Optimal cut points of plasma and urine neutrophil gelatinase-associated lipocalin for the prediction of acute kidney injury among critically ill adults: retrospective determination and clinical validation of a prospective multicentre study

Detection strip of anti-NGAL antibody coupled with fluorescent microspheres-A novel tool for reliable and accurate prediction of renal injury

OBJECTIVE

Neutrophil gelatinase-associated lipocalin (NGAL) has been identified by the International Nephrology Association (INA) as a promising biomarker for the early evaluation of renal injury. This study aimed to develop and evaluate NGAL test strips as a rapid, simple, and economical method for the early diagnosis of acute kidney injury (AKI).

METHODS

Recombinant prokaryotic expression vectors, purified NGAL protein, and anti-NGAL monoclonal antibodies were prepared. NGAL test strips were developed, and serum samples were collected from healthy individuals and patients with early-stage kidney injury at the Third Affiliated Hospital of Sun Yat-sen University between January 2023 and May 2024. Samples were tested using both the self-made strips and commercially available reagents.

RESULTS

The NGAL test strip comprised a conjugate pad containing 0.2 μL of fluorescent microspheres conjugated with anti-NGAL monoclonal antibody (McAb7#), a test line containing 1 mg/mL of a different anti-NGAL monoclonal antibody (McAb3#), and a control line containing 0.5 mg/mL of goat anti-mouse IgG. The test utilized 60 μL of sample (30 μL serum diluted with 30 μL of sample diluent) and was completed within 15 min at 25 °C and 35 %-85 % relative humidity. The developed strip accurately detected NGAL, demonstrating good linearity within the range of 0-160 ng/mL (R2 = 0.9943). The sensitivity and specificity of the NGAL strip for AKI diagnosis were 86.1 % and 78.8 %, respectively, comparable to the performance of commercially available testing reagents.

CONCLUSION

The developed test strip, utilizing anti-NGAL antibodies coupled with fluorescent microspheres, effectively detected trace amounts of NGAL protein in serum samples.

The role of biomarkers in early identification of acute kidney injury among non-critically ill patients

BACKGROUND

Prediction and/or early identification of acute kidney injury (AKI) and individuals at greater risk remains of great interest in clinical medicine. Acute kidney injury continues to be a common complication among hospitalized patients, with an incidence ranging from 6 to 58%, depending on the setting. Aim of this study was to determine the performance of Insulin-like growth factor binding protein-7 (IGFBP7), tissue metallopeptidase inhibitor 2 (TIMP2), and urinary neutrophil gelatinase-associated lipocalin (uNGAL) in early detection of AKI among non-critically ill patients.

METHODS

In this prospective observational study at Mayo Clinic Hospitals in Rochester, Minnesota, USA, non-critically ill patients admitted from the emergency department between October 31st, 2016 and May 1st, 2018, who had an acute kidney injury (AKI) probability of 5% or higher were included. Biomarkers were measured in residual urine samples collected in the emergency department. The primary outcome was biomarker performance in predicting AKI development within the first 72 h.

RESULTS

Among 368 included patients, the mean age was 79 ± 12 years, and 160 (43%) were male. Acute kidney injury occurred in 62 (17%) patients; 11.5% stage 1, 2.5% stage 2, and 3% stage 3. Twelve patients (3%) died during hospitalization and 102 (28%) within nine months after admission. The median uNGAL and IGFBP7-TIMP2 were 57 [20-236 ng/ml], and 0.3 [0.1-0.8], respectively. The C-statistic of uNGAL and IGFBP7-TIMP2 of > 0.3 and > 2.0 for AKI prediction were 0.56, 0.54, and 0.53, respectively. In a model where one point is assigned to each marker of AKI (elevated serum creatinine, IGFBP7-TIMP2 > 0.3, and uNGAL), a higher score correlated with higher nine-month mortality [OR of 1.32 per point (95% CI 1.02-1.71)].

CONCLUSION

Among non-critically ill hospitalized patients, the performance of uNGAL and IGFBP7-TIMP2 for AKI prediction within 72 h of admission was modest. This suggests a limited role for these biomarkers in AKI risk stratification among non-critically ill patients. Key learning points What was known Acute kidney injury (AKI) is a common complication among hospitalized patients. It is associated with increased morbidity and mortality. Various clinical prediction models and biomarkers have been developed to identify patients in special populations (such as ICU and cardiac surgery) who are at risk of AKI and diagnose AKI early. This study adds The performance of the biomarkers uNGAL, TIMP-2, and IGFBP-7 in predicting AKI within 72 h of admission in non-critically ill patients was modest. However, these biomarkers were found to have a prognostic value for predicting 9-month mortality. One potential application of these biomarkers is identifying patients at higher AKI risk before exposing them to nephrotoxic agents. Potential impact This study provides evidence regarding the real-world performance of current FDA-approved biomarkers (uNGAL, TIMP-2, and IGFBP-7) for predicting acute kidney injury (AKI) within 72 h of hospital admission among noncritically ill patients. While the performance of these biomarkers for predicting short-term AKI was modest, they may have a prognostic value for predicting 9-month mortality.

Impact of low pneumoperitoneum on renal function and acute kidney injury biomarkers during robot-assisted radical prostatectomy (RARP): a randomised clinical trial

The objective of this study was to evaluate the effect of low pneumoperitoneum pressure (Pnp) on renal function and renal injury biomarkers during robot-assisted radical prostatectomy (RARP). A single-centre, triple-blinded, randomised clinical trial was conducted with 98 patients undergoing RARP, who were assigned to either standard Pnp of 12 mmHg or low Pnp of 7 mmHg. The primary outcome was urinary neutrophil gelatinase-associated lipocalin (u-NGAL), and several other kidney injury biomarkers were assessed as secondary outcomes. Acute kidney injury (AKI) was evaluated using the Kidney Disease Improving Global Outcomes (KDIGO) criteria, the gold standard method for defining AKI. The trial was registered on ClinicalTrials.gov (NCT04755452). Patients in the low Pnp group had significantly lower levels of u-NGAL (mean difference - 39.9, 95% CI - 73.7 to - 6.1, p = 0.02) compared to the standard Pnp group. No significant differences were observed for other urinary biomarkers. Interestingly, there was a significant difference in intraoperative urine production between the groups (low Pnp median: 200 mL, IQR: 100-325 vs. standard Pnp median: 100 mL, IQR: 50-200, p = 0.01). Similarly, total postoperative urine production also varied significantly (low Pnp median: 1325 mL, IQR: 1025-1800 vs. standard Pnp median: 1000 mL, IQR: 850-1287, p = 0.001). The occurrence of AKI, as defined by the KDIGO criteria, did not differ significantly between the groups. Low Pnp during RARP resulted in lower u-NGAL levels, suggesting a potential benefit in terms of reduced renal injury. However, the lack of a notable difference in AKI as defined by the KDIGO criteria indicates that the clinical significance of this finding may be limited. Further research is needed to validate and expand on these results, ultimately defining the optimal Pnp strategy for RARP and improving patient outcomes.

Evaluation of plasma and urine neutrophil gelatinase-associated lipocalin (NGAL) as an early diagnostic marker of acute kidney injury (AKI) in critically ill trauma patients

Background and Aims

Acute kidney injury (AKI) is a frequent complication of severe trauma associated with high mortality. The aim of this study was to evaluate the diagnostic ability of plasma and urine neutrophil gelatinase-associated lipocalin (NGAL) as an early marker of AKI assessed by RIFLE criteria as reference in trauma patients in intensive care unit (ICU).

Material and Methods

This was a prospective observational study. Four hundred and eighteen patients admitted in the trauma ICU with age ≥18 years without known renal diseases were followed-up (serum creatinine, urine output, and estimated glomerular filtration rate) for 5 consecutive days. As per RIFLE criteria, 70 patients were broadly classified as AKI and rest of the patients (n = 348) as non-AKI. Plasma and urine samples of AKI (n = 70) and non-AKI (n = 70) patients were further assessed for 3 consecutive days following admission.

Results

Mean plasma NGAL (pNGAL) was significantly elevated in AKI patients as compared with non-AKI patients; on admission: 204.08 versus 93.74 ng/mL (P = 0.01); at 24 h: 216.73 versus 94.63 ng/mL (P = 0.01); and 48 h: 212.77 versus 86.32 ng/mL (P = 0.01). Mean urine NGAL (uNGAL) at 48 h was also significantly elevated: 15.45 ng/mL in AKI patients as compared with 13.48 ng/mL in non-AKI patients (P = 0.01). Plasma and urine NGAL levels were significantly associated with increased mortality.

Conclusion

pNGAL had good predictive value on admission (area under the receiver operative characteristic [AUROC] 0.84), at 24 h (AUROC 0.88) and 48 h (AUROC 0.87), while uNGAL had moderate performance at 24 h (AUROC 0.61) and 48 h (AUROC 0.71). pNGAL can be used as an early and potent diagnostic and predictive marker of AKI and mortality in critically ill trauma patients.

New Insights into Molecular Mechanisms of Chronic Kidney Disease

Chronic kidney disease (CKD) is a major public health problem with a developing incidence and prevalence. As a consequence of the growing number of patients diagnosed with renal dysfunction leading to the development of CKD, it is particularly important to explain the mechanisms of its underlying causes. In our paper, we discuss the molecular mechanisms of the development and progression of CKD, focusing on oxidative stress, the role of the immune system, neutrophil gelatinase-associated lipocalin, and matrix metalloproteinases. Moreover, growing evidence shows the importance of the role of the gut-kidney axis in the maintenance of normal homeostasis and of the dysregulation of this axis in CKD. Further, we discuss the therapeutic potential and highlight the future research directions for the therapeutic targeting of CKD. However, additional investigation is crucial to improve our knowledge of CKD progression and, more importantly, accelerate basic research to improve our understanding of the mechanism of pathophysiology.

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

Background

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

Methods

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

Results

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

Conclusions

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

Serum cystatin C, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, klotho and fibroblast growth factor-23 in the early prediction of acute kidney injury associated with sepsis in a Chinese emergency cohort study

Background

Acute kidney injury (AKI) is a common and critical complication of sepsis, and is associated with unacceptable morbidity and mortality. Current diagnostic criteria for AKI was insensitive for early detection. Novel biomarkers including cystatin C, kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), klotho and fibroblast growth factor-23 (FGF-23) can predict AKI earlier and allow immediate interventions. We aimed to determine the diagnostic performance of these biomarkers for detecting AKI in sepsis patients.

Methods

This prospective observational study was conducted between May 2018 and November 2020, enrolling 162 sepsis patients eventually. The AKI was defined in accordance with 2012 KDIGO criteria and we divided patients into non-AKI (n = 102) and AKI (n = 60) groups. Serum levels of several AKI biomarkers were detected by ELISA. The relationship between biomarker levels on admission of AKI was analyzed and discrimination performances comparison were performed.

Results

AKI incidence was up to 37.0% (60/162) during hospitalization. Compared with non-AKI group, both serum cystatin C, KIM-1, NGAL and FGF-23 were significantly elevated at admission in septic AKI patients. The areas under the receiver operating curves demonstrated that serum cystatin C had modest discriminative powers for predicting AKI after sepsis, and cystatin C combined with serum creatinine in the prediction of septic AKI increased the diagnostic sensitivity prominently.

Conclusion

Serum cystatin C, KIM-1, NGAL and FGF-23 levels were both increased in septic AKI patients. Our study provided reliable evidence that cystatin C solely and combined with serum creatinine may accurately and sensitively predict septic AKI of patients on admission.

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.

Balanced forced-diuresis compared to control as a reno-protective approach in cardiac surgery: secondary outcome of a randomized controlled trial, assessment of neutrophil gelatinase-associated lipocalin levels

Background

Neutrophil gelatinase-associated lipocalin (NGAL) is a recognised biomarker for acute kidney injury (AKI).This study investigated the impact of balanced forced-diuresis using RenalGuard® system (RG), in reducing acute kidney injury (AKI) rates and the associated NGAL levels (6-h post-CPB plasma level) post adult cardiac surgery with cardiopulmonary bypass (CPB).

Methods

Patients included in the study were at high-risk for AKI post cardiac surgery, namely history of diabetes and/or anaemia, e-GFR 20–60 ml/min/1.73 m², Logistic EuroScore > 5, anticipated CPB time > 120 min. Patients were randomized to either RG (n = 110) or managed as per current practice (control = 110). RIFLE-defined AKI rate (based on serum creatinine level increase) within first 3 days of surgery and 6-h post CPB NGAL levels were the primary and secondary end-points.

Results

Pre and intra-operative characteristics between the two groups were similar (p > 0.05) including the pre-op NGAL levels, the oxygen delivery (ecDO₂i) and the carbon dioxide production (ecVCO₂i) during CPB. Patients in the RG group had a significantly lower post-operative RIFLE-defined AKI rate compared to control (10% (11/110) v/s 20.9% (23/110), p = 0.03). Overall, median 6-h post CPB NGAL levels in patients with AKI were significantly higher than those who did not develop AKI (211 vs 150 ng/ml, p < 0.001). Patients managed by balanced forced-diuresis had lower post-operative NGAL levels (146 vs 178 ng/ml, p = 0.09). Using previously reported NGAL cut-off level for AKI (142 ng/ml), binary logistic regression analysis confirmed a beneficial effect of the RG system, with an increased risk of AKI of 2.2 times in the control group (OR 2.2, 95% CI 1.14–4.27, p = 0.02).

Conclusions

Overall, the 6-h post-CPB plasma NGAL levels were significantly higher in patients who developed AKI. Patients managed with the novel approach of balanced forced-diuresis, provided by the RenalGuard® system, had a lower AKI rate and lower NGAL levels indicating a lesser degree of renal tissue injury.

Trial registration ClinicalTrials.gov website, NCT02974946, https://clinicaltrials.gov/ct2/show/NCT02974946.

Biomarkers in Acute Kidney Injury

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

Neutrophil gelatinase-associated lipocalin as a biomarker of nephropathy in sickle cell disease

Sickle cell nephropathy (SCN) develops via altered hemodynamics and acute kidney injury, but conventional screening tests remain normal until advanced stages. Early diagnostic biomarkers are needed so that preventive measures can be taken. This study evaluates the role of neutrophil gelatinase–associated lipocalin (NGAL) as a biomarker of SCN in steady state and vaso-occlusive crisis (VOC). In this case-control study, 74 sickle cell disease (SCD) patients (37 in steady state and 37 in VOC) and 53 control subjects had hematological and biochemical measurements including plasma and urine NGAL. Univariate and logistic regression analyses were used to find the associations between variables. The receiver operating characteristic (ROC) curve was used to determine the diagnostic performance characteristics of plasma and urine NGAL for detection of VOC. Plasma and urine NGAL, urine microalbumin:creatinine ratio, and urine protein:creatinine ratio were significantly higher in VOC. Microalbuminuria was present in 17.1% steady state and 32.0% VOC patients. Microalbuminuria showed significant correlations with age, plasma NGAL, WBC, and hemolytic parameters. Area under the ROC curve for plasma NGAL was 0.69 (95%CI = 0.567–0.813; p = 0.006) and 0.86 (95%CI = 0.756–0.954; p < 0.001) for urine NGAL. Urine NGAL cut-off value of 12.0 ng/mL had 95% sensitivity and 65% specificity. These results confirm the presence of nephropathy during VOC and suggest that plasma and urine NGAL would be useful in the identification of SCN. Urine NGAL should be used as the screening biomarker, and patients with VOC and urine NGAL > 12.0 ng/mL should be selected for aggressive management to prevent progression of renal damage.

Effects of pneumoperitoneum on kidney injury biomarkers: A randomized clinical trial

Background

Increased intra-abdominal pressure causes hemodynamic changes that may affect renal biomarkers.

Methods

This randomized, single-blind, single-center clinical trial recruited patients undergoing laparoscopic cholecystectomy at a tertiary care center in Brazil. They were randomly allocated to a standard intra-abdominal pressure group (P_10-12, 10–12 mm Hg) and a low intra-abdominal pressure group (P_6-8, 6–8 mm Hg). The primary outcome was the change in neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C levels measured at the beginning of the procedure (T0), at the end of the procedure (T1), and 24 hours after the procedure (T2). P-values < 0.05 were considered statistically significant.

Results

In total, 64 patients completed the study—33 were given standard pressure and 31 were given low pressure. There was no significant difference in the biomarker between the groups (P = 0.580), but there was a significant difference between the time points with elevation at T1 (P < 0.001). Similar to NGAL, cystatin C had an elevation at T1 in both groups (P = 0.021), but no difference was found when comparing the groups.

Conclusions

In laparoscopic cholecystectomy, pneumoperitoneum increases NGAL and cystatin C levels intraoperatively, and the use of low-pressure pneumoperitoneum does not change the course of these biomarkers.

Effectiveness of Plasma and Urine Neutrophil Gelatinase-Associated Lipocalin for Predicting Acute Kidney Injury in High-Risk Patients

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is a useful biomarker for acute kidney injury (AKI) prediction. However, studies on whether using both plasma NGAL (PNGAL) and urine NGAL (UNGAL) can improve AKI prediction are limited. We investigated the best approach to predict AKI in high-risk patients when using PNGAL and UNGAL together.

METHODS

We enrolled 151 AKI suspected patients with one or more AKI risk factors. We assessed the diagnostic performance of PNGAL and UNGAL for predicting AKI according to chronic kidney disease (CKD) status by determining the areas under the receiver operating curve (AuROC). Independent predictors of AKI were assessed using univariate and multivariate logistic regression analyses.

RESULTS

In the multivariate logistic regression analysis for all patients (N=151), Model 2 and 3, including PNGAL (P=0.012) with initial serum creatinine (S-Cr), showed a better AKI prediction power (R2=0.435, both) than Model 0, including S-Cr only (R2=0.390). In the non-CKD group (N=135), the AuROC of PNGAL for AKI prediction was larger than that of UNGAL (0.79 vs 0.66, P=0.010), whereas in the CKD group (N=16), the opposite was true (0.94 vs 0.76, P=0.049).

CONCLUSIONS

PNGAL may serve as a useful biomarker for AKI prediction in high-risk patients. However, UNGAL predicted AKI better than PNGAL in CKD patients. Our findings provide guidance for selecting appropriate specimens for NGAL testing according to the presence of CKD in AKI high-risk patients.

Machine Learning to Predict Contrast-Induced Acute Kidney Injury in Patients With Acute Myocardial Infarction

Objective: To develop predictive models for contrast induced acute kidney injury (CI-AKI) among acute myocardial infarction (AMI) patients treated invasively.

Methods: Patients with AMI who underwent angiography therapy were enrolled and randomly divided into training cohort (75%) and validation cohort (25%). Machine learning algorithms were used to construct predictive models for CI-AKI. The predictive models were tested in a validation cohort.

Results: A total of 1,495 patients with AMI were included. Of all the patients, 226 (15.1%) cases developed CI-AKI. In the validation cohort, Random Forest (RF) model with top 15 variables reached an area under the curve (AUC) of 0.82 (95% CI: 0.76–0.87), while the best logistic model had an AUC of 0.69 (95% CI: 0.62–0.76). ACEF (age, creatinine, and ejection fraction) model reached an AUC of 0.62 (95% CI: 0.53–0.71). RF model with top 15 variables achieved a high recall rate of 71.9% and an accuracy of 73.5% in the validation group. Random Forest model significantly outperformed logistic regression in every comparison.

Conclusions: Machine learning algorithms especially Random Forest algorithm improves the accuracy of risk stratifying patients with AMI and should be used to accurately identify the risk of CI-AKI in AMI patients.

Serum Cystatin C, Klotho, and Neutrophil Gelatinase-Associated Lipocalin in the Risk Prediction of Acute Kidney Injury after Acute Myocardial Infarction

BACKGROUND

Patients with acute myocardial infarction (AMI) are at high risk for acute kidney injury (AKI). Novel biomarkers that can predict AKI after AMI may facilitate immediate interventions. Recently, cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), and klotho have been established as novel AKI biomarkers. However, their effects have not been studied in patients presenting with AMI. In this study, we will measure the serum levels of these three biomarkers to find reliable biomarkers for early diagnosis of AKI in AMI patients.

METHODS

This prospective observational cohort study was conducted between May 2016 and November 2017. A total of 285 consecutive patients with AMI were enrolled. The study was approved by the institutional review board of Peking University People's Hospital (No. 2016PHB 042-01). AKI was defined according to the KDIGO criteria in 2012. At admission, the clinical data of patients was collected and serum levels of several AKI biomarkers, including cystatin C, NGAL, and klotho, were measured by ELISA. The relationship between biomarker levels of AKI were analyzed and their discrimination performances were compared.

RESULTS

AKI incidence was 17.5% (50/285) during hospitalization. Compared to patients without AKI, the AKI group had higher mortality (20.0% vs. 0.4%, p < 0.001) and tended to be older, had higher incidence of chronic kidney disease, severe cardiac function, more cardiac complications, larger doses of diuretics, and less use of angiotensin-converting enzyme inhibitors/angiotensin receptor blocker and statins. Moreover, AKI patients experienced an increase in serum cystatin C (3,709.2 ± 2,281.5 vs. 1,918.5 ± 1,140.6 ng/mL, p < 0.001), NGAL (118.0 ± 70.3 vs. 91.8 ± 52.3 ng/mL, p = 0.003), and klotho (742.2 ± 497.4 vs. 470.3 ± 257.2 pg/mL, p <0.001). Furthermore, the areas under the receiver operating curves demonstrated that serum cystatin C levels at admission had modest discriminative powers for predicting AKI after AMI compared with serum creatinine (0.899, 95% CI, 0.855-0.944 vs. 0.734, 95% CI, 0.649-0.819, p <0.001). There was no difference between the discrimination performances of serum creatinine, NGAL, and klotho.

CONCLUSION

Elevated cystatin C levels are associated with AKI in patients with AMI. This study provides reliable evidence that cystatin C levels may be superior to serum creatinine for predicting AKI after AMI at admission.

Cardiorenal syndrome in thalassemia patients

Background

Cardiorenal syndrome (CRS), a serious condition with high morbidity and mortality, is characterized by the coexistence of cardiac abnormality and renal dysfunction. There is limited information about CRS in association thalassemia. This study aimed to investigate the prevalence of CRS in thalassemia patients and also associated risk factors.

Methods

Thalassemia patients who attended the out-patient clinic of a tertiary care university hospital from October 2016 to September 2017 were enrolled onto this cross-sectional study. Clinical and laboratory findings from 2 consecutive visits, 3 months apart, were assessed. The criteria for diagnosis of CRS was based on a system proposed by Ronco and McCullough. Cardiac abnormalities are assessed by clinical presentation, establishment of acute or chronic heart failure using definitions from 2016 ESC guidelines or from structural abnormalities shown in an echocardiogram. Renal dysfunction was defined as chronic kidney disease according to the 2012 KDIGO guidelines.

Results

Out of 90 thalassemia patients, 25 (27.8%) had CRS. The multivariable analysis showed a significant association between CRS and extramedullary hematopoiesis (EMH) (odds ratio (OR) 20.55, p = 0.016); thalassemia type [β⁰/β^E vs β⁰/β⁰ thalassemia (OR 0.005, p = 0.002)]; pulmonary hypertension (OR 178.1, p = 0.001); elevated serum NT-proBNP (OR 1.028, p = 0.022), and elevated 24-h urine magnesium (OR 1.913, p = 0.016). There was no association found between CRS and frequency of blood transfusion, serum ferritin, liver iron concentration, cardiac T2*, type of iron chelating agents, or urine neutrophil gelatinase-associated lipocalin level.

Conclusions

CRS is relatively common in thalassemia patients. Its occurrence is associated with laboratory parameters which are easily measured in clinical practice.

Neutrophil Gelatinase-Associated Lipocalin for the Early Prediction of Acute Kidney Injury in ST-Segment Elevation Myocardial Infarction Patients Treated with Primary Percutaneous Coronary Intervention

INTRODUCTION AND OBJECTIVE

Neutrophil gelatinase-associated lipocalin (NGAL), a glycoprotein released by renal tubular cells, can be used as a marker of early tubular damage. We evaluated plasma NGAL level utilization for the identification of acute kidney injury (AKI) among ST-elevation myocardial infarction (STEMI) patients undergoing primary coronary intervention (PCI).

METHODS

131 STEMI patients treated with PCI were prospectively included. Plasma NGAL levels were drawn prior to PCI (0 h) and 24 h afterwards. AKI was defined per KDIGO criteria of serum creatinine increase. Receiver-operating characteristic (ROC) methods were used to identify optimal sensitivity and specificity for the observed NGAL range.

RESULTS

Overall AKI incidence was 14%. NGAL levels were significantly higher for patients with AKI at both 0 h (164 ± 42 vs. 95 ± 30; p < 0.001) and 24 h (142 ± 41 vs. 93 ± 36; p < 0.001). Per ROC curve analysis, an optimal cutoff value of NGAL (>120 ng/mL) predicted AKI with 80% sensitivity and specificity (AUC 0.881, 95%, CI 0.801-0.961, p < 0.001). In a multivariate logistic regression model, NGAL levels were independently associated with AKI at 0 h (OR 1.044, 95% CI 1.013-1.076; p = 0.005) and 24 h (OR 1.018, 95% CI 1.001-1.036; p = 0.04).

CONCLUSIONS

Elevated NGAL levels, suggesting renal tubular damage, are independently associated with AKI in STEMI patients undergoing primary PCI.

Endothelial Glycocalyx

The endothelial glycocalyx (EG) is the most luminal layer of the blood vessel, growing on and within the vascular wall. Shedding of the EG plays a central role in many critical illnesses. Degradation of the EG is associated with increased morbidity and mortality. Certain illnesses and iatrogenic interventions can cause degradation of the EG. It is not known whether restitution of the EG promotes the survival of the patient. First trials that focus on the reorganization and/or restitution of the EG seem promising. Nevertheless, the step "from bench to bedside" is still a big one.

Serial Urinary Tissue Inhibitor of Metalloproteinase-2 and Insulin-Like Growth Factor-Binding Protein 7 and the Prognosis for Acute Kidney Injury over the Course of Critical Illness

INTRODUCTION

Over the course of critical illness, there is a risk of acute kidney injury (AKI), and when it occurs, it is associated with increased length of stay, morbidity, and mortality. The urinary cell-cycle arrest markers tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) have been utilized to predict the risk of AKI over the next 12 h from the time of sampling. The aim of this analysis was to evaluate the utility of [TIMP-2] × [IGFBP7] measured serially to anticipate the occurrence of AKI over the first 7 days of critical illness.

METHODS

This analysis is from a prospective, blinded, observational, international study of patients admitted to intensive care units. We designed the analysis to emulate a clinician-driven serial testing strategy. Urine samples collected every 12 h up to 3 days from 530 patients were considered for analysis. We evaluated [TIMP-2] × [IGFBP7] results for the first 3 measurements (baseline, 12 and 24 h) and continued to evaluate additional results if any of the first 3 were positive >0.3 (ng/mL)2/1,000. Patients were stratified by number of [TIMP-2] × [IGFBP7] results >0.3 (ng/mL)2/1,000 and number of results >2.0 (ng/mL)2/1,000. The primary endpoint was AKI stage 2-3 defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria.

RESULTS

The median (interquartile range) age was 64 (53-74) years, 61% were men, and 79% were Caucasian. The median APACHE III score was 71 (51-93), and 82% required mechanical ventilation. Baseline serum creatinine was 0.8 mg/dL and 164/530 (31%) developed the primary endpoint by day 7 with a median time from baseline to stage 2/3 AKI of 26 (8-56) h. In patients with negative values for the first 3 tests (≤0.3 (ng/mL)2/1,000), the cumulative incidence of the primary endpoint at 7 days was 13.0%. Conversely, for those with one, two, or three strongly positive values (>2.0 (ng/mL)2/1,000), the cumulative incidence for the primary endpoint at 7 days was 57.7, 75.0, and 94.4%, respectively, p < 0.001 for trend. There were 3.4% with test results between 0.3 and 2.0 (ng/mL)2/1,000 at all measurements; one third of those patients developed the primary endpoint. We observed a graded increase in the primary endpoint in Kaplan-Meier plots for successively positive test results over time.

CONCLUSION

Serial urinary [TIMP-2] × [IGFBP7] at baseline, 12 and 24 h, and up through 3 days are prognostic for the occurrence of stage 2/3 AKI over the course of critical illness. Three consecutive negative values (≤0.3 (ng/mL)2/1,000) are associated with very low (13.0%) incidence of stage 2/3 AKI over the course of 7 days. Conversely, emerging or persistent, strongly positive results [>2.0 [ng/mL]2/1,000] predict very high incidence rates (up to 94.4%) of stage 2/3 AKI. There was a low rate of test results between 0.3 and 2.0 (ng/mL)2/1,000, where the primary endpoint was observed in a third of cases.

New Insights Into Mechanisms of Acute Kidney Injury in Heart Disease

Acute kidney injury is a frequent occurrence in patients with heart disease, and is associated with higher risk of adverse outcomes, including mortality. In the setting of decompensated heart failure, acute kidney injury can occur from hemodynamic and neurohormonal activation, venous congestion, and nephrotoxic medications. Certain medications, such as loop diuretics, renin angiotensin system blockers, and mineralocorticoid antagonists can seemingly cause acute kidney injury. However, this increase in creatinine level is not always associated with adverse outcomes and should be carefully differentiated so as to allow deliberate continuation of these cardio- and nephroprotective agents. In other settings such as cardiac surgery, acute kidney injury can occur from factors related to the cardiopulmonary bypass, renal hypoperfusion, or other perioperative factors. Last, patients with heart disease commonly undergo imaging procedures that require contrast administration. Contrast can indeed cause acute kidney injury, but these interventional procedures also can result in kidney injury from atheroembolic phenomena. This is well documented by the recent data reporting a higher risk of acute kidney injury from femoral compared with radial access. The advent of biomarkers of kidney injury present an opportunity for early detection, accurate differential diagnosis, as well as potentially designing innovative biomarker-enriched adaptive clinical trials.

Biomarkers of Acute Kidney Injury after Cardiac Surgery: A Narrative Review

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a major and serious complication in patients undergoing cardiac surgery and is independently associated with perioperative mortality and mortality. Therapeutic intervention aiming at reversing kidney dysfunction seems disappointing across multiple settings. Consequently, attention has shifted from treatment to prevention and early detection. The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines have unified diagnostic standards mainly based on the serum creatinine (Scr) level or urine output, but neither marker is kidney specific. Efforts have been made to identify novel biomarkers with high sensitivity and specificity. The diagnostic capabilities of neutrophil gelatinase-associated lipocalin (NGAL) and G1 cell cycle arrest biomarker as biomarkers have been confirmed in a large number of clinical trials. The utility of biomarkers of cardiac function and inflammation has been validated in clinical studies. Aiming to offer valuable information for further research, we summarize the progress in defining current markers relevant to CSA-AKI in the last three years.

Community-Acquired Acute Kidney Injury as a Risk Factor of de novo Heart Failure Hospitalization

Objectives: Because patients with hospital-acquired acute kidney injury (AKI) are at risk for subsequent development of heart failure (HF) and little is known about the relation between community-acquired AKI (CA-AKI) and HF, we sought to determine if CA-AKI is a risk factor for incident HF hospitalization. Methods: We utilized Baylor Scott &amp; White Health databases at the primary care and inpatient hospitalization levels to identify adults without a prior history of HF who had 2 or more serum creatinine measurements within 13 months in the primary care setting. We defined CA-AKI as a serum creatinine increase ≥0.3 mg/dL or ≥1.5 times the baseline for consecutive values within a 13-month period. We created a flag for de novo HF hospitalization at 90, 180, and 365 days following CA-AKI evaluation. Results: In the analyses, 210,895 unique adults were included, of whom 5,358 (2.5%) had CA-AKI. Those with CA-AKI had higher rates of comorbidities, higher rate of males (48 vs. 42%, p < 0.001), and were older (61.5 [50.3, 73.1] vs. 54.1 [42.8, 64.7] years, p < 0.001) than those who did not have CA-AKI. In total, 607 (0.3%), 833 (0.4%), and 1,089 (0.5%) individuals had an incident HF hospitalization in the 90, 180, and 365 days following the CA-AKI evaluation, respectively. After adjusting for demographic and clinical characteristics, patients with CA-AKI had >2 times the risk of de novo HF hospitalization compared with patients who did not have CA-AKI (90 days: 2.35 [1.83–3.02], p < 0.001; 180 days: 2.52 [2.04–3.13], p < 0.001; 365 days: 2.16 [1.77–2.64], p < 0.001). These multivariable models yielded strong predictive abilities, with the areas under the receiver-operating characteristic curve >0.90. Conclusion: After controlling for baseline and clinical characteristics, patients with CA-AKI were at approximately twofold the risk of de novo HF hospitalization (within 90, 180, and 365 days) compared with those who did not have CA-AKI. Hence, detecting CA-AKI may provide an opportunity for early intervention at the primary care level to possibly delay HF development.

Cotreatment with Furosemide and Hypertonic Saline Decreases Serum Neutrophil Gelatinase-associated Lipocalin (NGAL) and Serum Creatinine Concentrations in Traumatic Brain Injury: A Randomized, Single-Blind Clinical Trial

Acute kidney injury (AKI) occurs both after traumatic brain injury (TBI) and after hypertonic saline administration; furosemide may be useful in preventing AKI indirectly. Serum neutrophil gelatinase-associated lipocalin (sNGAL) is superior to serum creatinine (sCr) in diagnosing early AKI. We compared the administration of hypertonic saline plus furosemide (HTS+F) versus hypertonic saline (HTS), using sCr and sNGAL to investigate kidney injury in patients with TBI. This randomized, single-blind clinical trial was conducted from August 2016 to July 2017 in a neurosurgical intensive care unit, and included patients with a Glasgow Coma Score (GCS) 7-13 and brain edema. One group (n = 22) received hypertonic saline 5% (100 mL over 60 min then 20 mL/h) plus furosemide (40 mg over 60 min then 0.05 mg/kg per hour) for 72 h. The other group (n = 21) received only hypertonic saline 5%, in the same dose as noted above. The sCr and sNGAL concentrations, GCS, and length of stay were measured. Mean ± SD differences were -51.15 (47.07) and 9.96 (64.23) ng/mL for sNGAL and -0.12 (0.22) and -0.005 (0.2) mg/dL for sCr in HTS+F group and HTS group respectively (both p < 0.001). The incidence of stage one AKI according to Improving Global Outcomes (KDIGO) criteria was 4.5% in the HTS+F group and 19.0% in the HTS group (p = 0.16). Hypokalemia was common in both groups. HTS+F group, compared with HTS group, was associated with lower concentrations of sCr and sNGAL. Incidence AKI (KDIGO criteria) did not have difference between groups.