The economic impact and cost-effectiveness of urinary neutrophil gelatinase-associated lipocalin after cardiac surgery

Urinary Neutrophil Gelatinase-Associated Lipocalin Predicts Intensive Care Unit Admission Diagnosis: A Prospective Cohort Study

BACKGROUND

Acute kidney injury (AKI) is most commonly caused by tubular injury and is associated with a wide variety of critical illnesses. It is well known that urinary biomarkers can lead to the early identification of AKI. However, the ability of urinary biomarkers to distinguish between different types of critical illness has been less studied.

METHODS

In this prospective cohort study, urinary neutrophil gelatinase-associated lipocalin (uNGAL) was measured in 107 patients consecutively admitted to the ICUs in our tertiary medical center. uNGAL samples were collected within 3-6 hours of admission to an ICU and measured by ELISA. All data were analyzed using R statistical software, and univariate analysis was used to determine the correlations of uNGAL levels with AKI stage, admission diagnoses, and ICU course.

RESULTS

uNGAL level increased by a mean of 24-fold (SD 10-59) in ICU patients with AKI and demonstrated a significant correlation with the different AKI stages. uNGAL predicted the need for RRT, with values increased by more than 15-fold (P<0.05) in patients needing RRT, and remained a useful tool to predict AKI in ICU patients with a urinary tract infection. uNGAL level was correlated with certain ICU admitting diagnoses whereby uNGAL levels were lower in ICU patients with cardiogenic shock compared with other admission diagnoses (β=-1.92, P<0.05).

CONCLUSIONS

uNGAL can be used as an early predictor of AKI and its severity in patients admitted to the ICU, including the need for RRT. uNGAL may also help in distinguishing patients with cardiogenic shock from those with other critical illnesses and identifying those at risk for poor outcomes irrespective of the presence of AKI.

Biomarkers of acute kidney injury after pediatric cardiac surgery: a meta-analysis of diagnostic test accuracy

Acute kidney injury (AKI) occurs frequently after cardiac surgery in children. Although current diagnostic criteria rely on serum creatinine and urine output, changes occur only after considerable loss of kidney function. This meta-analysis aimed to synthesize the knowledge on novel biomarkers and compare their ability to predict AKI. PubMed/MEDLINE, Embase, Scopus, and reference lists were searched for relevant studies published by March 2021. Diagnostic accuracy parameters were extracted and analyzed using hierarchical summary receiver operating characteristic (HSROC) method. Pooled estimates of the area under the curve (AUC) were calculated using conventional random-effects meta-analysis. Fifty-six articles investigating 49 biomarkers in 8617 participants fulfilled our eligibility criteria. Data from 37 studies were available for meta-analysis. Of the 10 biomarkers suitable for HSROC analysis, urinary neutrophil gelatinase-associated lipocalin (uNGAL) to creatinine (Cr) ratio yielded the highest diagnostic odds ratio (91.0, 95% CI 90.1-91.9), with a sensitivity of 91.3% (95% CI 91.2-91.3%) and a specificity of 89.7% (95% CI 89.6-89.7%). These results were confirmed in pooled AUC analysis, as uNGAL-to-Cr ratio and uNGAL were the only elaborately studied biomarkers (> 5 observations) with pooled AUCs ≥ 0.800. Liver fatty acid-binding protein (L-FABP), serum cystatin C (sCysC), serum NGAL (sNGAL), and interleukin-18 (IL-18) all had AUCs ≥ 0.700.

CONCLUSION

A variety of biomarkers have been proposed as predictors of cardiac surgery-associated AKI in children, of which uNGAL was the most prominent with excellent diagnostic qualities. However, more consolidatory evidence will be required before these novel biomarkers may eventually help realize precision medicine in AKI management.

WHAT IS KNOWN

• Acute kidney injury (AKI) occurs in about 30-60% of children undergoing cardiac surgery and is associated with increased in-hospital mortality and adverse short-term outcomes. However, in current clinical practice, AKI definitions and detection often rely on changes in serum creatinine and urine output, which are late and insensitive markers of kidney injury. • Although various novel biomarkers have been studied for the diagnosis of AKI in children after cardiac surgery, it remains unclear how these compare to one another in terms of diagnostic accuracy.

WHAT IS NEW

• Pooled analyses suggest that for the diagnosis of AKI in children who underwent cardiac surgery, NGAL is the most accurate among the most frequently studied biomarkers. • A number of other promising biomarkers have been reported, although they will require further research into their diagnostic accuracy and clinical applicability.

Biomarkers for assessing acute kidney injury for people who are being considered for admission to critical care: a systematic review and cost-effectiveness analysis

BACKGROUND

Acute kidney injury is a serious complication that occurs in the context of an acute critical illness or during a postoperative period. Earlier detection of acute kidney injury may facilitate strategies to preserve renal function, prevent further disease progression and reduce mortality. Acute kidney injury diagnosis relies on a rise in serum creatinine levels and/or fall in urine output; however, creatinine is an imperfect marker of kidney function. There is interest in the performance of novel biomarkers used in conjunction with existing clinical assessment, such as NephroCheck^® (Astute Medical, Inc., San Diego, CA, USA), ARCHITECT^® urine neutrophil gelatinase-associated lipocalin (NGAL) (Abbott Laboratories, Abbott Park, IL, USA), and urine and plasma BioPorto NGAL (BioPorto Diagnostics A/S, Hellerup, Denmark) immunoassays. If reliable, these biomarkers may enable earlier identification of acute kidney injury and enhance management of those with a modifiable disease course.

OBJECTIVE

The objective was to evaluate the role of biomarkers for assessing acute kidney injury in critically ill patients who are considered for admission to critical care.

DATA SOURCES

Major electronic databases, conference abstracts and ongoing studies were searched up to June 2019, with no date restrictions. MEDLINE, EMBASE, Health Technology Assessment Database, Cumulative Index to Nursing and Allied Health Literature, Cochrane Central Register of Controlled Trials, Web of Science, World Health Organization Global Index Medicus, EU Clinical Trials Register, International Clinical Trials Registry Platform and ClinicalTrials.gov were searched.

REVIEW METHODS

A systematic review and meta-analysis were conducted to evaluate the performance of novel biomarkers for the detection of acute kidney injury and prediction of other relevant clinical outcomes. Random-effects models were adopted to combine evidence. A decision tree was developed to evaluate costs and quality-adjusted life-years accrued as a result of changes in short-term outcomes (up to 90 days), and a Markov model was used to extrapolate results over a lifetime time horizon.

RESULTS

A total of 56 studies (17,967 participants), mainly prospective cohort studies, were selected for inclusion. No studies addressing the clinical impact of the use of biomarkers on patient outcomes, compared with standard care, were identified. The main sources of bias across studies were a lack of information on blinding and the optimal threshold for NGAL. For prediction studies, the reporting of statistical details was limited. Although the meta-analyses results showed the potential ability of these biomarkers to detect and predict acute kidney injury, there were limited data to establish any causal link with longer-term health outcomes and there were considerable clinical differences across studies. Cost-effectiveness results were highly uncertain, largely speculative and should be interpreted with caution in the light of the limited evidence base. To illustrate the current uncertainty, 15 scenario analyses were undertaken. Incremental quality-adjusted life-years were very low across all scenarios, ranging from positive to negative increments. Incremental costs were also small, in general, with some scenarios generating cost savings with tests dominant over standard care (cost savings with quality-adjusted life-year gains). However, other scenarios generated results whereby the candidate tests were more costly with fewer quality-adjusted life-years, and were thus dominated by standard care. Therefore, it was not possible to determine a plausible base-case incremental cost-effectiveness ratio for the tests, compared with standard care.

LIMITATIONS

Clinical effectiveness and cost-effectiveness results were hampered by the considerable heterogeneity across identified studies. Economic model predictions should also be interpreted cautiously because of the unknown impact of NGAL-guided treatment, and uncertain causal links between changes in acute kidney injury status and changes in health outcomes.

CONCLUSIONS

Current evidence is insufficient to make a full appraisal of the role and economic value of these biomarkers and to determine whether or not they provide cost-effective improvements in the clinical outcomes of acute kidney injury patients.

FUTURE WORK

Future studies should evaluate the targeted use of biomarkers among specific patient populations and the clinical impact of their routine use on patient outcomes and management.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42019147039.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Evidence Synthesis programme and will be published in full in Health Technology Assessment; Vol. 26, No. 7. See the NIHR Journals Library website for further project information.

A systematic review of cost-effectiveness analyses across the acute kidney injury landscape

Introduction: Acute kidney injury (AKI) is a complex and common condition associated with increased morbidity, mortality, and costs. Evidence from cost-effectiveness analysis (CEA) have targeted various aspects of AKI including detection with biomarkers, treatment with renal replacement therapy, and prevention when using contrast media. However, there has not been a systematic review of these studies across the entirety of AKI.Areas covered: PubMed, Embase, and Cochrane library were used to identify CEA studies that involved AKI from 2004 onwards. These studies compared AKI treatment through renal replacement therapies (n = 6), prevention of contrast-induced-AKI (CI-AKI) using different media (n = 3), and diagnosis with novel biomarkers (n = 2). Treatment strategies for AKI focused on continuous versus intermittent renal replacement therapy. While there was no consensus, the majority of studies favored the continuous form. For contrast media, both studies found iodixanol to be cost-effective compared to iohexol for preventing CI-AKI. Additionally, novel biomarkers showed potential to be cost-effective in risk assessment and detection of AKI.Expert opinion: Consistent criteria such as a lifetime time horizon would allow for better model comparisons. Further research on clinical parameters to capture transition probabilities between stages within AKI and progression to downstream kidney disease is needed.

Evaluation of Urinary NGAL as a Diagnostic Tool for Acute Kidney Injury in Critically Ill Patients With Infection: An Original Study

Background:

Acute kidney injury (AKI) is a common complication in critical care patients. The presence of AKI is a marker for poor outcomes such as longer hospitalization durations, more hospital readmissions, and especially, higher mortality rates. Sepsis is one of the major causes of AKI within the intensive care unit (ICU) population. Sepsis-related AKI occurs in approximately 20% of patients, reaching more than 50% in patients with septic shock. The diagnosis of AKI depends on urine output and/or serum creatinine measurements. Unfortunately, serum creatinine is a late and unreliable (insensitive and nonspecific) indicator of AKI. However, biomarkers of renal damage have great potential in facilitating early diagnosis of AKI. Several biomarkers, including urinary neutrophil gelatinase-associated lipocalin (uNGAL), have been used in the early detection of AKI.

Objectives:

The aim of this study was to evaluate uNGAL for the diagnosis and prognosis of AKI in critical ill patients with infections.

Design:

Original study (Cohort Prospective Observational).

Setting:

Study in 2 ICUs of different Brazilian hospitals, in the city of Curitiba: Hospital de Clínicas da Universidade Federal do Paraná and Hospital da Polícia Militar do Paraná, from November 12, 2016 to May 15, 2018.

Participants:

Critically ill patients with infections, sepsis, or septic shock were selected. The inclusion criteria were patients older than 18 years with infection. They were followed up for 30 days in the analysis of outcomes. We requested that consent forms be signed by all eligible patients or their caregivers.

Measurements:

The urinary neutrophil gelatinase-associated lipocalin (uNGAL) levels of the patients were measured on 4 consecutive days and was assayed using a chemiluminescent microparticle immunoassay system. The screening time occurred within 72 hours of admission to the ICU. The first urine sample was collected within the first 24 hours of the screening hours. Mortality and AKI were assessed during first 30 days.

Methods:

clinical and laboratory data, including daily uNGAL levels, were assessed. The AKI stage using the KDIGO criteria was evaluated. Sensitivity, specificity, and the area under the curve-receiver operating characteristic (AUC-ROC) values were calculated to determine the optimal uNGAL level for predicting AKI.

Results:

We had 38 patients who completed the study during the screening period. The incidence of AKI was 76.3%. The hospitalization period was longer in the group that developed AKI, with 21 days of median (interquartile range [IQR]: 13.5-25); non-AKI group had a median of 13 days (IQR 7-18; P = .019). We found a direct relationship between uNGAL levels and the progression to AKI. Increased values of the biomarker were associated with the worsening of AKI (P < .05). The cutoff levels of uNGAL that identified patients who would progress to AKI were the following: (d1) >116 ng/mL, (d2) >100 ng/mL, and (d3) 284 ng/mL. The value of the fourth and last measurement was not predictive of patients who would progress to AKI. The median urinary uNGAL was also associated with mortality on Days 1, 3, and 4: d1, P = .039; d3, P = .005; d4, P = .005. The performance of uNGAL in detecting AKI patients (AUC-ROC = 0.881). There were no risk factors other than AKI that could be correlated with increased uNGAL levels on Day 1.

Limitations:

The study was carried out in 2 centers, having used only 1 biomarker, and our small number of patients were limitations.

Conclusion:

the uNGAL had an association in its values with the diagnosis and prognosis of patients with severe infections and AKI. We suggest that studies with a greater number of patients could better establish the cutoff values of uNGAL and/or serum NGAL in the identification of infected patients who are at a high risk of developing AKI.

The future for diagnostic tests of acute kidney injury in critical care: evidence synthesis, care pathway analysis and research prioritisation

BACKGROUND

Acute kidney injury (AKI) is highly prevalent in hospital inpatient populations, leading to significant mortality and morbidity, reduced quality of life and high short- and long-term health-care costs for the NHS. New diagnostic tests may offer an earlier diagnosis or improved care, but evidence of benefit to patients and of value to the NHS is required before national adoption.

OBJECTIVES

To evaluate the potential for AKI in vitro diagnostic tests to enhance the NHS care of patients admitted to the intensive care unit (ICU) and identify an efficient supporting research strategy.

DATA SOURCES

We searched ClinicalTrials.gov, The Cochrane Library databases, Embase, Health Management Information Consortium, International Clinical Trials Registry Platform, MEDLINE, metaRegister of Current Controlled Trials, PubMed and Web of Science databases from their inception dates until September 2014 (review 1), November 2015 (review 2) and July 2015 (economic model). Details of databases used for each review and coverage dates are listed in the main report.

REVIEW METHODS

The AKI-Diagnostics project included horizon scanning, systematic reviewing, meta-analysis of sensitivity and specificity, appraisal of analytical validity, care pathway analysis, model-based lifetime economic evaluation from a UK NHS perspective and value of information (VOI) analysis.

RESULTS

The horizon-scanning search identified 152 potential tests and biomarkers. Three tests, Nephrocheck^® (Astute Medical, Inc., San Diego, CA, USA), NGAL and cystatin C, were subjected to detailed review. The meta-analysis was limited by variable reporting standards, study quality and heterogeneity, but sensitivity was between 0.54 and 0.92 and specificity was between 0.49 and 0.95 depending on the test. A bespoke critical appraisal framework demonstrated that analytical validity was also poorly reported in many instances. In the economic model the incremental cost-effectiveness ratios ranged from £11,476 to £19,324 per quality-adjusted life-year (QALY), with a probability of cost-effectiveness between 48% and 54% when tests were compared with current standard care.

LIMITATIONS

The major limitation in the evidence on tests was the heterogeneity between studies in the definitions of AKI and the timing of testing.

CONCLUSIONS

Diagnostic tests for AKI in the ICU offer the potential to improve patient care and add value to the NHS, but cost-effectiveness remains highly uncertain. Further research should focus on the mechanisms by which a new test might change current care processes in the ICU and the subsequent cost and QALY implications. The VOI analysis suggested that further observational research to better define the prevalence of AKI developing in the ICU would be worthwhile. A formal randomised controlled trial of biomarker use linked to a standardised AKI care pathway is necessary to provide definitive evidence on whether or not adoption of tests by the NHS would be of value.

STUDY REGISTRATION

The systematic review within this study is registered as PROSPERO CRD42014013919.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Financial Impact of Acute Kidney Injury After Cardiac Operations in the United States

BACKGROUND

Acute kidney injury (AKI) after major cardiac operations is a potentially avoidable complication associated with increased morbidity, death, and costly long-term treatment. The financial impact of AKI at the population level has not been well defined. We sought to determine the incremental index hospital cost associated with the development of AKI.

METHODS

All patients undergoing coronary artery bypass grafting (CABG) or valve replacement operations, or both (clinical classification software codes 43 and 44), between 2008 and 2011 were identified from the Nationwide Inpatient Sample. AKI was identified using International Classification of Diseases, 9th Revision, Clinical Modification diagnosis codes (584.xx); patients with chronic renal failure were excluded. Mean total index hospitalization costs were compared between patients with and without AKI.

RESULTS

At the population level, 1,078,036 individuals underwent major cardiac procedures from 2008 to 2011, with AKI developing in 105,648 (9.8%). Specifically, AKI developed in 8.0% of CABG, 11.4% of valve replacement, and 17.0% of CABG plus valve replacement patients (p < 0.001). Death was more common among patients with AKI vs those without (13.9% vs 1.3%, p < 0.001). Mean total index hospitalization cost was $77,178 for patients with AKI vs $38,820 for those without (p < 0.001). At the national level, the overall incremental annual index hospitalization cost associated with AKI was $1.01 billion.

CONCLUSIONS

AKI developed in 1 in every 10 patients nationwide after a cardiac operation. Achieving a 10% reduction in AKI in this population would likely result in an annual savings of approximately $100,000,000 in index-hospital costs alone. Support for research on mechanisms to detect impending damage and prevent AKI may lead to reduced patient morbidity and death and to substantial health care cost savings.

Neutrophil Gelatinase-Associated Lipocalin as a Biomarker of Allograft Function After Renal Transplantation: Evaluation of the Current Status and Future Insights

Neutrophil gelatinase‐associated lipocalin (NGAL), a protein belonging to the lipocalin superfamily initially found in activated neutrophils, is expressed by several cell types, including kidney tubule. The increase in NGAL production and release from tubular cells in response to various insults has been proven to predict acute kidney injury (AKI). For this reason, it has emerged as a valuable noninvasive biomarker of AKI in clinical nephrology. Also in the renal transplant setting, different studies have indicated NGAL as a valuable tool, especially in the early postoperative period, since the currently available clinical and laboratory parameters remain poorly sensitive to monitor immediate posttransplant graft function. This is an analysis of the recent literature to assess the utility of plasma and urinary NGAL, exosomal mRNA for NGAL, and NGAL levels in the perfusate of machine‐perfused kidneys for the prediction of graft function recovery in the early postsurgery phase after renal transplantation. We found that NGAL appears as a promising troponin‐like biomarker to detect short‐term impairment of graft function after renal transplant, but there are still some limitations in its clinical application, essentially related to its low specificity. Moreover, comparing NGAL assayed in serum, urine, machine‐perfusate, or as exosomal mRNA, each one has shown limitations and benefits in terms of predictive performance for DGF, according to various existing studies, feasibly due to different cut‐off levels, designs and patient sample sizes.

Early detection of acute kidney injury after pediatric cardiac surgery

Acute kidney injury (AKI) is increasingly recognized as a common problem in children undergoing cardiac surgery, with well documented increases in morbidity and mortality in both the short and the long term. Traditional approaches to the identification of AKI such as changes in serum creatinine have revealed a large incidence in this population with significant negative impact on clinical outcomes. However, the traditional diagnostic approaches to AKI diagnosis have inherent limitations that may lead to under-diagnosis of this pathologic process. There is a dearth of randomized controlled trials for the prevention and treatment of AKI associated with cardiac surgery, at least in part due to the paucity of early predictive biomarkers. Novel non-invasive biomarkers have ushered in a new era that allows for earlier detection of AKI. With these new diagnostic tools, a more consistent approach can be employed across centers that may facilitate a more accurate representation of the actual prevalence of AKI and more importantly, clinical investigation that may minimize the occurrence of AKI following pediatric cardiac surgery. A thoughtful management approach is necessary to mitigate the effects of AKI after cardiac surgery, which is best accomplished in close collaboration with pediatric nephrologists. Long-term surveillance for improvement in kidney function and potential development of chronic kidney disease should also be a part of the comprehensive management strategy.

A Systematic Review of Health Economic Evaluations of Diagnostic Biomarkers

BACKGROUND

Diagnostic biomarkers have multiple applications along the care process and have a large potential in optimizing treatment decisions. However, many diagnostic biomarkers struggle to gain market access and obtain appropriate coverage because of a lack of evidence on their health economic impact.

OBJECTIVES

The aim was to review the (methodological) characteristics of recent economic evaluations on diagnostic biomarkers and examine whether these studies dealt with specific issues such as different payer perspectives, preference heterogeneity, and multiple applications in subpopulations.

METHODS

The PubMed database and the National Health Service Economic Evaluation Database were searched. Full economic evaluations published after 2009 assessing diagnostic biomarkers for the main non-communicable diseases in middle-income or high-income countries were considered eligible. Empirical and methodological study characteristics were summarized, as was the handling of specific issues related to the economic evaluation of personalized medicine.

RESULTS

Thirty-three economic evaluations were included, of which 25 were model-based analyses. The number of strategies compared ranged from two to 17 per study, and was especially large in studies assessing genetic testing in patients and their relatives. Cost-effectiveness results were most sensitive to test accuracy and costs of the biomarker (N = 7), the relative risk of an event (N = 4), and the proportion of people accepting genetic testing (N = 2). One study incorporated patient preferences, and none of the studies considered different payer perspectives, cost sharing arrangements or variable opportunity costs due to population density variability.

CONCLUSIONS

Published health economic evaluations of biomarkers used for diagnosing, staging diseases, and guiding treatment selection are characterized by a large number of comparators to model the potential clinical applications and to determine their value. Assessing outcomes beyond health as well as specific issues, such as different payer perspectives and patient preferences, is crucial to fully capture the potential health economic impact of diagnostic biomarkers and to inform value-based reimbursement.

Renalase and Biomarkers of Contrast-Induced Acute Kidney Injury

BACKGROUND

Contrast-induced acute kidney injury (CI-AKI) remains one of the crucial issues related to the development of invasive cardiology. The massive use of contrast media exposes patients to a great risk of contrast-induced nephropathy and chronic kidney disease development, and increases morbidity and mortality rates. The serum creatinine concentration does not allow for a timely and accurate CI-AKI diagnosis; hence numerous other biomarkers of renal injury have been proposed. Renalase, a novel catecholamine-metabolizing amine oxidase, is synthesized mainly in proximal tubular cells and secreted into urine and blood. It is primarily engaged in the degradation of circulating catecholamines. Notwithstanding its key role in blood pressure regulation, renalase remains a potential CI-AKI biomarker, which was shown to be markedly downregulated in the aftermath of renal injury. In this sense, renalase appears to be the first CI-AKI marker revealing an actual loss of renal function and indicating disease severity.

SUMMARY

The purpose of this review is to summarize the contemporary knowledge about the application of novel biomarkers of CI-AKI and to highlight the potential role of renalase as a functional marker of contrast-induced renal injury.

KEY MESSAGES

Renalase may constitute a missing biochemical link in the mutual interplay between kidney and cardiac pathology known as the cardiorenal syndrome.

Cost-effectiveness analysis of acute kidney injury biomarkers in pediatric cardiac surgery

Introduction

Acute kidney injury (AKI) is significant problem in children with congenital heart disease (CHD) who undergo cardiac surgery. The economic impact of a biomarker-based diagnostic strategy for AKI in pediatric populations undergoing CHD surgery is unknown. The aim of this study was to perform the cost effectiveness analysis of using serum cystatin C (sCysC), urine neutrophil gelatinase-associated lipocalin (uNGAL) and urine liver fatty acid-binding protein (uL-FABP) for the diagnosis of AKI in children after cardiac surgery compared with current diagnostic method (monitoring of serum creatinine (sCr) level).

Materials and methods

We developed a decision analytical model to estimate incremental cost-effectiveness of different biomarker-based diagnostic strategies compared to current diagnostic strategy. The Markov model was created to compare the lifetime cost associated with using of sCysC, uNGAL, uL-FABP with monitoring of sCr level for the diagnosis of AKI. The utility measurement included in the analysis was quality-adjusted life years (QALY). The results of the analysis are presented as the incremental cost-effectiveness ratio (ICER).

Results

Analysed biomarker-based diagnostic strategies for AKI were cost-effective compared to current diagnostic method. However, uNGAL and sCys C strategies yielded higher costs and lower effectiveness compared to uL-FABP strategy. uL-FABP added 1.43 QALY compared to current diagnostic method at an additional cost of $8521.87 per patient. Therefore, ICER for uL-FABP compared to sCr was $5959.35/QALY.

Conclusions

Our results suggest that the use of uL-FABP would represent cost effective strategy for early diagnosis of AKI in children after cardiac surgery.

Assessing the value of cardiac biomarkers: going beyond diagnostic accuracy?

In this era of scrutinized resource utilization, providers and payers are focused on the value of healthcare interventions more than ever. Cost-effectiveness evaluations are required by some health authorities and requested by others in order to guide budget allocation decisions. In the past, these evaluations did not methodologically consider laboratory diagnostics. We set out to explore the current requirements of health technology agencies that include laboratory diagnostics and describe, through a review of the literature, alternative methods for establishing the value of a biomarker or labroatory diagnostic beyond assay specifications and performance. The aim of this study was to evaluate the current use of a linked evidence approach in cost-effectiveness studies for cardiac laboratory tests in the last 5 years.

How has urinary proteomics contributed to the discovery of early biomarkers of acute kidney injury?

In the past decade, analysis of the urinary proteome (urinary proteomics) has intensified in response to the need for novel biomarkers that support early diagnosis of kidney diseases. In particular, this also applies to acute kidney injury, which is a heterogeneous complex syndrome with a still-increasing incidence at the intensive care unit. Unfortunately, this major need remains largely unmet to date. The current report aims to explain why attempts to implement urinary proteomic-discovered acute kidney injury diagnostic candidates in the intensive care unit setting have not yet led to success. Subsequently, some key notes are provided that should enhance the chance of translating selected urinary proteomic candidates to valuable tools for the nephrologist and intensivist in the near future.

Postoperative neutrophil gelatinase-associated lipocalin predicts acute kidney injury after pediatric cardiac surgery*

OBJECTIVE

We investigated the temporal pattern and predictive value of neutrophil gelatinase-associated lipocalin for early identification of acute kidney injury in children undergoing cardiac surgery.

DESIGN

Prospective observational cohort study.

SETTING

One PICU in a tertiary medical center in Madrid, Spain.

PATIENTS

One hundred six children older than 15 days and younger than 16 years undergoing surgery for congenital cardiac lesions.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Urine samples were obtained before and at intervals after surgery. Acute kidney injury was defined according to pediatric Risk, Injury, Failure, Loss, and End-stage kidney disease criteria. The temporal pattern of both urine neutrophil gelatinase-associated lipocalin absolute concentration elevation and normalized to urine creatinine concentration was correlated with the development of acute kidney injury and other clinical outcomes. We evaluated the predictive ability of both urine neutrophil gelatinase-associated lipocalin and urine neutrophil gelatinase-associated lipocalin/creatinine by area under the curve, when added to a clinical predictive model. Data from 106 pediatric patients were analyzed. Acute kidney injury occurred in 42 patients (39.6%). Urine neutrophil gelatinase-associated lipocalin significantly increased in patients with acute kidney injury at 1, 3, and 15 hours postoperatively. Urine neutrophil gelatinase-associated lipocalin and urine neutrophil gelatinase-associated lipocalin/creatinine correlated with surgical variables and clinical outcomes. Acute kidney injury prediction improved when urine neutrophil gelatinase-associated lipocalin was added to a clinical model (area under the curve increased at 1 hr from 0.85 to 0.91 and at 3 hr to 0.92). Neither the urine neutrophil gelatinase-associated lipocalin nor the urine neutrophil gelatinase-associated lipocalin/creatinine values were significantly different between patients with prerenal and sustained acute kidney injury.

CONCLUSIONS

Urine neutrophil gelatinase-associated lipocalin is a predictive biomarker for acute kidney injury after pediatric cardiac surgery, and it may permit earlier intervention that improves outcome of acute kidney injury. Urine neutrophil gelatinase-associated lipocalin normalized to urine creatinine improves the prediction of acute kidney injury severity but offers no advantage in acute kidney injury diagnosis.

Neutrophil gelatinase-associated lipocalin: pathophysiology and clinical applications

Neutrophil gelatinase-associated lipocalin (NGAL), a 25 kDa protein produced by injured nephron epithelia, is one of the most promising new markers of renal epithelial injury. In contrast to serum creatinine and urinary output, which are the measures of kidney function, NGAL is specifically induced in the damaged nephron and then released into blood and urine, where it can be readily measured. Careful proof-of-concept studies using defined animal models have uncovered the sources and trafficking of NGAL in acute kidney injury (AKI) and have addressed the contributions of renal and non-renal sources. Clinical studies indicate that NGAL, unlike creatinine, is a marker responsive to tissue stress and nephron injury, but less so to adaptive hemodynamic responses. In certain clinical settings, NGAL is an earlier marker compared with serum creatinine. In addition, clinical studies have shown that NGAL is a powerful predictor of poor clinical outcomes, which can be used to risk stratify patients when combined with serum creatinine. NGAL has important limitations, including its responsiveness in systemic inflammation, which is partially uncoupled from its response to kidney injury and which needs to be considered when interpreting NGAL results clinically. This review covers the biology and pathophysiology of NGAL and summarizes the results of the growing body of clinical studies that have addressed the utility of NGAL in the early diagnosis of AKI, in the distinction of intrinsic AKI and in the prognostic assessment of broad patient populations.

Advances in acute kidney injury associated with cardiac surgery: the unfolding revolution in early detection

Cardiac surgery-associated acute kidney injury (CSA-AKI) is important because it remains common and serious. A major limitation in the management of CSA-AKI has been ongoing delayed diagnosis by standard clinical approaches, including serum creatinine and calculated glomerular filtration rate. Recent advances in the understanding of CSA-AKI have highlighted the utility of novel biomarkers that diagnose CSA-AKI within the first 24 hours. The biomarkers that have been evaluated in clinical trials include neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, kidney injury molecule 1 and interleukin-18. The biomarker with the greatest clinical promise is NGAL. Although it has multiple advantages over serum creatinine, it is still not the ideal biomarker for CSA-AKI. It is likely that a panel of early biomarkers will be developed to facilitate rapid and reliable detection of CSA-AKI, combining their different characteristics to optimize patient management. Future clinical trials likely will focus on whether these biomarkers predict adverse outcomes independent of serum creatinine fluctuations and whether therapies guided by biomarker profiles improve renal salvage and overall clinical outcomes. Given their clinical utility, these novel biomarkers have been evaluated beyond cardiac surgery for AKI in multiple clinical environments, including the emergency department, the operating room, the cardiac catheterization laboratory, and the intensive care unit. Their integration into clinical practice seems likely in the near future.