Biomarkers of acute kidney injury: the pathway from discovery to clinical adoption

Urinary microRNAs miR-15b and miR-30a as novel noninvasive biomarkers for gentamicin-induced acute kidney injury

MicroRNAs serve as potential biomarkers in various pathological models, and are stable and detectable in biofluids. We investigated the urinary microRNA expression profile in a gentamicin-induced acute kidney injury canine model using RNA sequencing. A total of 234 differentially expressed microRNAs were screened after 12 consecutive days of gentamicin administration (P < 0.05). Six candidate microRNAs (miR-15b, -15b-3p, -16, -30a, -30a-3p, and -30c-2-3p) were selected according to a set criterion, and validated by real-time quantitative PCR. The diagnostic values of these six candidate microRNAs were better than the traditional serum biomarkers (all P < 0.05). Further, using receiver operating characteristic curve analysis, we found that miR-15b and -15b-3p were superior to urinary kidney injury molecule-1 (both P < 0.05). Moreover, miR-15b and -30a levels in the urine samples significantly correlated with their respective levels in the kidney tissue samples (r=0.512 and 0.505, respectively, both P < 0.05). Our data concluded that miR-15b and -30a may be promising biomarkers for renal toxicity.

Neutrophil Gelatinase-Associated Lipocalin Measured on Clinical Laboratory Platforms for the Prediction of Acute Kidney Injury and the Associated Need for Dialysis Therapy: A Systematic Review and Meta-analysis

RATIONALE & OBJECTIVE

The usefulness of measures of neutrophil gelatinase-associated lipocalin (NGAL) in urine or plasma obtained on clinical laboratory platforms for predicting acute kidney injury (AKI) and AKI requiring dialysis (AKI-D) has not been fully evaluated. We sought to quantitatively summarize published data to evaluate the value of urinary and plasma NGAL for kidney risk prediction.

STUDY DESIGN

Literature-based meta-analysis and individual-study-data meta-analysis of diagnostic studies following PRISMA-IPD guidelines.

SETTING & STUDY POPULATIONS

Studies of adults investigating AKI, severe AKI, and AKI-D in the setting of cardiac surgery, intensive care, or emergency department care using either urinary or plasma NGAL measured on clinical laboratory platforms.

SELECTION CRITERIA FOR STUDIES

PubMed, Web of Science, Cochrane Library, Scopus, and congress abstracts ever published through February 2020 reporting diagnostic test studies of NGAL measured on clinical laboratory platforms to predict AKI.

DATA EXTRACTION

Individual-study-data meta-analysis was accomplished by giving authors data specifications tailored to their studies and requesting standardized patient-level data analysis.

ANALYTICAL APPROACH

Individual-study-data meta-analysis used a bivariate time-to-event model for interval-censored data from which discriminative ability (AUC) was characterized. NGAL cutoff concentrations at 95% sensitivity, 95% specificity, and optimal sensitivity and specificity were also estimated. Models incorporated as confounders the clinical setting and use versus nonuse of urine output as a criterion for AKI. A literature-based meta-analysis was also performed for all published studies including those for which the authors were unable to provide individual-study data analyses.

RESULTS

We included 52 observational studies involving 13,040 patients. We analyzed 30 data sets for the individual-study-data meta-analysis. For AKI, severe AKI, and AKI-D, numbers of events were 837, 304, and 103 for analyses of urinary NGAL, respectively; these values were 705, 271, and 178 for analyses of plasma NGAL. Discriminative performance was similar in both meta-analyses. Individual-study-data meta-analysis AUCs for urinary NGAL were 0.75 (95% CI, 0.73-0.76) and 0.80 (95% CI, 0.79-0.81) for severe AKI and AKI-D, respectively; for plasma NGAL, the corresponding AUCs were 0.80 (95% CI, 0.79-0.81) and 0.86 (95% CI, 0.84-0.86). Cutoff concentrations at 95% specificity for urinary NGAL were>580ng/mL with 27% sensitivity for severe AKI and>589ng/mL with 24% sensitivity for AKI-D. Corresponding cutoffs for plasma NGAL were>364ng/mL with 44% sensitivity and>546ng/mL with 26% sensitivity, respectively.

LIMITATIONS

Practice variability in initiation of dialysis. Imperfect harmonization of data across studies.

CONCLUSIONS

Urinary and plasma NGAL concentrations may identify patients at high risk for AKI in clinical research and practice. The cutoff concentrations reported in this study require prospective evaluation.

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®.

Acute Kidney Injury is Associated with Lowered Plasma-Free Thiol Levels

Acute kidney injury (AKI) is associated with the abrupt loss of kidney function. Oxidative stress plays an important role in the pathophysiology of AKI. Free thiols (R-SH) are crucial components of the extracellular antioxidant machinery and reliably reflect systemic oxidative stress. Lower levels of thiols represent higher levels of oxidative stress. In this preliminary study, we hypothesized that plasma-free thiols are associated with AKI upon admission to the intensive care unit (ICU). In this study, 301 critically ill patients were included. Plasma samples were taken upon admission, and albumin-adjusted plasma-free thiols were determined. Albumin-adjusted plasma-free thiols were lower in patients with AKI (n = 43, median (interquartile range) 7.28 µmol/g (3.52, 8.95)) compared to patients without AKI (8.50 μmol/g (5.82, 11.28); p < 0.05) upon admission to the ICU. Higher age (B = -0.72), higher levels of neutrophil gelatinase-associated lipocalin (B = -0.002), creatinine (B = -0.01) and lower serum albumin (B = 0.47) were associated with lower free thiol levels. Further, albumin-adjusted free thiol levels were significantly reduced in patients with sepsis (8.30 (5.52-10.64) µmol/g) compared to patients without sepsis (6.95 (3.72-8.92) µmol/g; p < 0.05). Together, albumin-adjusted plasma-free thiols were significantly reduced in patients with AKI and patients with sepsis compared with patients without AKI and sepsis.

Calprotectin and Neutrophil Gelatinase-Associated Lipocalin As Biomarkers of Acute Kidney Injury in Acute Coronary Syndrome

BACKGROUND

Acute kidney injury (AKI) is increasingly being seen in patients with acute coronary syndromes (ACS) and it is associated with higher short-term and long-term morbidity and mortality. Therefore, it is of paramount importance to identify those ACS patients at risk for the development of AKI. The objective of this study was to evaluate two different plasma biomarkers calprotectin and neutrophil gelatinase-associated lipocalin (NGAL) in early detecting the development of AKI in ACS patients.

METHODS

172 ACS patients admitted to the Coronary Care Unit in Yantai Yuhuangding Hospital were prospectively enrolled. Their blood samples were obtained on admission and subjected to enzyme-linked immunosorbent assay to determine the levels of novel biomarkers. The clinical data and biomarkers were recorded and analyzed.

RESULTS

In this study, 23 (13.4%) patients had a diagnosis of AKI. Statistical analysis demonstrated that in ACS patients with AKI, the following two biomarkers were significantly higher than these without AKI: plasma calprotectin (5942.26 ± 1955.88 ng/mL vs. 3210.29 ± 1833.60 ng/mL, p < 0.001) and plasma NGAL (164.91 ± 43.63 ng/mL vs. 122.48 ± 27.33 ng/mL, p < 0.001). Plasma calprotectin and NGAL could discriminate the development of AKI respectively with an area under the ROC curve (AUC) of 0.864 and 0.850. A combination of the two plasma biomarkers calprotectin and NGAL could early discriminate AKI in ACS patients with an AUC of 0.898.

CONCLUSIONS

This study demonstrated a promising panel of plasma calprotectin and NGAL as early diagnostic biomarkers for AKI in ACS patients.

Incidence and impact of acute kidney injury on patients with implantable left ventricular assist devices: a Meta-analysis

Background: We aimed to evaluate the acute kidney injury (AKI) incidence and its associated risk of mortality in patients with implantable left ventricular assist devices (LVAD).Methods: A systematic literature search in Ovid MEDLINE, EMBASE, and Cochrane Databases was conducted through January 2020 to identify studies that provided data on the AKI incidence and AKI-associated mortality risk in adult patients with implantable LVADs. Pooled effect estimates were examined using random-effects, generic inverse variance method of DerSimonian-Laird.Results: Fifty-six cohort studies with 63,663 LVAD patients were enrolled in this meta-analysis. The pooled incidence of reported AKI was 24.9% (95%CI: 20.1%-30.4%) but rose to 36.9% (95%CI: 31.1%-43.1%) when applying the standard definition of AKI per RIFLE, AKIN, and KDIGO criteria. The pooled incidence of severe AKI requiring renal replacement therapy (RRT) was 12.6% (95%CI: 10.5%-15.0%). AKI incidence did not differ significantly between types of LVAD (p = .35) or indication for LVAD use (p = .62). While meta-regression analysis did not demonstrate a significant association between study year and overall AKI incidence (p = .55), the study year was negatively correlated with the incidence of severe AKI requiring RRT (slope = -0.068, p < .001). The pooled odds ratios (ORs) of mortality at 30 days and one year in AKI patients were 3.66 (95% CI, 2.00-6.70) and 2.22 (95% CI, 1.62-3.04), respectively. The pooled ORs of mortality at 30 days and one year in severe AKI patients requiring RRT were 7.52 (95% CI, 4.58-12.33) and 5.41 (95% CI, 3.63-8.06), respectively.Conclusion: We found that more than one-third of LVAD patients develop AKI based on standard definitions, and 13% develop severe AKI requiring RRT. There has been a potential improvement in the incidence of severe AKI requiring RRT for LVAD patients. AKI in LVAD patients was associated with increased 30-day and 1 year mortality.

Heparin-binding protein as a novel biomarker for sepsis-related acute kidney injury

Background

Sepsis-related acute kidney injury (AKI) is associated with high morbidity and mortality among patients. Underlying pathomechanisms include capillary leakage and fluid loss into the interstitial tissue and constant exposure to pathogens results in activation of inflammatory cascades, organ dysfunction and subsequently organ damage.

Methods

To identify novel factors that trigger sepsis-related acute kidney injury, plasma levels of Granzyme A, as representative of a lymphocyte-derived protease, and heparin-binding protein as indicator for neutrophil-derived mediators, were investigated retrospectively in 60 sepsis patients.

Results

While no association was found between plasma levels of lymphocyte-derived Granzyme A and the incidence of sepsis-related AKI, sepsis patients with AKI had significantly higher plasma levels of heparin-binding protein compared to those without AKI. This applies both to heparin-binding protein peak values (43.30 ±  23.34 vs. 30.25 ±  15.63 pg/mL; p = 0.005) as well as mean values (27.93 ±  14.39 vs. 22.02 ±  7.65 pg/mL; p = 0.021). Furthermore, a heparin-binding protein cut-off value of 23.89 pg/mL was established for AKI diagnosis.

Conclusion

This study identifies the neutrophil-derived heparin-binding protein as a valuable new biomarker for AKI in sepsis. Beyond the diagnostic perspective, this offers prospect for further research on pathogenesis of AKI and novel therapeutic approaches.

Kidney physiology and pathophysiology during heat stress and the modification by exercise, dehydration, heat acclimation and aging

The kidneys' integrative responses to heat stress aid thermoregulation, cardiovascular control, and water and electrolyte regulation. Recent evidence suggests the kidneys are at increased risk of pathological events during heat stress, namely acute kidney injury (AKI), and that this risk is compounded by dehydration and exercise. This heat stress related AKI is believed to contribute to the epidemic of chronic kidney disease (CKD) occurring in occupational settings. It is estimated that AKI and CKD affect upwards of 45 million individuals in the global workforce. Water and electrolyte disturbances and AKI, both of which are representative of kidney-related pathology, are the two leading causes of hospitalizations during heat waves in older adults. Structural and physiological alterations in aging kidneys likely contribute to this increased risk. With this background, this comprehensive narrative review will provide the first aggregation of research into the integrative physiological response of the kidneys to heat stress. While the focus of this review is on the human kidneys, we will utilize both human and animal data to describe these responses to passive and exercise heat stress, and how they are altered with heat acclimation. Additionally, we will discuss recent studies that indicate an increased risk of AKI due to exercise in the heat. Lastly, we will introduce the emerging public health crisis of older adults during extreme heat events and how the aging kidneys may be more susceptible to injury during heat stress.

Critical appraisal and meta-analysis of biological variation estimates for kidney related analytes

Objective

Kidney markers are some of the most frequently used laboratory tests in patient care, and correct clinical decision making depends upon knowledge and correct application of biological variation (BV) data. The aim of this study was to review available BV data and to provide updated BV estimates for the following kidney markers in serum and plasma; albumin, creatinine, cystatin C, chloride, potassium, sodium and urea.

Content

Relevant studies were identified from a historical BV database as well as by systematic literature searches. Retrieved publications were appraised by the Biological Variation Data Critical Appraisal Checklist (BIVAC). Meta-analyses of BIVAC compliant studies with similar design were performed to deliver global estimates of within-subject (CVI) and between-subject (CVG) BV estimates. Out of the 61 identified papers, three received a BIVAC grade A, four grade B, 48 grade C, five grade D grade and one was not appraised as it did not report numerical BV estimates. Most studies were identified for creatinine (n=48). BV estimates derived from the meta-analysis were in general lower than previously reported estimates for all analytes except urea. For some measurands, BV estimates may be influenced by age or states of health, but further data are required.

Summary

This review provides updated global BV estimates for kidney related measurands. For all measurands except for urea, these estimates were lower than previously reported.

Outlook

For the measurands analyzed in this review, there are sufficient well-designed studies available to publish a trustworthy estimate of BV. However, for a number of newly appearing kidney markers no suitable data is available and additional studies are required.

Recommendations on Acute Kidney Injury Biomarkers From the Acute Disease Quality Initiative Consensus Conference: A Consensus Statement

IMPORTANCE

In the last decade, new biomarkers for acute kidney injury (AKI) have been identified and studied in clinical trials. Guidance is needed regarding how best to incorporate them into clinical practice.

OBJECTIVE

To develop recommendations on AKI biomarkers based on existing data and expert consensus for practicing clinicians and researchers.

EVIDENCE REVIEW

At the 23rd Acute Disease Quality Initiative meeting, a meeting of 23 international experts in critical care, nephrology, and related specialties, the panel focused on 4 broad areas, as follows: (1) AKI risk assessment; (2) AKI prediction and prevention; (3) AKI diagnosis, etiology, and management; and (4) AKI progression and kidney recovery. A literature search revealed more than 65 000 articles published between 1965 and May 2019. In a modified Delphi process, recommendations and consensus statements were developed based on existing data, with 90% agreement among panel members required for final adoption. Recommendations were graded using the Grading of Recommendations, Assessment, Development and Evaluations system.

FINDINGS

The panel developed 11 consensus statements for biomarker use and 14 research recommendations. The key suggestions were that a combination of damage and functional biomarkers, along with clinical information, be used to identify high-risk patient groups, improve the diagnostic accuracy of AKI, improve processes of care, and assist the management of AKI.

CONCLUSIONS AND RELEVANCE

Current evidence from clinical studies supports the use of new biomarkers in prevention and management of AKI. Substantial gaps in knowledge remain, and more research is necessary.

Acute Kidney Injury in Septic Patients Treated by Selected Nephrotoxic Antibiotic Agents-Pathophysiology and Biomarkers-A Review

Acute kidney injury is a common complication in critically ill patients with sepsis and/or septic shock. Further, some essential antimicrobial treatment drugs are themselves nephrotoxic. For this reason, timely diagnosis and adequate therapeutic management are paramount. Of potential acute kidney injury (AKI) biomarkers, non-protein-coding RNAs are a subject of ongoing research. This review covers the pathophysiology of vancomycin and gentamicin nephrotoxicity in particular, septic AKI and the microRNAs involved in the pathophysiology of both syndromes. PubMED, UptoDate, MEDLINE and Cochrane databases were searched, using the terms: biomarkers, acute kidney injury, antibiotic nephrotoxicity, sepsis, miRNA and nephrotoxicity. A comprehensive review describing pathophysiology and potential biomarkers of septic and toxic acute kidney injury in septic patients was conducted. In addition, five miRNAs: miR-15a-5p, miR-192-5p, miR-155-5p, miR-486-5p and miR-423-5p specific to septic and toxic acute kidney injury in septic patients, treated by nephrotoxic antibiotic agents (vancomycin and gentamicin) were identified. However, while these are at the stage of clinical testing, preclinical and clinical trials are needed before they can be considered useful biomarkers or therapeutic targets of AKI in the context of antibiotic nephrotoxicity or septic injury.

Factor analysis of acute kidney injury in patients administered liposomal amphotericin B in a real-world clinical setting in Japan

Liposomal amphotericin B (L-AMB) is a broad-spectrum antifungal drug that is used to treat fungal infections. However, clinical evidence of its use in patients with renal failure is limited. Here, we aimed to identify factors associated with acute kidney injury (AKI) in patients administered L-AMB. We retrospectively utilized a combination of Diagnosis Procedure Combination data and laboratory data obtained from hospitals throughout Japan between April 2008 and January 2018. In total, 507 patients administered L-AMB were identified. After L-AMB treatment initiation, AKI, which was defined as a ≥ 1.5-fold increase within 7 days or ≥ 0.3 mg/dL increase within 2 days in serum creatinine according to the KDIGO criteria, was recognized in 37% of the total patients (189/507). The stages of AKI were stage 1 in 20%, stage 2 in 11%, and stage 3 in 7%. Five factors were associated with AKI of all stages: prior treatment with angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers or carbapenem; concomitant administration of catecholamines or immunosuppressants; and ≥ 3.52 mg/kg/day of L-AMB dosing. Serum potassium < 3.5 mEq/L before L-AMB therapy was associated with severe AKI of stage 2 and 3. Altogether, these factors should be carefully considered to reduce the occurrence of AKI in patients administered L-AMB.

Management of Acute Kidney Injury Following Major Abdominal Surgery: A Contemporary Review

Acute kidney injury (AKI) is a frequent occurrence following major abdominal surgery and is independently associated with both in-hospital and long-term mortality, as well as with a higher risk of progressing to chronic kidney disease (CKD) and cardiovascular events. Postoperative AKI can account for up to 40% of in-hospital AKI cases. Given the differences in patient characteristics and the pathophysiology of postoperative AKI, it is inappropriate to assume that the management after noncardiac and nonvascular surgery are the same as those after cardiac and vascular surgery. This article provides a comprehensive review on the available evidence on the management of postoperative AKI in the setting of major abdominal surgery.

Changes in Novel AKI Biomarkers after Exercise. A Systematic Review

More than 100 substances have been identified as biomarkers of acute kidney injury. These markers can help to diagnose acute kidney injury (AKI) in its early phase, when the creatinine level is not increased. The two markers most frequently studied in plasma and serum are cystatin C and neutrophil gelatinase-associated lipocalin (NGAL). The former is a marker of kidney function and the latter is a marker of kidney damage. Some other promising serum markers, such as osteopontin and netrin-1, have also been proposed and studied. The list of promising urinary markers is much longer and includes cystatin C, NGAL, kidney injury molecule-1 (KIM-1), liver-type fatty-acid-binding protein (L-FABP), interleukin 18, insulin-like growth factor binding protein 7 (IGFBP-7), tissue inhibitor of metalloproteinases-2 (TIMP-2) and many others. Although these markers are increased in urine for no longer than a few hours after nephrotoxic agent action, they are not widely used in clinical practice. Only combined IGFBP-7/TIMP-2 measurement was approved in some countries as a marker of AKI. Several studies have shown that the levels of urinary AKI biomarkers are increased after physical exercise. This systematic review focuses on studies concerning changes in new AKI biomarkers in healthy adults after single exercise. Twenty-seven papers were identified and analyzed in this review. The interpretation of results from different studies was difficult because of the variety of study groups, designs and methodology. The most convincing data concern cystatin C. There is evidence that cystatin C is a better indicator of glomerular filtration rate (GFR) in athletes after exercise than creatinine and also at rest in athletes with a lean mass lower or higher than average. Serum and plasma NGAL are increased after prolonged exercise, but the level also depends on inflammation and hypoxia; therefore, it seems that in physical exercise, it is too sensitive for AKI diagnosis. It may, however, help to diagnose subclinical kidney injury, e.g., in rhabdomyolysis. Urinary biomarkers are increased after many types of exercise. Increases in NGAL, KIM-1, cystatin-C, L-FABP and interleukin 18 are common, but the levels of most urinary AKI biomarkers decrease rapidly after exercise. The importance of this short-term increase in AKI biomarkers after exercise is doubtful. It is not clear if it is a sign of mild kidney injury or physiological metabolic adaptation to exercise.

Remote Ischemic Preconditioning and Contrast-Induced Acute Kidney Injury in Patients Undergoing Elective Percutaneous Coronary Intervention: A Randomized Clinical Trial

Background

Contrast-induced acute kidney injury (CI-AKI) is a common cause of hospital-acquired AKI and a serious complication of percutaneous coronary intervention.

Objective

The aim of the present study was to assess whether remote ischemic preconditioning (RIPC) reduces the incidence of CI-AKI.

Methods

We conducted a prospective, randomized, sham-controlled clinical study. The study included 101 patients admitted to the Intensive Cardiac Therapy Clinic of Medical University of Lodz for elective percutaneous coronary intervention. The participants were randomly assigned in a 1:1 ratio to either a control group (n = 51) or an RIPC group (n = 50). In the latter, RIPC was achieved before percutaneous coronary intervention by 4 cycles of 5-minute inflation of a cuff on the left upper arm to 200 mm Hg followed by 5-minute deflation. In the control group, a deflated cuff was placed on the left arm for 40 minutes. Serum creatinine concentration was measured to check for the presence of CI-AKI within 48 to 72 hours of percutaneous coronary intervention. Serum neutrophil gelatinase-associated lipocalin level was also measured within 3 hours.

Results

CI-AKI occurred in 2 patients from the RIPC group (4%) and 3 patients from the control group (5.9%), but the difference was not significant (P = 0.98). The patients who developed CI-AKI also demonstrated increased serum neutrophil gelatinase-associated lipocalin concentrations (the area under the receiver operator characteristic curve = 0.97; 95% CI, 0.938–1.00; P < 0.00) and the optimal cutoff point value was 118.9 ng/mL.

Conclusions

The use of RIPC before elective percutaneous coronary intervention was not found to prevent CI-AKI. ClinicalTrials.gov identifier: NCT03761368. (Curr Ther Res Clin Exp. 2020; 81:XXX–XXX)

Impact of admission serum ionized calcium levels on risk of acute kidney injury in hospitalized patients

This study aimed to investigate the risk of acute kidney injury (AKI) in hospitalized patients based on admission serum ionized calcium levels. This is a cohort study of all hospitalized adult patients, from January 2009 to December 2013 at a tertiary referral hospital, who had available serum ionized calcium at the time of admission. We excluded patients who had end-stage kidney disease or AKI at admission. We stratified admission serum ionized calcium into 6 groups; ≤ 4.39, 4.40-4.59, 4.60-4.79, 4.80-4.99, 5.00-5.19, and ≥ 5.20 mg/dL. We used serum creatinine criterion of KDIGO definition for diagnosis of AKI. We performed logistic regression analysis to assess the risk of in-hospital AKI occurrence based on admission serum ionized calcium, using serum ionized calcium of 5.00-5.19 mg/dL as the reference group. We studied a total of 25,844 hospitalized patients. Of these, 3,294 (12.7%) developed AKI in hospital, and 622 (2.4%) had AKI stage 2 or 3. We observed a U-shaped association between admission serum ionized calcium and in-hospital AKI, with nadir in-hospital AKI was in serum ionized calcium of 5.00-5.19 mg/dL. After adjustment for confounders, low serum ionized calcium of 4.40-4.59, ≤ 4.39 mg/dL and elevated serum ionized calcium ≥ 5.20 mg/dL were associated with increased risk of AKI with odds ratio of 1.33 (95% CI 1.14-1.56), 1.45 (95% CI 1.21-1.74), and 1.26 (95% CI 1.04-1.54), respectively. Both hypocalcemia, and hypercalcemia at the time of admission were associated with an increased risk of hospital-acquired AKI.

Novel renal biomarkers show that creatine supplementation is safe: a double-blind, placebo-controlled randomized clinical trial

The aim of this study was to evaluate the impact of creatine supplementation (CS) on renal function in young, healthy, and active subjects. We used a randomized, double-blind, placebo-controlled clinical trial as the study design. Thirty-six healthy male university students were recruited and divided into three groups: group placebo, group G3 (3 g/day of CS), and group G5 (5 g/day of CS). To assess renal function, new kidney biomarkers, kidney injury molecule-1 (KIM-1) and monocyte chemoattractant protein-1 (MCP-1), were quantified. Serum albumin, serum creatinine, serum urea, estimated glomerular filtration rate (eGFR), proteinuria, and albuminuria were also measured. All groups were evaluated at two times: prior CS or placebo (pre) and after 35 days on CS or placebo (post). After 35 days of intervention, all characteristics were maintained without significant difference (P > 0.05) between the groups, including serum creatinine, eGFR, and more sensitive kidney biomarker concentrations (KIM-1 and MCP-1). The paired analysis showed that the supplemented groups (G3 and 5G) had increased serum creatinine and decreased eGFR levels (P < 0.05). However, the values were still within the normal reference range. In conclusion, the results of renal function evaluation did not show any difference between the evaluated groups. Increased serum creatinine and decreased eGFR levels in CS groups can be explained by increased creatine stores and metabolism, since creatinine is a by-product of creatine metabolism. These findings indicate that the use of CS at doses of 3 g and 5 g/day for a short period (35 days) is safe and did not impair the kidneys or renal function in young healthy subjects.

Combined use of GM2AP and TCP1-eta urinary levels predicts recovery from intrinsic acute kidney injury

Deficient recovery from acute kidney injury (AKI) has immediate and long-term health, clinical and economic consequences. Pre-emptive recovery estimation may improve nephrology referral, optimize decision making, enrollment in trials, and provide key information for subsequent clinical handling and follow-up. For this purpose, new biomarkers are needed that predict outcome during the AKI episode. We hypothesized that damage pattern-specific biomarkers are expected to more closely associate to outcome within distinct subpopulations (i.e. those affected by specific pathological processes determining a specific outcome), as biomarker pleiotropy (i.e. associated to phenomena unrelated to AKI) introduced by unselected, heterogeneous populations may blur statistics. A panel of urinary biomarkers was measured in patients with AKI and their capacity to associate to normal or abnormal recovery was studied in the whole cohort or after sub-classification by AKI etiology, namely pre-renal and intrinsic AKI. A combination of urinary GM2AP and TCP1-eta best associates with recovery from AKI, specifically within the sub-population of renal AKI patients. This two-step strategy generates a multidimensional space in which patients with specific characteristics (i.e. renal AKI patients with good or bad prognosis) can be identified based on a collection of biomarkers working serially, applying pathophysiology-driven criteria to estimate AKI recovery, to facilitate pre-emptive and personalized handling.

Analysis of the association between kidney injury biomarkers concentration and nephritis in immunoglobulin A vasculitis: A pediatric cohort study

OBJECTIVE

The aim of this study was to investigate the clinical course, selected biochemical parameters and concentrations of renal injury biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1) and liver-fatty acid binding protein (L-FABP) in patients with immunoglobulin A vasculitis (IgAV) to identify the markers associated with nephritis in the course of the disease (IgAVN).

METHODS

The study involved 29 children with IgAV and 34 healthy controls. Eleven (38%) patients had renal involvement (IgAV-N) and 18 (62%) did not exhibit nephritis (IgAV-noN). Initial laboratory tests, determining the concentrations of NGAL, KIM-1 and L-FABP in serum and urine, were conducted on children from the study group in an acute phase of IgAV as well as after an average of 6 months, during a follow-up visit. The interconnection between renal involvement, anthropometric measurements, epidemiological data, laboratory parameters and levels of examined biomarkers have been thoroughly evaluated.

RESULTS

The serum and urine levels of NGAL, KIM-1 and L-FABP were significantly higher in children with an acute phase of IgAV as compared to the control group (P < .001) and markedly lower during follow-up retesting in comparison with the values obtained at inclusion (P < .001). However, the concentration of none of the evaluated biomarkers correlated with nephrological indices. Among all examined parameters, only male subjects were associated with nephritis (P = .017).

CONCLUSIONS

We have established no evident association between the concentrations of NGAL, KIM-1 and L-FABP and nephritis in the course of IgAV in children. Additionally, we confirmed a significant male predominance in patients with nephritis.

Elevated Urinary Neutrophil Gelatinase-Associated Lipocalin Is a Biomarker for Lupus Nephritis: A Systematic Review and Meta-Analysis

Objective

Lupus nephritis (LN) is a major and severe complication of systemic lupus erythematosus (SLE). Neutrophil gelatinase-associated lipocalin (NGAL), as a promising next-generation biomarker in clinical nephrology, has received extensive attention. However, its diagnostic performance in LN has high variability. Therefore, we performed an updated meta-analysis to further evaluate the diagnostic accuracy of urinary NGAL (uNGAL).

Materials and Methods

PubMed, Embase, and Cochrane Library were searched from inception to October 27, 2019. Meta-analysis was performed with a bivariate random effects model. Additionally, the summary receiver operating characteristic (SROC) curves were established. The sources of heterogeneity were explored by meta-regression, subgroup analysis, and sensitivity analysis. Publication bias was assessed using the Deeks test.

Results

19 articles consisting of 21 eligible studies were included. In diagnosing LN, the estimates (95% confidence interval (CI)) were as follows: sensitivity, 0.84 (0.71-0.91); specificity, 0.91 (0.70-0.98); and the SROC-AUC value, 0.92 (0.90-0.94). In identifying active LN, the estimates were as follows: sensitivity, 0.72 (0.56-0.84); specificity, 0.71 (0.51-0.84); and the AUC value, 0.77 (0.74-0.81). With respect to predicting renal flare, the estimates were as follows: sensitivity, 0.80 (0.57-0.92); specificity, 0.67 (0.58-0.75); and the AUC value, 0.74 (0.70-0.78). For the studies to distinguish proliferative LN, the estimates were as follows: sensitivity, 0.87 (0.66-0.97), and specificity, 0.69 (0.39-0.91). Deeks' funnel plot suggested that there was no significant publication bias.

Conclusions

Our meta-analysis indicates that uNGAL was a useful biomarker for diagnosis, estimation of activity, and prediction of renal flare of LN. In addition, the usefulness of uNGAL to distinguish pathological types of LN needs to be further investigated.

KIM-1 and Kidney Disease Progression in Autosomal Dominant Polycystic Kidney Disease: HALT-PKD Results

BACKGROUND

Cyst compression of renal tubules plays a role in the progression of autosomal dominant polycystic kidney disease (ADPKD) and may induce expression of kidney injury molecule-1 (KIM-1). Whether urinary KIM-1 indexed for creatinine (uKIM-1/Cr) is a prognostic marker of disease progression in ADPKD is unknown.In this secondary analysis of a prospective cohort study, we sought to determine whether patients with high as opposed to low uKIM-1/CR at baseline had greater rates of eGFR loss and height-adjusted total kidney volume (HtTKV) increase.

METHODS

Baseline uKIM-1/Cr values were obtained from 754 participants in Halt Progression of Polycystic Kidney Disease (HALT-PKD) studies A (early ADPKD) and B (late ADPKD). The predictor was uKIM-1/Cr, which was dichotomized by a median value of 0.2417 pg/g, and the primary outcomes were measured longitudinally over time. Mixed-effects linear models were used in the analysis to calculate the annual slope of change in eGFR and HtTKV.

RESULTS

Patients with high uKIM-1/Cr (above the median) had an annual decline in eGFR that was 0.47 mL/min greater than that in those with low uKIM-1/Cr (p = 0.0015) after adjustment for all considered covariates. This association was seen in study B patients alone (0.45 mL/min; p = 0.009), but not in study A patients alone (0.42 mL/min; p = 0.06). High baseline uKIM-1/Cr was associated with higher HtTKV in the baseline cross-sectional analysis compared to low uKIM-1/Cr (p = 0.02), but there was no difference between the groups in the mixed-effects model annual slopes.

CONCLUSION

Elevated baseline uKIM-1/Cr is associated with a greater decline in eGFR over time. Further research is needed to determine whether uKIM-1/Cr improves risk stratification in patients with ADPKD.

Acute Kidney Injury: From Diagnosis to Prevention and Treatment Strategies

Acute kidney injury (AKI) is characterized by an acute decrease in renal function that can be multifactorial in its origin and is associated with complex pathophysiological mechanisms. In the short term, AKI is associated with an increased length of hospital stay, health care costs, and in-hospital mortality, and its impact extends into the long term, with AKI being associated with increased risks of cardiovascular events, progression to chronic kidney disease (CKD), and long-term mortality. Given the impact of the prognosis of AKI, it is important to recognize at-risk patients and improve preventive, diagnostic, and therapy strategies. The authors provide a comprehensive review on available diagnostic, preventive, and treatment strategies for AKI.

The Use of Donor-Derived Cell-Free DNA for Assessment of Allograft Rejection and Injury Status

Patient monitoring after kidney transplantation (KT) for early detection of allograft rejection remains key in preventing allograft loss. Serum creatinine has poor predictive value to detect ongoing active rejection as its increase is not sensitive, nor specific for acute renal allograft rejection. Diagnosis of acute rejection requires allograft biopsy and histological assessment, which can be logistically challenging in some cases and carries inherent risk for complications related to procedure. Donor-derived cell-free DNA (dd-cfDNA), DNA of donor origin in the blood of KT recipient arising from cells undergoing injury and death, has been examined as a potential surrogate marker for allograft rejection. A rise in dd-cfDNA levels precedes changes in serum creatinine allows early detections and use as a screening tool for allograft rejection. In addition, when used in conjunction with donor-specific antibodies (DSA), it increases the pre-biopsy probability of antibody-mediated rejection (ABMR) aiding the decision-making process. Advancements in noninvasive biomarker assays such as dd-cfDNA may offer the opportunity to improve and expand the spectrum of available diagnostic tools to monitor and detect risk for rejection and positively impact outcomes for KT recipients. In this this article, we discussed the evolution of dd-cfDNA assays and recent evidence of assessment of allograft rejection and injury status of KT by the use of dd-cfDNA.

A Furosemide Excretion Stress Test Predicts Mortality in Mice After Sepsis and Outperforms the Furosemide Stress Test During Vasopressin Administration

Supplemental Digital Content is available in the text.

Objectives:

The furosemide stress test measures the volume of urine produced after a furosemide challenge. Furosemide stress test has previously demonstrated sensitive and specific prediction of progression to Kidney Disease: Improving Global Outcomes guideline defined acute kidney injury stage III in the ICU. Furosemide is actively excreted into the nephron lumen where it inhibits the sodium-potassium-chloride cotransporter, causing diuresis. We hypothesize that furosemide excretion is a more direct measure of tubule health than diuresis.

Design:

We developed a furosemide excretion stress test to evaluate this hypothesis in a murine model of septic-acute kidney injury.

Setting:

Basic science laboratory.

Subjects:

Male and female 8-week old CD-1 mice.

Interventions:

Sepsis was induced by cecal ligation and puncture in male and female mice. Furosemide stress test/furosemide excretion stress test started 42 hours post-cecal ligation and puncture with a 1 mg/kg furosemide bolus and urine was collected for 12 hours. The mice were then euthanized or monitored until 7 days post-cecal ligation and puncture. In another cohort, mice were treated with vasopressin, which decreases urine volume. Furosemide concentration was determined by high performance liquid chromatography.

Measurements and Main Results:

Urine production during the 12-hour collection varied from 0.08 to 2.62 mL. Both urine production (furosemide stress test) and furosemide excretion (furosemide excretion stress test) predicted mortality (area under the receiver operating characteristic curve = 0.925 and 0.916) and time of death (R² = 0.26 and 0.74). Male and female mice demonstrated consistent results. Following vasopressin treatment, furosemide stress test specificity fell to 33% (p = 0.016) but furosemide excretion stress test specificity was maintained.

Conclusions:

The furosemide stress test and furosemide excretion stress test performed similarly in predicting mortality; however, furosemide excretion stress test was superior in predicting time to death and maintained performance when challenged with vasopressin treatment in a mouse sepsis model.

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.

Analysis of neutrophil gelatinase-associated lipocalin, vascular endothelial growth factor, and soluble receptor for advanced glycation end-products in bone marrow supernatant in hematologic malignancies

BACKGROUND

Inflammation is a known risk factor of cancer development, including inflammation-driven leukemogenesis. Evaluation of inflammation-related cytokines in early diagnosis stages is crucial to understand the development of hematologic malignancy. Our aim was to measure three cytokines- neutrophil gelatinase-associated lipocalin (NGAL), vascular endothelial growth factor (VEGF), and soluble receptor for advanced glycation end-products (sRAGE) in bone marrow (BM) samples from patients diagnosed with hematologic malignancy and compare these measurements with the control. Additionally, we evaluated whether NGAL was significantly associated with sRAGE, VEGF, and several hematological parameters.

METHODS

BM samples were collected from 73 patients, who were classified into myeloproliferative neoplasm (MPN), acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), plasma cell neoplasm (PCN) and control groups according to the BM smear and pathology review. An immunoassay, a Luminex assay, and an enzyme-linked immunosorbent assay were used to quantitate NGAL, VEGF, and sRAGE, respectively, while all measurements of NGAL, VEGF and sRAGE were performed on BM supernatants. Data on hematological parameters were collected from medical records. Intergroup comparisons were performed using the Kruskal-Wallis H-test and Pearson Chi-Square test. Single and multiple regression analyses were performed to analyze the relationships among the parameters.

RESULTS

The independent factors associated with NGAL were neutrophil counts and VEGF. As for both NGAL and VEGF, the MPN (n = 23) group showed the highest level, while the MDS (n = 12) group showed low levels. NGAL levels in the AML (n = 13) and MDS groups were lower than in the control group (n = 14). The MPN group demonstrated higher VEGF levels than the AML and MDS groups. The MDS group showed lower VEGF levels than the PCN (n = 11) group. No statistical difference between the hematologic malignancy and control groups or among the hematologic malignancy groups was observed for sRAGE levels.

CONCLUSION

NGAL was related to neutrophil count and VEGF. NGAL and VEGF showed similar intergroup patterns, reflecting that NGAL was associated with VEGF.

Absolute quantification of urinary neutrophil gelatinase-associated lipocalin by ultra-high-performance liquid chromatography/tandem mass spectrometry and the diagnostic efficacy of acute kidney injury

RATIONALE

To establish an absolute quantification method for neutrophil gelatinase-associated lipocalin (NGAL) by ultra-high-performance liquid chromatography tandem positive ion electrospray ionization mass spectrometry (UHPLC/MS/MS) and evaluate its diagnostic efficacy for acute kidney injury (AKI).

METHODS

Three target peptides of NGA were prescreened by Skyline software, and two of them could be detected in tryptic peptides of NGAL recombinant protein and human urinary NGAL (uNGAL). Peptide (WYVVGLAGNAILR) was then selected as surrogate peptide. The corresponding isotope-labeled peptide as the internal standard was next synthesized. Quantification of uNGAL was based on equations of linear regression, and method validation was then conducted. The diagnostic efficacy of uNGAL for AKI was also evaluated using receiver operating characteristic curve (ROC) analysis. Lastly, the UHPLC/MS/MS and the particle-enhanced turbidimetric immunoassay (PETIA) methods for uNGAL quantification were compared.

RESULTS

For the y⁹ and y¹⁰ product ions, the linear regression equations were y = 2.5519x-4.6955 (R² = 0.994, P<.01) and y = 2.4619x-4.3 (R² =0.993, P<.01), respectively, and both of the linear ranges were from 0.5 to 15 mg/L. The limits of detection and quantification were 0.037 mg/L and 0.081 mg/L, respectively. The recoveries were from 97.32% to 107.28% at different uNGAL levels, and the within- and between-day CVs for uNGAL quantification were from 0.22% to 7.65% and from 0.66% to 5.97%, respectively. The carryover rates of uNGAL were in the range of 0.70%-0.99%. The area under the ROC curve (AUC) of uNGAL was 0.96 (P<0.01), and the sensitivity and specificity of uNGAL for AKI diagnosis were 90.0% and 92.5%, respectively. In addition, the UHPLC/MS/MS and PETIA methods showed good agreement for uNGAL quantification (y = 0.7112x-0.0139, P = 0.34).

CONCLUSIONS

The UHPLC/MS/MS method for uNGAL quantification has a wide linear range, high sensitivity, precision, and recovery, and low carryover rates, and uNGAL detected by this method had high sensitivity and specificity for AKI diagnosis.

Diagnostics, Risk Factors, Treatment and Outcomes of Acute Kidney Injury in a New Paradigm

Acute kidney injury (AKI) is a common clinical condition among patients admitted in the hospitals. The condition is associated with both increased short-term and long-term mortality. With the development of a standardized definition for AKI and the acknowledgment of the impact of AKI on patient outcomes, there has been increased recognition of AKI. Two advances from past decades, the usage of computer decision support and the discovery of AKI biomarkers, have the ability to advance the diagnostic method to and further management of AKI. The increasingly widespread use of electronic health records across hospitals has substantially increased the amount of data available to investigators and has shown promise in advancing AKI research. In addition, progress in the finding and validation of different forms of biomarkers of AKI within diversified clinical environments and has provided information and insight on testing, etiology and further prognosis of AKI, leading to future of precision and personalized approach to AKI management. In this this article, we discussed the changing paradigms in AKI: from mechanisms to diagnostics, risk factors, and management of AKI.

Promises of Big Data and Artificial Intelligence in Nephrology and Transplantation

Kidney diseases form part of the major health burdens experienced all over the world. Kidney diseases are linked to high economic burden, deaths, and morbidity rates. The great importance of collecting a large quantity of health-related data among human cohorts, what scholars refer to as “big data”, has increasingly been identified, with the establishment of a large group of cohorts and the usage of electronic health records (EHRs) in nephrology and transplantation. These data are valuable, and can potentially be utilized by researchers to advance knowledge in the field. Furthermore, progress in big data is stimulating the flourishing of artificial intelligence (AI), which is an excellent tool for handling, and subsequently processing, a great amount of data and may be applied to highlight more information on the effectiveness of medicine in kidney-related complications for the purpose of more precise phenotype and outcome prediction. In this article, we discuss the advances and challenges in big data, the use of EHRs and AI, with great emphasis on the usage of nephrology and transplantation.

Biomarker Panels in Critical Care

Biomarker panels have the potential to advance the field of critical care medicine by stratifying patients according to prognosis and/or underlying pathophysiology. This article discusses the discovery and validation of biomarker panels, along with their translation to the clinical setting. The current literature on the use of biomarker panels in sepsis, acute respiratory distress syndrome, and acute kidney injury is reviewed.

Effects of flexible ureteroscopy on kidney: A prospective clinical trial

OBJECTIVE

To investigate the effects of flexible ureteroscopy (F-URS) on the operated side of a kidney by assessing the renal damage markers, urine neutrophil gelatinase-related lipocalin (NGAL) and serum cystatin-C (Cys-C), and overall kidney function with the measurements of standard serum creatinine and urine albumin and protein levels.

MATERIAL AND METHODS

A total of 30 patients who underwent F-URS for treatment of upper urinary stone disease were prospectively evaluated. Preoperative serum urea, creatinine, and Cys-C levels were noted. Levels of urine albumin, protein, creatinine, and NGAL in spot urine samples from the operated side of a kidney obtained through the access sheath preoperatively and through the ureteral catheter 1 and 24 hours postoperatively were also measured. Preoperative and postoperative parameter levels were statistically compared.

RESULTS

The patients' mean age was 46.6±15.9 years. The mean operative and fluoroscopy times were 90.67±32.5 and 3.15±1.43 minutes, respectively. The urine creatinine, albumin, protein, albumin/creatinine, and protein/creatinine levels were similar in preoperative and postoperative periods. Postoperative serum urea, creatinine, and Cys-C levels and urine NGAL and NGAL/creatinine levels were not also found with remarkable changes from the baseline levels.

CONCLUSION

F-URS is a safe therapeutic intervention in the treatment of urolithiasis, especially regarding renal damage, and functional outcomes.

Calcium Kidney Stones are Associated with Increased Risk of Carotid Atherosclerosis: The Link between Urinary Stone Risks, Carotid Intima-Media Thickness, and Oxidative Stress Markers

Previous studies have suggested that kidney stone formers are associated with a higher risk of cardiovascular events. To our knowledge, there have been no previous examinations of the relationship between carotid intima-media thickness (IMT) and urinary stone risk factors. This study was aimed toward an investigation of the association between dyslipidemia, IMT, and 24-hour urinalysis in patients with calcium oxalate (CaOx) or calcium phosphate (CaP) stones. We prospectively enrolled 114 patients with kidney stones and 33 controls between January 2016 and August 2016. All patients were divided into four groups, according to the stone compositions—CaOx ≥ 50% group, CaP group, struvite group, and uric acid stones group. Carotid IMT and the carotid score (CS) were evaluated using extracranial carotid artery doppler ultrasonography. The results of a multivariate analysis indicated that a higher serum total cholesterol (TC) and low-density lipoprotein (LDL) were all associated with lower urinary citrate and higher CS in both the CaOx ≥ 50% and CaP groups. Higher serum TC and LDL were also associated with increased serum 8-OHdG levels in both groups. The levels of carotid IMT and CS in the CaOx ≥ 50% and CaP groups were all significantly higher than in the controls. These findings suggest a strong link between dyslipidemia, carotid atherosclerosis, and calcium kidney stone disease.

Artificial Intelligence in Acute Kidney Injury Risk Prediction

Acute kidney injury (AKI) is a frequent complication in hospitalized patients, which is associated with worse short and long-term outcomes. It is crucial to develop methods to identify patients at risk for AKI and to diagnose subclinical AKI in order to improve patient outcomes. The advances in clinical informatics and the increasing availability of electronic medical records have allowed for the development of artificial intelligence predictive models of risk estimation in AKI. In this review, we discussed the progress of AKI risk prediction from risk scores to electronic alerts to machine learning methods.

Emerging microRNA biomarkers for acute kidney injury in acute decompensated heart failure

Acute decompensated heart failure (ADHF) is associated with a high incidence of acute kidney injury (AKI), an abrupt loss of kidney function associated with a near doubling of mortality at 1 year. In addition to the direct threat acute HF itself poses to kidney function, the beneficial effects of commonly prescribed HF treatments must be weighed against their potentially adverse effects on glomerular perfusion. Consequently, there is an urgent need to identify early markers for AKI in ADHF to facilitate timely implementation of supportive measures to minimize kidney damage and improve outcomes. The recent recognition of the diagnostic potential of circulating microRNAs presents the potential to address this gap if microRNAs specific for AKI can be identified in serial plasma, serum and/or urine samples from well-phenotyped cohorts of ADHF patients, including a proportion with AKI. This review summarizes emerging circulating diagnostic and prognostic microRNA biomarkers (serum, plasma or urine) in HF and AKI.

Novel kidney injury biomarkers in tropical infections: a review of the literature

Tropical diseases are mainly found in the tropical regions of Asia, Africa and Latin America. They are a major Public Health problem in these regions, most of them are considered neglected diseases and remain as important contributors to the development of AKI (Acute Kidney Injury), which is associated with increased patients' morbidity and mortality. In most countries, kidney disease associated to tropical diseases is attended at health services with poor infrastructure and inadequate preventive measures. The long-term impacts of these infections on kidney tissue may be a main cause of future kidney disease in these patients. Therefore, the investigation of novel kidney injury biomarkers in these tropical diseases is of utmost importance to explain the mechanisms of kidney injury, to improve their diagnosis and prognosis, as well as the assessment to health systems by these patients. Since 2011, our group has been studying renal biomarkers in visceral and cutaneous leishmaniasis, schistosomiasis, leptospirosis and leprosy. This study has increased the knowledge on the pathophysiology of kidney disease in the presence of these infections and has contributed to the early diagnosis of kidney injury, pointing to glomerular, endothelial and inflammatory involvement as the main causes of the mechanisms leading to nephropathy and clinical complications. Future perspectives comprise establishing long-term cohort groups to assess the development of kidney disease and the patients' survival, as well as the use of new biomarkers such as urinary exosomes to detect risk groups and to understand the progression of kidney injuries.

Subclinical Contrast-Induced Acute Kidney Injury in Patients Undergoing Cerebral Computed Tomography

INTRODUCTION

The nephrotoxicity of modern contrast media remains controversial. Novel biomarkers of kidney damage may help in identifying a subclinical structural renal injury not revealed by widely used markers of kidney function.

OBJECTIVE

The aim of this study was to investigate clinical (contrast-induced acute kidney injury [CI-AKI]) and subclinical CI-AKI (SCI-AKI) after intra-arterial administration of Iodixanol and Iopamidol in patients with an estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2.

METHODS

This is a prospective observational monocentric study. Urinary sample was collected at 4-8 h after contrast medium exposure to measure neutrophil gelatinase associated lipocalin (NGAL) and the product tissue inhibitor of metalloproteinase-2 and insulin-like growth factor-binding protein 7 ([TIMP-2] × [IGFBP7]), while blood samples were collected at 24 and 48 h after exposure to measure serum creatinine.

RESULTS

One hundred patients were enrolled, of whom 53 were exposed to Iodixanol and 47 to Iopamidol. Patients in Iodixanol and Iopamidol groups were comparable in terms of demographics, pre-procedural and procedural data. No patient developed CI-AKI according KDIGO criteria, while 13 patients reported SCI-AKI after exposure to iodine-based medium contrast (3 patients in Iodixanol group and 10 patients in Iopamidol group), defined by positive results of NGAL and/or [TIMP-2] × [IGFBP7]. A positive correlation was found between NGAL and [TIMP-2] × [IGFBP7] in the analysed population (Spearman's rho 0.49, p < 0.001). In logistic regression analysis, Iopamidol exposure showed higher risk for SCI-AKI compared to Iodixanol (OR 4.5 [95% CI 1.16-17.52], p = 0.030), even after controlling for eGFR and volume of contrast medium used.

CONCLUSIONS

This study showed that intra-arterial modern contrast media administration may have a nephrotoxic effect in a population without pre-existing chronic kidney disease. Further investigations on larger scale are warranted to confirm if Iopamidol exposed patients to increased risk of SCI-AKI compared to Iodixanol.

The Sick Adult Horse: Renal Clinical Pathologic Testing and Urinalysis

Clinicopathologic evaluation of renal function and renal disease in sick adult horses remains grounded in detection of azotemia, assessment of serum and urine electrolyte concentrations, and evaluation of urinalysis findings, including specific gravity, reagent strip analysis, and sediment examination. Because increases in serum or plasma urea nitrogen and creatinine concentrations are insensitive indicators of a decreased glomerular filtration rate, there is considerable interest in identifying novel biomarkers of renal function or injury in blood and urine, with serum symmetric dimethylarginine concentration being the most recent addition to the commercial market.

A narrative review of the impact of surgery and anaesthesia on acute kidney injury

The epidemiology of peri-operative acute kidney injury varies depending on the definition, type of surgery and acute and chronic comorbidities. Haemodynamic instability, disturbance of the microcirculation, endothelial dysfunction, inflammation and tubular cell injury are the main factors contributing to the pathogenesis. There are no specific therapies. The most effective strategies to protect renal function during the peri-operative period are: the avoidance of nephrotoxic insults; optimisation of haemodynamics; prevention of hypotension; and meticulous fluid management, including avoidance of both hypovolaemia and hypervolaemia. Peri-operative acute kidney injury is associated with an increased risk of short- and long-term postoperative complications, including a longer stay in hospital, development of premature chronic kidney disease and increased mortality. Resource utilisation and healthcare costs are also higher. In future, the development of advanced clinical prediction scores, new imaging and monitoring techniques and the application of new biomarkers for acute kidney injury have the prospect of identifying acute kidney injury earlier and allowing a more personalised management approach with the aim of reducing the global burden of acute kidney injury.

Early diagnosis of acute kidney injury by urinary YKL-40 in critically ill patients in ICU: a pilot study

PURPOSE

In critically ill patients, acute kidney injury (AKI) is a devastating problem often associated with adverse outcomes. Depending on the conventional markers for diagnosis of AKI, an undesirable delay in the diagnosis and initiation of treatment has occurred. Thus, it is challenging to find a biomarker for early diagnosis of AKI. We sought to evaluate urinary YKL-40 as a biomarker for early diagnosis of AKI among critically ill patients compared with conventional markers and to assess its relation to the severity of AKI.

METHODS

Thirty-six patients without AKI at the time of ICU admission who enrolled in this prospective cohort study had the following measured: serum creatinine as well as urine YKL-40 at admission and thereafter at 4 time intervals (0, 12, and 24 ± 48 h) (therefore, we studied 94 urine samples in 36 patients). Urine YKL-40 was quantified by enzyme-linked immunosorbent assay (ELISA). AKI was defined using the Kidney Disease Improving Global Outcomes (KDIGO) criteria, which include three stages (1, 2, and 3) of progressive renal dysfunction.

RESULTS

In this study, 18 (50%) patients developed AKI within 48-72 h. Moreover, urine YKL-40 increased significantly within 12 h in patients who developed AKI (n = 18, 11.75 ± 1.94), but not in non-AKI patients (n = 18, 5.66 ± 3.42) ng/ml (P < 0.001) and, at the same time, we did not find any significant difference in the serum creatinine levels between the two groups. In addition, AKI group showed rising levels with KIDGO classes.

CONCLUSION

In this pilot study we found that urinary YKL-40 can be used as a valuable and noninvasive marker for early diagnosis of AKI among critically ill patients in ICU as compared to conventional markers and its level is increasing with the severity of AKI classes. However, the small sample size is important limitation. Therefore, large multicenter studies may be needed to confirm it.

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.

Value of early diagnosis of sepsis complicated with acute kidney injury by renal contrast-enhanced ultrasound

BACKGROUND

The incidence of acute kidney injury (AKI) in patients with sepsis is high, and the prognosis of patients with septic AKI is poor. The early diagnosis and treatment of septic AKI is of great significance in improving the prognosis of patients with sepsis.

AIM

To explore the value of contrast-enhanced ultrasound (CEUS), serum creatinine (Scr), and other indicators in the early diagnosis of septic AKI.

METHODS

Ninety patients with sepsis during hospitalization at Tongji Hospital of Tongji University were recruited as subjects. Each patient was recorded with relevant basic data, clinical indicators, and CEUS results. The patients were divided into AKI group and non-AKI group according to the results of renal function diagnosis after 48 h. On the 7th day, the renal function of the non-AKI group was re-evaluated and the patients were further divided into AKI subgroup and non-AKI subgroup. The differences of the indicators in different groups were compared, and the diagnostic value of each indicator and their combination for septic AKI was analyzed.

RESULTS

Systemic inflammatory response score (2.58 ± 0.75), blood lactic acid (3.01 ± 1.33 mmol/L), Scr (141.82 ± 27.19 μmol/L), blood urea nitrogen (4.41 ± 0.81mmol/L), and rise time (10.23 ± 2.63 s) in the AKI group were higher than those in the non-AKI group. Peak intensity (PI) (10.78 ± 3.98 dB) and wash in slope (WIS) (1.07 ± 0.53 dB/s) were lower than those in the non-AKI group. The differences were statistically significant (P < 0.05). The PI (12.83 ± 3.77 dB) and WIS (1.22 ± 0.68 dB/s) in the AKI subgroup were lower than those in the non-AKI subgroup, and the differences were statistically significant (P < 0.05). The area under curve (AUC) of Scr for the diagnosis of septic AKI was 0.825 with a sensitivity of 56.76% and a specificity of 100%. The AUCs of WIS and PI (0.928 and 0.912) were higher than those of Scr. Their sensitivities were 100%, but the specificities were 71.70% and 75.47%. The AUC of the combination of three indicators for the diagnosis of septic AKI was 0.943, which was significantly higher than the AUC diagnosed by each single indicator. The sensitivity was 94.59%, and the specificity was 81.13%.

CONCLUSION

The combination of Scr, PI, and WIS can improve the diagnostic accuracy of septic AKI. PI and WIS are expected to predict the occurrence of early septic AKI.

Economic and clinical benefits of early identification of acute kidney injury using a urinary biomarker

Purpose: To evaluate the budget impact of adding a diagnostic test of tissue inhibitor of metalloproteinase 2 and insulin-like growth factor binding protein 7 ([TIMP-2]·[IGFBP7]), which identifies patients at risk of moderate-to-severe acute kidney injury (AKI), to the current standard of care (SOC) in a hospital setting.Materials and methods: A budget impact model (2017 USD) was developed from the perspective of a hypothetical US hospital system serving 10,000 inpatients annually. The model estimated the impact of assessing the risk of AKI using SOC vs a combination of SOC and the US Food and Drug Administration-approved assay [TIMP-2]·[IGFBP7] over a 1-year period. Potential cost implications were assessed using estimates for payer mix among patients, diagnostic efficacy, and patient healthcare resource utilization. The model also considered provider adoption rates and the estimated costs of [TIMP-2]·[IGFBP7].Results: Compared to SOC alone, adding [TIMP-2]·[IGFBP7] to SOC was associated with a $1,855 reduction in uncompensated care per patient tested, which, after accounting for the additional costs of the test ($277), resulted in net savings of $1,578 per patient tested. The findings were robust to input parameter variations, as demonstrated by deterministic and probabilistic sensitivity analyses. In the probabilistic sensitivity analyses, net cost savings to the hospital ranged from $50,308-$3,971,514, or $101-$7,943 per tested patient (mean = $1,710; 95% confidence interval = $1,691-$1,729).Conclusions: The introduction of [TIMP-2]·[IGFBP7] as a novel tool in the identification of AKI risk may result in considerable cost savings from a hospital perspective under this model's base-case assumptions. Further prospective studies are needed to confirm these findings in a real-world setting.Key points for decision makersAn economic model was constructed to determine the budget impact of adding a diagnostic test ([TIMP-2]·[IGFBP7]), which identifies patients at risk of moderate-to-severe acute kidney injury, to the current standard of care (SOC) in a hospital setting.According to the present model, the use of [TIMP-2]·[IGFBP7] to identify acute kidney injury risk may reduce costs for hospitals by ∼$1,578 per patient tested.

Acute Kidney Injury in Pediatric Patients on Extracorporeal Membrane Oxygenation: A Systematic Review and Meta-analysis

Background: Acute kidney injury (AKI) is a well-established complication of extra-corporal membrane oxygenation (ECMO) in the adult population. The data in the pediatric and neonatal population is still limited. Moreover, the mortality risk of AKI among pediatric patients requiring ECMO remains unclear. Thus, this meta-analysis aims to assess the incidence of AKI, AKI requiring renal replacement therapy and AKI associated mortality in pediatric/neonatal patients requiring ECMO. Methods: A literature search was performed utilizing MEDLINE, EMBASE, and the Cochrane Database from inception through June 2019. We included studies that evaluated the incidence of AKI, severe AKI requiring renal replacement therapy (RRT) and the risk of mortality among pediatric patients on ECMO with AKI. Random-effects meta-analysis was used to calculate the pooled incidence of AKI and the odds ratios (OR) for mortality. Results: 13 studies with 3523 pediatric patients on ECMO were identified. Pooled incidence of AKI and AKI requiring RRT were 61.9% (95% confidence interval (CI): 39.0-80.4%) and 40.9% (95%CI: 31.2-51.4%), respectively. A meta-analysis limited to studies with standard AKI definitions showed a pooled estimated AKI incidence of 69.2% (95%CI: 59.7-77.3%). Compared with patients without AKI, those with AKI and AKI requiring RRT while on ECMO were associated with increased hospital mortality ORs of 1.70 (95% CI, 1.38-2.10) and 3.64 (95% CI: 2.02-6.55), respectively. Conclusions: The estimated incidence of AKI and severe AKI requiring RRT in pediatric patients receiving ECMO are high at 61.9% and 40.9%, respectively. AKI among pediatric patients on ECMO is significantly associated with reduced patient survival.

Neutrophil-lymphocyte count ratio as a diagnostic marker for acute kidney injury: a systematic review and meta-analysis

BACKGROUND

The neutrophil-to-lymphocyte ratio (NLR) is calculated from the white cell differential blood count. Recently, NLR was identified as a potential biomarker for the prediction of acute kidney injury (AKI). We conducted this systematic review and meta-analysis to evaluate the diagnostic value of NLCR for AKI in adult patients.

METHODS

Studies in the PubMed, EMBASE, Web of Science and Cochrane Library databases were systematically searched from the date of database inception to February 28, 2019. The predictive value of NLR for AKI was evaluated by the pooled sensitivity, specificity, and summary receiver operating characteristic curve (SROC) analyses. Review Manager and Stata were used for all statistical analyses. The sources of potential heterogeneity were explored by a sensitivity analysis and subgroup analysis.

RESULTS

This meta-analysis returned 89 reports, of which 9 fulfilled the inclusion criteria, accounting for 9766 patients. Bivariate analysis yielded a mean sensitivity of 0.736 (95% CI 0.675-0.790) and specificity of 0.686 (95% CI 0.601-0.759). The SROC was 0.77 (95% CI 0.74-0.81). The studies had no significant heterogeneity (Q = 0.675, p = 0.357, I² = 0).

CONCLUSIONS

Our findings indicate that the NLR may be a reliable biomarker for the early detection of AKI. Our findings also provide important information and assistance for clinicians in the prediction of AKI.

Acute Kidney Injury after Lung Transplantation: A Systematic Review and Meta-Analysis

Background: Lung transplantation has been increasingly performed worldwide and is considered an effective therapy for patients with various causes of end-stage lung diseases. We performed a systematic review to assess the incidence and impact of acute kidney injury (AKI) and severe AKI requiring renal replacement therapy (RRT) in patients after lung transplantation. Methods: A literature search was conducted utilizing Ovid MEDLINE, EMBASE, and Cochrane Database from inception through June 2019. We included studies that evaluated the incidence of AKI, severe AKI requiring RRT, and mortality risk of AKI among patients after lung transplantation. Pooled incidence and odds ratios (ORs) with 95% confidence interval (CI) were obtained using random-effects meta-analysis. The protocol for this meta-analysis is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42019134095). Results: A total of 26 cohort studies with a total of 40,592 patients after lung transplantation were enrolled. Overall, the pooled estimated incidence rates of AKI (by standard AKI definitions) and severe AKI requiring RRT following lung transplantation were 52.5% (95% CI: 45.8–59.1%) and 9.3% (95% CI: 7.6–11.4%). Meta-regression analysis demonstrated that the year of study did not significantly affect the incidence of AKI (p = 0.22) and severe AKI requiring RRT (p = 0.68). The pooled ORs of in-hospital mortality in patients after lung transplantation with AKI and severe AKI requiring RRT were 2.75 (95% CI, 1.18–6.41) and 10.89 (95% CI, 5.03–23.58). At five years, the pooled ORs of mortality among patients after lung transplantation with AKI and severe AKI requiring RRT were 1.47 (95% CI, 1.11–1.94) and 4.79 (95% CI, 3.58–6.40), respectively. Conclusion: The overall estimated incidence rates of AKI and severe AKI requiring RRT in patients after lung transplantation are 52.5% and 9.3%, respectively. Despite advances in therapy, the incidence of AKI in patients after lung transplantation does not seem to have decreased. In addition, AKI after lung transplantation is significantly associated with reduced short-term and long-term survival.

Clinical prospects of biomarkers for the early detection and/or prediction of organ injury associated with pharmacotherapy

Several biomarkers are used to monitor organ damage caused by drug toxicity. Traditional markers of kidney function, such as serum creatinine and blood urea nitrogen are commonly used to estimate glomerular filtration rate. However, these markers have several limitations including poor specificity and sensitivity. A number of serum and urine biomarkers have recently been described to detect kidney damage caused by drugs such as cisplatin, gentamicin, vancomycin, and tacrolimus. Neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid-binding protein (L-FABP), kidney injury molecule-1 (KIM-1), monocyte chemotactic protein-1 (MCP-1), and cystatin C have been identified as biomarkers for early kidney damage. Hy's Law is widely used as to predict a high risk of severe drug-induced liver injury caused by drugs such as acetaminophen. Recent reports have indicated that glutamate dehydrogenase (GLDH), high-mobility group box 1 (HMGB-1), Keratin-18 (k18), MicroRNA-122 and ornithine carbamoyltransferase (OCT) are more sensitive markers of hepatotoxicity compared to the traditional markers including the blood levels of amiotransferases and total bilirubin. Additionally, the rapid development of proteomic technologies in biofluids and tissue provides a new multi-marker panel, leading to the discovery of more sensitive biomarkers. In this review, an update topics of biomarkers for the detection of kidney or liver injury associated with pharmacotherapy.

Machine learning versus physicians' prediction of acute kidney injury in critically ill adults: a prospective evaluation of the AKIpredictor

Background

Early diagnosis of acute kidney injury (AKI) is a major challenge in the intensive care unit (ICU). The AKIpredictor is a set of machine-learning-based prediction models for AKI using routinely collected patient information, and accessible online. In order to evaluate its clinical value, the AKIpredictor was compared to physicians’ predictions.

Methods

Prospective observational study in five ICUs of a tertiary academic center. Critically ill adults without end-stage renal disease or AKI upon admission were considered for enrollment. Using structured questionnaires, physicians were asked upon admission, on the first morning, and after 24 h to predict the development of AKI stages 2 or 3 (AKI-23) during the first week of ICU stay. Discrimination, calibration, and net benefit of physicians’ predictions were compared against the ones by the AKIpredictor.

Results

Two hundred fifty-two patients were included, 30 (12%) developed AKI-23. In the cohort of patients with predictions by physicians and AKIpredictor, the performance of physicians and AKIpredictor were respectively upon ICU admission, area under the receiver operating characteristic curve (AUROC) 0.80 [0.69–0.92] versus 0.75 [0.62–0.88] (n = 120, P = 0.25) with net benefit in ranges 0–26% versus 0–74%; on the first morning, AUROC 0.94 [0.89–0.98] versus 0.89 [0.82–0.97] (n = 187, P = 0.27) with main net benefit in ranges 0–10% versus 0–48%; after 24 h, AUROC 0.95 [0.89–1.00] versus 0.89 [0.79–0.99] (n = 89, P = 0.09) with main net benefit in ranges 0–67% versus 0–50%.

Conclusions

The machine-learning-based AKIpredictor achieved similar discriminative performance as physicians for prediction of AKI-23, and higher net benefit overall, because physicians overestimated the risk of AKI. This suggests an added value of the systematic risk stratification by the AKIpredictor to physicians’ predictions, in particular to select high-risk patients or reduce false positives in studies evaluating new and potentially harmful therapies. Due to the low event rate, future studies are needed to validate these findings.

Trial registration

ClinicalTrials.gov, NCT03574896 registration date: July 2nd, 2018

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2563-x) contains supplementary material, which is available to authorized users.

Development of a risk stratification-based model for prediction of acute kidney injury in critically ill patients

Acute kidney injury (AKI) is a complex syndrome with a variety of possible etiologies and symptoms. It is characterized by high mortality and poor recovery of renal function. The incidence and mortality rates of patients with AKI in intensive care units are extremely high. It is generally accepted that early identification and prompt treatment of AKI are essential to improve outcomes. This study aimed to develop a model based on risk stratification to identify and diagnose early stage AKI for improved prognosis in critically ill patients.This was a single-center, retrospective, observational study. Based on relevant literature, we selected 13 risk factors (age, sex, hypertension, diabetes, coronary heart disease, chronic kidney disease, total bilirubin, emergency surgery, mechanical ventilation, sepsis, heart failure, cancer, and hypoalbuminemia) for AKI assessment using the Kidney Disease Improving Global Outcomes (KDIGO) diagnostic criteria. Univariate and multivariate analyses were used to determine risk factors for eventual entry into the predictive model. The AKI predictive model was established using binary logistic regression, and the area under the receiver operating characteristic curve (AUROC or AUC) was used to evaluate the predictive ability of the model and to determine critical values.The AKI predictive model was established using binary logistic regression. The AUROC of the predictive model was 0.81, with a sensitivity of 69.8%, specificity of 83.4%, and positive likelihood ratio of 4.2.A predictive model for AKI in critically ill patients was established using 5 related risk factors: heart failure, chronic kidney disease, emergency surgery, sepsis, and total bilirubin; however, the predictive ability requires validation.