Predicting Acute Kidney Injury in Intensive Care Unit Patients: The Role of Tissue Inhibitor of Metalloproteinases-2 and Insulin-Like Growth Factor-Binding Protein-7 Biomarkers

The Ultrasound Renal Stress Test for the Assessment of Functional Renal Reserve in Kidney Transplantation: A Pilot Study in Living Donors

In the evolving landscape of nephrology and kidney transplants, assessing renal functional reserve (RFR) in living kidney donors is essential for ensuring donor safety and successful transplantation. This study explores the use of the Intra-Parenchymal Renal Resistive Index Variation (IRRIV) test, a novel non-invasive method, to measure RFR in living donors. Our observational study included 11 participants undergoing living kidney donations, evaluated using the IRRIV-based Renal Stress Test (RST) before and 12 months post-nephrectomy. The study demonstrated significant changes in creatinine and eGFR CKD-EPI levels post-donation, with an average creatinine rise from 69 to 97 µmol/L and a reduction in eGFR from 104 to 66 mL/min/1.73 m2. These variations align with the expected halving of nephron mass post-nephrectomy and the consequent recruitment of RFR and hyperfiltration in the remaining nephrons. This pilot study suggests that the IRRIV-based RST is a practical, safe, and reproducible tool, potentially revolutionizing the assessment of RFR in living kidney donors, with implications for broader clinical practice in donor eligibility evaluation, even in borderline renal cases. Furthermore, it confirms the feasibility of RST in living kidney donors and allows us to assess the sample size in 48 donors for a future study.

Cell cycle arrest biomarkers for the early detection of acute allograft dysfunction and acute rejection in living donor kidney transplantation: a cross-sectional study from Egypt

Background

Urinary tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) are G1 cell arrest biomarkers that have demonstrated accuracy and validity in predicting and diagnosing acute kidney injury (AKI). This study aimed to evaluate the validity of [TIMP-2]×[IGFBP7] in diagnosing acute allograft dysfunction and its utility in distinguishing acute rejection (AR) from nonrejection causes in kidney transplantation.

Methods

This study included 48 adult living donor kidney transplant recipients (KTRs; 18 with AR, 15 with nonrejection causes of AKI, and 15 with stable grafts). Urinary TIMP-2 and IGFBP7 were measured, and [TIMP-2]×[IGFBP7] was calculated in all subjects.

Results

IGFBP7, TIMP-2, and [TIMP-2]×[IGFBP7] were statistically significantly higher in KTRs with acute allograft dysfunction than in those with stable grafts. [TIMP-2]×[IGFBP7] was statistically significantly higher in KTRs with AR than in those with nonrejection AKI. [TIMP-2]×[IGFBP7] at a cutoff level of 0.278 (ng/mL)2/1,000 had an area under the curve (AUC) of 0.99 with a sensitivity of 100% and a specificity of 93.3% in diagnosing acute allograft dysfunction, while at a cutoff level of 0.803 (ng/mL)2/1,000 had an AUC of 0.939 with a sensitivity of 94.4% and a specificity of 83.3% in diagnosing AR.

Conclusions

Besides its role in the early detection of acute allograft dysfunction, [TIMP-2]×[IGFBP7] may help to differentiate between AR and nonrejection causes in KTRs. However, whether and how urinary [TIMP-2]×[IGFBP7] can be used in clinical diagnosis still requires further research.

Development and validation of a digital biomarker predicting acute kidney injury following cardiac surgery on an hourly basis

Objectives

To develop and validate a digital biomarker for predicting the onset of acute kidney injury (AKI) on an hourly basis up to 24 hours in advance in the intensive care unit after cardiac surgery.

Methods

The study analyzed data from 6056 adult patients undergoing coronary artery bypass graft and/or valve surgery between April 1, 2012, and December 31, 2018 (development phase, training, and testing) and 3572 patients between January 1, 2019, and June 30, 2022 (validation phase). The study used 2 dynamic predictive modeling approaches, namely logistic regression and bootstrap aggregated regression trees machine (BARTm), to predict AKI. The mean area under the receiver operating characteristic curve (AUC), sensitivity, specificity, and positive and negative predictive values across all lead times before the occurrence of AKI were reported. The clinical practicality was assessed using calibration.

Results

Of all included patients, 8.45% and 16.66% had AKI in the development and validation phases, respectively. When applied to testing data, AKI was predicted with the mean AUC of 0.850 and 0.802 by BARTm and logistic regression, respectively. When applied to validation data, BARTm and LR resulted in a mean AUC of 0.844 and 0.786, respectively.

Conclusions

This study demonstrated the successful prediction of AKI on an hourly basis up to 24 hours in advance. The digital biomarkers developed and validated in this study have the potential to assist clinicians in optimizing treatment and implementing preventive strategies for patients at risk of developing AKI after cardiac surgery in the intensive care unit.

Recent Advances of Proteomics in Management of Acute Kidney Injury

Acute Kidney Injury (AKI) is currently recognized as a life-threatening disease, leading to an exponential increase in morbidity and mortality worldwide. At present, AKI is characterized by a significant increase in serum creatinine (SCr) levels, typically followed by a sudden drop in glomerulus filtration rate (GFR). Changes in urine output are usually associated with the renal inability to excrete urea and other nitrogenous waste products, causing extracellular volume and electrolyte imbalances. Several molecular mechanisms were proposed to be affiliated with AKI development and progression, ultimately involving renal epithelium tubular cell-cycle arrest, inflammation, mitochondrial dysfunction, the inability to recover and regenerate proximal tubules, and impaired endothelial function. Diagnosis and prognosis using state-of-the-art clinical markers are often late and provide poor outcomes at disease onset. Inappropriate clinical assessment is a strong disease contributor, actively driving progression towards end stage renal disease (ESRD). Proteins, as the main functional and structural unit of the cell, provide the opportunity to monitor the disease on a molecular level. Changes in the proteomic profiles are pivotal for the expression of molecular pathways and disease pathogenesis. Introduction of highly-sensitive and innovative technology enabled the discovery of novel biomarkers for improved risk stratification, better and more cost-effective medical care for the ill patients and advanced personalized medicine. In line with those strategies, this review provides and discusses the latest findings of proteomic-based biomarkers and their prospective clinical application for AKI management.

Safety of Citrate Anticoagulation in CKRT: Monocentric Experience of a Dynamic Protocol of Calcium Monitoring

Regional Citrate Anticoagulation (RCA) is considered the first-line anticoagulation for Continuous Kidney Replacement Therapy (CKRT). The RCA requires strict protocols and trained staff to avoid unsafe use and ensure its benefit. We have analyzed all our CKRT prescriptions from December 2020 to April 2022 anonymously, collecting data on CKRT, lab tests, clinical conditions, and complications of RCA. In addition, in order to better detect citrate accumulation, we have performed an RCA protocol by reducing the CaTot/Ca2+ ratio cut-off from 2.50 to 2.40 and increasing the number of calcium checks according to its trend. Among the 374 patients in CKRT, 104 received RCA prescriptions, of which 11 (10.6%) were discontinued: 4 for the suspicion of citrate accumulation, 1 for the development of metabolic alkalosis, 1 for the shift to a different CKRT procedure due to the need for a higher bicarbonate dose, 4 for the elevation of hepatocytolysis indexes, and 1 due to a preemptive discontinuation following massive post-surgery bleeding. None of the patients have had citrate toxicity as indicated by a CaTot/Ca2+ greater than 2.50, and our protocol has allowed the early identification of patients who might develop clinical citrate toxicity.

Biomarkers as Prognostic Predictors and Therapeutic Guide in Critically Ill Patients: Clinical Evidence

A biomarker is a molecule that can be measured in a biological sample in an objective, systematic, and precise way, whose levels indicate whether a process is normal or pathological. Knowing the most important biomarkers and their characteristics is the key to precision medicine in intensive and perioperative care. Biomarkers can be used to diagnose, in assessment of disease severity, to stratify risk, to predict and guide clinical decisions, and to guide treatments and response to them. In this review, we will analyze what characteristics a biomarker should have and how to ensure its usefulness, and we will review the biomarkers that in our opinion can make their knowledge more useful to the reader in their clinical practice, with a future perspective. These biomarkers, in our opinion, are lactate, C-Reactive Protein, Troponins T and I, Brain Natriuretic Peptides, Procalcitonin, MR-ProAdrenomedullin and BioAdrenomedullin, Neutrophil/lymphocyte ratio and lymphopenia, Proenkephalin, NefroCheck, Neutrophil gelatinase-associated lipocalin (NGAL), Interleukin 6, Urokinase-type soluble plasminogen activator receptor (suPAR), Presepsin, Pancreatic Stone Protein (PSP), and Dipeptidyl peptidase 3 (DPP3). Finally, we propose an approach to the perioperative evaluation of high-risk patients and critically ill patients in the Intensive Care Unit (ICU) based on biomarkers.

Slow Continuous Ultrafiltration in Regional Citrate Anticoagulation Performed with a Standard Fluid Infusion Central Venous Catheter in Intensive Care Unit for Fluid Overload in Acute on Chronic Heart Failure: A Case Report

Slow continuous ultrafiltration (SCUF) is an extracorporeal therapy able to reduce fluid overload in chronic or acute heart failure resistant to diuretics. An in-vitro study demonstrated the SCUF feasibility using a standard fluid infusion central venous catheter (CVC). We describe the clinical application of this SCUF in regional citrate anticoagulation (SCUF-RCA) in a patient admitted to the Intensive Care Unit for acute decompensate heart failure with severe systemic fluid overload resistant to diuretics. To avoid risks deriving from a new catheterization, we used a pre-existing multi-lumen CVC for drug administration to provide 10 h of SCUF-RCA with a blood flow of 35 mL/min and 100 mL/h of ultrafiltration with a final weight loss of 1 Kilogram without technical and clinical complications. The patient had a hemodynamics improvement with the diuresis recovery from the previous oliguria after the SCUF-RCA. This clinical case can open the use of the SCUF-RCA in the clinical practice to treat the fluid overload unresponsive to maximal diuretic therapy not exposing the patient to the risks and complications related to the use of SCUF with CVC for dialysis and systemic anticoagulation with heparin. Accordingly, this technique may be useful in the treatment of fluid overload in outpatients.

The Assessment of Renal Functional Reserve in β-Thalassemia Major Patients by an Innovative Ultrasound and Doppler Technique: A Pilot Study

Beta-thalassemia syndromes are the most common inherited monogenic disorders worldwide. The most common pathophysiologic and clinical renal disease manifestations of in β-TM patients is the tubular dysfunctions related to iron overload, chronic anemia, and the need for chronic iron chelation therapy. The aim of this pilot study is to apply an innovative ultrasound and Doppler technique to assess the Renal Functional Reserve (RFR) in β-TM patients, and to evaluate its reliability in iron overload tubulopathy. Ultrasound assessment of intra-parenchymal renal resistive index variation (IRRIV) has recently been proposed as a safe and reproducible technique to identify RFR presence. We define the preserved RFR when the Delta Renal Resistive Index (RRI) is >0.05 (baseline RRI—minimum RRI value during stress) in the Renal Stress Test (RST). Nineteen β-TM patients were enrolled for this study. In our series, we found a strong negative correlation between mean ferritin values and Delta RRI (R = −0.51, p = 0.03). This pilot study suggested the RST as reliable tool for assessing the RFR by ultrasound. Specifically, RST could help in clinical practice suggesting the patient’s management and iron chelation therapy.

The Supporting Role of Combined and Sequential Extracorporeal Blood Purification Therapies in COVID-19 Patients in Intensive Care Unit

Critical clinical forms of COVID-19 infection often include Acute Kidney Injury (AKI), requiring kidney replacement therapy (KRT) in up to 20% of patients, further worsening the outcome of the disease. No specific medical therapies are available for the treatment of COVID-19, while supportive care remains the standard treatment with the control of systemic inflammation playing a pivotal role, avoiding the disease progression and improving organ function. Extracorporeal blood purification (EBP) has been proposed for cytokines removal in sepsis and could be beneficial in COVID-19, preventing the cytokines release syndrome (CRS) and providing Extra-corporeal organ support (ECOS) in critical patients. Different EBP procedures for COVID-19 patients have been proposed including hemoperfusion (HP) on sorbent, continuous kidney replacement therapy (CRRT) with adsorbing capacity, or the use of high cut-off (HCO) membranes. Depending on the local experience, the multidisciplinary capabilities, the hardware, and the available devices, EBP can be combined sequentially or in parallel. The purpose of this paper is to illustrate how to perform EBPs, providing practical support to extracorporeal therapies in COVID-19 patients with AKI.

Update on prognosis driven classification of pediatric AKI

Acute kidney injury (AKI) affects a large proportion of hospitalized children and increases morbidity and mortality in this population. Initially thought to be a self-limiting condition with uniformly good prognosis, we now know that AKI can persist and progress to acute kidney disease (AKD) and chronic kidney disease (CKD). AKI is presently categorized by stage of injury defined by increase in creatinine, decrease in eGFR, or decrease in urine output. These commonly used biomarkers of acute kidney injury do not change until the injury is well established and are unable to detect early stage of the disease when intervention is likely to reverse injury. The kidneys have the ability to compensate and return serum creatinine to a normal or baseline level despite nephron loss in the setting of AKI possibly masking persistent dysfunction. Though these definitions are important, classifying children by their propensity for progression to AKD and CKD and defining these risk strata by other factors besides creatinine may allow for better prognosis driven discussion, expectation setting, and care for our patients. In order to develop a classification strategy, we must first be able to recognize children who are at risk for AKD and CKD based on modifiable and non-modifiable factors as well as early biomarkers that identify their risk of persistent injury. Prevention of initial injury, prompt evaluation and treatment if injury occurs, and mitigating further injury during the recovery period may be important factors in decreasing risk of AKD and CKD after AKI. This review will cover presently used definitions of AKI, AKD, and CKD, recent findings in epidemiology and risk factors for AKI to AKD to CKD progression, novel biomarkers for early identification of AKI and AKI that may progress to CKD and future directions for improving outcome in children with AKI.

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.

Renal Impairment Detectors: IGFBP-7 and NGAL as Tubular Injury Markers in Multiple Myeloma Patients

Background and Objectives: Urine insulin-like growth factor-binding protein 7 (IGFBP-7), tissue inhibitor of matrix metalloproteinase 2 (TIMP-2), and neutrophil gelatinase-associated lipocalin (NGAL) monomer are novel tubular kidney injury biomarkers. In multiple myeloma (MM), immunoglobulin free light chains (FLCs) play an integral role in renal impairment. This study aimed to investigate the correlation between new biomarkers and acclaimed parameters of renal failure, MM stage, and prognosis. Materials and Methods: The examined parameters included: urinary and serum cystatin-C, IGFBP-7, and TIMP-2, and urinary NGAL monomer in 124 enrolled patients. Results: Urinary and serum IGFBP-7 and urinary NGAL were higher among patients with an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2, and positively correlated with urine light chains. Serum and urine IGFBP-7 and urine NGAL were greater among patients with a higher disease stage. In the whole study group, urinary concentrations of the studied markers were positively correlated with each other. In multiple linear regression, urinary IGFBP-7 and NGAL were associated with lower eGFR, independently of other urinary markers. Conclusions: Urinary IGFBP-7 and NGAL monomer may be useful markers of tubular renal damage in patients with MM. Biomarker-based diagnostics may contribute to earlier treatment that may improve renal outcomes and life expectancy in MM.

Intermittent Urine Oxygen Tension Monitoring for Predicting Acute Kidney Injury After Cardiovascular Surgery: A Preliminary Prospective Observational Study

Introduction

Novel biomarkers of acute kidney injury (AKI) are being developed and commercialized. However, none are universally available. The aim of this preliminary prospective observational study was to explore the effectiveness of intermittent urine oxygen tension (PuO₂) monitoring without special equipment (using a blood gas analyzer) for predicting AKI after elective cardiovascular surgery requiring cardiopulmonary bypass (CPB).

Methods

Fifty patients who underwent elective cardiovascular surgery requiring CPB were enrolled in the study with written informed consent. Urine samples were intermittently collected from a urethral catheter at four points: T1, immediately after induction of general anesthesia in the operating room; T2, immediately after intensive care unit (ICU) admission; T3, six hours after ICU admission; and T4, 12 hours after ICU admission. PuO₂ was measured with a blood gas analyzer. The Kidney Disease Improving Global Outcomes classification was used for the diagnosis of AKI, then patients were followed up until postoperative day 7. By generating the receiver operating characteristic curves, the cut-off value of PuO₂ and area under the curve (AUC) for predicting the onset of AKI was calculated. The odds ratio (OR) and 95% confidence interval (CI) of each time point were calculated using logistic regression analysis or exact logistic regression method. P < 0.05 was considered significant.

Results

Twelve patients were diagnosed with AKI (24% morbidity). The cut-off values of PuO₂ for predicting onset of AKI at the four time points were T1, PuO₂ ≥ 132.4 mmHg (OR 3.1, 95% CI 0.78-12.0, p = 0.11, AUC 0.57); T2, PuO₂ ≥ 153.3 mmHg (OR 5.8, 95% CI 1.08-31.4, p = 0.04, AUC 0.51); T3, PuO₂ ≥ 130.1 mmHg (OR 0.19, 95% CI 0.05-0.75, p = 0.018, AUC 0.68); T4, PuO₂ ≥ 88.6 mmHg (OR 0.07, 95% CI 0-0.486, p = 0.011, AUC 0.64).

Conclusion

Intermittent PuO₂ values at six and 12 hours after ICU admission may be predictors of AKI, although the AUCs to predict AKI were low (0.68 and 0.64). AKI prediction by PuO₂ was not possible immediately after induction of general anesthesia (not statistically significant) and immediately after ICU admission (AUC was very low). Further studies are required to confirm the validity of intermittent PuO₂ monitoring.

Usefulness of the Biomarker TIMP-2•IGFBP7 for Acute Kidney Injury Assessment in Critically Ill Patients: A Narrative Review

OBJECTIVES

To review the clinical usefulness of the biomarker TIMP-2•IGFBP7 in adult, general medical-surgical intensive care unit (ICU) settings.

DATA SOURCES

PubMed (1946 to mid-February 2021) and EMBASE (1947 to mid-February 2021) with bibliographies of retrieved articles reviewed for additional articles.

STUDY SELECTION AND DATA EXTRACTION

Studies evaluating use of the urinary TIMP-2•IGFBP7 assay in adult patients in ICU settings.

DATA SYNTHESIS

Studies published after investigations leading to TIMP-2•IGFBP7 assay approval confirm the appropriateness of considerations discussed in product labeling, such as use of the test within 12 hours of assessment, use of a dichotomous 0.3 (ng/mL)²/1000 cutoff, and use only in combination with other assessments of acute kidney injury (AKI). However, as a biomarker routinely used for early identification of patients at risk for AKI in mixed ICU populations, the additional resources required for TIMP-2•IGFBP monitoring are difficult to justify because of limited data demonstrating usefulness in preventing or ameliorating AKI and its attendant complications.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Biomarkers are potentially useful not only for assessment and diagnosis of AKI, but also for practitioners involved in the management of nephrotoxic medications and medications needing adjustment for decreased kidney function.

CONCLUSIONS

Although there is evidence to suggest that the urinary TIMP-2•IGFBP7 biomarker is helpful in predicting AKI progression in general medical-surgical ICU patients when used within 12 hours of patient assessment in combination with routine testing, including serum creatinine and urine output, there is little evidence that its use leads to improvements in clinically important patient outcomes.

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®.

Influence of patients’ clinical features at intensive care unit admission on performance of cell cycle arrest biomarkers in predicting acute kidney injury

Objectives

Identification of acute kidney injury (AKI) can be challenging in patients with a variety of clinical features at intensive care unit (ICU) admission, and the capacity of biomarkers in this subpopulation has been poorly studied. In our study we examined the influence that patients’ clinical features at ICU admission have over the predicting ability of the combination of urinary tissue inhibitor of metalloproteinase-2 (TIMP2) and insulin-like growth factor binding protein 7 (IGFBP7).

Methods

Urinary [TIMP2]•[IGFBP7] were measured for all patients upon admission to ICU. We calculated the receiver operating characteristics (ROC) curves for AKI prediction in the overall cohort and for subgroups of patients according to etiology of ICU admission, which included: sepsis, trauma, neurological conditions, cardiovascular diseases, respiratory diseases, and non-classifiable causes.

Results

In the overall cohort of 719 patients, 239 (33.2%) developed AKI in the first seven days. [TIMP2]•[IGFBP7] at ICU admission were significantly higher in AKI patients than in non-AKI patients. This is true not only for the overall cohort but also in the other subgroups. The area under the ROC curve (AUC) for [TIMP2]•[IGFBP7] in predicting AKI in the first seven days was 0.633 (95% CI 0.588–0.678), for the overall cohort, with sensitivity and specificity of 66.1 and 51.9% respectively. When we considered patients with combined sepsis, trauma, and respiratory disease we found a higher AUC than patients without these conditions (0.711 vs. 0.575; p=0.002).

Conclusions

The accuracy of [TIMP2]•[IGFBP7] in predicting the risk of AKI in the first seven days after ICU admission has significant variability when the reason for ICU admission is considered.

Estimated Glomerular Filtration Rate as a Risk Stratification Tool for Early Complications in Revision Total Hip and Knee Arthroplasty

BACKGROUND

Establishing an association between postoperative outcomes and the spectrum of renal function would allow for more informed decisions to manage surgical risks and improved patient-specific care. Estimated glomerular filtration rate (eGFR) can be calculated from standard prescreening measurements to gauge renal function. This work investigates the effect of eGFR, as a continuous and categorical variable, on mortality and major and minor complications in patients undergoing revision total knee and hip arthroplasty.

METHODS

25,056 patients having undergone revision total hip and knee arthroplasty from 2013 to 2016 were identified using the National Quality Improvement Program database. The investigated outcomes included 30-day mortality, major complications, and minor complications. Multivariate regression models were created to evaluate the effect of eGFR on the outcomes of interest. Multivariate spline regressions were generated to assess for nonlinear relationships between eGFR as a continuous variable and the outcomes.

RESULTS

Our study revealed that as eGFR decreased <60 mL/min/1.73 m², mortality (P = .0001), any major complication (P < .001), and any minor complication (P < .001) increased. Patients with eGFR 15-30 mL/min/1.73 m² had increased risk for mortality (P = .033). There was an increased risk for any major complication at an eGFR 30-60 and <15 mL/min/1.73 m², (P < .05). There was an increased risk of minor complications for those with hyperfiltration and <60 mL/min/1.73 m².

CONCLUSION

Patients with lower preoperative eGFR generally display an increased risk for complications after revision total hip and knee arthroplasty. Proper consideration should be given to this patient population before surgical intervention to allow for preventative measures to be taken to improve patient outcomes.

Pre-existing chronic kidney disease and acute kidney injury among critically ill patients

BACKGROUND

The impact of pre-existing chronic kidney disease (CKD) and acute kidney injury (AKI) on health outcomes in critically ill patients is unclear. Yet, CKD complicated by AKI in critically ill patients is common.

OBJECTIVES

To compare risk of death within one-month of admission in critically ill patients with and without pre-existing CKD who developed AKI.

METHODS

A multicenter retrospective comparative study using medical records review was conducted. Study participants consisted of 826 adult patients who received mechanical ventilation for at least 6 h in the critical care units from January 2012 to December 2017. Assessment of kidney function was established by serum creatinine. Severity and staging of AKI were defined using RIFLE criteria: Risk, Injury, Failure, Loss and End stage of renal disease. Chronic kidney disease was defined as eGFR > 60 ml/mg/1.73 m² on admission.

RESULTS

Pre-existing CKD was present in 55% of patients and 7% had AKI within 7 days of admission. The overall mortality rate among these patients was 87.3%. The mortality rate was highest in patients with CKD (70.1%) followed by that of patients without pre-existing CKD but with AKI (20.7%) and that of patients with pre-existing CKD (7.1%) and AKI. Risks associated with mortality were APACHE II score (1.03; 95% CI 1.02-1.05;(P<0.001) and AKI (1.68; 95% CI 1.12-2.5;P<0.01) in patients with pre-existing CKD. Only APACHI-II (1.03; 95% CI 1.0-1.1; p < 0.001) was predictive of death in patients without pre-existing CKD.

CONCLUSION

Pre-existing comorbid CKD increases risks of death among critically ill patients compared to patients without CKD and regardless of whether they develop AKI or not. Early identification of CKD and recognition of the risk for mortality among these patients may result in earlier intervention that could reduce mortality.

Evaluating Nephrocheck® as a Predictive Tool for Acute Kidney Injury

Acute kidney injury (AKI) is a common complication in critically ill patients in the intensive settings with increased risks of short- and long-term complications and mortality. AKI is also associated with an increased length of stay in intensive care units (ICU) and worse kidney function recovery at hospital discharge. The management of AKI is one of the major challenges for nephrologists and intensivists overall for its early diagnosis. The current KDIGO criteria used to define AKI include the serum creatinine and urinary output that are neither sensitive nor specific markers of kidney function, since they can be altered only after hours from the kidney injury. In order to allow an early AKI detection, in the last years, several studies focused on the identification of new biomarkers. Among all these markers, urinary insulin-like growth factor-binding protein (IGFBP-7) and tissue inhibitor of metalloproteinase (TIMP-2) have been proven as the best-performing and have been proposed as a predictive tool for the AKI detection in the critical settings in order to perform an early diagnosis. Patients undergoing major surgery, cardiac surgery, those with hemodynamic instability or those with sepsis are believed to be the top priority patient populations for the biomarker test. In this view, the urinary [TIMP-2] x [IGFBP-7] becomes an important tool for the early detection of patients at high risk for AKI and its integration with the local ICU experience has to provide a multidisciplinary management of AKI with the institution of a rapid response team in order to assess patients and customize AKI management.

Current understanding and future directions in the application of TIMP-2 and IGFBP7 in AKI clinical practice

NephroCheck® is the commercial name of a combined product of two urinary biomarkers, tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7), expressed as [TIMP-2]·[IGFBP7], used to identify patients at high risk of acute kidney injury (AKI). AKI is a common and harmful complication especially in critically-ill patients, which can induce devastating short- and long-term outcomes. Over the past decade, numerous clinical studies have evaluated the utility of several biomarkers (e.g. neutrophil gelatinase-associated lipocalin, interleukin-18, liver-type fatty acid binding protein and kidney injury molecule-1, cystatin C) in the early diagnosis and risk stratification of AKI. Among all these biomarkers, [TIMP-2]·[IGFBP7] was confirmed to be superior in early detection of AKI, before the decrease of renal function is evident. In 2014, the US Food and Drug Administration permitted marketing of NephroCheck® (Astute Medical) (measuring urinary [TIMP-2]·[IGFBP7]) to determine if certain critically-ill patients are at risk of developing moderate to severe AKI. It has since been applied to clinical work in many hospitals of the United States and Europe to improve the diagnostic accuracy and outcomes of AKI patients. Now, more and more research is devoted to the evaluation of its application value, meaning and method in different clinical settings. In this review, we summarize the current research status of [TIMP-2]·[IGFBP7] and point out its future directions.

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.

Tissue inhibitor metalloproteinase-2 (TIMP-2) • IGF-binding protein-7 (IGFBP7) levels are associated with adverse outcomes in patients in the intensive care unit with acute kidney injury

The G1 cell cycle inhibitors tissue inhibitor metalloproteinase-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) have been identified as novel biomarkers for the prediction of moderate to severe acute kidney injury (AKI) risk. However, the prognostic value of [TIMP-2]•[IGFBP7] in predicting adverse outcomes in intensive care unit (ICU) patients with AKI was not previously described. To evaluate this, we conducted a cohort study, measuring [TIMP2]•[IGFBP7] levels in critically ill patients admitted to the ICU and classified the patients as NephroCheck (NC) (+) or NC (-) according to [TIMP-2]•[IGFBP7] values and AKI (+) or AKI (-) according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. We then evaluated the incidence of continuous renal replacement therapy initiation, all-cause mortality and a composite endpoint of both in the four groups. Baseline [TIMP-2]•[IGFBP7] values were available for 719 patients, of whom 239 developed AKI and 151 met the composite endpoint. Compared to NC (-)/AKI (+) patients, NC (+)/AKI (+) patients had a significant risk of ICU mortality and the composite endpoint. Kaplan-Meier curves showed that the survival estimate for the composite endpoint of NC (+)/AKI (+) patients was 34.4%; significantly worse than NC (-)/AKI (+) patients (67.4%). Multivariate analyses showed strong association between NC positivity and the composite endpoint. The inflammatory marker, procalcitonin, was an additional prognostic biomarker to compare and confirm the incremental value of NephroCheck. No association between procalcitonin and the composite endpoint was found, especially in patients with AKI, suggesting that NephroCheck may be more kidney specific. Thus, the [TIMP-2]•[IGFBP7] values can serve to identify patients with AKI at increased risk for adverse outcomes in the ICU.