Implementation of novel biomarkers in the diagnosis, prognosis, and management of acute kidney injury: executive summary from the tenth consensus conference of the Acute Dialysis Quality Initiative (ADQI)

Cardio-Pulmonary-Renal Interactions: A Multidisciplinary Approach

Over the past decade, science has greatly advanced our understanding of interdependent feedback mechanisms involving the heart, lung, and kidney. Organ injury is the consequence of maladaptive neurohormonal activation, oxidative stress, abnormal immune cell signaling, and a host of other mechanisms that precipitate adverse functional and structural changes. The presentation of interorgan crosstalk may include an acute, chronic, or acute on chronic timeframe. We review the current, state-of-the-art understanding of cardio-pulmonary-renal interactions and their related pathophysiology, perpetuating nature, and cycles of increased susceptibility and reciprocal progression. To this end, we present a multidisciplinary approach to frame the diverse spectrum of published observations on the topic. Assessment of organ functional reserve and use of biomarkers are valuable clinical strategies to screen and detect disease, assist in diagnosis, assess prognosis, and predict recovery or progression to chronic disease.

Evaluation of biomarkers for in vitro prediction of drug-induced nephrotoxicity: comparison of HK-2, immortalized human proximal tubule epithelial, and primary cultures of human proximal tubular cells

There has been intensive effort to identify in vivo biomarkers that can be used to monitor drug-induced kidney damage and identify injury before significant impairment occurs. Kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and human macrophage colony stimulating factor (M-CSF) have been validated as urinary and plasma clinical biomarkers predictive of acute and chronic kidney injury and disease. Similar validation of a high throughput in vitro assay predictive of nephrotoxicity could potentially be implemented early in drug discovery lead optimization to reduce attrition at later stages of drug development. To assess these known in vivo biomarkers for their potential for in vitro screening of drug-induced nephrotoxicity, we selected a panel of nephrotoxic agents and examined their effects on the overexpression of nephrotoxicity biomarkers in immortalized (HK-2) and primary (commercially available and freshly in-house produced) human renal proximal tubule epithelial cells. Traditional cytotoxicity was contrasted with expression levels of KIM-1, NGAL, and M-CSF assessed using ELISA and real-time quantitative reverse transcription PCR. Traditional cytotoxicity assays and biomarker assays using HK-2 cells were both unsuitable for prediction of nephrotoxicity. However, increases in protein levels of KIM-1 and NGAL in primary cells were well correlated with dose levels of known nephrotoxic compounds, with limited correlation seen in M-CSF protein and mRNA levels. These results suggest that profiling compounds against primary cells with monitoring of biomarker protein levels may have potential as in vitro predictive assays of drug-induced nephrotoxicity.

Urine neutrophil gelatinase associated lipocalin as an early marker of acute kidney injury in hematopoietic stem cell transplantation patients

Acute kidney injury (AKI) is common in hematopoietic stem cell transplantation (HSCT) patients with an incidence of 21-73%. Prevention and early diagnosis reduces the frequency and severity of this complication. Predictive biomarkers are of major importance to timely diagnosis. Neutrophil gelatinase associated lipocalin (NGAL) is a widely investigated novel biomarker for early diagnosis of AKI. However, no study assessed NGAL for AKI diagnosis in HSCT patients. We performed further analyses on gathered data from our recent trial to evaluate the performance of urine NGAL (uNGAL) as an indicator of AKI in 72 allogeneic HSCT patients. AKI diagnosis and severity were assessed using Risk-Injury-Failure-Loss-End-stage renal disease and AKI Network criteria. We assessed uNGAL on days -6, -3, +3, +9 and +15. Time-dependent Cox regression analysis revealed a statistically significant relationship between uNGAL and AKI occurrence. (HR = 1.04 (1.008-1.07), p = 0.01). There was a relation between uNGAL day + 9 to baseline ratio and incidence of AKI (unadjusted HR = 1.047 (1.012-1.083), p < 0.01). The area under the receiver-operating characteristic curve for day + 9 to baseline ratio was 0.86 (0.74-0.99, p < 0.01) and a cut-off value of 2.62 was 85% sensitive and 83% specific in predicting AKI. Our results indicated that increase in uNGAL augmented the risk of AKI and the changes of day +9 uNGAL concentrations from baseline could be of value for predicting AKI in HSCT patients. Additionally uNGAL changes preceded serum Cr raises by nearly 2 days.

Urinary neutrophil gelatinase-associated lipocalin in critically ill surgical cancer patients

BACKGROUND AND AIMS

Neutrophil gelatinase-associated lipocalin (N-GAL) is an early biomarker of acute kidney injury (AKI) due to various etiologies. On the other hand, N-GAL is also elevated in patients with acute inflammatory conditions and in several solid neoplasms. The goal of this study was to assess the efficacy of N-GAL as a predictor of AKI and mortality in oncological surgical patients postoperatively in the intensive care unit (ICU).

METHODS

This was a prospective cohort observation study on adult cancer patients submitted to elective or emergency surgeries and admitted in the ICU. Urinary N-GAL was measured at the first 2 h after admission. AKI incidence and other complications were assessed, including hospital mortality.

RESULTS

A total of 22 patients were assessed (77% male, age 52.8 years, Acute Physiology and Chronic Health Evaluation II [APACHE II] 17.3) in whom the most frequent site of cancer was the gastrointestinal tract. AKI incidence was 13.6%. Urinary N-GAL was a predictor of AKI (22.0 ng/ml in patients without AKI vs. 239.1 ng/ml in patients with AKI, P < 0.001). Multivariate analysis showed that the main predictors of AKI were age, APACHE II, and N-GAL. N-GAL was also higher, although not statistically significant in patients who died in the hospital.

CONCLUSIONS

In oncological postoperative patients admitted to the ICU, urinary N-GAL was an independent predictor of AKI; moreover, its level was higher in the deceased patients.

Assessment of Worldwide Acute Kidney Injury, Renal Angina and Epidemiology in Critically Ill Children (AWARE): A Prospective Study to Improve Diagnostic Precision

BACKGROUND

Acute kidney injury (AKI) is associated with poor outcomes in critically ill children. Recent international consensus panels recommend standardized classification systems to improve the precision of AKI diagnosis, but there is a paucity of data to enable this refinement, particularly in pediatric critical care.

METHODS/DESIGN

This is a prospective observational study. We anticipate collecting data from more than 5500 critically ill children admitted to 32 pediatric intensive care units (PICUs) across the world, during the calendar year of 2014. Data will be collected continuously for three months at each center on all children older than 90 days and younger than 25 years admitted to the ICU. Demographic, resuscitative, and daily physiological and lab data will be captured at individual centers using MediData Rave™, a commercial system designed to manage and report clinical research data. Kidney specific measured variables include changes in serum creatinine and urine output, cumulative fluid overload (%), serum creatinine corrected for fluid balance, and KDIGO AKI stage. Urinary AKI biomarkers to be measured include: urinary neutrophil gelatinase lipocalin (NGAL), kidney injury molecule-1 (KIM-1), liver-type fatty acid binding protein (l-FABP), and interleukin-18 (IL-18). Biomarker combinations will be created from different pairs and triplets of urinary biomarkers. The primary analysis will compare the discrimination of these panels versus changes in creatinine for prediction of severe AKI by Day 7 of ICU admission. Secondary analysis will investigate the prediction of biomarkers for injury 'time based phenotypes': duration (>2 days), severity (KDIGO stage, use of renal replacement therapy), reversibility (time to return of serum creatinine to baseline), association with fluid overload > 10%, and disease association (sepsis, hypovolemia, hypoxemia, or nephrotoxic).

DISCUSSION

The Assessment of Worldwide Acute Kidney Injury, Renal Angina and Epidemiology (AWARE) study will be the largest ever prospective study of any disease process in pediatric critical care. Data from AWARE will enable refinement of AKI classification. AWARE creates the largest ever all-cause pediatric AKI data warehouse and biologic sample repository, providing a broad and invaluable resource for critical care nephrologists seeking to study risk factors, prediction, identification, and treatment options for a disease syndrome with high associated morbidity affecting a significant proportion of hospitalized children. Improving the precision of AKI diagnosis using biomarker combinations provides a foundation for targeted, personalized therapy for different injury phenotypes.

TRIAL REGISTRATION NUMBER

NCT01987921.

Combining functional and tubular damage biomarkers improves diagnostic precision for acute kidney injury after cardiac surgery

BACKGROUND

Increases in serum creatinine (ΔSCr) from baseline signify acute kidney injury (AKI) but offer little granular information regarding its characteristics. The 10th Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) suggested that combining AKI biomarkers would provide better precision for AKI course prognostication.

OBJECTIVES

This study investigated the value of combining a functional damage biomarker (plasma cystatin C [pCysC]) with a tubular damage biomarker (urine neutrophil gelatinase-associated lipocalin [uNGAL]), forming a composite biomarker for prediction of discrete characteristics of AKI.

METHODS

Data from 345 children after cardiopulmonary bypass (CPB) were analyzed. Severe AKI was defined as Kidney Disease Global Outcomes Initiative stages 2 to 3 (≥100% ΔSCr) within 7 days of CPB. Persistent AKI lasted >2 days. SCr in reversible AKI returned to baseline ≤48 h after CPB. The composite of uNGAL (>200 ng/mg urine Cr = positive [+]) and pCysC (>0.8 mg/l = positive [+]), uNGAL+/pCysC+, measured 2 h after CPB initiation, was compared to ΔSCr increases of ≥50% for correlation with AKI characteristics by using predictive probabilities, likelihood ratios (LR), and area under the curve receiver operating curve (AUC-ROC) values [Corrected].

RESULTS

Severe AKI occurred in 18% of patients. The composite uNGAL+/pCysC+ demonstrated a greater likelihood than ΔSCr for severe AKI (+LR: 34.2 [13.0:94.0] vs. 3.8 [1.9:7.2]) and persistent AKI (+LR: 15.6 [8.8:27.5] versus 4.5 [2.3:8.8]). In AKI patients, the uNGAL-/pCysC+ composite was superior to ΔSCr for prediction of transient AKI. Biomarker composites carried greater probability for specific outcomes than ΔSCr strata.

CONCLUSIONS

Composites of functional and tubular damage biomarkers are superior to ΔSCr for predicting discrete characteristics of AKI.

Assessment of Worldwide Acute Kidney Injury, Renal Angina and Epidemiology in critically ill children (AWARE): study protocol for a prospective observational study

Background

Acute kidney injury (AKI) is associated with poor outcome in critically ill children. While data extracted from retrospective study of pediatric populations demonstrate a high incidence of AKI, the literature lacks focused and comprehensive multicenter studies describing AKI risk factors, epidemiology, and outcome. Additionally, very few pediatric studies have examined novel urinary biomarkers outside of the cardiopulmonary bypass population.

Methods/Design

This is a prospective observational study. We anticipate collecting data on over 5000 critically ill children admitted to 31 pediatric intensive care units (PICUs) across the world during the calendar year of 2014. Data will be collected for seven days on all children older than 90 days and younger than 25 years without baseline stage 5 chronic kidney disease, chronic renal replacement therapy, and outside of 90 days of a kidney transplant or from surgical correction of congenital heart disease. Data to be collected includes demographic information, admission diagnoses and co-morbidities, and details on fluid and vasoactive resuscitation used. The renal angina index will be calculated integrating risk factors and early changes in serum creatinine and fluid overload. On days 2–7, all hemodynamic and pertinent laboratory values will be captured focusing on AKI pertinent values. Daily calculated values will include % fluid overload, fluid corrected creatinine, and KDIGO AKI stage. Urine will be captured twice daily for biomarker analysis on Days 0–3 of admission. Biomarkers to be measured include neutrophil gelatinase lipocalin (NGAL), kidney injury molecule-1 (KIM-1), liver-type fatty acid binding protein (l-FABP), and interleukin-18 (IL-18). The primary outcome to be quantified is incidence rate of severe AKI on Day 3 (Day 3 – AKI). Prediction of Day 3 – AKI by the RAI and after incorporation of biomarkers with RAI will be analyzed.

Discussion

The Assessment of Worldwide Acute Kidney Injury, Renal Angina and Epidemiology (AWARE) study, creates the first prospective international pediatric all cause AKI data warehouse and biologic sample repository, providing a broad and invaluable resource for critical care nephrologists seeking to study risk factors, prediction, identification, and treatment options for a disease syndrome with high associated morbidity affecting a significant proportion of hospitalized children.

Trial registration

ClinicalTrials.gov: NCT01987921

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0016-6) contains supplementary material, which is available to authorized users.

Urinary early kidney injury molecules in children with beta-thalassemia major

BACKGROUND

The aim of this study was to investigate novel urinary biomarkers including N-acetyl-β-D-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and liver-type fatty acid binding protein (L-FABP) in children with β-thalassemia major (β-TM).

MATERIALS AND METHODS

Totally, 52 patients (29 boys, 23 girls) with β-TM and 29 healthy controls (3-17 years) were included. Various demographic characteristics and blood transfusions/year, disease duration, and chelation therapy were recorded. Serum urea, creatinine, electrolytes, and ferritin and urinary creatinine, protein, calcium, phosphorus, sodium, potassium, and uric acid in first morning urine samples were measured and estimated glomerular filtration rate (eGFR) was calculated. Routine serum and urinary biochemical variables, urinary NAG to Creatinine (U(NAG/Cr)), U(NGAL/Cr), U(KIM-1/Cr), and U(L-FABP/Cr) ratios were determined.

RESULTS

Patients had similar mean serum urea, creatinine and eGFR levels compared with controls (p > 0.05 for all). The mean urinary protein to creatinine (U(Protein/Cr)) ratio was significantly higher in patients compared to the healthy subjects (0.13 ± 0.09 mg/mg and 0.07 ± 0.04 mg/mg, respectively; p < 0.001). Significantly increased U(NAG/Cr) (0.48 ± 0.58 vs. 0.23 ± 0.16, p = 0.026) and U(NGAL/Cr) (22.1 ± 18.5 vs. 11.5 ± 6.17, p = 0.01) ratios were found in β-TM patients compared with healthy controls. However, no differences were found in serum and urinary electrolytes or U(KIM-1/Cr) and U(L-FABP/Cr) ratios between patients and controls (p > 0.05). Significant correlations were found between urinary biomarkers and urinary electrolytes (p < 0.05).

CONCLUSIONS

Our results suggest that urinary NAG and NGAL may be considered to be reliable markers to monitor renal injury in β-TM patients.

Quantification of urinary TIMP-2 and IGFBP-7: an adequate diagnostic test to predict acute kidney injury after cardiac surgery?

Introduction

Postoperative acute kidney injury (AKI) is a frequently observed complication after on-pump cardiac surgery (CS) and is associated with adverse patient outcomes. Early identification of patients at risk is essential for the prevention of AKI after CS. In this study, we analysed whether urinary tissue inhibitor of metalloproteinase 2 (TIMP-2) combined with urine insulin-like growth factor binding protein 7 (IGFBP-7) ([TIMP-2] × [IGFBP-7]) is an adequate diagnostic test to identify early AKI after on-pump CS.

Methods

In 42 patients undergoing coronary artery bypass graft surgery, we surveyed individual risk factors for AKI and defined AKI by applying the Kidney Disease: Improving Global Outcomes (KDIGO) classification during the day of surgery and the following 2 days after surgery. Concentrations of urinary TIMP-2 multiplied by IGFBP-7 were recorded at four time points: at baseline pre-surgery, at the end of surgery, 4 hours after cardiopulmonary bypass (CPB) and at 8:00 am on the first postoperative day.

Results

In total, 38% of the patients experienced AKI. The results showed a median baseline [TIMP-2] × [IGFBP-7] concentration of 0.3 (ng/ml)²/1,000, decreasing at the end of surgery and then increasing at the next measurement point 4 hours after CPB and further on the first postoperative day. On the first postoperative day, patients with AKI had significantly higher concentrations of [TIMP-2] × [IGFBP-7]. On the day of surgery, the concentration did not significantly differ between patients classified as KDIGO 0 or KDIGO 1 or 2. Previously published cutoff points of 0.3 and 2 were not confirmed in our study cohort.

Conclusion

[TIMP-2] × [IGFBP-7] concentration can be used as a diagnostic test to identify patients at increased risk of AKI after CS on the first postoperative day. At earlier time points, no significant difference in [TIMP-2] × [IGFBP-7] concentration was found between patients classified as KDIGO 0 or KDIGO 1 or 2.

Trial registration

German Clinical Trials Register (DRKS) DRKS00005457. Registered 26 November 2013.

Patients with cardiorenal syndrome revealed increased neurohormonal activity, tubular and myocardial damage compared to heart failure patients with preserved renal function

BACKGROUND

Cardiorenal syndrome (CRS) is associated with increased cardiovascular morbidity and mortality; still, its biomarker pattern has been poorly evaluated so far. The aim of this study was to measure the inflammatory activation, neurohormonal status and kidney and myocardial damage in patients with CRS compared to patients with heart failure (HF) without renal impairment (RI).

METHODS

We analyzed 246 patients on the basis of renal function (group 1: 120 HF patients without RI; group 2: 126 CRS patients). In each group, interleukin-6, tumor necrosis factor-α, B-type natriuretic peptide (BNP), neutrophil gelatinase-associated lipocalin (NGAL), troponin T (TnT), osteoprotegerin and blood urea nitrogen (BUN) were measured. The diagnostic power of all laboratory parameters to detect CRS was evaluated by the receiver operating characteristic (ROC) curve and logistic regression analysis.

RESULTS

A significant increase in BNP [626.4 pg/ml, confidence interval (CI) 518-749 vs. 487.8 pg/ml, CI 411-578; p < 0.05], NGAL (156 ng/ml, CI 129-186 vs. 89.1 ng/ml, CI 72-109; p < 0.0001), BUN (108.9 mg/dl, CI 98-120 vs. 51 mg/dl, CI 46-55; p < 0,0001) and TnT (0.62 ng/ml, CI 0.51-0.75 vs. 0.21 ng/ml, CI 0.15-0.28; p < 0.001) was seen in CRS patients compared to HF patients without RI. ROC curve analysis showed that only NGAL, BUN, BUN/creatinine ratio and TnT can discriminate patients with CRS from patients without RI.

CONCLUSIONS

In CRS patients, renal tubular damage and neurohormonal and cardiac injury activation are increased compared to patients without RI. The current biomarker pattern could be used for an early diagnosis of RI in acute and chronic HF.

Biomarkers of calcineurin inhibitor nephrotoxicity in transplantation

Over 35 years of use has demonstrated the revolutionary therapeutic benefits of calcineurin inhibitors (CNI) in not only preventing transplant rejection, but also the renal and nonrenal toxicity of CNI. Acute reversible and insidious irreversible forms of CNI nephrotoxicity have been identified, with ischemia from an imbalance between vasoconstrictors and vasodilators playing an important role. The ongoing search to define toxicity pathways has been enriched by ‘Omics’ studies. Changes in proteins including those involved in activation of pro-inflammatory responses, oxidative stress, ER stress and the unfolded protein response have been identified, and these may serve as biomarkers of toxicity. However, the current standard of CNI toxicity, histology, lacks specificity, which creates challenges for biomarker validation. This review focuses on progress in nephrotoxic pathway identification of CNI and biomarker validation.

Academic College of Emergency Experts in India's INDO-US Joint Working Group and OPUS12 Foundation Consensus Statement on Creating A Coordinated, Multi-Disciplinary, Patient-Centered, Global Point-of-Care Biomarker Discovery Network

Biomarker science brings great promise to clinical medicine. This is especially true in the era of technology miniaturization, rapid dissemination of knowledge, and point-of-care (POC) implementation of novel diagnostics. Despite this tremendous progress, the journey from a candidate biomarker to a scientifically validated biomarker continues to be an arduous one. In addition to substantial financial resources, biomarker research requires considerable expertise and a multidisciplinary approach. Investigational designs must also be taken into account, with the randomized controlled trial remaining the “gold standard”. The authors present a condensed overview of biomarker science and associated investigational methods, followed by specific examples from clinical areas where biomarker development and/or implementation resulted in tangible enhancements in patient care. This manuscript also serves as a call to arms for the establishment of a truly global, well-coordinated infrastructure dedicated to biomarker research and development, with focus on delivery of the latest discoveries directly to the patient via point-of-care technology.

The definition of acute kidney injury and its use in practice

Acute kidney injury (AKI) is a common syndrome that is independently associated with increased mortality. A standardized definition is important to facilitate clinical care and research. The definition of AKI has evolved rapidly since 2004, with the introduction of the Risk, Injury, Failure, Loss, and End-stage renal disease (RIFLE), AKI Network (AKIN), and Kidney Disease Improving Global Outcomes (KDIGO) classifications. RIFLE was modified for pediatric use (pRIFLE). They were developed using both evidence and consensus. Small rises in serum creatinine are independently associated with increased mortality, and hence are incorporated into the current definition of AKI. The recent definition from the international KDIGO guideline merged RIFLE and AKIN. Systematic review has found that these definitions do not differ significantly in their performance. Health-care staff caring for children or adults should use standard criteria for AKI, such as the pRIFLE or KDIGO definitions, respectively. These efforts to standardize AKI definition are a substantial advance, although areas of uncertainty remain. The new definitions have enabled the use of electronic alerts to warn clinicians of possible AKI. Novel biomarkers may further refine the definition of AKI, but their use will need to produce tangible improvements in outcomes and cost effectiveness. Further developments in AKI definitions should be informed by research into their practical application across health-care providers. This review will discuss the definition of AKI and its use in practice for clinicians and laboratory scientists.

The growth of acute kidney injury: a rising tide or just closer attention to detail?

Acute kidney injury (AKI), previously termed acute renal failure, is associated with increased mortality, prolonged hospital stay, and accelerated chronic kidney disease (CKD). Over the past 2 decades, dramatic rises in the incidences of AKI have been reported, particularly within the United States. The question arises as to whether these changes reflect actual increases in disease incidence, or are potentially explained by the introduction of consensus definitions that rely on small standardized changes in serum creatinine, changes in coding and reimbursement, or increasingly available and more liberal use of dialysis. In this review, we explore the secular trends in AKI incidence in North America and Western Europe and its potential contributors.

Contrast-Induced Nephropathy: Definitions, Epidemiology, and Implications

Contrast-induced nephropathy, now termed contrast-induced acute kidney injury (CI-AKI), has been a long-recognized complication of administering intravascular iodinated contrast. This article reviews the newest literature on subclinical CI-AKI detected by novel biomarkers, and clinical CI-AKI recognized by an increase in serum creatinine and a reduction in urine output. Both components of CI-AKI are associated with adverse outcomes, including in-hospital complications, increased length of stay, need for renal replacement therapy, rehospitalization, permanent loss in renal filtration function, and death.

Novel biomarkers for contrast-induced acute kidney injury

Biomarkers of acute kidney injury (AKI) may be classified in 2 groups: (1) those representing changes in renal function (e.g., serum creatinine or cystatin C and urine flow rate) and (2) those reflecting kidney damage (e.g., kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18, etc.). According to these 2 fundamental criteria, 4 subgroups have been proposed: (1) no marker change; (2) damage alone; (3) functional change alone; and (4) combined damage and functional change. Therefore, a new category of patients with “subclinical AKI” (that is, an increase in damage markers alone without simultaneous loss of kidney function) has been identified. This condition has been associated with higher risk of adverse outcomes (including renal replacement therapy and mortality) at followup. The ability to measure these physiological variables may lead to identification of patients at risk for AKI and early diagnosis of AKI and may lead to variables, which may inform therapeutic decisions.

Prognostic factors in continuous hemofiltration therapy for patients with cardiorenal syndrome

AIMS

The aims of this study were to investigate the efficacy and identify the prognostic factors of continuous hemofiltration in patients with cardiorenal syndrome (CRS) and, finally, to optimally select patients who could benefit more from this therapy.

METHODS

A total of 59 patients with CRS type 1 or type 2 treated with continuous hemofiltration were enrolled. We collected their clinical data and divided them into 2 groups according to their survival or death during hospitalization to conduct a retrospective analysis on factors affecting mortality.

RESULTS

The following items were significantly different between the survival (n = 30) and death (n = 29) groups: serum creatinine, serum total bilirubin, direct bilirubin, white blood cells, hemoglobin, hematocrit, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, systolic blood pressure and mean arterial pressure before hemofiltration, and average dehydration volume during the hemofiltration process. Leukocytosis was a risk factor for death (OR 1.242, 95% CI 1.242-1.480), and elevated sCr was not a key negative factor in the prognosis of CRS (OR 0.994, 95% CI 0.989-1.000).

CONCLUSIONS

Cardiac function before hemofiltration and the amount of dehydration during the hemofiltration process both affected the prognosis. Infection and fluid overload condition at the beginning of hemofiltration were independently associated with mortality during hospitalization.

Acute kidney injury-epidemiology, outcomes and economics

Acute kidney injury (AKI) is a widespread problem of epidemic status. Compelling evidence indicates that the incidence of AKI is rapidly increasing, particularly among hospitalized patients with acute illness and those undergoing major surgery. This increase might be partially attributable to greater recognition of AKI, improved ascertainment in administrative data and greater sensitivity of consensus diagnostic and classification schemes. Other causes could be an ageing population, increasing incidences of cardiovascular disease, diabetes mellitus and chronic kidney disease (CKD), and an expanding characterization of modifiable risk factors, such as sepsis, administration of contrast media and exposure to nephrotoxins. The sequelae of AKI are severe and characterized by increased risk of short-term and long-term mortality, incident CKD and accelerated progression to end-stage renal disease. AKI-associated mortality is decreasing, but remains unacceptably high. Moreover, the absolute number of patients dying as a result of AKI is increasing as the incidence of the disorder increases, and few proven effective preventative or therapeutic interventions exist. Survivors of AKI, particularly those who remain on renal replacement therapy, often have reduced quality of life and consume substantially greater health-care resources than the general population as a result of longer hospitalizations, unplanned intensive care unit admissions and rehospitalizations.

The definition and detection of acute kidney injury

The first consensus definition of Acute Kidney Injury (AKI) was published a decade ago. In this mini narrative review we look at the history of the changes in the definition of AKI and consider how it may change again in the near future. The epidemiology of small changes in creatinine and the difficulties with determining baseline creatinine have driven the changes. Recent evidence on urinary output and the application of structural injury biomarkers are likely to change the definition once more.

The clinical utility of plasma neutrophil gelatinase-associated lipocalin in acute kidney injury

BACKGROUND AND AIM

Neutrophil gelatinase-associated lipocalin (NGAL) is derived from the distal tubule and is both reabsorbed and filtered and also shed into the urine after tubular injury. Plasma NGAL is unique amongst the candidate biomarkers of acute kidney injury (AKI) since elevated concentrations may reflect either a change in renal glomerular function or in structural tubular injury or both. In this study, we compared the performance of plasma NGAL in the diagnosis of functional changes and in the diagnosis of structural injury.

METHODS

Plasma and urine samples from 528 patients were collected on entry to an intensive care unit (ICU) as well as 12 and 24 h later. Plasma NGAL diagnostic performance was independently assessed for Functional-AKI and Structural-AKI. Functional-AKI was defined by changes in plasma creatinine, whereas Structural-AKI was defined by elevations in urinary NGAL.

RESULTS

On ICU entry, the area under the curve (AUC) for the diagnosis of Functional-AKI was 0.74 (95% CI: 0.69-0.79), and for Structural-AKI it was 0.79 (0.74-0.83). Plasma NGAL also predicted the need for dialysis (0.79; 0.66-0.81), but not for death. A principal component analysis demonstrated that the maximum plasma NGAL in 24 h reflected structural injury marginally more than functional changes. Plasma NGAL added value to an AKI diagnostic model comprising plasma creatinine, sepsis, age, and APACHE II score (integrated discrimination improvement: 0.073; 0.034-0.12).

CONCLUSION

Increased plasma NGAL reflects both decreased filtration and structural injury. For patients at a low calculated risk, the addition of NGAL reduced the risk, and for those at a higher risk, NGAL correctly assigned patients to even a higher risk.

Renal dendritic cells: an update

Discovery into the role of renal dendritic cells (rDCs) in health and disease of the kidney is rapidly accelerating. Progress in deciphering DC precursors and the heterogeneity of monocyte subsets in mice and humans is providing insight into the biology of rDCs. Recent findings have extended knowledge of the origins, anatomy and function of the rDC network at steady state and during periods of injury to the renal parenchyma. This brief review highlights these new findings and provides an update on the study of rDCs.