract infections

BACKGROUND

The accurate prediction of acute kidney injury (AKI) is an unmet clinical need. A combined assessment of cardiac stress and renal tubular damage might improve early AKI detection.

METHODS

A total of 372 consecutive patients presenting to the Emergency Department with lower respiratory tract infections were enrolled. Plasma B-type natriuretic peptide (BNP) and neutrophil gelatinase-associated lipocalin (NGAL) levels were measured in a blinded fashion at presentation. The potential of these biomarkers to predict AKI was assessed as the primary endpoint. AKI was defined according to the AKI Network classification.

RESULTS

Overall, 16 patients (4%) experienced early AKI. These patients were more likely to suffer from preexisting chronic cardiac disease or diabetes mellitus. At presentation, BNP (334 pg/mL [130-1119] vs 113 pg/mL [52-328], P <.01) and NGAL (269 ng/mL [119-398] vs 96 ng/mL [60-199], P <.01) levels were significantly higher in AKI patients. The predictive accuracy of presentation BNP and NGAL levels was comparable (BNP 0.74; 95% confidence interval [CI], 0.64-0.84 vs NGAL 0.74; 95% CI, 0.61-0.87). In a combined logistic model, a joint BNP/NGAL approach improved the predictive accuracy for early AKI over either biomarker alone (area under the receiver operating characteristic curve: 0.82; 95% CI, 0.74-0.89). The combined categorical cut point defined by BNP >267 pg/mL or NGAL >231 ng/mL correctly identified 15 of 16 early AKI patients (sensitivity 94%, specificity 61%). During multivariable regression analysis, the combined BNP/NGAL cutoff remained the independent predictor of early AKI (hazard ratio 10.82; 95% CI, 1.22-96.23; P = .03).

CONCLUSION

A model combining the markers BNP and NGAL is a powerful predictor of early AKI in patients with lower respiratory tract infection.

Prognostic utility of plasma neutrophil gelatinase-associated lipocalin in patients with acute heart failure: the NGAL EvaLuation Along with B-type NaTriuretic Peptide in acutely decompensated heart failure (GALLANT) trial

Aims

Neutrophil gelatinase-associated lipocalin (NGAL) is a measure of acute kidney injury. Renal dysfunction portends significant risk after discharge from acute heart failure (AHF). Thus, a sensitive marker of renal injury might also help to risk stratify HF patients.

Methods and results

GALLANT [NGAL EvaLuation Along with B-type NaTriuretic Peptide (BNP) in acutely Decompensated Heart Failure] was a multicentre, prospective study to assess the utility of plasma NGAL, alone and in combination with BNP, as an early risk marker of adverse outcomes. We studied 186 patients (61% male). There were 29 events (AHF readmissions and all-cause mortality) at 30 days (16%). Patients with events had higher levels of NGAL than those without (134 vs. 84 ng/mL, P < 0.001). The area under the receiver operating characteristic curve was higher for NGAL (0.72) than BNP (0.65), serum creatinine (0.57), or estimated glomerular filtration rate (eGFR; 0.55). In multivariable analyses, NGAL predicted events (P= 0.001), BNP approached significance (P= 0.052 and 0.070 without creatinine and GFR, respectively) while neither serum creatinine nor eGFR were significant. The addition of discharge NGAL over BNP alone improved classification by a net 10.3% in those with events and 19.5% in those without events, for a net reclassification improvement of 29.8% (P= 0.010). Subjects with both BNP and NGAL elevated were at significant risk [hazard ratio (HR) = 16.85, P= 0.006], as were subjects with low BNP and high NGAL (HR = 9.95, P= 0.036).

Conclusions

Plasma NGAL is a measure of kidney injury that at the time of discharge is a strong prognostic indicator of 30 days outcomes in patients admitted for AHF.

Clinical trial registration number: NCT 00693745

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

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

Plasma neutrophil gelatinase-associated lipocalin for the prediction of acute kidney injury in acute heart failure

Introduction

The accurate prediction of acute kidney injury (AKI) in patients with acute heart failure (AHF) is an unmet clinical need. Neutrophil gelatinase-associated lipocalin (NGAL) is a novel sensitive and specific marker of AKI.

Methods

A total of 207 consecutive patients presenting to the emergency department with AHF were enrolled. Plasma NGAL was measured in a blinded fashion at presentation and serially thereafter. The potential of plasma NGAL levels to predict AKI was assessed as the primary endpoint. We defined AKI according to the AKI Network classification.

Results

Overall 60 patients (29%) experienced AKI. These patients were more likely to suffer from pre-existing chronic cardiac or kidney disease. At presentation, creatinine (median 140 (interquartile range (IQR), 91 to 203) umol/L versus 97 (76 to 132) umol/L, P < 0.01) and NGAL (114.5 (IQR, 67.1 to 201.5) ng/ml versus 74.5 (60 to 113.9) ng/ml, P < 0.01) levels were significantly higher in AKI compared to non-AKI patients. The prognostic accuracy for measurements obtained at presentation, as quantified by the area under the receiver operating characteristic curve was mediocre and comparable for the two markers (creatinine 0.69; 95%CI 0.59 to 0.79 versus NGAL 0.67; 95%CI 0.57 to 0.77). Serial measurements of NGAL did not further increase the prognostic accuracy for AKI. Creatinine, but not NGAL, remained an independent predictor of AKI (hazard ratio (HR) 1.12; 95%CI 1.00 to 1.25; P = 0.04) in multivariable regression analysis.

Conclusions

Plasma NGAL levels do not adequately predict AKI in patients with AHF.

Serum neutrophil gelatinase-associated lipocalin in ballistic injuries: a comparison between blast injuries and gunshot wounds

Neutrophil gelatinase-associated lipocalin (NGAL) is part of a functionally diverse family of proteins that generally bind small, hydrophobic ligands. Neutrophil gelatinase-associated lipocalin is expressed in a number of human tissues including gastrointestinal, respiratory, and urinary tracts and tends to rise in response to inflammation. For this reason, we hypothesized that levels of NGAL might be expressed at higher levels after blast injury compared with other ballistic injury.

PURPOSE

The purpose of this study is to test the hypothesis that NGAL may be a marker of injury severity in blast injury.

MATERIALS

Twenty-three combat casualties (13 blast, 10 gunshot wounds) admitted to the multinational role 3 facility in Helmand province were studied. Serum NGAL was measured using a Biosite Triage point-of-care monitor at 5 time points after injury.

RESULTS

Neutrophil gelatinase-associated lipocalin rose in both groups of casualties and was significantly predictive of death or renal failure at intensive care unit admission, 12 and 24 hours after injury.

CONCLUSIONS

Neutrophil gelatinase-associated lipocalin is not a specific marker of blast injury but is predictive of both renal failure and poor outcome.

The RIFLE and AKIN classifications for acute kidney injury: a critical and comprehensive review

In May 2004, a new classification, the RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) classification, was proposed in order to define and stratify the severity of acute kidney injury (AKI). This system relies on changes in the serum creatinine (SCr) or glomerular filtration rates and/or urine output, and it has been largely demonstrated that the RIFLE criteria allows the identification of a significant proportion of AKI patients hospitalized in numerous settings, enables monitoring of AKI severity, and is a good predictor of patient outcome. Three years later (March 2007), the Acute Kidney Injury Network (AKIN) classification, a modified version of the RIFLE, was released in order to increase the sensitivity and specificity of AKI diagnosis. Until now, the benefit of these modifications for clinical practice has not been clearly demonstrated.

Here we provide a critical and comprehensive discussion of the two classifications for AKI, focusing on the main differences, advantages and limitations.

Urinary NT-proBNP, NGAL, and H-FABP may predict hemodynamic relevance of patent ductus arteriosus in very low birth weight infants

BACKGROUND

Hemodynamically significant patent ductus arteriosus (hsPDA) is the most common functional cardiovascular disease in preterm infants. The necessity to treat hsPDA can neither be derived solely from clinical nor from echocardiographic criteria.

OBJECTIVE

The aim of this study was to establish non-invasive parameters which can differentiate hsPDA from non-hsPDA.

METHODS

Urinary protein levels of NT-proBNP, NGAL, and H-FABP were measured and correlated with the necessity of therapy for PDA. In 37 neonates (<1,500 g), urinary protein concentrations were tested on days 0, 2, and 7 by ELISA methodology. Of 37 infants, 12 required therapeutic interventions according to current treatment standards.

RESULTS

Infants receiving an intervention for PDA showed significantly higher levels of pro-BNP, NGAL, and H-FABP at all time points except for NT-proBNP on day 0. Infants requiring a second or third course of ibuprofen had significantly higher levels of H-FABP and NGAL. In all samples, the concentration of the three proteins correlated positively with each other.

CONCLUSIONS

The present study shows that measurement of urinary proteins is a powerful and non-invasive method to quantify the effect of PDA on systemic perfusion in preterm infants. Furthermore, NGAL and H-FABP may be used to indicate the necessity of pharmacological or surgical treatment of PDA.

Acute kidney injury biomarkers: renal angina and the need for a renal troponin I

Acute kidney injury (AKI) in hospitalized patients is independently associated with increased morbidity and mortality in pediatric and adult populations. Continued reliance on serum creatinine and urine output to diagnose AKI has resulted in our inability to provide successful therapeutic and supportive interventions to prevent and mitigate AKI and its effects. Research efforts over the last decade have focused on the discovery and validation of novel urinary biomarkers to detect AKI prior to a change in kidney function and to aid in the differential diagnosis of AKI. The aim of this article is to review the AKI biomarker literature with a focus on the context in which they should serve to add to the clinical context facing physicians caring for patients with, or at-risk for, AKI. The optimal and appropriate utilization of AKI biomarkers will only be realized by understanding their characteristics and placing reasonable expectations on their performance in the clinical arena.

Neutrophil Gelatinase Associated Lipocalin: An Emerging Biomarker for Acute Kidney Injury in Cardiovascular Disease

Acute kidney injury (AKI) commonly occurs in hospitalised patients resulting in short and long-term morbidity and mortality. A subset of patients especially those with cardiovascular diseases appear particularly vulnerable. The diagnosis of AKI currently depends on changes in serum creatinine and is usually made at least 24 to 48 hours after the initial renal insult. This hinders formulation of possible early therapeutic strategies which could otherwise reduce the clinical sequelae of AKI. Neutrophil gelatinase-associated lipocalin (NGAL) is released in both serum and urine, and has shown great promise in identifying AKI as early as two to four hours after renal injury. NGAL has been demonstrated to be both specific and sensitive in a variety of renal conditions associated with AKI, compared to serum creatinine. This article discusses the emerging role of NGAL in the diagnostic and prognostic evaluation of AKI secondary to cardiovascular diseases and interventions including its benefits and pitfalls. NGAL has been shown to be useful in the diagnosis of AKI particularly for contrast induced nephropathy (CIN) after percutaneous coronary intervention (PCI) and renal dysfunction complicating acute and chronic heart failure. Larger prospective outcome studies with therapeutic interventions are warranted to further validate the role of NGAL in the diagnosis of AKI and in cardiorenal syndrome.

Renal safety in pediatric imaging: randomized, double-blind phase IV clinical trial of iobitridol 300 versus iodixanol 270 in multidetector CT

BACKGROUND

It is debated whether iso-osmolar and low-osmolar contrast media are associated with different incidences of contrast medium-induced nephropathy (CIN) in patients with renal insufficiency.

OBJECTIVE

To compare the incidence of CIN in children undergoing contrast-enhanced multidetector computer tomography (MDCT) with intravenous injection of low-osmolar (iobitridol, Xenetix® 300) or an iso-osmolar (iodixanol, Visipaque® 270) iodinated contrast medium.

MATERIALS AND METHODS

One hundred forty-six children with normal renal function were included in this multicenter trial and underwent contrast-enhanced MDCT. The primary endpoint was the relative change in creatinine clearance from 48 h pre- to 72 h postcontrast medium administration using a noninferiority analysis in the intent-to-treat (ITT, n = 128) and per protocol (n = 68) populations. Secondary endpoints were incidence of CIN, global image quality, diagnostic efficacy and clinical safety.

RESULTS

In the ITT population, the noninferiority of iobitridol over iodixanol was demonstrated. CIN incidence was 4.8% (three cases) with iobitridol and 10.6% (seven cases) with iodixanol (not significant). No statistically significant differences were observed for the secondary endpoints.

CONCLUSION

Comparable satisfactory safety profiles were confirmed for both contrast media, with no significant difference in the incidence of CIN in children with normal renal function.

Biomarkers of acute kidney injury

Acute kidney injury (AKI) is a common problem in both the inpatient and outpatient setting and often results from drug toxicities. Traditional methods of identifying AKI, through measurement of blood urea nitrogen and serum creatinine, are problematic in that they are slow to detect decreases in glomerular filtration rate (GFR) and are influenced by a variety of factors that are not related to GFR changes. The problems inherent in a creatinine-based diagnosis of AKI have impeded the development of proper therapeutics in AKI and posed problems in evaluating nephrotoxicity of drugs and other chemical exposures. In recent years, a number of new biomarkers of AKI with more favorable test characteristics than creatinine have been identified and studied in a variety of experimental and clinical settings. This review will consider the most well-established biomarkers and appraise the literature, with particular attention given to the use of biomarkers in identifying toxin-mediated AKI.

Imperfect gold standards for kidney injury biomarker evaluation

Clinicians have used serum creatinine in diagnostic testing for acute kidney injury for decades, despite its imperfect sensitivity and specificity. Novel tubular injury biomarkers may revolutionize the diagnosis of acute kidney injury; however, even if a novel tubular injury biomarker is 100% sensitive and 100% specific, it may appear inaccurate when using serum creatinine as the gold standard. Acute kidney injury, as defined by serum creatinine, may not reflect tubular injury, and the absence of changes in serum creatinine does not assure the absence of tubular injury. In general, the apparent diagnostic performance of a biomarker depends not only on its ability to detect injury, but also on disease prevalence and the sensitivity and specificity of the imperfect gold standard. Assuming that, at a certain cutoff value, serum creatinine is 80% sensitive and 90% specific and disease prevalence is 10%, a new perfect biomarker with a true 100% sensitivity may seem to have only 47% sensitivity compared with serum creatinine as the gold standard. Minimizing misclassification by using more strict criteria to diagnose acute kidney injury will reduce the error when evaluating the performance of a biomarker under investigation. Apparent diagnostic errors using a new biomarker may be a reflection of errors in the imperfect gold standard itself, rather than poor performance of the biomarker. The results of this study suggest that small changes in serum creatinine alone should not be used to define acute kidney injury in biomarker or interventional studies.

Biomarker strategies to predict need for renal replacement therapy in acute kidney injury

The early detection and diagnosis of acute kidney injury (AKI) with the standardization of novel kidney-injury-specific biomarkers is one of the highest research priorities in nephrology. Accordingly, the majority of studies of novel AKI biomarkers have focused on the early diagnosis of AKI using serum creatinine-based definitions as the gold standard. However, another potential application of kidney-injury-specific biomarkers is for guiding decisions on when to initiate renal replacement therapy (RRT). The purpose of this review is to summarize recent findings concerning some of the more promising AKI biomarkers on their capacity, either alone or integrated with traditional surrogate measures of kidney injury, for early prediction of whether patients will develop severe AKI requiring RRT. Some studies that have examined neutrophil gelatinase-associated lipocalin, cystatin-C, N-acetyl-β-d-glucosaminidase, kidney injury molecule-1, and α(1)-microglobulin, among others, have suggested that these novel biomarkers have the potential to distinguish patients in whom RRT will be needed. This would imply that these biomarkers may be integrated into clinical decision algorithms and could synergistically improve our current ability to predict worsening AKI and need for RRT. However, published studies have many recognized limitations, which preclude our ability to adapt their findings into clinical practice today. While currently available data are not sufficient to conclude that biomarkers should be used routinely for clinical decision making for RRT initiation, additional data may in the future significantly modify the clinical variability for initiation of RRT, and potentially translate into improved outcomes and cost-effectiveness. Finally, we propose a potential approach to future biomarker strategies for RRT initiation, integrating these biomarkers with "traditional" clinical factors.

Early detection and intervention using neutrophil gelatinase-associated lipocalin (NGAL) may improve renal outcome of acute contrast media induced nephropathy: a randomized controlled trial in patients undergoing intra-arterial angiography (ANTI-CIN Study)

BACKGROUND

Patients with pre-existing impaired renal function are prone to develop acute contrast media induced nephropathy (CIN). Neutrophil gelatinase-associated lipocalin (NGAL), a new biomarker predictive for acute kidney injury (AKI), has been shown to be useful for earlier diagnosis of CIN; however, urinary NGAL values may be markedly increased in chronic renal failure at baseline. Results from those studies suggested that urinary NGAL values may not be helpful for the clinician. An intravenous volume load is a widely accepted prophylactic measure and possibly a reasonable intervention to prevent deterioration of renal function. The aim of our study is to evaluate NGAL as an early predictor of CIN and to investigate the clinical benefit of early post-procedural i.v. hydration.

METHODS/DESIGN

The study will follow a prospective, open-label, randomized controlled design. Patients requiring intra-arterial contrast media (CM) application will be included and receive standardized, weight-based, intravenous hydration before investigation. Subjects with markedly increased urinary NGAL values after CM application will be randomized into one of two study groups. Group A will receive 3-4 ml/kg BW/h 0.9% saline intravenously for 6 hours. Group B will undergo only standard treatment consisting of unrestricted oral fluid intake. The primary outcome measure will be CIN defined by an increase greater than 25% of baseline serum creatinine. Secondary outcomes will include urinary NGAL values, cystatin C values, contrast media associated changes in cardiac parameters such as NT-pro-BNP/troponin T, changes in urinary cytology, need for renal replacement treatment, length of stay in hospital and death.We assume that 20% of the included patients will show a definite rise in urinary NGAL. Prospective statistical power calculations indicate that the study will have 80% statistical power to detect a clinically significant decrease of CIN of 40% in the treatment arm if 1200 patients are recruited into the study.

DISCUSSION

A volume expansion strategy showing a benefit from earlier intervention for patients with markedly elevated urinary NGAL values, indicating a CIN, might arise from data from this study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01292317.

New biomarkers of acute kidney injury and the cardio-renal syndrome

Changes in renal function are one of the most common manifestations of severe illness. There is a clinical need to intervene early with proven treatments in patients with potentially deleterious changes in renal function. Unfortunately progress has been hindered by poor definitions of renal dysfunction and a lack of early biomarkers of renal injury. In recent years, the definitional problem has been addressed with the establishment of a new well-defined diagnostic entity, acute kidney injury (AKI), which encompasses the wide spectrum of kidney dysfunction, together with clearer definition and sub-classification of the cardio-renal syndromes. From the laboratory have emerged new biomarkers which allow early detection of AKI, including neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C. This review describes the new concepts of AKI and the cardio-renal syndromes as well as novel biomarkers which allow early detection of AKI. Panels of AKI biomarker tests are likely to revolutionise the diagnosis and management of critically ill patients in the coming years. Earlier diagnosis and intervention should significantly reduce the morbidity and mortality associated with acute kidney damage.

Neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker for early acute kidney injury

Based on information to date, although limitations in the accuracy of NGAL in predicting AKI persist, the preponderance of published studies demonstrate that NGAL, when measured in the plasma and in the urine, is a reliable biomarker for the subsequent development of clinically apparent AKI. If very early detection of AKI, via the measurement of plasma or urinary NGAL, can be followed by effective treatment to abort the development or limit the severity of AKI, and therefore decrease the rate of RRT, length of hospitalization stay, and/or mortality risk, NGAL measurement will become a critically important diagnostic tool in critical care medicine, pediatrics, and surgery.

Urinary biomarkers and renal recovery in critically ill patients with renal support

BACKGROUND AND OBJECTIVES

Despite significant advances in the epidemiology of acute kidney injury (AKI), prognostication remains a major clinical challenge. Unfortunately, no reliable method to predict renal recovery exists. The discovery of biomarkers to aid in clinical risk prediction for recovery after AKI would represent a significant advance over current practice.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted the Biological Markers of Recovery for the Kidney study as an ancillary to the Acute Renal Failure Trial Network study. Urine samples were collected on days 1, 7, and 14 from 76 patients who developed AKI and received renal replacement therapy (RRT) in the intensive care unit. We explored whether levels of urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary hepatocyte growth factor (uHGF), urinary cystatin C (uCystatin C), IL-18, neutrophil gelatinase-associated lipocalin/matrix metalloproteinase-9, and urine creatinine could predict subsequent renal recovery.

RESULTS

We defined renal recovery as alive and free of dialysis at 60 days from the start of RRT. Patients who recovered had higher uCystatin C on day 1 (7.27 versus 6.60 ng/mg·creatinine) and lower uHGF on days 7 and 14 (2.97 versus 3.48 ng/mg·creatinine; 2.24 versus 3.40 ng/mg·creatinine). For predicting recovery, decreasing uNGAL and uHGF in the first 14 days was associated with greater odds of renal recovery. The most predictive model combined relative changes in biomarkers with clinical variables and resulted in an area under the receiver-operator characteristic curve of 0.94.

CONCLUSIONS

We showed that a panel of urine biomarkers can augment clinical risk prediction for recovery after AKI.

Contrast-induced nephropathy in interventional cardiology

Development of contrast-induced nephropathy (CIN), ie, a rise in serum creatinine by either ≥0.5 mg/dL or by ≥25% from baseline within the first 2-3 days after contrast administration, is strongly associated with both increased inhospital and late morbidity and mortality after invasive cardiac procedures. The prevention of CIN is critical if long-term outcomes are to be optimized after percutaneous coronary intervention. The prevalence of CIN in patients receiving contrast varies markedly (from <1% to 50%), depending on the presence of well characterized risk factors, the most important of which are baseline chronic renal insufficiency and diabetes mellitus. Other risk factors include advanced age, anemia, left ventricular dysfunction, dehydration, hypotension, renal transplant, low serum albumin, concomitant use of nephrotoxins, and the volume of contrast agent. The pathophysiology of CIN is likely to be multifactorial, including direct cytotoxicity, apoptosis, disturbances in intrarenal hemodynamics, and immune mechanisms. Few strategies have been shown to be effective to prevent CIN beyond hydration, the goal of which is to establish brisk diuresis prior to contrast administration, and to avoid hypotension. New strategies of controlled hydration and diuresis are promising. Studies are mixed on whether prophylactic oral N-acetylcysteine reduces the incidence of CIN, although its use is generally recommended, given its low cost and favorable side effect profile. Agents which have been shown to be ineffective or harmful, or for which data supporting routine use do not exist, include fenoldopam, theophylline, dopamine, calcium channel blockers, prostaglandin E(1), atrial natriuretic peptide, statins, and angiotensin-converting enzyme inhibitors.

New biomarkers for acute renal injury

Incidence of acute kidney injury (AKI) is increasing rapidly to epidemic proportions. Development of AKI, especially in intensive care settings, is associated with increased morbidity, mortality and hospitalization costs. Currently available diagnostic tools are mostly insensitive for early diagnosis, however prompt diagnosis and risk stratification are necessary for guiding therapy and preventing progression of disease. Finding an early, reliable, suitable, easily reproducible, economical and accurate biomarker for AKI is a top research priority. In recent years, many urinary and serum proteins have been investigated as possible early markers of AKI and some of them have shown great promise. This topic reviews some of the emerging biomarkers of AKI.

Plasma neutrophil gelatinase-associated lipocalin predicts recovery from acute kidney injury following community-acquired pneumonia

Although plasma neutrophil gelatinase-associated lipocalin (NGAL) is a promising biomarker for early detection of acute kidney injury, its ability to predict recovery is unknown. Using RIFLE criteria to define kidney injury, we tested whether higher plasma NGAL concentrations on the first day of RIFLE-F would predict failure to recover in a post hoc analysis of a multicenter, prospective, cohort study of patients with community-acquired pneumonia. Recovery was defined as alive and not requiring renal replacement therapy during hospitalization or having a persistent RIFLE-F classification at hospital discharge. Median plasma NGAL concentrations were significantly lower among the 93 of 181 patients who recovered. Plasma NGAL alone predicted failure to recover with an area under the receiver operating characteristic curve of 0.74. A clinical model using age, serum creatinine, pneumonia severity, and nonrenal organ failure predicted failure to recover with area under the curve of 0.78. Combining this clinical model with plasma NGAL concentrations did not improve prediction. The reclassification of risk of renal recovery, however, significantly improved by 17% when plasma NGAL was combined with the clinical model. Thus, in this cohort of patients with pneumonia-induced severe acute kidney injury, plasma NGAL appears to be a useful biomarker for predicting renal recovery.

Acute kidney insufficiency in the critically ill

Acute kidney insufficiency (AKI), or injury, is common in the critically ill patient. Minimal increases in serum creatinine (Scr) have been associated with greater morbidity, mortality, and hospital cost. In 2002, the Acute Dialysis Quality Initiative (ADQI) proposed a consensus definition (the RIFLE classification) which was modified after continuing evidence suggested that small changes in Scr (≥0.3 mg/dL) led to worsening outcomes. This group, known as the Acute Kidney Injury Network (AKIN), suggests 3 stages of worsening kidney function. Such definitions may aid in identifying patients at greatest risk and further the development of preventive strategies. This review will focus on the epidemiology and etiology of AKI as well as provide a mechanistic description of drug-induced AKI. In addition, a brief review of continuous renal replacement therapies is provided.

Acute kidney injury in childhood: should we be worried about progression to CKD?

While emerging evidence indicates that the incidence of both acute kidney injury (AKI) and chronic kidney disease (CKD) in children is rising and that the etiologies are dramatically changing, relatively little is currently known regarding the potential for transition from AKI to CKD. Major barriers to assessing for a potential AKI to CKD link have included lack of a standard pediatric AKI definition, narrow focus only on children with AKI who receive renal replacement therapy, and reliance on serum creatinine as the main biomarker to detect and diagnose AKI and CKD. Recent data have validated a multi-dimensional AKI classification system for children and have suggested chronic kidney sequelae in pediatric populations with AKI or at risk for AKI. In addition, a number of novel AKI biomarkers are being rigorously validated as early indicators of incipient CKD. Our goals for this article are to (1) review the recent changes in pediatric AKI and CKD epidemiology, (2) explore the evidence for a potential AKI to CKD link, and (3) propose new clinical and research paradigms to better elucidate the progression from AKI to CKD.

Biomarkers for the early detection of acute kidney injury

PURPOSE OF REVIEW

Acute kidney injury (AKI) is a common and serious condition, the diagnosis of which depends on serum creatinine, which is a delayed and unreliable indicator of AKI. Fortunately, understanding the early stress response of the kidney to acute injuries has revealed a number of potential biomarkers. The current status of the most promising of these novel AKI biomarkers, including neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), liver-type fatty acid binding protein (L-FABP), and interleukin (IL)-18, is reviewed.

RECENT FINDINGS

In particular, NGAL is emerging as an excellent biomarker in the urine and plasma, for the early prediction of AKI, for monitoring clinical trials in AKI, and for the prognosis of AKI in several common clinical scenarios. However, biomarker combinations may be required to improve our ability to predict AKI and its outcomes in a context-specific manner.

SUMMARY

It is vital that additional large future studies demonstrate the association between biomarkers and hard clinical outcomes independent of serum creatinine concentrations and that randomization to a treatment for AKI based on high biomarker levels results in an improvement in clinical outcomes.

Urinary neutrophil gelatinase-associated lipocalin distinguishes pre-renal from intrinsic renal failure and predicts outcomes

In established acute kidney injury (AKI), serum creatinine poorly differentiates prerenal from intrinsic AKI. In this study, we tested whether urinary neutrophil gelatinase-associated lipocalin (NGAL) distinguishes between intrinsic and prerenal AKI, and tested its performance in predicting a composite outcome that included progression to a higher RIFLE (Risk, Injury, Failure, Loss of function, End stage renal disease) class, dialysis, or death. Urinary NGAL was measured using a standardized clinical platform in 161 hospitalized patients with established AKI. Sixteen patients were excluded because of postrenal obstruction or insufficient clinical information. Of the remaining 145 patients, 75 had intrinsic AKI, 32 had prerenal AKI, and 38 patients could not be classified. Urinary NGAL levels effectively discriminated between intrinsic and prerenal AKI (area under the receiver-operating characteristic curve 0.87). An NGAL level over 104 μg/l indicated intrinsic AKI (likelihood ratio 5.97), whereas an NGAL level <47 μg/l made intrinsic AKI unlikely (likelihood ratio 0.2). Patients experiencing the composite outcome had significantly higher median urinary NGAL levels on inclusion. In logistic regression analysis, NGAL independently predicted the composite outcome when corrected for demographics, comorbidities, creatinine, and RIFLE class. Hence, urinary NGAL is useful in classifying and stratifying patients with established AKI.

Effect and clinical prediction of worsening renal function in acute decompensated heart failure

We aimed to establish the prevalence and effect of worsening renal function (WRF) on survival among patients with acute decompensated heart failure. Furthermore, we sought to establish a risk score for the prediction of WRF and externally validate the previously established Forman risk score. A total of 657 consecutive patients with acute decompensated heart failure presenting to the emergency department and undergoing serial creatinine measurements were enrolled. The potential of the clinical parameters at admission to predict WRF was assessed as the primary end point. The secondary end point was all-cause mortality at 360 days. Of the 657 patients, 136 (21%) developed WRF, and 220 patients had died during the first year. WRF was more common in the nonsurvivors (30% vs 41%, p = 0.03). Multivariate regression analysis found WRF to independently predict mortality (hazard ratio 1.92, p <0.01). In a single parameter model, previously diagnosed chronic kidney disease was the only independent predictor of WRF and achieved an area under the receiver operating characteristic curve of 0.60. After the inclusion of the blood gas analysis parameters into the model history of chronic kidney disease (hazard ratio 2.13, p = 0.03), outpatient diuretics (hazard ratio 5.75, p <0.01), and bicarbonate (hazard ratio 0.91, p <0.01) were all predictive of WRF. A risk score was developed using these predictors. On receiver operating characteristic curve analysis, the Forman and Basel prediction rules achieved an area under the curve of 0.65 and 0.71, respectively. In conclusion, WRF was common in patients with acute decompensated heart failure and was linked to significantly worse outcomes. However, the clinical parameters failed to adequately predict its occurrence, making a tailored therapy approach impossible.

Neutrophil gelatinase-associated lipocalin in the diagnosis of type 1 cardio-renal syndrome in the general ward

BACKGROUND AND OBJECTIVES

The early identification of acute heart failure (HF) patients with type 1 cardio-renal syndrome should be the first step for developing prevention and treatment strategies for these patients. This study aimed to assess the performance of neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C in the early detection of type 1 cardio-renal syndrome in patients with acute HF.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

One-hundred nineteen patients admitted with acute HF were studied. NGAL and creatinine were measured in the first hospitalization morning; creatinine was also measured at least after 48 to 72 hours. Physicians were blinded to NGAL and cystatin C levels. Type 1 cardio-renal syndrome was defined as an increase in the creatinine level of at least 0.3 mg/dl or 50% of basal creatinine.

RESULTS

Type 1 cardio-renal syndrome developed within 48 to 72 hours in 14 patients (11.8%). Admission NGAL levels were higher in these patients: 212 versus 83 ng/dl. At a cutoff value of 170 ng/L, NGAL determined type 1 cardio-renal syndrome with a sensitivity of 100% and a specificity of 86.7%. The area under the receiver-operating characteristic curve of NGAL was 0.93 and that of cystatin C was 0.68.

CONCLUSIONS

Above a cutoff value of 170 ng/L, NGAL predicts 48- to 72-hour development of type 1 cardio-renal syndrome with a negative predictive value of 100% and a positive predictive value of 50%. NGAL independently associates with type 1 cardio-renal syndrome and might be a useful biomarker in the early recognition of these patients.

Acute kidney injury in critically ill infants: the role of urine Neutrophil Gelatinase-Associated Lipocalin (NGAL)

Acute kidney injury (AKI) has emerged as an important health problem in the intensive care units, especially among infants delivered prematurely. Recent efforts to define and characterize AKI have led to studies of early AKI detection and will ultimately contribute to improvements in AKI outcomes. The discovery of biomarkers for AKI that might enable early recognition and clinical intervention to limit renal injury is therefore of intense contemporary interest. Neutrophil gelatinase-associated lipocalin (NGAL) is the most promising among all emerging markers for AKI; specifically, urine NGAL (uNGAL) predicts renal failure much earlier than serum creatinine. The recent availability of an automated immunoassay for measuring uNGAL in the clinical practice permits to introduce the test in emergency, having a turn around time (TAT) closely comparable with that of serum creatinine. On the basis of data reported in the literature, it is reasonable to forecast an increasing clinical use of uNGAL capable to change our approach to the diagnosis and leading to better preventative and therapeutic interventions which will improve outcomes of critically ill infants with acute kidney disease.

Proteomic analysis of acute kidney injury: biomarkers to mechanisms

Acute kidney injury (AKI) is a devastating clinical condition, both in terms of mortality and costs, and is occurring with increasing incidence. Despite better clinical care, the outcomes of AKI have changed little in the last 50 years. This lack of progress is due in part to a lack of early diagnostic biomarkers and a poor understanding of the disease mechanisms. This review will focus on the rapid progress being made in both the understanding of AKI and the promising panel of early biomarkers for AKI that have come out of both direct proteomic analysis of body fluids of AKI patients and more targeted proteomic approaches using clues from other methods such as transcriptomics. This review concludes with a discussion of the future of proteomics and personalized medicine in AKI and the challenges presented in translating these exciting proteomic results to the clinic.

Biomarkers of acute kidney injury in children: discovery, evaluation, and clinical application

Acute kidney injury (AKI) in children is associated with increased mortality and prolonged length of hospital stay and may also be associated with long-term chronic kidney disease development. Despite encouraging results on AKI treatment in animal studies, no specific treatment has yet been successful in humans. One of the important factors contributing to this problem is the lack of an early AKI diagnostic test. Serum creatinine, the current main diagnostic test for AKI, rises late in AKI pathophysiology and is an inaccurate marker of acute changes in glomerular filtration rate. Therefore, new biomarkers of AKI are needed. With great advancements in genomics, proteomics, and metabolomics, new AKI biomarkers, mainly consisting of urinary proteins that appear in response to renal tubular cell injury, have been, and continue to be, discovered. These new biomarkers offer promise for early AKI diagnosis and for the depiction of severity of renal injury occurring with AKI. This review provides a summary of what a biomarker is, why we need new biomarkers of AKI, and how biomarkers are discovered and should be evaluated. The review also provides a summary of selected AKI biomarkers that have been studied in children.

Neutrophil gelatinase-associated lipocalin (NGAL): validation of commercially available ELISA

BACKGROUND

Neutrophil Gelatinase-Associated Lipocalin (NGAL) has been described as an excellent marker of acute kidney injury (AKI) using the enzyme-linked immunosorbent assay (ELISA) from BioPorto Diagnostics, DK. Validation of the ELISA kit and investigation of stability of the NGAL protein is a prerequisite before introducing NGAL as a marker for AKI in clinical research.

METHODS

Plasma and urine samples from a healthy adult and from 16 children undergoing surgery for congenital heart disease were used to validate the 036 NGAL ELISA kit from BioPorto Diagnostics and study stability of the NGAL protein.

RESULTS

Median intra-assay variation in plasma and urine from the healthy adult was <5% and median inter-assay variation was <10%. For children undergoing surgery for congenital heart disease intra-assay variation was <10%. ELISA kit batch-to-batch variation for plasma was 14.6%. We observed excellent results on analysis of linearity and spike-recovery and found no clinically important variation of NGAL measurements throughout the ELISA plate. Haemolysis significantly interfered with measurement of NGAL, whereas repeated thawing or 48 h of 4-5 degrees C-storage before centrifugation and storage at -80 degrees C did not influence NGAL measurements (ANOVA; n.s.). The NGAL protein is stable in plasma for at least 11 months at -80 degrees C.

CONCLUSION

036 NGAL ELISA kit from BioPorto Diagnostics can be used with acceptable precision for plasma and urine. However, the presence of haemolysis in blood samples or the use of different batches of ELISA kits may seriously decrease the accuracy of measurements.

The use of targeted biomarkers for chronic kidney disease

There is a paucity of sensitive and specific biomarkers for the early prediction of CKD progression. The recent application of innovative technologies such as functional genomics, proteomics, and biofluid profiling has uncovered several new candidates that are emerging as predictive biomarkers of CKD. The most promising among these include urinary proteins such as neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, and liver-type fatty acid binding protein. In addition, an improved understanding of the complex pathophysiologic processes underlying CKD progression has also provided discriminatory biomarkers of CKD progression that are being actively evaluated. Candidates included in this category are plasma proteins such as asymmetric dimethylarginine, adiponectin, apolipoprotein A-IV, fibroblast growth factor 23, neutrophil gelatinase-associated lipocalin, and the natriuretic peptides, as well as urinary N-acetyl-β-d-glucosaminidase. This review represents a critical appraisal of the current status of these emerging CKD biomarkers. Currently, none of these are ready for routine clinical use. Additional large, multicenter prospective studies are needed to validate the biomarkers, identify thresholds and cut-offs for prediction of CKD progression and adverse events, assess the effects of confounding variables, and establish the ideal assays.

Review: neutrophil gelatinase-associated lipocalin: a troponin-like biomarker for human acute kidney injury

Acute kidney injury (AKI) is a common and serious condition, the diagnosis of which currently depends on functional markers such as serum creatinine measurements. Unfortunately, creatinine is a delayed and unreliable indicator of AKI. The lack of early biomarkers of structural kidney injury (akin to troponin in acute myocardial injury) has hampered our ability to translate promising experimental therapies to human AKI. Fortunately, understanding the early stress response of the kidney to acute injuries has revealed a number of potential biomarkers. The discovery, translation and validation of neutrophil gelatinase-associated lipocalin (NGAL), possibly the most promising novel AKI biomarker, is reviewed. NGAL is emerging as an excellent stand-alone troponin-like structural biomarker in the plasma and urine for the early diagnosis of AKI, and for the prediction of clinical outcomes such as dialysis requirement and mortality in several common clinical scenarios. The approach of using NGAL as a trigger to initiate and monitor therapies for AKI, and as a safety biomarker when using potentially nephrotoxic agents, is also promising. In addition, it is hoped that the use of sensitive and specific biomarkers such as NGAL as endpoints in clinical trials will result in a reduction in required sample sizes, and hence the cost incurred. Furthermore, predictive biomarkers like NGAL may play a critical role in expediting the drug development process. However, given the complexity of AKI, additional biomarkers (perhaps a panel of plasma and urinary biomarkers) may eventually need to be developed and validated for optimal progress to occur.

Update on the diagnosis and management of acute kidney injury

Acute kidney injury (AKI) is an independent risk factor for morbidity and mortality. This review provides essential information for the diagnosis and management of AKI. Blood urea nitrogen and serum creatinine are used for the diagnosis of AKI. The review also focuses on recent studies on the diagnosis of AKI using the RIFLE (R-renal risk, I-injury, F-failure, L-loss of kidney function, E-end stage kidney disease) and Acute Kidney Injury Network criteria, and serum and urine AKI biomarkers. Dialysis is the only Food and Drug Administration-approved therapy for AKI. Recent studies on the dose of dialysis in AKI are reviewed.

Normal-range albuminuria does not exclude nephropathy in diabetic children

Clinically detectable diabetic nephropathy (DN) begins with the development of microalbuminuria (MA). However, early renal dysfunction may be overlooked despite using that method. On the other hand, the gold standard in DN detection-that is, renal biopsy-is highly invasive. The aim of this study was to evaluate the level of neutrophil-gelatinase-associated lipocalin (NGAL) and interleukin (IL)-18 and their relations to albumin excretion rate (AER) in children with normal-range albuminuria, e.g. in those considered as not presenting diabetic nephropathy. The study group consisted of 22 children (age 12.7 +/- 3.5 years) with type 1 diabetes mellitus (T1DM). Long-term glycemic control was assessed on hemoglobin A1c (HbA1c) levels (8.52 +/- 1.78%). All patients presented normal estimated glomerular filtration rate (eGFR) (141 +/- 23 ml/min/1.73 m(2)) and normal urinary albumin excretion (13.09 +/- 7.63 mg/24 h). Fourteen healthy children served as a control group. Children with T1DM showed increased NGAL values with respect to controls-interestingly, both in serum (sNGAL) (867.43 +/- 341.98 vs. 655.29 +/- 196.17 ng/ml; p = 0.04) and in urine (uNGAL) (420.04 +/- 374.16 vs. 156.53 +/- 185.18 ng/ml, p = 0.04). IL-18 levels were not different in both groups both in serum (58.52 +/- 20.11 vs. 69.79 +/- 58.76 ng/ml; NS) and in urine (14.53 +/- 12.74 vs. 14.60 +/- 10.92 ng/ml; NS). Despite the relatively small study group, the positive correlation between sNGAL and AER was found [AER (mg/24 h) = 3.1893 + 0.01141 x sNGAL (ng/ml); r = 0.51; p = 0.014] as well as between uNGAL and AER [AER (mg/24 h) = 8.7538 + 0.01032 x uNGAL (ng/ml); r = 0.51; p = 0.016]. No relationship between sNGAL and uNGAL, and GFR and HbA1c were found. Normal-range albuminuria does not exclude diabetic nephropathy defined as increased sNGAL and uNGAL concentration. NGAL measurement can be more sensitive than MA and may become a useful tool for evaluating renal involvement in diabetic children.

Serum and urinary neutrophil gelatinase-associated lipocalin levels in children with chronic renal diseases

BACKGROUND

Recent studies showed that serum and urinary neutrophil gelatinase-associated lipocalin (NGAL) represents a novel, sensitive, specific biomarker for early detection of acute kidney injury. However, the clinical significance of measuring serum and urinary NGAL on chronic renal diseases remains unclear.

METHODS

In this study, we measured serum and urinary NGAL levels in patients with several common pediatric renal diseases such as renal dysfunction (estimated glomerular filtration rate < 90 mL/min/1.73 m(2)), proliferative glomerulonephritis, steroid-resistant and steroid-sensitive nephrotic syndrome, and tubular dysfunction.

RESULTS

Urinary NGAL level was significantly increased compared with the control in all of these disease groups except in patients with a remission stage of steroid-sensitive nephrotic syndrome, although a significant increase in serum NGAL level was observed in the renal dysfunction group only. Both serum and urinary NGAL levels showed significant inverse correlations with an estimated glomerular filtration rate in the analysis with total subjects, and also in the analysis with the renal dysfunction group in urinary NGAL. In proteinuric patients, the extent of proteinuria significantly correlated with urinary NGAL level. In patients with tubular dysfunction, the increase of urinary NGAL level was remarkable compared with the other disease groups.

CONCLUSION

These results indicated that urinary NGAL level is a better biomarker for chronic renal diseases in children than serum NGAL level, although multiple pathological mechanisms should be considered in evaluating these NGAL values.

SDMA is an early marker of change in GFR after living-related kidney donation

BACKGROUND

Early detection of changes in the glomerular filtration rate (GFR) is crucial in detecting acute kidney injury. There is burgeoning evidence from preclinical and clinical studies that symmetrical dimethylarginine (SDMA) correlates well with different parameters of renal function. In some studies, SDMA even outperformed creatinine as a marker of GFR. It is however unknown how fast SDMA is increasing after reduction in GFR. The aim of our study was therefore to determine the temporal change of SDMA in comparison with cystatin C after a defined reduction in GFR.

METHODS

Blood samples from 24 healthy living-related kidney donors (19 F/5 M), mean age 55.2 ± 8.3 years, were collected prior to donation of the kidney as well as 1, 6, 12, 24, 72 and 168 h after unilateral nephrectomy. SDMA levels were measured using a liquid chromatography-mass spectrometry-based method.

RESULTS

Within 6 h after unilateral nephrectomy, i.e. reduction of GFR by 50%, SDMA rose from 0.571 ± 0.120 to 0.659 ± 0.135 µmol/L (P < 0.001). Baseline cystatin C levels increased from 0.87 ± 0.16 to 1.07 ± 0.15 mg/L (P < 0.001). Also, serum creatinine rose significantly within 6 h after removal of one kidney from 65.4 ± 8.4 to 88.8 ± 10.2 µmol/L (P < 0.001).

DISCUSSION

SDMA might be a valuable and early marker of change in GFR in the clinical and experimental setting. Future studies will have to clarify whether sensitivity, specificity and temporal resolution of SDMA make it an attractive candidate for the assessment of renal function in both the experimental and clinical setting.

Urinary neutrophil gelatinase-associated lipocalin: A potential biomarker for predicting rapid progression of drug-induced chronic tubulointerstitial nephritis

INTRODUCTION

The role of urinary biomarkers of kidney injury in the prediction of adverse clinical outcomes in drug-induced chronic tubulointerstitial nephritis (D-CTIN) has not been well described.

METHODS

A total of 36 patients with D-CTIN were enrolled in the study. The baseline urinary excretion of neutrophil gelatinase-associated lipocalin (NGAL), alpha1-microglobin (alpha1-MG), albumin (mAlb) and total protein were measured, and estimated glomerular filtration rate change rates within a period of 6 to 33 (mean: 24 months) follow-up months were recorded.

RESULTS

Areas under the receiver-operator characteristic curve of urinary NGAL, alpha1-MG, mAlb and total protein for predicting deterioration of estimated glomerular filtration rate were 0.707, 0.631, 0.685 and 0.678, respectively. The cutoff points that maximized the combined sensitivity and specificity for NGAL, alpha1-MG, mAlb and total protein were 37.71 ng/mL, 33.20 microg/mL, 6.91 mg/L and 60.00 mg/L, respectively. At these thresholds, the sensitivity and specificity was 64.7% and 78.9% for NGAL, 66.7% and 50.0% for alpha1-MG, 80.0% and 50.0% for mAlb and 70.6% and 63.2% for total protein, respectively. The median renal survival time (years) of patients with urinary NGAL level exceeding 37.705 ng/mL was shorter than that of patients with urinary NGAL level below 37.705 ng/mL (1.59 +/- 0.79 versus 2.09 +/- 0.63, P = 0.040, chi(2) = 4.218).

CONCLUSIONS

Increase of baseline urinary NGAL was better than alpha1-MG, mAlb and total protein in predicting renal function deterioration in patients with D-CTIN. This noninvasive approach has potential to serve as a practical tool in D-CTIN prognosis.

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

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

Neutrophil gelatinase-associated lipocalin: a promising biomarker for detecting cardiac surgery-associated acute kidney injury

Acute kidney injury is a common and significant problem that occurs in a wide variety of clinical settings. Cardiac surgery-associated acute kidney injury continues to be a well-recognized complication of cardiac surgery with associated morbidity and mortality. A lack of early biomarkers for acute kidney injury has prevented timely interventions to mitigate the effects of acute kidney injury. Because serum creatinine is not a timely marker of acute kidney injury, it cannot be used to institute potentially effective therapies to treat acute kidney injury in patients during phases when the injury is still potentially reversible. Neutrophil gelatinase-associated lipocalin has been identified as a promising biomarker for early detection of acute kidney injury. Several studies have shown that neutrophil gelatinase-associated lipocalin levels increase significantly in patients with acute kidney injury 24 to 48 hours before an increase in serum creatinine is detectable. Recent studies suggest that measurements of neutrophil gelatinase-associated lipocalin levels in patients at risk for cardiac surgery-associated acute kidney injury can facilitate its early diagnosis and allow clinicians to implement therapeutic adjustments that have the potential to reverse renal cellular damage and minimize further kidney injury.