Urinary [TIMP-2]·[IGFBP7]-guided randomized controlled intervention trial to prevent acute kidney injury in the emergency department

Biomarkers in acute kidney injury

Acute kidney injury (AKI) is a multifactorial syndrome with a high risk of short- and long-term complications as well as increased health care costs. The traditional biomarkers of AKI, serum creatinine and urine output, have important limitations. The discovery of new functional and damage/stress biomarkers has enabled a more precise delineation of the aetiology, pathophysiology, site, mechanisms, and severity of injury. This has allowed earlier diagnosis, better prognostication, and the identification of AKI sub-phenotypes. In this review, we summarize the roles and challenges of these new biomarkers in clinical practice and research.

Effect of care bundles for acute kidney injury: A systematic review and meta-analysis

PURPOSE

Acute kidney injury (AKI) is frequent among in-hospital patients with high incidence and mortality. Implementing a series of evidence-based AKI care bundles may improve patient outcomes by reducing changeable standards of care. The aim of this meta-analysis was therefore to appraise the influences of AKI care bundles on patient outcomes.

MATERIALS AND METHODS

We explored three international databases (PubMed, Embase, and Cochrane Central Register of Controlled Trials) and two Chinese databases (Wanfang Data and China National Knowledge Infrastructure) for studies from databases inception until November 30, 2022, comparing the impact of different AKI care bundles with usual standards of care in patients with or at risk for AKI. The study quality of non-randomized controlled trials and randomized controlled trials was evaluated by the NIH Study Quality Assessment Tool and the Cochrane risk of bias tool. Heterogeneity between studies was appraised by Cochran's Q test and I2 statistics. The possible origins of heterogeneity between studies were assessed adopting Meta-regression and subgroup analyses. Funnel plot asymmetry and Egger regression and Begg correlation tests were performed to discover potential publication bias. Data analysis was completed by software (RevMan 5.3 and Stata 15.0). The primary outcome was short- or long-term mortality. The secondary outcomes involved the incidence and severity of AKI.

RESULTS

Sixteen studies containing 25,690 patients and 25,903 AKI episodes were included. In high-risk AKI patients determined by novel biomarkers, electronic alert or risk prediction score, the application of AKI care bundles significantly reduced the AKI incidence (OR, 0.71; 95% CI, 0.53-0.96; p = 0.02; I2 = 84%) and AKI severity (OR, 0.59; 95% CI, 0.39-0.89; p = 0.01; I2 = 65%). No strong evidence is available to prove that care bundles can significantly reduce mortality (OR, 1.16; 95% CI, 0.58-2.30; p = 0.68; I2 = 97%).

CONCLUSIONS

The introduction of AKI care bundles in routine clinical practice can effectively improve the outcomes of patients with or at-risk of AKI. However, the accumulated evidence is limited and not strong enough to make definite conclusions.

New biomarkers in acute kidney injury

Acute kidney injury (AKI) is a commonly encountered clinical syndrome. Although it often complicates community acquired illness, it is more common in hospitalized patients, particularly those who are critically ill or who have undergone major surgery. Approximately 20% of hospitalized adult patients develop an AKI during their hospital care, and this rises to nearly 60% in the critically ill, depending on the population being considered. In general, AKI is more common in older adults, in those with preexisting chronic kidney disease and in those with known risk factors for AKI (including diabetes and hypertension). The development of AKI is associated with an increase in both mortality and morbidity, including the development of post-AKI chronic kidney disease. Currently, AKI is defined by a rise in serum creatinine from either a known or derived baseline value and/or oliguria or anuria. However, clinicians may fail to recognize the initial development of AKI because of a delay in the rise of serum creatinine or because of inaccurate urine output monitoring. This, in turn, delays any putative measures to treat AKI or to limit its degree. Consequently, efforts have focused on new biomarkers associated with AKI that may allow early recognition of this syndrome with the intent that this will translate into improved patient outcomes. Here we outline current biomarkers associated with AKI and explore their potential in aiding diagnosis, understanding the pathophysiology and directing therapy.

Improvement of composite kidney outcomes by AKI care bundles: a systematic review and meta-analysis

INTRODUCTION

Various approaches have been suggested to identify acute kidney injury (AKI) early and to initiate kidney-protective measures in patients at risk or with AKI. The objective of this study was to evaluate whether care bundles improve kidney outcomes in these patients.

METHODS

We conducted a systematic review of the literature to evaluate the clinical effectiveness of AKI care bundles with or without urinary biomarkers in the recognition and management of AKI. The main outcomes were major adverse kidney events (MAKEs) consisting of moderate-severe AKI, receipt of renal replacement therapy (RRT), and mortality.

RESULTS

Out of 7434 abstracts screened, 946 published studies were identified. Thirteen studies [five randomized controlled trials (RCTs) and eight non-RCTs] including 16,540 patients were eligible for inclusion in the meta-analysis. Meta-analysis showed a lower incidence of MAKE in the AKI care bundle group [odds ratio (OR) 0.73, 95% confidence interval (CI) 0.66-0.81] with differences in all 3 individual outcomes [moderate-severe AKI (OR 0.65, 95% CI 0.51-0.82), RRT (OR 0.63, 95% CI = 0.46-0.88) and mortality]. Subgroup analysis of the RCTs, all adopted biomarker-based approach, decreased the risk of MAKE (OR 0.55, 95% CI 0.41-0.74). Network meta-analysis could reveal that the incorporation of biomarkers in care bundles carried a significantly lower risk of MAKE when compared to care bundles without biomarkers (OR = 0.693, 95% CI = 0.50-0.96), while the usual care subgroup had a significantly higher risk (OR = 1.29, 95% CI = 1.09-1.52).

CONCLUSION

Our meta-analysis demonstrated that care bundles decreased the risk of MAKE, moderate-severe AKI and need for RRT in AKI patients. Moreover, the inclusion of biomarkers in care bundles had a greater impact than care bundles without biomarkers.

Real-World Use of AKI Biomarkers: A Quality Improvement Project Using Urinary Tissue Inhibitor Metalloprotease-2 and Insulin-Like Growth Factor Binding Protein 7 ([TIMP-2]*[IGFBP7])

INTRODUCTION

Novel urinary biomarkers, including tissue inhibitor metalloprotease-2 and insulin-like growth factor binding protein 7 ([TIMP-2]*[IGFBP7]), have been developed to identify patients at risk for acute kidney injury (AKI). We investigated the "real-world" clinical utility of [TIMP-2]*[IGFBP7] in preventing AKI.

METHODS

We performed a before and after single-center quality improvement study of intensive care unit (ICU) patients at risk for severe (KDIGO stage 2 or 3) AKI. In the prospective cohort, ICU providers were allowed to order [TIMP-2]*[IGFBP7] for patients at their discretion, then offered AKI practice recommendations based on the results. Outcomes were compared to a historical cohort in which biomarker values were not reported to clinical teams.

RESULTS

There was no difference in 7-day progression to severe AKI between the prospective (n = 116) and historical cohorts (n = 63) when [TIMP-2]*[IGFBP7] ≥0.3 (24 [28%] versus 8 [21%], p = 0.38) despite more stage 1 AKI at time of biomarker measurement in the prospective cohort (58 [67%] versus 9 [23%], p < 0.001). In the prospective cohort, patients with higher [TIMP-2]*[IGFBP7] values were more likely to receive a nephrology consult. Early consultation (within 24 h of biomarker measurement, n = 20) had a nonsignificant trend toward net negative volume balance (-1,787 mL [6,716 mL] versus + 4,974 mL [15,540 mL]) and more diuretic use (19 [95%] versus 8 [80%]) and was associated with less severe AKI (9 [45%] versus 10 [100%], p = 0.004) and inpatient dialysis (2 [10%] versus 7 [70%], p = 0.002) compared to delayed consultation (n = 10).

CONCLUSIONS

Despite the prospective cohort having more preexisting stage 1 AKI, there were equal rates of progression to severe AKI in the prospective and historical cohorts. In the setting of [TIMP-2]*[IGFBP7] reporting, there were more nephrology consults in response to elevated biomarker levels. Early nephrology consultation resulted in improved volume balance and favorable outcomes compared to delayed consultation.

A risk-stratified assessment of biomarker-based acute kidney injury phenotypes in children

BACKGROUND

The functional acute kidney injury (AKI) diagnostic tests serum creatinine (SCr) and urine output are imprecise and make management challenging. Combining tubular injury biomarkers with functional markers reveal AKI phenotypes that may facilitate personalized care. However, when and in whom to obtain injury biomarkers remains unclear.

METHODS

This was a prospective, observational study of patients admitted to a pediatric intensive care unit (PICU). Using the Renal Angina Index (RAI), subjects were screened for the presence (RAI+) or absence (RAI-) of renal angina 12 h post-admission and assigned an AKI phenotype using urinary NGAL (NGAL+: ≥150 ng/ml) and SCr (SCr+: ≥KDIGO Stage 1). Outcomes for each AKI phenotype were assessed and compared by RAI status.

RESULTS

In all, 200/247 (81%) subjects were RAI+. RAI+ subjects who were NGAL+ had higher risk of Day 3 AKI, renal replacement therapy use, and mortality and fewer ventilator- and PICU-free days, compared to NGAL-, irrespective of Day 0 SCr. Similar findings were not demonstrated in RAI- subjects, though NGAL+/SCr+ was associated with fewer ventilator- and PICU-free days compared to NGAL-/SCr+.

CONCLUSIONS

NGAL- and SCr-based AKI phenotypes provide improved prognostic information in children with renal angina (RAI+) and/or with SCr elevation. These populations may be appropriate for targeted biomarker testing.

IMPACT

New consensus recommendations encourage the integration of kidney tubular injury biomarkers such as urinary NGAL with serum creatinine for diagnosis and staging of acute kidney injury; however, no structured testing framework exists guiding when to test and in whom. Urinary NGAL- and serum creatinine-based acute kidney injury phenotypes increase diagnostic precision in critically ill children experiencing renal angina (RAI+) or serum creatinine-defined acute kidney injury. These data provide preliminary evidence for a proposed framework for directed urinary NGAL assessment in the pediatric intensive care unit.

Algorithm-based detection of acute kidney injury according to full KDIGO criteria including urine output following cardiac surgery: a descriptive analysis

BACKGROUND

Automated data analysis and processing has the potential to assist, improve and guide decision making in medical practice. However, by now it has not yet been fully integrated in a clinical setting. Herein we present the first results of applying algorithm-based detection to the diagnosis of postoperative acute kidney injury (AKI) comprising patient data from a cardiac surgical intensive care unit (ICU).

METHODS

First, we generated a well-defined study population of cardiac surgical ICU patients by implementing an application programming interface (API) to extract, clean and select relevant data from the archived digital patient management system. Health records of N = 21,045 adult patients admitted to the ICU following cardiac surgery between 2012 and 2022 were analyzed. Secondly, we developed a software functionality to detect the incidence of AKI according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria, including urine output. Incidence, severity, and temporal evolution of AKI were assessed.

RESULTS

With the use of our automated data analyzing model the overall incidence of postoperative AKI was 65.4% (N = 13,755). Divided by stages, AKI 2 was the most frequent maximum disease stage with 30.5% of patients (stage 1 in 17.6%, stage 3 in 17.2%). We observed considerable temporal divergence between first detections and maximum AKI stages: 51% of patients developed AKI stage 2 or 3 after a previously identified lower stage. Length of ICU stay was significantly prolonged in AKI patients (8.8 vs. 6.6 days, p <  0.001) and increased for higher AKI stages up to 10.1 days on average. In terms of AKI criteria, urine output proved to be most relevant, contributing to detection in 87.3% (N = 12,004) of cases.

CONCLUSION

The incidence of postoperative AKI following cardiac surgery is strikingly high with 65.4% when using full KDIGO-criteria including urine output. Automated data analysis demonstrated reliable early detection of AKI with progressive deterioration of renal function in the majority of patients, therefore allowing for potential earlier therapeutic intervention for preventing or lessening disease progression, reducing the length of ICU stay, and ultimately improving overall patient outcomes.

Biomarker Rule-in or Rule-out in Patients With Acute Diseases for Validation of Acute Kidney Injury in the Emergency Department (BRAVA): A Multicenter Study Evaluating Urinary TIMP-2/IGFBP7

Background

Urine tissue inhibitor of metalloproteinases-2/insulin-like growth factor-binding protein 7 (TIMP-2/IGFBP7) (NephroCheck, Ortho Clinical Diagnostics, Raritan, NJ, USA) is a US Food and Drug Administration-approved biomarker for risk assessment of acute kidney injury (AKI) in critically ill adult patients in intensive care units; however, its clinical impact in the emergency department (ED) remains unproven. We evaluated the utility of NephroCheck for predicting AKI development and short-term mortality in the ED.

Methods

This was a prospective, observational, five-center international study. We consecutively enrolled ED patients admitted with ≥30% risk of AKI development (assessed by ED physician: ED score) or acute diseases. Serum creatinine was tested on ED arrival (T0), day 1, and day 2 (T48); urine for NephroCheck was collected at T0 and T48. We performed ROC curve and reclassification analyses.

Results

Among the 529 patients enrolled (213 females; median age, 65 years), AKI developed in 59 (11.2%) patients. The T0 NephroCheck value was higher in the AKI group than in the non-AKI group (median 0.77 vs. 0.29 (ng/m)2/1,000, P=0.001), and better predicted AKI development than the ED score (area under the curve [AUC], 0.64 vs. 0.53; P=0.04). In reclassification analyses, adding NephroCheck to the ED score improved the prediction of AKI development (P<0.05). The T0 NephroCheck value predicted 30-day mortality (AUC, 0.68; P<0.001).

Conclusions

NephroCheck can predict both AKI development and short-term mortality in at-risk ED patients. NephroCheck would be a useful biomarker for early ruling-in or ruling-out of AKI in the ED.

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.

Trends in Adaptive Design Methods in Dialysis Clinical Trials: A Systematic Review

Rationale & Objective

Adaptive design methods are intended to improve the efficiency of clinical trials and are relevant to evaluating interventions in dialysis populations. We sought to determine the use of adaptive designs in dialysis clinical trials and quantify trends in their use over time.

Study Design

We completed a novel full-text systematic review that used a machine learning classifier (RobotSearch) for filtering randomized controlled trials and adhered to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines.

Setting & Study Populations

We searched MEDLINE (PubMed) and ClinicalTrials.gov using sensitive dialysis search terms.

Selection Criteria for Studies

We included all randomized clinical trials with patients receiving dialysis or clinical trials with dialysis as a primary or secondary outcome. There was no restriction of disease type or intervention type.

Data Extraction & Analytical Approach

We performed a detailed data extraction of trial characteristics and a completed a narrative synthesis of the data.

Results

57 studies, available as 68 articles and 7 ClinicalTrials.gov summaries, were included after full-text review (initial search, 209,033 PubMed abstracts and 6,002 ClinicalTrials.gov summaries). 31 studies were conducted in a dialysis population and 26 studies included dialysis as a primary or secondary outcome. Although the absolute number of adaptive design methods is increasing over time, the relative use of adaptive design methods in dialysis trials is decreasing over time (6.12% in 2009 to 0.43% in 2019, with a mean of 1.82%). Group sequential designs were the most common type of adaptive design method used. Adaptive design methods affected the conduct of 50.9% of trials, most commonly resulting in stopping early for futility (41.2%) and early stopping for safety (23.5%). Acute kidney injury was studied in 32 trials (56.1%), kidney failure requiring dialysis was studied in 24 trials (42.1%), and chronic kidney disease was studied in 1 trial (1.75%). 27 studies (47.4%) were supported by public funding. 44 studies (77.2%) did not report their adaptive design method in the title or abstract and would not be detected by a standard systematic review.

Limitations

We limited our search to 2 databases (PubMed and ClinicalTrials.gov) due to the scale of studies sourced (209,033 and 6,002 results, respectively).

Conclusions

Adaptive design methods are used in dialysis trials but there has been a decline in their relative use over time.

Impact of AKI care bundles on kidney and patient outcomes in hospitalized patients: a systematic review and meta-analysis

Background

A bundle of preventive measures can be taken to avoid acute kidney injury (AKI) or progression of AKI. We performed a systematic review and meta-analysis to evaluate the compliance to AKI care bundles in hospitalized patients and its impact on kidney and patient outcomes.

Methods

Randomized controlled trials, observational and interventional studies were included. Studied outcomes were care bundle compliance, occurrence of AKI and moderate-severe AKI, use of kidney replacement therapy (KRT), kidney recovery, mortality (ICU, in-hospital and 30-day) and length-of-stay (ICU, hospital). The search engines PubMed, Embase and Google Scholar were used (January 1, 2012 - June 30, 2021). Meta-analysis was performed with the Mantel Haenszel test (risk ratio) and inverse variance (mean difference). Bias was assessed by the Cochrane risk of bias tool (RCT) and the NIH study quality tool (non-RCT).

Results

We included 23 papers of which 13 were used for quantitative analysis (4 RCT and 9 non-randomized studies with 25,776 patients and 30,276 AKI episodes). Six were performed in ICU setting. The number of trials pooled per outcome was low. There was a high variability in care bundle compliance (8 to 100%). Moderate-severe AKI was less frequent after bundle implementation [RR 0.78, 95%CI 0.62–0.97]. AKI occurrence and KRT use did not differ between the groups [resp RR 0.90, 95%CI 0.76–1.05; RR 0.67, 95%CI 0.38–1.19]. In-hospital and 30-day mortality was lower in AKI patients exposed to a care bundle [resp RR 0.81, 95%CI 0.73–0.90, RR 0.95 95%CI 0.90–0.99]; this could not be confirmed by randomized trials. Hospital length-of-stay was similar in both groups [MD -0.65, 95%CI -1.40,0.09].

Conclusion

This systematic review and meta-analysis shows that implementation of AKI care bundles in hospitalized patients reduces moderate-severe AKI. This result is mainly driven by studies performed in ICU setting. Lack of data and heterogeneity in study design impede drawing firm conclusions about patient outcomes. Moreover, compliance to AKI care bundles in hospitalized patients is highly variable. Additional research in targeted patient groups at risk for moderate-severe AKI with correct and complete implementation of a feasible, well-tailored AKI care bundle is warranted. (CRD42020207523).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02534-4.

Biomarkers in Acute Kidney Injury

Biomarkers have become a pillar of precision medicine in acute kidney injury (AKI). Traditional markers for diagnosis of AKI are insensitive and insufficient to provide comprehensive information for prognostication. Several emerging biomarkers have shown promising results in large-scale clinical studies. These novel markers likely will be beneficial for personalized AKI prevention and treatment.

Use of Biomarkers to Identify Acute Kidney Injury to Help Detect Sepsis in Patients With Infection

OBJECTIVES

Although early recognition of sepsis is vital to improving outcomes, the diagnosis may be missed or delayed in many patients. Acute kidney injury is one of the most common organ failures in patients with sepsis but may not be apparent on presentation. Novel biomarkers for acute kidney injury might improve organ failure recognition and facilitate earlier sepsis care.

DESIGN

Retrospective, international, Sapphire study.

SETTING

Academic Medical Center.

PATIENTS

Adults admitted to the ICU without evidence of acute kidney injury at time of enrollment.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We stratified patients enrolled in the Sapphire study into three groups-those with a clinical diagnosis of sepsis (n = 216), those with infection without sepsis (n = 120), and those without infection (n = 387) at enrollment. We then examined 30-day mortality stratified by acute kidney injury within each group. Finally, we determined the operating characteristics for kidney stress markers (tissue inhibitor of metalloproteinases-2) × (insulin-like growth factor binding protein 7) for prediction of acute kidney injury as a sepsis-defining organ failure in patients with infection without a clinical diagnosis of sepsis at enrollment. Combining all groups, 30-day mortality was 23% for patients who developed stage 2-3 acute kidney injury within the first 3 days compared with 14% without stage 2-3 acute kidney injury. However, this difference was greatest in the infection without sepsis group (34% vs 11%; odds ratio, 4.09; 95% CI, 1.53-11.12; p = 0.005). Using a (tissue inhibitor of metalloproteinases-2) × (insulin-like growth factor binding protein 7) cutoff of 2.0 units, 14 patients (11.7%), in the infection/no sepsis group, tested positive of which 10 (71.4%) developed stage 2-3 acute kidney injury. The positive test result occurred a median of 19 hours (interquartile range, 0.8-34.0 hr) before acute kidney injury manifested by serum creatinine or urine output. Similar results were obtained using a cutoff of 1.0 for any stage of acute kidney injury.

CONCLUSIONS

Use of the urinary (tissue inhibitor of metalloproteinases-2) × (insulin-like growth factor binding protein 7) test could identify acute kidney injury in patients with infection, possibly helping to detect sepsis, nearly a day before acute kidney injury is apparent by clinical criteria.

Rational selection of a biomarker panel targeting unmet clinical needs in kidney injury

The pipeline of biomarker translation from bench to bedside is challenging and limited biomarkers have been adopted to routine clinical care. Ideally, biomarker research and development should be driven by unmet clinical needs in health care. To guide researchers, clinical chemists and clinicians in their biomarker research, the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) has developed a structured questionnaire in which the clinical gaps in current clinical pathways are identified and desirable performance specifications are predefined. In kidney injury, the high prevalence of the syndrome acute kidney injury (AKI) in the hospital setting has a significant impact on morbidity, patient survival and health care costs, but the use of biomarkers indicating early kidney injury in daily patient care remains limited. Routinely, medical labs measure serum creatinine, which is a functional biomarker, insensitive for detecting early kidney damage and cannot distinguish between renal and prerenal AKI. The perceived unmet clinical needs in kidney injury were identified through the EFLM questionnaire. Nephrologists within our tertiary care hospital emphasized that biomarkers are needed for (1) early diagnosis of in-hospital AKI after a medical insult and in critically ill patients, (2) risk stratification for kidney injury prior to a scheduled (elective) intervention, (3) kidney injury monitoring in patients scheduled to receive nephrotoxic medication and after kidney transplantation and (4) differentiation between prerenal AKI and structural kidney damage. The biomarker search and selection strategy resulted in a rational selection of an eleven-protein urinary panel for kidney injury that target these clinical needs. To assess the clinical utility of the proposed biomarker panel in kidney injury, a multiplexed LC-MS test is now in development for the intended translational research.

Current concepts and advances in biomarkers of acute kidney injury

Despite advancements in standardizing the criteria for acute kidney injury (AKI), its definition remains based on changes in serum creatinine and urinary output that do not specifically represent tubular function or injury and that have significant limitations in the acute hospital setting. Much effort in nephrology has centered on identifying biomarkers of AKI to address these limitations. This review summarizes recent advances in our knowledge of biomarkers involved in pathophysiological processes during AKI and describes their potential clinical implications. Blood and urine biomarkers are released via various mechanisms during renal tubular injury. Urinary kidney injury molecule-1 (KIM-1), liver-type fatty acid binding protein (L-FABP), insulin-like growth factor-binding protein-7 (IGFBP-7), and tissue inhibitor of metalloprotease-2 (TIMP-2) are released from the proximal tubule while uromodulin (UMOD) is secreted from the loop of Henle and neutrophil gelatinase-associated lipocalin (NGAL) is released from the distal tubule. These biomarkers could therefore be used to localize specific segments of injured tubules. Biomarkers also have diverse roles in pathophysiological processes in AKI, including inflammation, repair, and fibrosis. Current evidence suggests that these biomarkers could be used to predict the transition to chronic kidney disease (CKD), decrease discard of AKI kidneys, differentiate between kidney dysfunction and injury, guide AKI management, and improve diagnosis of diseases such as acute interstitial nephritis (AIN). They could differentiate between disease phenotypes, facilitate the inclusion of a homogenous patient population in future trials of AKI, and shed light on therapeutic pathways to prevent the transition from AKI to CKD. However, a major limitation of current biomarker research in AKI is the lack of tissue correlation. The Kidney Precision Medicine Project, a large-scale national effort, is currently underway to construct a kidney tissue atlas and expand the use of biomarkers to assess nephron health. Numerous biomarkers are involved in distinct pathophysiological processes after kidney injury and have demonstrated potential to improve diagnosis and risk stratification as well as provide a prognosis for patients with AKI. Some biomarkers are ready for use in clinical trials of AKI and could guide management in various clinical settings. Further investigation of these biomarkers will provide insight that can be applied to develop novel therapeutic agents for AKI.

Value of the cell cycle arrest biomarkers in the diagnosis of pregnancy-related acute kidney injury

Background: Pregnancy-related acute kidney injury (PRAKI) is still a common serious problem in developing countries. Insulin-like growth factor-binding protein 7 (IGFBP7) and tissue inhibitor metalloproteinases-2 (TIMP-2) can identify critically ill patients at risk for the development of severe AKI. Aim: To identify main causes and timing of PRAKI and to study the G1 cell cycle arrest biomarkers in cases diagnosed with (PRAKI) as a diagnostic tool. Methods: 80 pregnant women diagnosed with PRAKI were recruited from a single hospital as well as 30 age-matched pregnant women with normal pregnancy participated in the present study. A urine specimen was collected from all study participants with established AKI within 24 h of ICU admission to measure [TIMP-2]*[IGFBP7]. Results: The incidence of PRAKI was 1.1%. The most common cause of PRAKI is pre-eclampsia/eclampsia spectrum (61%). Most of the cases occur in the third trimester (60%) and postpartum period (23%). At a cutoff 0.33 ng/ml, the estimated sensitivity and specificity of urinary [TIMP-2]*[IGFBP7] in predicting PRAKI is 100% (95% CI) with NPV and PPV are 100%. Conclusion: Urinary [TIMP-2]*[IGFBP7] serves as a sensitive and specific biomarker in the diagnosis of PRAKI.

Clinical adoption of Nephrocheck® in the early detection of acute kidney injury

Acute kidney injury is a common complication of acute illnesses and is associated with increased morbidity and mortality. Over the past years several acute kidney injury biomarkers for diagnostication, decision-making processes, and prognosis of acute kidney injury and its outcomes have been developed and validated. Among these biomarkers, tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7), the so-called cell cycle arrest biomarkers, showed a superior profile of accuracy and stability even in patients with substantial comorbidities. Therefore, in 2014, the US Food and Drug Administration approved the use of the product of TIMP-2 and IGFBP7 ([TIMP-2] × [IGFBP7]), known as cell cycle arrest biomarkers, to aid critical care physicians and nephrologists in the early prediction of acute kidney injury in the critical care setting. To date, Nephrocheck® is the only commercially available test for [TIMP-2] × [IGFBP7]. In this narrative review, we describe the growing clinical and investigational momentum of biomarkers, focusing on [TIMP-2] × [IGFBP7], as one of the most promising candidate biomarkers. Additionally, we review the current state of clinical implementation of Nephrocheck®.

Quality of care after AKI development in the hospital: Consensus from the 22nd Acute Disease Quality Initiative (ADQI) conference

BACKGROUND

Acute kidney injury (AKI) is independently associated with increased morbidity and mortality. Quality improvement has been identified as an important goal in the care of patients with AKI. Different settings can be targeted to improve AKI care, broadly classified these include the inpatient and outpatient environments. In this paper, we will emphasize quality indicators associated with the management and secondary prevention of AKI in hospitalized patients to limit the severity, duration, and complications.

METHODS

During the 22nd Acute Disease Quality Initiative (ADQI) consensus conference, a multidisciplinary group of experts discussed the evidence and used a modified Delphi process to achieve consensus on recommendations for AKI-related quality indicators (QIs) and care processes to improve patient outcomes. The management and secondary prevention of AKI in hospitalized patients were discussed, and recommendations were summarized.

RESULTS

The first step in optimizing the quality of AKI management is the determination of baseline performance. Data regarding each institution's/center's performance can provide a reference point from which to benchmark quality efforts. Quality program initiatives should prioritize achievable goals likely to have the highest impact according to the setting and context. Key AKI quality metrics should include improvement in timely recognition, appropriate diagnostic workup, and implementation of known interventions that limit progression and severity, facilitating recovery, and mitigating AKI-associated complications. We propose the Recognition-Action-Results framework to plan, measure, and report the progress toward improving AKI management quality.

CONCLUSIONS

These recommendations identified and outlined an approach to define and evaluate the quality of AKI management in hospitalized patients.

A Multinational Observational Study Exploring Adherence With the Kidney Disease: Improving Global Outcomes Recommendations for Prevention of Acute Kidney Injury After Cardiac Surgery

BACKGROUND

The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend a bundle of different measures for patients at increased risk of acute kidney injury (AKI). Prospective, single-center, randomized controlled trials (RCTs) have shown that management in accordance with the KDIGO recommendations was associated with a significant reduction in the incidence of postoperative AKI in high-risk patients. However, compliance with the KDIGO bundle in routine clinical practice is unknown.

METHODS

This observational prevalence study was performed in conjunction with a prospective RCT investigating the role of the KDIGO bundle in high-risk patients undergoing cardiac surgery. A 2-day observational prevalence study was performed in all participating centers before the RCT to explore routine clinical practice. The participating hospitals provided the following data: demographics and surgical characteristics, AKI rates, and compliance rates with the individual components of the bundle.

RESULTS

Ninety-five patients were enrolled in 12 participating hospitals. The incidence of AKI within 72 hours after cardiac surgery was 24.2%. In 5.3% of all patients, clinical management was fully compliant with all 6 components of the bundle. Nephrotoxic drugs were discontinued in 52.6% of patients, volume optimization was performed in 70.5%, 52.6% of the patients underwent functional hemodynamic monitoring, close monitoring of serum creatinine and urine output was undertaken in 24.2% of patients, hyperglycemia was avoided in 41.1% of patients, and no patient received radiocontrast agents. The patients received on average 3.4 (standard deviation [SD] ±1.1) of 6 supportive measures as recommended by the KDIGO guidelines. There was no significant difference in the number of applied measures between AKI and non-AKI patients (3.2 [SD ±1.1] vs 3.5 [SD ±1.1]; P = .347).

CONCLUSIONS

In patients after cardiac surgery, compliance with the KDIGO recommendations was low in routine clinical practice.

Routine Adoption of Urinary [IGFBP7]∙[TIMP-2] to Assess Acute Kidney Injury at Any Stage 12 hours After Intensive Care Unit Admission: a Prospective Cohort Study

The urinary tissue inhibitor of metalloproteinases-2 and insulin-like growth factor-binding protein 7 ([TIMP-2]∙[IGFBP7]) have been introduced to improve risk prediction of severe acute kidney injury (AKI) within 12 hours of measurement. We performed a prospective cohort study to evaluate if the predictive value of [TIMP-2]∙[IGFBP7] for AKI might continue after 12 hours. We enrolled 442 critically ill adult patients from June to December 2016. Urine samples were collected at admission for [TIMP-2]∙[IGFBP7] measurement. Baseline patient characteristics were recorded including patients' demographics, prior health history, and the main reason for admission to build a logistic regression model to predict AKI. AKI occurrence differed between patients with [TIMP-2]∙[IGFBP7] ≤0.3 and >0.3 (ng/ml)2/1000 (31.9% and 68.10% respectively; p < 0.001). Patients with AKI had higher biomarker values compared to those without AKI (0.66 (0.21-2.84) vs 0.22 (0.08-0.63) (ng/ml)2/1000; p < 0.001). [TIMP-2]∙[IGFBP7] at ICU admission had a lower performance in predicting AKI at any stage within 48 hours and 7 days after measurement (area under the receiver operating characteristic curve (AUC) equal to 0.70 (95%CI 0.65-0.76), AUC 0.68 (95%CI 0.63-0.73)). In the logistic regression model, 0.1 (ng/ml)2/1000-unit increment was likely to increase the risk of AKI by 2% (p = 0.002).

Development and validation of quick Acute Kidney Injury-score (q-AKI) to predict acute kidney injury at admission to a multidisciplinary intensive care unit

AKI is associated with increased risk of death, prolonged length of stay and development of de-novo chronic kidney disease. The aim of our study is the development and validation of prediction models to identify the risk of AKI in ICU patients up to 7 days. We retrospectively recruited 692 consecutive patients admitted to the ICU at San Bortolo Hospital (Vicenza, Italy) from 1 June 2016 to 31 March 2017: 455 patients were treated as the derivation group and 237 as the validation group. Candidate variables were selected based on a literature review and expert opinion. Admission eGFR< 90 ml/min /1.73 mq (OR 2.78; 95% CI 1.78–4.35; p<0.001); SOFAcv ≥ 2 (OR 2.23; 95% CI 1.48–3.37; p<0.001); lactate ≥ 2 mmol/L (OR 1.81; 95% CI 1.19–2.74; p = 0.005) and (TIMP-2)•(IGFBP7) ≥ 0.3 (OR 1.65; 95% CI 1.08–2.52; p = 0.019) were significantly associated with AKI. For the q-AKI score, we stratified patients into different AKI Risk score levels: 0–2; 3–4; 5–6; 7–8 and 9–10. In both cohorts, we observed that the proportion of AKI patients was higher in the higher score levels.

Quality Improvement Goals for Acute Kidney Injury

AKI is a global concern with a high incidence among patients across acute care settings. AKI is associated with significant clinical consequences and increased health care costs. Preventive measures, as well as rapid identification of AKI, have been shown to improve outcomes in small studies. Providing high-quality care for patients with AKI or those at risk of AKI occurs across a continuum that starts at the community level and continues in the emergency department, hospital setting, and after discharge from inpatient care. Improving the quality of care provided to these patients, plausibly mitigating the cost of care and improving short- and long-term outcomes, are goals that have not been universally achieved. Therefore, understanding how the management of AKI may be amenable to quality improvement programs is needed. Recognizing this gap in knowledge, the 22nd Acute Disease Quality Initiative meeting was convened to discuss the evidence, provide recommendations, and highlight future directions for AKI-related quality measures and care processes. Using a modified Delphi process, an international group of experts including physicians, a nurse practitioner, and pharmacists provided a framework for current and future quality improvement projects in the area of AKI. Where possible, best practices in the prevention, identification, and care of the patient with AKI were identified and highlighted. This article provides a summary of the key messages and recommendations of the group, with an aim to equip and encourage health care providers to establish quality care delivery for patients with AKI and to measure key quality indicators.

Integration of urinary neutrophil gelatinase-associated lipocalin with serum creatinine delineates acute kidney injury phenotypes in critically ill children

PURPOSE

Acute kidney injury (AKI) is prevalent in critically ill patients and associated with poor outcomes. Current AKI diagnostics- changes to serum creatinine (SCr) and urine output- are imprecise. Integration of injury biomarkers with SCr may improve diagnostic precision.

METHODS

We performed a secondary analysis of a study of critically ill children. Measurements of urine neutrophil gelatinase-associated lipocalin (uNGAL) and SCr samples from ICU admission facilitated the creation of four groups for comparison, based on elevation of SCr from baseline and reference NGAL cut-off value: uNGAL-/SCr-, uNGAL+/SCr-, uNGAL-/SCr + and uNGAL+/SCr+. The primary outcome assessed was AKI severity on Day 3.

RESULTS

178 children were studied. Compared to uNGAL-/SCr-, uNGAL+/SCr- patients had increased risk for all-stage Day 3 AKI (≥ KDIGO stage 1) (OR 3.83, [1.3-11.3], p = .025). Compared to uNGAL-/SCr+, uNGAL+/SCr + patients had increased risk for severe Day 3 AKI (≥ KDIGO stage 2) (OR 12, [1.4-102], p = .018). The only patients to suffer all-stage Day 3 AKI and mortality were uNGAL+ (3.2% uNGAL+/SCr-; 6.5% uNGAL+/SCr+).

CONCLUSIONS

Unique biomarker combinations on admission are predictive of distinct Day 3 AKI severity phenotypes. These classifications may enable a more personalized approach to the early management of AKI. Expanded study in larger populations is warranted.

Kidney Injury Biomarkers in an Academic Hospital Setting: Where Are We Now?

Acute kidney injury (AKI) is a frequent complication in hospitalised patients and is diagnosed by urinary output and serum creatinine. Serum creatinine is an indirect marker for renal glomerular filtration, but lacks specificity for damage to kidney tissue and the relatively late response to injury precludes early recognition of AKI. Timely diagnosis of kidney injury using biomarkers that provide information about the aetiology of kidney injury is an unmet clinical need. To overcome the suboptimal performance of serum creatinine, injury biomarkers have been proposed that predict AKI in diverse clinical settings. The clinical performance of these markers is considered moderate due to the lack of specificity for kidney tissue or the underlying injury mechanisms, poor test specificity and confounding by interventions or comorbidities. Hence, it is not unequivocally beneficial to implement current kidney injury biomarkers in the clinical laboratory for diagnostic purposes. In this article we review biomarkers that might fulfil AKI-related unmet clinical needs in the academic hospital setting.