Predicting acute kidney injury using urinary liver-type fatty-acid binding protein and serum N-terminal pro-B-type natriuretic peptide levels in patients treated at medical cardiac intensive care units

AKIMLpred: An interpretable machine learning model for predicting acute kidney injury within seven days in critically ill patients based on a prospective cohort study

BACKGROUND

Early recognition and timely intervention for AKI in critically ill patients were crucial to reduce morbidity and mortality. This study aimed to use biomarkers to construct a optimal machine learning model for early prediction of AKI in critically ill patients within seven days.

METHODS

The prospective cohort study enrolled 929 patients altogether who were admitted in ICU including 680 patients in training set (Jiefang Campus) and 249 patients in external testing set (Binjiang Campus). After performing strict inclusion and exclusion criteria, 421 patients were selected in training set for constructing predictive model and 167 patients were selected in external testing for evaluating the predictive performance of resulting model. Urine and blood samples were collected for kidney injury associated biomarkers detection. Baseline clinical information and laboratory data of the study participants were collected. We determined the average prediction efficiency of six machine learning models through 10-fold cross validation.

RESULTS

In total, 78 variables were collected when admission in ICU and 43 variables were statistically significant between AKI and non-AKI cohort. Then, 35 variables were selected as independent features for AKI by univariate logistic regression. Spearman correlation analysis was used to remove two highly correlated variables. Three ranking methods were used to explore the influence of 33 variables for further determining the best combination of variables. The gini importance ranking method was found to be applicable for variables filtering. The predictive performance of AKIMLpred which constructed by the XGBoost algorithm was the best among six machine learning models. When the AKIMLpred included the nine features (NGAL, IGFBP7, sCysC, CAF22, KIM-1, NT-proBNP, IL-6, IL-18 and L-FABP) with the highest influence ranking, its model had the best prediction performance, with an AUC of 0.881 and an accuracy of 0.815 in training set, similarly, with an AUC of 0.889 and an accuracy of 0.846 in validation set. Moreover, the performace was slightly outperformed in testing set with an AUC of 0.902 and an accuracy of 0.846. The SHAP algorithm was used to interpret the prediction results of AKIMLpred. The web-calculator of AKIMLpred was shown for predicting AKI with more convenient(https://www.xsmartanalysis.com/model/list/predict/model/html?mid=8065&symbol=11gk693982SU6AE1ms21). AKIMLpred was better than the optimal model built with only routine tests for predicting AKI in critically ill patients within 7 days.

CONCLUSION

The model AKIMLpred constructed by the XGBoost algorithm with selecting the nine most influential biomarkers in the gini importance ranking method had the best performance in predicting AKI in critically ill patients within 7 days. This data-driven predictive model will help clinicians to make quick and accurate diagnosis.

Urinary L-FABP as an Early Biomarker for Pediatric Acute Kidney Injury Following Cardiac Surgery with Cardiopulmonary Bypass: A Systematic Review and Meta-Analysis

Acute kidney injury (AKI) following surgery with cardiopulmonary bypass (CPB-AKI) is common in pediatrics. Urinary liver-type fatty acid binding protein (uL-FABP) increases in some kidney diseases and may indicate CPB-AKI earlier than current methods. The aim of this systematic review with meta-analysis was to evaluate the potential role of uL-FABP in the early diagnosis and prediction of CPB-AKI. Databases Pubmed/MEDLINE, Scopus, and Web of Science were searched on 12 November 2023, using the MeSH terms "Children", "CPB", "L-FABP", and "Acute Kidney Injury". Included papers were revised. AUC values from similar studies were pooled by meta-analysis, performed using random- and fixed-effect models, with p < 0.05. Of 508 studies assessed, nine were included, comprising 1658 children, of whom 561 (33.8%) developed CPB-AKI. Significantly higher uL-FABP levels in AKI versus non-AKI patients first manifested at baseline to 6 h post-CPB. At 6 h, uL-FABP correlated with CPB duration (r = 0.498, p = 0.036), postoperative serum creatinine (r = 0.567, p < 0.010), and length of hospital stay (r = 0.722, p < 0.0001). Importantly, uL-FABP at baseline (AUC = 0.77, 95% CI: 0.64-0.89, n = 365), 2 h (AUC = 0.71, 95% CI: 0.52-0.90, n = 509), and 6 h (AUC = 0.76, 95% CI: 0.72-0.80, n = 509) diagnosed CPB-AKI earlier. Hence, higher uL-FABP levels associate with worse clinical parameters and may diagnose and predict CPB-AKI earlier.

Predictive Performance of Neutrophil Gelatinase Associated Lipocalin, Liver Type Fatty Acid Binding Protein, and Cystatin C for Acute Kidney Injury and Mortality in Severely Ill Patients

Background

Acute kidney injury (AKI) is a common condition in severely ill patients associated with poor outcomes. We assessed the associations between urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary liver-type fatty acid-binding protein (uLFABP), and urinary cystatin C (uCysC) concentrations and patient outcomes.

Methods

We assessed the predictive performances of uNGAL, uLFABP, and uCysC measured in the early phase of intensive care unit (ICU) management and at discharge from the ICU in severely ill patients for short- and long-term outcomes. The primary outcome was the occurrence of AKI during ICU stay; secondary outcomes were 28-day and 1-yr allcause mortality.

Results

In total, 1,759 patients were admitted to the ICU, and 728 (41.4%) developed AKI. Median (interquartile range, IQR) uNGAL, uLFABP, and uCysC concentrations on admission were 147.6 (39.9-827.7) ng/mL, 32.4 (10.5-96.0) ng/mL, and 0.33 (0.12-2.05) mg/L, respectively. Biomarker concentrations on admission were higher in patients who developed AKI and associated with AKI severity. Three hundred fifty-six (20.3%) and 647 (37.9%) patients had died by 28 days and 1-yr, respectively. Urinary biomarker concentrations at ICU discharge were higher in non-survivors than in survivors. The areas under the ROC curve (95% confidence interval) of uLFABP for the prediction of AKI, 28-day mortality, and 1-yr mortality (0.70 [0.67-0.72], 0.63 [0.59-0.66], and 0.57 [0.51-0.63], respectively) were inferior to those of the other biomarkers.

Conclusions

uNGAL, uLFABP, and uCysC concentrations on admission were associated with poor outcomes. However, their predictive performance, individually and in combination, was limited. Further studies are required to confirm our results.

Biomarker array for prediction of acute kidney injury after percutaneous coronary intervention for patients who had acute ST segment elevation myocardial infarction

Acute kidney injury (AKI) is a common complication after Percutaneous Coronary Intervention (PCI) for ST segment elevation myocardial infarction (STEMI) and is associated with poor outcomes. AKI is diagnosed by the dynamic change of serum Cr, but it could not predict AKI. This study aimed to evaluate a biomarker array that may fulfill this shortage. Setting: Cardiology Department, Tanta University Hospital. Design: Prospective interventional study included 280 acute STEMI patients who underwent emergency PCI. Serial samples of blood and urine were obtained at the time of admission to the hospital (T0) and PCI unit (T1) and at 12 h and 72 h (T12 and T72) after coronary revascularization to estimate levels of serum Cr, creatine phosphokinase, and heart-type fatty acid-binding protein (H-FABP) and calculation of neutrophil/lymphocyte ratio (NLR) and urinary liver-type FABP (L-FABP). AKI was diagnosed according to the recommendations of the European Renal Best Practice as the times of increased serum Cr concerning baseline level. 85 patients developed AKI. Regression analyses defined a high NLR ratio in the T0 sample as the most significant predictor for early AKI diagnosed at T1 time, while high NLR and serum H-FABP levels in T1 samples as the significant predictors for AKI defined at T12 time. However, high urinary L-FABP levels in T12 samples and high NLR are significant predictors for AKI at T72 time. Combined estimations of serum H-FABP and urinary L-FABP with the calculation of NLR could predict the oncoming AKI and discriminate its pathogenesis. The study protocol was approved by the Local Ethical Committee at Tanta Faculty of Medicine by approval number: 35327/3/22. For blindness purposes, the authors will be blinded about the laboratory results till the end of 72 h after revascularization and the clinical pathologist will be blinded about the indication for the requested investigations.

Assessment of the renal angina index in patients hospitalized in a cardiac intensive care unit

The renal angina index (RAI) is a validated scoring tool for predicting acute kidney injury (AKI). We investigated the efficacy of the RAI in 2436 heterogeneous patients (mean age, 70 years) treated in cardiac intensive care units (CICUs). The RAI was calculated from creatinine and patient condition scores. AKI was diagnosed by the Kidney Disease: Improving Global Outcome criteria. The primary and secondary endpoints were the development of severe AKI and all-cause mortality, respectively. Four hundred thirty-three patients developed AKI, 87 of them severe. In multivariate analyses, the RAI was a significant independent predictor of severe AKI. During the 12-month follow-up period, 210 patients suffered all-cause death. Elevated RAI was independently associated with all-cause mortality, as was NT-proBNP (p < 0.001). The RAI is a potent predictor not only of severe AKI but also of adverse outcomes and substantially improved the 12-month risk stratification of patients hospitalized in CICUs.

Fatty-Acid-Binding Proteins: From Lipid Transporters to Disease Biomarkers

Fatty-acid-binding proteins (FABPs) serve a crucial role in the metabolism and transport of fatty acids and other hydrophobic ligands as an intracellular protein family. They are also recognized as a critical mediator in the inflammatory and ischemic pathways. FABPs are found in a wide range of tissues and organs, allowing them to contribute to various disease/injury developments that have not been widely discussed. We have collected and analyzed research journals that have investigated the role of FABPs in various diseases. Through this review, we discuss the findings on the potential of FABPs as biomarkers for various diseases in different tissues and organs, looking at their expression levels and their roles in related diseases according to available literature data. FABPs have been reported to show significantly increased expression levels in various tissues and organs associated with metabolic and inflammatory diseases. Therefore, FABPs are a promising novel biomarker that needs further development to optimize disease diagnosis and prognosis methods along with previously discovered markers.

Urinary N-Terminal Pro-Brain Natriuretic Peptide Predicts Acute Kidney Injury and Severe Disease in COVID-19

INTRODUCTION

The ongoing COVID-19 pandemic is placing an extraordinary burden on our health care system with its limited resources. Accurate triage of patients is necessary to ensure medical care for those most severely affected. In this regard, biomarkers could contribute to risk evaluation. The aim of this prospective observational clinical study was to assess the relationship between urinary N-terminal pro-brain natriuretic peptide (NT-proBNP) and acute kidney injury (AKI) as well as severe disease in patients with COVID-19.

METHODS

125 patients treated with an acute respiratory infection in the emergency department of the University Hospital Regensburg were analyzed. These patients were divided into a COVID-19 cohort (n = 91) and a cohort with infections not caused by severe acute respiratory syndrome-coronavirus-2 (n = 34). NT-proBNP was determined from serum and fresh urine samples collected in the emergency department. Clinical endpoints were the development of AKI and a composite one consisting of AKI, intensive care unit admission, and in-hospital death.

RESULTS

11 (12.1%) COVID-19 patients developed AKI during hospitalization, whereas 15 (16.5%) reached the composite endpoint. Urinary NT-proBNP was significantly elevated in COVID-19 patients who suffered AKI or reached the composite endpoint (each p < 0.005). In a multivariate regression analysis adjusted for age, chronic kidney disease, chronic heart failure, and arterial hypertension, urinary NT-proBNP was identified as independent predictor of AKI (p = 0.017, OR = 3.91 [CI: 1.28-11.97] per standard deviation [SD]), as well as of the composite endpoint (p = 0.026, OR 2.66 [CI: 1.13-6.28] per SD).

CONCLUSION

Urinary NT-proBNP might help identify patients at risk for AKI and severe disease progression in COVID-19.

Association of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and acute kidney disease in patients undergoing coronary angiography: a cohort study

BACKGROUND

Acute kidney disease (AKD) following coronary angiography (CAG) indicates a higher risk of chronic kidney disease and follow-up cardiovascular comorbidities. However, the predictive risk factor of AKD is not clear. We sought to verify whether preoperative N-terminal pro-B-type natriuretic peptide (NT-proBNP) level was associated with AKD in patients undergoing CAG.

METHOD

We analyzed 7602 patients underwent CAG in this multi-center registry cohort study. Cardiorenal ImprovemeNt II (CIN-II) in five Chinese tertiary hospitals from 2007 to 2020. The primary outcome was AKD, defined as a ≥ 50% increase of serum creatinine within 7-90 days. Multivariable logistic regressions were used to assess the association between NT-proBNP and AKD.

RESULT

1009 patients (13.27%) eventually developed AKD, who were more likely to be female, older, and with comorbidities of chronic heart failure and anemia. After adjusting to the potential confounders, the NT-proBNP level remained an independent predictor of AKD (lnNT-proBNP OR: 1.20, 95% CI 1.13-1.28, p < 0.005). Restricted cubic spline analysis demonstrated a linear relationship between elevated NT-proBNP and AKD (p for trend < 0.001). In the subgroup analysis, elevated NT-proBNP level in patients with percutaneous coronary intervention (p for interaction < 0.001) or without previous congestive heart failure (p for interaction = 0.0346) has a more significant value of AKD prediction.

CONCLUSION

Pre-operative NT-proBNP level was independently associated with the risk of AKD in patients following CAG. Perioperative strategies are warranted to prevent AKD in patients with elevated NT-proBNP levels.

Serum N-terminal pro-B-type natriuretic peptide and cystatin C for acute kidney injury detection in critically ill adults in China: a prospective, observational study

OBJECTIVE

Serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) and cystatin C (sCysC) are available clinically and beneficial in diagnosing acute kidney injury (AKI). Our purpose is to identify the performance of their combined diagnosis for AKI in critically ill patients.

DESIGN

A prospectively recruited, observational study was performed.

SETTING

Adults admitted to the intensive care unit of a tertiary hospital in China.

PARTICIPANTS

A total of 1222 critically ill patients were enrolled in the study.

MAIN OUTCOME MEASURES

To identify the performance of the combined diagnosis of serum NT-proBNP and sCysC for AKI in critically ill patients. The area under the receiver operating characteristic curve (AUC-ROC), category-free net reclassification index (NRI) and incremental discrimination improvement (IDI) were utilised for comparing the discriminative powers of a combined and single biomarker adjusted model of clinical variables enriched with NT-proBNP and sCysC for AKI.

RESULTS

AKI was detected in 256 out of 1222 included patients (20.9%). AUC-ROC for NT-proBNP and sCysC to detect AKI had a significantly higher accuracy than any individual biomarker (p<0.05). After multivariate adjustment, a level of serum NT-proBNP ≥204 pg/mL was associated with 3.5-fold higher odds for AKI compared with those below the cut-off value. Similar results were obtained for sCysC levels (p<0.001). To detect AKI, adding NT-proBNP and sCysC to a clinical model further increased the AUC-ROC to 0.859 beyond that of the clinical model with or without sCysC (p<0.05). Moreover, the addition of these two to the clinical model significantly improved risk reclassification of AKI beyond that of the clinical model alone or with single biomarker (p<0.05), as measured by NRI and IDI.

CONCLUSIONS

In critically ill individuals, serum NT-proBNP, sCysC and clinical risk factors combination improve the discriminative power for diagnosing AKI.

Using a machine learning model to predict the development of acute kidney injury in patients with heart failure

Background

Heart failure (HF) is a life-threatening complication of cardiovascular disease. HF patients are more likely to progress to acute kidney injury (AKI) with a poor prognosis. However, it is difficult for doctors to distinguish which patients will develop AKI accurately. This study aimed to construct a machine learning (ML) model to predict AKI occurrence in HF patients.

Materials and methods

The data of HF patients from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database was retrospectively analyzed. A ML model was established to predict AKI development using decision tree, random forest (RF), support vector machine (SVM), K-nearest neighbor (KNN), and logistic regression (LR) algorithms. Thirty-nine demographic, clinical, and treatment features were used for model establishment. Accuracy, sensitivity, specificity, and the area under the receiver operating characteristic curve (AUROC) were used to evaluate the performance of the ML algorithms.

Results

A total of 2,678 HF patients were engaged in this study, of whom 919 developed AKI. Among 5 ML algorithms, the RF algorithm exhibited the highest performance with the AUROC of 0.96. In addition, the Gini index showed that the sequential organ function assessment (SOFA) score, partial pressure of oxygen (PaO₂), and estimated glomerular filtration rate (eGFR) were highly relevant to AKI development. Finally, to facilitate clinical application, a simple model was constructed using the 10 features screened by the Gini index. The RF algorithm also exhibited the highest performance with the AUROC of 0.95.

Conclusion

Using the ML model could accurately predict the development of AKI in HF patients.

Preoperative NT-proBNP and LVEF for the prediction of acute kidney injury after noncardiac surgery: a single-centre retrospective study

BACKGROUND

Acute kidney injury (AKI) is one of the most common postoperative complications in noncardiac surgical patients, has an important impact on prognosis and is difficult to predict. Whether preoperative N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations and left ventricular ejection fraction (LVEF) levels can predict postoperative AKI in noncardiac surgical patients is unclear.

METHODS

We included 3,314 patients who underwent noncardiac surgery and had measurements of preoperative NT-proBNP concentrations and LVEF levels at a tertiary academic hospital in China between 2008 and 2018. Multiple logistic regression analysis was used to construct a postoperative AKI risk prediction model for this cohort. Then, NT-proBNP concentrations and LVEF levels were included in the abovementioned model as independent variables, and the predictive ability of these two models was compared.

RESULTS

Postoperative AKI occurred in 223 (6.72%) patients within 1 week after surgery. Preoperative NT-proBNP concentrations and LVEF levels were independent predictors of AKI after adjustment for clinical variables. The area under the receiver operating characteristic curve (AUROC) of the AKI risk predictive model established with clinical baseline variables was 0.767 (95% CI: 0.732, 0.802). When NT-proBNP concentrations and LVEF levels were added to the base model, the AUROC was 0.811 (95% CI: 0.779, 0.843). The addition of NT-proBNP concentrations and LVEF levels improved reclassification by 22.9% (95% CI 10.5-34.4%) for patients who developed postoperative AKI and by 36.3% (95% CI 29.5-43.9%) for those who did not, resulting in a significant overall improvement in net reclassification (NRI: 0.591, 95% CI 0.437-0.752, P < 0.000). The integral discrimination improvement was 0.100 (95% CI: 0.075, 0.125, P < 0.000).The final postoperative AKI prediction model was constructed, and had a good discriminative ability and fitted to the dataset.

CONCLUSIONS

Preoperative NT-proBNP concentrations and LVEF levels were independently associated with the risk of AKI after noncardiac surgery, and they could improve the predictive ability of logistic regression models based on conventional clinical risk factors.

TRIAL REGISTRATION

The protocol was preregistered in the Chinese Clinical Trial Registry ( ChiCTR1900024056 ).

Urinary liver-type fatty acid-binding protein as a prognostic marker in patients with acute heart failure

Aims

Urinary liver‐type fatty acid‐binding protein (L‐FABP) is expressed in proximal tubular epithelial cells and excreted into the urine during tubular injury. We hypothesized that high urinary L‐FABP is associated with poor prognosis in patients with acute heart failure (AHF).

Methods and results

We analysed 623 patients (74 ± 13 years old; 60.0% male patients) with AHF. Urinary L‐FABP levels were measured at the time of admission and adjusted for the urinary creatinine concentration. The primary endpoint was all‐cause mortality. The median value and interquartile range of urinary L‐FABP levels were 6.66 and 3.37–21.1 μg/gCr, respectively. Urinary L‐FABP levels were significantly correlated with both beta‐2 microglobulin and cystatin C levels; the correlation with the former was higher than that with the latter. During the follow‐up of 631 (interquartile range: 387–875) days, 142 deaths occurred. A high tertile of urinary L‐FABP level was associated with high mortality; this association was retained after adjusting for other covariates (second tertile hazard ratio 1.40, P = 0.152 vs. first tertile; third tertile hazard ratio 1.94, P = 0.005 vs. first tertile).

Conclusions

Urinary L‐FABP is more closely associated with tubular dysfunction than with glomerular dysfunction. Tubular dysfunction, which was evaluated based on urinary L‐FABP levels, in patients with AHF is associated with all‐cause mortality and is independent of pre‐existing risk factors. L‐FABP should be considered for use in the prognosis of AHF.

Combined evaluation of plasma B-type natriuretic peptide and urinary liver-type fatty acid-binding protein/creatinine ratio is related to worsening renal function in patients undergoing elective percutaneous coronary intervention

BACKGROUND

There are few reports on the significance for the combined evaluation of blood humoral factors and urinary biomarkers in terms of worsening renal function (WRF) after coronary angiography (CAG)/percutaneous coronary arterial intervention (PCI).

METHOD AND RESULTS

Urinary liver type-fatty acid-binding protein (L-FABP), neutrophil gelatinase associated lipocalin (NGAL), and adrenomedullin (AM) were measured less than 24 h before and 3 h, 6 h, 1 day, and 2 days after CAG/PCI. WRF was defined as a > 20% decrease in the estimated GFR. WRF occurred in seven of 100 patients and the increase in L-FABP/creatinine (Cr) at 1 day after CAG/PCI was significantly higher in the WRF group than in the non-WRF group. Plasma B-type natriuretic peptide (BNP) before CAG/PCI and L-FABP/Cr at 1 day after CAG/PCI were independent predictors for WRF. The areas under the receiver-operating characteristic curves were as follows: 0.760 for BNP before CAG/PCI, 0.731 for L-FABP/Cr at 1 day after CAG/PCI, and 0.892 for BNP and L-FABP/Cr. Urinary AM levels after PCI/CAG were negatively correlated only to serum potassium levels. Gene expressions of AM and AM-receptor were detectable in renal tubule epithelial cells. AM increased intracellular second messenger levels in a dose-dependent manner.

CONCLUSIONS

Our results suggest that combined evaluation of plasma BNP and urinary L-FABP/Cr is useful as a predictor of renal dysfunction in CAG/PCI patients.

Pre-operative N-terminal pro-B-type natriuretic peptide for prediction of acute kidney injury after noncardiac surgery: A retrospective cohort study

BACKGROUND

Acute kidney injury (AKI) is associated with poor outcomes after noncardiac surgery. Whether pre-operative N-terminal pro-B-type natriuretic peptide (NT-proBNP) predicts AKI after noncardiac surgery is unclear.

OBJECTIVE

To investigate the predictive role of pre-operative NT-proBNP on postoperative AKI.

DESIGN

Retrospective cohort study.

SETTING

Nanfang Hospital, Southern Medical University, China.

PATIENTS

Adult patients who had a serum creatinine and NT-proBNP measurement within 30 pre-operative days and at least one serum creatinine measurement within 7 days after noncardiac surgery between February 2008 and May 2018 were identified.

MAIN OUTCOME MEASURES

The primary outcome was postoperative AKI, defined by the kidney disease: improving global outcomes creatinine criteria.

RESULTS

In all, 6.1% (444 of 7248) of patients developed AKI within 1 week after surgery. Pre-operative NT-proBNP was an independent predictor of AKI after adjustment for clinical variables (OR comparing top to bottom quintiles 2.29, 95% CI, 1.47 to 3.65, P < 0.001 for trend; OR per 1-unit increment in natural log transformed NT-proBNP 1.27, 95% CI, 1.16 to 1.39). Compared with clinical variables alone, the addition of NT-proBNP improved model fit, modestly improved the discrimination (change in area under the curve from 0.764 to 0.773, P = 0.005) and reclassification (continuous net reclassification improvement 0.210, 95% CI, 0.111 to 0.308, improved integrated discrimination 0.0044, 95% CI, 0.0016 to 0.0072) of AKI and non-AKI cases, and achieved higher net benefit in decision curve analysis.

CONCLUSIONS

Pre-operative NT-proBNP concentrations provided predictive information for AKI in a cohort of patients undergoing noncardiac surgery, independent of and incremental to conventional risk factors. Prospective studies are required to confirm this finding and examine its clinical impact.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1900024056. www.chictr.org.cn/showproj.aspx?proj=40385.

Urinary liver-type fatty acid-binding protein is independently associated with graft failure in outpatient kidney transplant recipients

Urinary liver-type fatty acid-binding protein (uL-FABP) is a biomarker of kidney hypoxia and ischemia, and thus offers a novel approach to identify early kidney insults associated with increased risk of graft failure in outpatient kidney transplant recipients (KTR). We investigated whether uL-FABP is associated with graft failure and whether it improves risk prediction. We studied a cohort of 638 outpatient KTR with a functional graft ≥1-year. During a median follow-up of 5.3 years, 80 KTR developed graft failure. uL-FABP (median 2.11, interquartile range 0.93-7.37 µg/24"/>h) was prospectively associated with the risk of graft failure (hazard ratio 1.75; 95% confidence interval 1.27-2.41 per 1-SD increment; P = .001), independent of potential confounders including estimated glomerular filtration rate and proteinuria. uL-FABP showed excellent discrimination ability for graft failure (c-statistic of 0.83) and its addition to a prediction model composed by established clinical predictors of graft failure significantly improved the c-statistic to 0.89 (P for F-test <.001). These results were robust to several sensitivity analyses. Further validation studies are warranted to evaluate the potential use of a risk-prediction model including uL-FABP to improve identification of outpatient KTR at high risk of graft failure in clinical care.

Urinary biomarkers of kidney tubule injury, risk of acute kidney injury, and mortality in patients with acute ischaemic stroke treated at a stroke care unit

BACKGROUND AND PURPOSE

Urinary liver-type fatty-acid binding protein (L-FABP), which is a biomarker of kidney tubule injury, has been studied extensively and established as a risk marker of acute kidney injury (AKI). The aim of this study was to investigate whether kidney tubule injury is associated with the development of AKI and mortality in patients with acute ischaemic stroke.

METHODS

Acute ischaemic stroke patients hospitalized in the stroke care unit (SCU) within 24 h after symptom onset were prospectively investigated. AKI was defined on the basis of Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Baseline urinary L-FABP was measured on admission. We evaluated the associations among urinary L-FABP, incidence of AKI, and 90-day mortality adjusted for renal function, albuminuria and other potentially predictive variables, using multivariable analysis.

RESULTS

In total, 527 acute ischaemic stroke patients (342 men, median age 74 years) were enrolled in the study. Twenty-seven patients (5.1%) experienced AKI within 7 days of admission. In the univariate analysis, high urinary L-FABP level had positive associations with AKI [53.8 μg/g creatinine (Cr) vs. 3.9 μg/g Cr; P < 0.001] and 90-day mortality (15.5 μg/g Cr vs. 4.0 μg/g Cr; P < 0.001). In the multivariate analysis, elevated urinary L-FABP level (per 10-μg/g Cr increase) was independently associated with AKI (odds ratio 1.225, 95% confidence interval (CI) 1.083-1.454; P = 0.003) and 90-day mortality (hazard ratio 1.091, 95% CI 1.045-1.138; P < 0.001).

CONCLUSION

Urinary biomarkers of kidney tubule injury are independently associated with the development of AKI and 90-day mortality in patients with acute ischaemic stroke treated at the SCU.

Urinary Liver-Type Fatty-Acid-Binding Protein Predicts Long-Term Adverse Outcomes in Medical Cardiac Intensive Care Units

We prospectively investigated the prognostic value of urinary liver-type fatty-acid-binding protein (L-FABP) levels on hospital admission, both independently and in combination with serum creatinine-defined acute kidney injury (AKI), to predict long-term adverse outcomes in 1119 heterogeneous patients (mean age; 68 years) treated at medical (non-surgical) cardiac intensive care units (CICUs). Patients with stage 5 chronic kidney disease were excluded from the study. Of these patients, 47% had acute coronary syndrome and 38% had acute decompensated heart failure. The creatinine-defined AKI was diagnosed according to the "Kidney Disease: Improving Global Outcomes" criteria. The primary endpoint was a composite of all-cause death or progression to end-stage kidney disease, indicating the initiation of maintenance dialysis therapy or kidney transplantation. Creatinine-defined AKI occurred in 207 patients, with 44 patients having stage 2 or 3 disease. During a mean follow-up period of 41 months after enrollment, the primary endpoint occurred in 242 patients. Multivariate Cox regression analyses revealed L-FABP levels as independent predictors of the primary endpoint (p < 0.001). Adding L-FABP to a baseline model with established risk factors further enhanced reclassification and discrimination beyond that of the baseline model alone, for primary-endpoint prediction (both; p < 0.01). On Kaplan-Meier analyses, increased L-FABP (≥4th quintile value of 9.0 ng/mL) on admission or presence of creatinine-defined AKI, correlated with an increased risk of the primary endpoint (p < 0.001). Thus, urinary L-FABP levels on admission are potent and independent predictors of long-term adverse outcomes, and they might improve the long-term risk stratification of patients admitted at medical CICUs, when used in combination with creatinine-defined AKI.

Serum N-terminal Pro-B-type Natriuretic Peptide Predicts Mortality in Cardiac Surgery Patients Receiving Renal Replacement Therapy

Background: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a useful cardiac biomarker that is associated with acute kidney injury (AKI) and mortality after cardiac surgery. However, its prognostic value in cardiac surgical patients receiving renal replacement therapy (RRT) remains unclear. Objectives: Our study aimed to assess the prognostic value of NT-proBNP in patients with established AKI receiving RRT after cardiac surgery. Methods: A total of 163 cardiac surgical patients with AKI requiring RRT were enrolled in this study. Baseline characteristics, hemodynamic variables at RRT initiation, and NT-proBNP level before surgery, at RRT initiation, and on the first day after RRT were collected. The primary outcome was 28-day mortality after RRT initiation. Results: Serum NT-proBNP levels in non-survivors was markedly higher than survivors before surgery (median: 4,096 [IQR, 962.0-9583.8] vs. 1,339 [IQR, 446-5,173] pg/mL; P < 0.01), at RRT initiation (median: 10,366 [IQR, 5,668-20,646] vs. 3,779 [IQR, 1,799-11,256] pg/mL; P < 0.001), and on the first day after RRT (median: 9,055.0 [IQR, 4,392-24,348] vs. 5,255 [IQR, 2,134-9,175] pg/mL; P < 0.001). The area under the receiver operating characteristic curve of NT-proBNP before surgery, at RRT initiation, and on the first day after RRT for predicting 28-day mortality was 0.64 (95% CI, 0.55-0.73), 0.71 (95% CI, 0.63-0.79), and 0.68 (95% CI, 0.60-0.76), respectively. Consistently, Cox regression revealed that NT-proBNP levels before surgery (HR: 1.27, 95% CI, 1.06-1.52), at RRT initiation (HR: 1.11, 95% CI, 1.06-1.17), and on the first day after RRT (HR: 1.17, 95% CI, 1.11-1.23) were independently associated with 28-day mortality. Conclusions: Serum NT-proBNP was an independent predictor of 28-day mortality in cardiac surgical patients with AKI requiring RRT. The prognostic role of NT-proBNP needs to be confirmed in the future.

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.

Protein biomarkers for cardiorenal syndrome

INTRODUCTION

The term cardiorenal syndrome (CRS) describes the progressive pathology and interactions that develop upon heart and kidney failure. The definition of CRS is not firmly established and has evolved gradually during the last decade. The main clinical challenges associated with CRS are the lack of tools for early disease diagnosis and the inability to predict the development of cardiorenal pathophysiology. Currently several biomarkers have been proposed for improving CRS patient management. However, validation studies are needed to implement these initial findings to the clinical setting. Areas covered: In this review the database PubMed was used for a literature search on the definition and classification of CRS as well as biomarkers for CRS diagnosis and prognosis. Expert opinion: A universally acceptable classification system for CRS is not available. Thus, acquiring mechanistic insights relative to the pathophysiology of the disease is challenging. Reported biomarkers include well-established markers for heart/renal dysfunction and inflammation. Some proteins expressed in both organs have also been associated with CRS, yet their link to disease pathophysiology and organ cross-talk is missing. Establishing the link between deregulated molecular pathways and CRS phenotypes is required to define biological relevance of existing findings and ultimately biology-driven markers and targets.