Combination of two urinary biomarkers predicts acute kidney injury after adult cardiac surgery

Blood perfusion with polymyxin B immobilized columns in patients with COVID-19 requiring oxygen therapy

Extracorporeal blood purification with polymyxin B immobilized fiber column direct hemoperfusion (PMX-DHP), is reported to be effective in treating COVID-19 pneumonitis with oxygen demand. This multicenter prospective study evaluated the efficacy and safety of PMX-DHP in oxygen-requiring patients with COVID-19 admitted between September 28, 2020, and March 31, 2022. The primary endpoint was the percentage of clinical improvement 15 days after treatment. The secondary endpoint was the percentage of worsened disease status. Data from the COVID-19 patient registry were used for the synthetic control group. The improvement rate on Day 15 did not differ between PMX-treated patients and controls; however, the deterioration rate was 0.38 times lower in the PMX-treated group, and the death rates on Day 29 were 0 and 11.1% in the PMX-treated and control groups, respectively. The PMX group showed a 0.73 times higher likelihood for reduced intensive care demand, as 16.7% of PMX-treated patients and 22.8% of controls worsened. After treatment blood oxygenation improved, urinary β2-microglobulin and liver-type fatty acid-binding protein showed significant decreases, and IL-6 decreased once during treatment but did not persist. In this study, PMX treatment effectively prevented the worsening of COVID-19 pathology, accompanied by improved oxygenation. PMX treatment to remove activated cells may effectively improve patient outcomes.

Renal Biomarkers in the Early Detection of Acute Kidney Injury After Off-Pump Coronary Artery Bypass Grafting

BACKGROUND

Cardiac surgery-associated (CSA) acute kidney injury (AKI) is a severe postoperative complication in patients undergoing off-pump coronary artery bypass grafting (OPCAB). Early detection of postoperative CSA-AKI may be key to improving patient outcomes. This study explored the use of renal biomarkers measured immediately after surgery for the early detection of CSA-AKI in patients undergoing OPCAB.Methods and Results: In all, 111 patients who underwent OPCAB at Kumamoto University Hospital between June 2020 and October 2022 were included in this study. Urinary neutrophil gelatinase-associated lipocalin, liver-type fatty acid-binding protein, and N-acetyl-β-D-glucosaminidase (NAG) were measured upon arrival in the intensive care unit (ICU) after surgery. AKI was diagnosed using KDIGO criteria. Of the 111 patients, 32 (28.8%) developed postoperative AKI. Regarding AKI staging, 19 (59.4%), 11 (34.4%), and 2 (6.3%) patients had Stage 1, 2, and 3 AKI, respectively. There were significant differences in chronic kidney disease, preoperative estimated glomerular filtration rate (eGFR), and NAG between the AKI and non-AKI groups. Multivariate analysis showed that preoperative eGFR (odds ratio [OR] for 5-mL/min/1.73 m2increase in eGFR 0.75; 95% confidence interval [CI] 0.63-0.89) and increasing urinary NAG concentrations at ICU admission (OR 2.44; 95% CI 1.30-4.60) were significant risk factors for CSA-AKI in OPCAB patients.

CONCLUSIONS

NAG and eGFR may be valuable biomarkers for the early detection of CSA-AKI in patients undergoing OPCAB.

Urinary liver-type fatty acid-binding protein level as a prognostic indicator of acute kidney injury secondary to severe falciparum malaria

Acute kidney injury (AKI) secondary to severe falciparum malaria possesses a high mortality rate; however, a prognostic marker of renal dysfunction has not yet been identified. Thus, we reported a case of a patient with AKI secondary to falciparum malaria who underwent hemodialysis and a renal biopsy due to prolonged renal dysfunction. The male patient, in his 50 s, presented to our hospital with vomiting, diarrhea, fever, and decreased level of consciousness. The Giemsa-stained peripheral blood film revealed approximately 5% parasitemia, and a rapid diagnostic test was positive for Plasmodium falciparum. He was diagnosed with severe falciparum malaria and was started on quinine hydrochloride. Hemodialysis was initiated due to the decreased urine output and fluid retention. Subsequently, he was weaned off hemodialysis. The histopathological analysis of a renal biopsy revealed interstitial fibrosis, tubular atrophy, and chronic inflammatory cell infiltration; thus, malarial nephropathy was diagnosed. Thereafter, his renal function stabilized, and he was discharged from the hospital. The urinary liver-type fatty acid-binding protein (L-FABP) level decreased before renal function improved. Our report highlighted that long-term follow-up is essential for severe AKI secondary to malaria. The urinary L-FABP level may be a useful prognostic indicator of AKI secondary to severe falciparum malaria.

Prediction of acute kidney injury after total aortic arch replacement with serum cystatin C and urine N-acetyl-β-d-glucosaminidase: A prospective observational study

BACKGROUND

Acute kidney injury (AKI) after total aortic arch replacement (TAAR) is frequent and associated with adverse outcomes, whereas its early detection remains a challenge. Serum cystatin C (sCysC) and urinary N-acetyl-β-d-glucosaminidase (uNAG) are clinically available renal biomarkers, but their combination for AKI detection requires more evidence. This study aimed to assess the discriminative abilities of these biomarkers in AKI after TAAR.

MATERIALS AND METHODS

Patients undergoing TAAR were included in this prospective observational study. The AKI prediction model was developed and internal verificated, and the significance of each variable was analyzed by random forest (RF). Finally, the best predictive critical values of sCysC and uNAG were explored by the AUC-ROC curve.

RESULTS

The AUC-ROC of the prediction model was substantially enhanced by adding sCysC and uNAG (0.909 vs 0.844, p < 0.001), and the clinical utility and risk reclassification were significantly improved. Additionally, the RF showed that sCysC and uNAG ranked first and second. The AUC-ROC for each were 0.864 and 0.802 respectively, and the cut-off values were 1.395 mg/L and 31.90 U/g Cre respectively.

CONCLUSION

The prediction model incorporating functional marker sCysC and tubular injury marker uNAG can improve the discriminative abilities of AKI after TAAR.

Roles of NAD+ in Acute and Chronic Kidney Diseases

Nicotinamide adenine dinucleotide (oxidized form, NAD⁺) is a critical coenzyme, with functions ranging from redox reactions and energy metabolism in mitochondrial respiration and oxidative phosphorylation to being a central player in multiple cellular signaling pathways, organ resilience, health, and longevity. Many of its cellular functions are executed via serving as a co-substrate for sirtuins (SIRTs), poly (ADP-ribose) polymerases (PARPs), and CD38. Kidney damage and diseases are common in the general population, especially in elderly persons and diabetic patients. While NAD⁺ is reduced in acute kidney injury (AKI) and chronic kidney disease (CKD), mounting evidence indicates that NAD⁺ augmentation is beneficial to AKI, although conflicting results exist for cases of CKD. Here, we review recent progress in the field of NAD⁺, mainly focusing on compromised NAD⁺ levels in AKI and its effect on essential cellular pathways, such as mitochondrial dysfunction, compromised autophagy, and low expression of the aging biomarker αKlotho (Klotho) in the kidney. We also review the compromised NAD⁺ levels in renal fibrosis and senescence cells in the case of CKD. As there is an urgent need for more effective treatments for patients with injured kidneys, further studies on NAD⁺ in relation to AKI/CKD may shed light on novel therapeutics.

Comparative accuracy of biomarkers for the prediction of hospital-acquired acute kidney injury: a systematic review and meta-analysis

Background

Several biomarkers have been proposed to predict the occurrence of acute kidney injury (AKI); however, their efficacy varies between different trials. The aim of this study was to compare the predictive performance of different candidate biomarkers for AKI.

Methods

In this systematic review, we searched PubMed, Medline, Embase, and the Cochrane Library for papers published up to August 15, 2022. We selected all studies of adults (> 18 years) that reported the predictive performance of damage biomarkers (neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), liver-type fatty acid-binding protein (L-FABP)), inflammatory biomarker (interleukin-18 (IL-18)), and stress biomarker (tissue inhibitor of metalloproteinases-2 × insulin-like growth factor-binding protein-7 (TIMP-2 × IGFBP-7)) for the occurrence of AKI. We performed pairwise meta-analyses to calculate odds ratios (ORs) and 95% confidence intervals (CIs) individually. Hierarchical summary receiver operating characteristic curves (HSROCs) were used to summarize the pooled test performance, and the Grading of Recommendations, Assessment, Development and Evaluations criteria were used to appraise the quality of evidence.

Results

We identified 242 published relevant studies from 1,803 screened abstracts, of which 110 studies with 38,725 patients were included in this meta-analysis. Urinary NGAL/creatinine (diagnostic odds ratio [DOR] 16.2, 95% CI 10.1–25.9), urinary NGAL (DOR 13.8, 95% CI 10.2–18.8), and serum NGAL (DOR 12.6, 95% CI 9.3–17.3) had the best diagnostic accuracy for the risk of AKI. In subgroup analyses, urinary NGAL, urinary NGAL/creatinine, and serum NGAL had better diagnostic accuracy for AKI than urinary IL-18 in non-critically ill patients. However, all of the biomarkers had similar diagnostic accuracy in critically ill patients. In the setting of medical and non-sepsis patients, urinary NGAL had better predictive performance than urinary IL-18, urinary L-FABP, and urinary TIMP-2 × IGFBP-7: 0.3. In the surgical patients, urinary NGAL/creatinine and urinary KIM-1 had the best diagnostic accuracy. The HSROC values of urinary NGAL/creatinine, urinary NGAL, and serum NGAL were 91.4%, 85.2%, and 84.7%, respectively.

Conclusions

Biomarkers containing NGAL had the best predictive accuracy for the occurrence of AKI, regardless of whether or not the values were adjusted by urinary creatinine, and especially in medically treated patients. However, the predictive performance of urinary NGAL was limited in surgical patients, and urinary NGAL/creatinine seemed to be the most accurate biomarkers in these patients. All of the biomarkers had similar predictive performance in critically ill patients.

Trial registrationCRD42020207883, October 06, 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04223-6.

Machine learning in predicting cardiac surgery-associated acute kidney injury: A systemic review and meta-analysis

Background

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common complication following cardiac surgery. Early prediction of CSA-AKI is of great significance for improving patients' prognoses. The aim of this study is to systematically evaluate the predictive performance of machine learning models for CSA-AKI.

Methods

Cochrane Library, PubMed, EMBASE, and Web of Science were searched from inception to 18 March 2022. Risk of bias assessment was performed using PROBAST. Rsoftware (version 4.1.1) was used to calculate the accuracy and C-index of CSA-AKI prediction. The importance of CSA-AKI prediction was defined according to the frequency of related factors in the models.

Results

There were 38 eligible studies included, with a total of 255,943 patients and 60 machine learning models. The models mainly included Logistic Regression (n = 34), Neural Net (n = 6), Support Vector Machine (n = 4), Random Forest (n = 6), Extreme Gradient Boosting (n = 3), Decision Tree (n = 3), Gradient Boosted Machine (n = 1), COX regression (n = 1), κNeural Net (n = 1), and Naïve Bayes (n = 1), of which 51 models with intact recording in the training set and 17 in the validating set. Variables with the highest predicting frequency included Logistic Regression, Neural Net, Support Vector Machine, and Random Forest. The C-index and accuracy wer 0.76 (0.740, 0.780) and 0.72 (0.70, 0.73), respectively, in the training set, and 0.79 (0.75, 0.83) and 0.73 (0.71, 0.74), respectively, in the test set.

Conclusion

The machine learning-based model is effective for the early prediction of CSA-AKI. More machine learning methods based on noninvasive or minimally invasive predictive indicators are needed to improve the predictive performance and make accurate predictions of CSA-AKI. Logistic regression remains currently the most commonly applied model in CSA-AKI prediction, although it is not the one with the best performance. There are other models that would be more effective, such as NNET and XGBoost.

Systematic review registration

https://www.crd.york.ac.uk/; review registration ID: CRD42022345259.

Machine learning for the prediction of acute kidney injury in patients after cardiac surgery

Cardiac surgery-associated acute kidney injury (CSA-AKI) is the most prevalent major complication of cardiac surgery and exerts a negative effect on a patient's prognosis, thereby leading to mortality. Although several risk assessment models have been developed for patients undergoing cardiac surgery, their performances are unsatisfactory. In this study, a machine learning algorithm was employed to obtain better predictive power for CSA-AKI outcomes relative to statistical analysis. In addition, random forest (RF), logistic regression with LASSO regularization, extreme gradient boosting (Xgboost), and support vector machine (SVM) methods were employed for feature selection and model training. Moreover, the calibration capacity and differentiation ability of the model was assessed using net reclassification improvement (NRI) along with Brier scores and receiver operating characteristic (ROC) curves, respectively. A total of 44 patients suffered AKI after surgery. Fatty acid-binding protein (FABP), hemojuvelin (HJV), neutrophil gelatinase-associated lipocalin (NGAL), mechanical ventilation time, and troponin I (TnI) were correlated significantly with the incidence of AKI. RF was the best model for predicting AKI (Brier score: 0.137, NRI: 0.221), evidenced by an AUC value of 0.858 [95% confidence interval (CI): 0.792–0.923]. Overall, RF exhibited the best performance as compared to other machine learning algorithms. These results thus provide new insights into the early identification of CSA-AKI.

Vitamin D Binding Protein and Renal Injury in Acute Decompensated Heart Failure

Background

Renal function in acute decompensated heart faiulre (ADHF) is a strong predictor of disease evolution and poor outcome. Current biomarkers for early diagnostic of renal injury in the setting of ADHF are still controversial, and their association to early pathological changes needs to be established. By applying a proteomic approach, we aimed to identify early changes in the differential urine protein signature associated with development of renal injury in patients hospitalised due to ADHF.

Materials and Methods

Patients (71 [64–77] years old) admitted at the emergency room with ADHF and hospitalised were investigated (N = 64). Samples (urine/serum) were collected at hospital admission (day 0) and 72 h later (day 3). Differential serum proteome was analysed by two-dimensional electrophoresis and matrix-assisted laser desorption/ionisation-time of flight (MALDI-ToF/ToF). Validation studies were performed using ELISA.

Results

Proteomic analysis depicted urinary vitamin D binding protein (uVDBP) as a two spots protein with increased intensity in ADHF and significant differences depending on the glomerular filtration rate (GFR). Urinary VDBP in patients with ADHF at hospitalisation was &gt; threefold higher than in healthy subjects, with the highest levels in those patients with ADHF already presenting renal dysfunction. At day 3, urine VDBP levels in patients maintaining normal renal function dropped to normal values (P = 0.03 vs. day 0). In contrast, urine VDBP levels remained elevated in the group developing renal injury, with values twofold above the normal range (P &lt; 0.05), while serum creatinine and GF levels were within the physiological range in this group. Urinary VDBP in ADHF positively correlated with markers of renal injury such as cystatin C and Kidney Injury Molecule 1 (KIM-1). By ROC analysis, urinary VDBP, when added to cystatin C and KIM-1, improved the prediction of renal injury in patients with ADHF.

Conclusion

We showed increased urine VDBP in patients with ADHF at hospital admission and a differential uVDBP evolution pattern at early stage of renal dysfunction, before pathological worsening of GFR is evidenced.

Biomarkers in Cardiorenal Syndrome and Potential Insights Into Novel Therapeutics

Heart and kidney failure often co-exist and confer high morbidity and mortality. The complex bi-directional nature of heart and kidney dysfunction is referred to as cardiorenal syndrome, and can be induced by acute or chronic dysfunction of either organ or secondary to systemic diseases. The five clinical subtypes of cardiorenal syndrome are categorized by the perceived primary precipitant of organ injury but lack precision. Traditional biomarkers such as serum creatinine are also limited in their ability to provide an early and accurate diagnosis of cardiorenal syndrome. Novel biomarkers have the potential to assist in the diagnosis of cardiorenal syndrome and guide treatment by evaluating the relative roles of implicated pathophysiological pathways such as hemodynamic dysfunction, neurohormonal activation, endothelial dysfunction, inflammation and oxidative stress, and fibrosis. In this review, we assess the utility of biomarkers that correlate with kidney and cardiac (dys)function, inflammation/oxidative stress, fibrosis, and cell cycle arrest, as well as emerging novel biomarkers (thrombospondin-1/CD47, glycocalyx and interleukin-1β) that may provide prediction and prognostication of cardiorenal syndrome, and guide potential development of targeted therapeutics.

Early biomarkers for kidney injury in heat-related illness patients: a prospective observational study at Japanese Self-Defense Force Fuji Hospital

BACKGROUND

Since heatstroke-induced acute kidney injury (AKI) can progress to chronic kidney disease, it would be useful to detect heatstroke-induced AKI and severe heat-related illness in the early phase. We studied the epidemiology of heat-related illness among patients in the Japanese Ground Self-Defense Force and evaluated the relationship between heat-related illness severity and early urinary biomarkers for AKI.

METHODS

We enrolled patients who were diagnosed with heat-related illness at the Self-Defense Force Fuji Hospital from 1 May to 30 September 2020. We compared the urinary kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), liver fatty acid-binding protein (L-FABP), N-acetyl-β-D-glucosaminidase (NAG) and β2-microglobulin levels according to the severity of heat-related illness as defined by positive scores for the Japanese Association of Acute Medicine Heatstroke Working Group (JAAM-HS-WG) criteria (0, mild; 1, moderate; ≥2, severe).

RESULTS

Of the 44 patients, kidney injury, defined as serum creatinine (sCr) ≥1.2 mg/dL, was seen in 9 (20.5%) patients. Urinary NAG, NGAL and L-FABP levels were significantly higher in the ≥2 JAAM-HS-WG criteria group than in the 0 group. Furthermore, urinary L-FABP levels were positively correlated with sCr levels. In contrast, the urinary KIM-1 levels showed the best correlation with serum cystatin C (sCysC) among these biomarkers.

CONCLUSIONS

We conclude even mild to moderate heatstroke could lead to AKI. Urinary L-FABP is useful for detecting heatstroke-induced AKI and patients with severe heat-related illness requiring immediate treatment. Urinary KIM-1 may detect heatstroke-induced AKI in terms of sCysC, although it was not related to the severity of heat-related illness.

Association of intraoperative gross hematuria with acute kidney injury after cytoreductive surgery

Objectives

Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) has been established in the management of peritoneal carcinomatosis. Although it is still necessary to take adequate measures against major postoperative complications including acute kidney injury (AKI), consensus is lacking on how to assess and stratify risk for patients with postoperative AKI after CRS-HIPEC. The aim of this retrospective cohort study was to investigate the association of intraoperative gross hematuria as a surrogate marker of ureter injury with postoperative AKI incidence.

Methods

This retrospective cohort study investigated patients without impaired preoperative kidney function who underwent CRS-HIPEC at a single referral center, and evaluated the relationship between intraoperative gross hematuria and incidence of postoperative AKI as defined by the Kidney Disease Improving Global Outcomes practice guidelines. Logistic regression analysis was performed to calculate the odds ratio of intraoperative gross hematuria for AKI, adjusting for confounding factors and other risk factors for AKI.

Results

We enrolled 185 patients (males, 37%). Twenty-five patients developed intraoperative gross hematuria. Postoperative AKI occurred in 10 (40%) of 25 patients with hematuria and 28 (17.5%) of 160 patients without hematuria. The crude odds ratio for exposure to hematuria was 3.14 (95% confidence interval, 1.30–7.60; p=0.020) for postoperative AKI. Adjusted odds ratio as estimated by multivariate logistic regression was 4.57 (95% confidence interval, 1.55–13.45; p=0.006).

Conclusions

Intraoperative gross hematuria is significantly associated with postoperative AKI incidence after CRS-HIPEC.

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Early detection and treatment of postoperative acute kidney injury is essential.

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How to prevent acute kidney injury after cytoreductive surgery is unclear.

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Intraoperative hematuria is related to postoperative acute kidney injury.

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Hematuria is easily detectable and may reflect ureter injury.

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This may improve long-term outcomes for patients undergoing cytoreductive surgery.

Metformin use in patients hospitalized with COVID-19: lower inflammation, oxidative stress, and thrombotic risk markers and better clinical outcomes

Diabetes mellitus (DM) is associated with a greater risk of COVID-19 and an increased mortality when the disease is contracted. Metformin use in patients with DM is associated with less COVID-19-related mortality, but the underlying mechanism behind this association remains unclear. Our aim was to explore the effects of metformin on markers of inflammation, oxidative stress, and hypercoagulability, and on clinical outcomes. Patients with DM on metformin (n = 34) and metformin naïve (n = 41), and patients without DM (n = 73) were enrolled within 48 h of hospital admission for COVID-19. Patients on metformin compared to naïve patients had a lower white blood cell count (p = 0.02), d-dimer (p = 0.04), urinary 11-dehydro thromboxane B₂ (p = 0.01) and urinary liver-type fatty acid binding protein (p = 0.03) levels and had lower sequential organ failure assessment score (p = 0.002), and intubation rate (p = 0.03), fewer hospitalized days (p = 0.13), lower in-hospital mortality (p = 0.12) and lower mortality plus nonfatal thrombotic event occurrences (p = 0.10). Patients on metformin had similar clinical outcomes compared to patients without DM. In a multiple regression analysis, metformin use was associated with less days in hospital and lower intubation rate. In conclusion, metformin treatment in COVID-19 patients with DM was associated with lower markers of inflammation, renal ischemia, and thrombosis, and fewer hospitalized days and intubation requirement. Further focused studies are required to support these findings.

The Role of Urinary N-Acetyl-β-d-glucosaminidase in Cirrhotic Patients with Acute Kidney Injury: Multicenter, Prospective Cohort Study

Background and Aims: Currently, it is difficult to predict the reversibility of renal function and to discriminate renal parenchymal injury in cirrhotic patients with acute kidney injury (AKI). The aim of this study is to evaluate whether urine N-acetyl-β-d-Glucosaminidase (NAG) can predict the survival and response to terlipressin in cirrhotic patients with AKI. Methods: Two hundred sixty-two cirrhotic consecutive patients who developed AKI were prospectively enrolled from 11 tertiary medical centers in Korea between 2016 to 2019. AKI was defined as an increase in serum Cr (SCr) of 0.3 mg/dL or a 50% increase in baseline SCr. Patients diagnosed with hepatorenal syndrome (HRS-AKI) were treated with terlipressin plus albumin. Results: The patients were 58.8 ± 12.9 years old on average and were predominantly male (72.5%). The mean MELD score was 25.3 ± 9.1. When classified according to the AKI phenotype, there were 119 pre-renal, 52 acute tubular necrosis, 18 miscellaneous, and 73 HRS-AKI patients. However, the urine NAG was not effective at discriminating AKI phenotypes, except for HRS-AKI. The baseline urine NAG increased as the baseline AKI stage increased (p < 0.001). In addition, within the same AKI stage, the urine NAG values were significantly lower in the AKI-resolved group than in the unresolved group. The urine NAG level was significantly lower in living patients compared with those who died or who underwent a liver transplant within 3 months (p = 0.005). In the multivariate analysis, the increased urine NAG was a significant risk factor for the 3-month transplant-free survival (TFS) rate, especially in patients with Child–Pugh class ≤ B or MELD < 24. The urine NAG did not predict the response to terlipressin treatment in patients with HRS. Conclusions: Urine NAG is strongly associated with the severity of AKI in patients with liver cirrhosis and is useful for predicting the 3-month TFS.

Assessment of Cardiopulmonary Bypass Duration Improves Novel Biomarker Detection for Predicting Postoperative Acute Kidney Injury after Cardiovascular Surgery

Urinary liver-type fatty acid binding protein (L-FABP) is a novel biomarker with promising performance in detecting kidney injury. Previous studies reported that L-FABP showed moderate discrimination in patients that underwent cardiac surgery, and other studies revealed that longer duration of cardiopulmonary bypass (CPB) was associated with a higher risk of postoperative acute kidney injury (AKI). This study aims to examine assessing CPB duration first, then examining L-FABP can improve the discriminatory ability of L-FABP in postoperative AKI. A total of 144 patients who received cardiovascular surgery were enrolled. Urinary L-FABP levels were examined at 4 to 6 and 16 to 18 h postoperatively. In the whole study population, the AUROC of urinary L-FABP in predicting postoperative AKI within 7 days was 0.720 at 16 to 18 h postoperatively. By assessing patients according to CPB duration, the urinary L-FABP at 16 to 18 h showed more favorable discriminating ability with AUROC of 0.742. Urinary L-FABP exhibited good performance in discriminating the onset of AKI within 7 days after cardiovascular surgery. Assessing postoperative risk of AKI through CPB duration first and then using urinary L-FABP examination can provide more accurate and satisfactory performance in predicting postoperative AKI.

Association between plasma aldosterone and markers of tubular and glomerular damage in primary aldosteronism

OBJECTIVE

Although renal impairments are observed in patients with primary aldosteronism (PA), the association between plasma aldosterone concentration (PAC) and specific structural kidney damage remains unknown. Thus, we analysed the association between PAC, and markers of glomerular and tubular damage.

DESIGN

This was a retrospective cross-sectional study of 96 PA patients, in which we analysed the association between PAC and markers of kidney damage, including urinary albumin-creatinine ratio (ACR) for glomerular damage, and urinary liver fatty acid-binding protein (L-FABP), N-acetyl-β-D-glucosaminidase (NAG) and β2-microglobulin (β2-MG) for tubular damage. In addition, we evaluated the association between PAC and N-terminal pro-brain natriuretic peptide (NT-proBNP) as a marker for body fluid volume.

RESULTS

Urinary ACR, L-FABP, NAG, β2-MG and NT-proBNP significantly correlated with PAC. PAC (<415 pmol/L, 415-550, 550-740, 740 <)-based quartile analysis revealed that both elevated markers of kidney damage and NT-proBNP could be observed in PA patients with a PAC over 550 pmol/L. Logistic regression analysis showed that PAC was significantly associated with a risk of both microalbuminuria and lowered eGFR (<60 mL/min/1.73 m² ), with its optimal cut-offs for predicting each, 558 and 594 pmol/L, respectively.

CONCLUSIONS

Increased PAC, especially over 550 pmol/L, is associated with excessive damage to the tubule and glomerulus.

First Experience Addressing the Prognostic Utility of Novel Urinary Biomarkers in Patients With COVID-19

Urine 11-dehydro-thromboxane B₂ (u11-dh-TxB₂), 8-hydroxy-2’-deoxyguanosine (8-OHdG), and liver-type fatty acid binding protein levels (L-FABP) at the time of hospitalization were higher in coronavirus disease 2019 (COVID-19) patients with adverse events vs without events. Higher u11-dh-TxB₂ and L-FABP levels were associated with longer hospitalization, more thrombotic events, and greater mortality, providing evidence for potential utility as early prognostic biomarkers for COVID-19.

Biochemical Markers in the Prediction of Contrast-induced Acute Kidney Injury

For many years clinicians have been searching for "kidney troponin"- a simple diagnostic tool to assess the risk of acute kidney injury (AKI). Recently, the rise in the variety of contrast-related procedures (contrast computed tomography (CT), percutaneous coronary intervention (PCI) and angiography) has resulted in the increased number of contrast-induced acute kidney injuries (CI-AKI). CIAKI remains an important cause of overall mortality, prolonged hospitalisation and it increases the total costs of therapy. The consequences of kidney dysfunction affect the quality of life and they may lead to disability as well. Despite extensive worldwide research, there are no sensitive and reliable methods of CI-AKI prediction. Kidney Injury Molecule 1 (KIM-1) and Neutrophil Gelatinase Lipocalin (NGAL) have been considered as kidney-specific molecules. High concentrations of these substances before the implementation of contrast-related procedures have been suggested to enable the estimation of kidney vulnerability to CI-AKI and they seem to have the predictive potential for cardiovascular events and overall mortality. According to other authors, routine determination of known inflammation factors (e.g., CRP, WBC, and neutrophil count) may be helpful in the prediction of CIAKI. However, the results of clinical trials provide contrasting results. The pathomechanism of contrast- induced nephropathy remains unclear. Due to its prevalence, the evaluation of the risk of acute kidney injury remains a serious problem to be solved. This paper reviews pathophysiology and suggested optimal markers facilitating the prediction of contrast-induced acute kidney injury.

Direct hemoperfusion using a polymyxin B-immobilized polystyrene column for COVID-19

Objective

To evaluate the efficacy and safety of direct hemoperfusion using a polymyxin B‐immobilized polystyrene column (PMX‐DHP) in severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)‐positive pneumonia patients.

Methods

This study was a case series conducted at a designated infectious diseases hospital. Twelve SARS‐CoV‐2‐positive patients with partial pressure of arterial oxygen/percentage of inspired oxygen (P/F) ratio < 300 were treated with PMX‐DHP on two consecutive days each during hospitalization. We defined day 1 as the first day when PMX‐DHP was performed. PMX‐DHP efficacy was assessed on days 7 and 14 after the first treatment based on eight categories. Subsequently, improvement in P/F ratio and urinary biomarkers on days 4 and 8, malfunctions, and ventilator and extracorporeal membrane oxygenation avoidance rates were also evaluated.

Results

On day 14 after the first treatment, disease severity decreased in 58.3% of the patients. P/F ratio increased while urine β2‐microglobulin decreased on days 4 and 8. Cytokine measurement pre‐ and post‐PMX‐DHP revealed decreased levels of interleukin‐6 and the factors involved in vascular endothelial injury, including vascular endothelial growth factor. Twenty‐two PMX‐DHPs were performed, of which seven and five PMX‐DHPs led to increased inlet pressure and membrane coagulation, respectively. When the membranes coagulated, the circuitry needed to be reconfigured. Circuit problems were usually observed when D‐dimer and fibrin degradation product levels were high before PMX‐DHP.

Conclusions

Future studies are expected to determine the therapeutic effect of PMX‐DHP on COVID‐19. Because of the relatively high risk of circuit coagulation, coagulation capacity should be assessed beforehand.

Urinary neutrophil gelatinase-associated lipocalin values alone and combined with Prognostic Index predict septic AKI, DIC, and shock: a pilot study

Objective

Sepsis is a syndrome involving life-threatening organ dysfunction. The present study aimed to determine whether septic AKI, ARDS, DIC, and shock can be predicted more readily by combining uNGAL values and inflammation-based prognostic scores, over the use of uNGAL values alone.

Results

ROC curve analyses yielded the following cut-off values: AKI: 438.5 (ng/ml) for uNGAL at Day 1 (AUC, 0.8), 476.9 (ng/ml) for uNGAL at Day 2 (AUC, 0.86), 123.8 (ng/ml) for uNGAL at Day 3 (AUC, 0.81), 133.6 (ng/ml) for uNGAL at Day 4 (AUC, 0.78), 1.0 for iNS NGAL-NLR (AUC, 0.75), 2.0 for iNS NGAL-PI (AUC, 0.77), DIC; 648.5 (ng/ml) for uNGAL at Day 1 (AUC, 0.77); shock; 123.8 (ng/ml) for uNGAL at Day 3 (AUC, 0.71) and 9 for SOFA (AUC, 0.71). Multivariate logistic regression analyses revealed iNS NGAL-PI to be a significant independent predictor of AKI (OR, 20.62; 95% CI, 1.03–412.3; p = 0.048).

Anemia following acute kidney injury after noncardiac surgery and long-term outcomes: the NARA-AKI cohort study

Background

This study was conducted to investigate whether acute kidney injury (AKI) is an independent predictor of anemia and whether anemia following AKI is a mediator of mortality after AKI.

Methods

This is a retrospective cohort study. Adults with noncardiac surgery from 2007 to 2011 were included. Obstetric or urological surgery, missing data or preoperative dialysis were excluded. Subjects were followed until the end of 2015 or lost to follow-up. Exposures of interest were postoperative AKI. Outcome variables were hematocrit values at 3, 6 and 12 months postoperatively and mortality. Associations between AKI and hematocrit or association between AKI and mortality were examined by multivariable linear regression or Cox regression, respectively.

Results

Among 6692 subjects, 445 (6.6%) developed AKI. Among those with postoperative data, AKI was independently associated with lower hematocrit at 3, 6 and 12 months postoperatively, with coefficients of −0.79 [95% confidence interval (CI) −1.47 to −0.11; n = 1750], −1.35 (−2.11 to −0.60; n = 1558) and −0.91 (−1.59 to −0.22; n = 2463), respectively. Higher stages or longer duration of AKI were associated with more severe anemia. AKI was associated with higher mortality after 3 months postoperatively with a hazard ratio of 1.54 (95% CI 1.12–2.12). Further adjustment with hematocrit at 3 months attenuated the association. The mediation effect was significant (P = 0.02) by mediation analysis.

Conclusions

AKI was an independent predictor of anemia following AKI. Higher mortality associated with AKI was at least partially mediated by anemia following AKI. Whether correction of anemia following AKI improves mortality requires further research.

Novel Blood Cytokine-Based Model for Predicting Severe Acute Kidney Injury and Poor Outcomes After Cardiac Surgery

Background Alterations in serum creatinine levels delay the identification of severe cardiac surgery-associated acute kidney injury. To provide timely diagnosis, novel predictive tools should be investigated. Methods and Results This prospective observational study consists of a screening cohort (n=204) and a validation cohort (n=198) from 2 centers from our hospital. Thirty-two inflammatory cytokines were measured via a multiplex cytokine assay. Least absolute shrinkage and selection operator regression was conducted to select the cytokine signatures of severe cardiac surgery-associated acute kidney injury. Afterwards, the significant candidates including interferon-γ, interleukin-16, and MIP-1α (macrophage inflammatory protein-1 alpha) were integrated into the logistic regression model to construct a predictive model. The predictive accuracy of the model was evaluated in these 2 cohorts. The cytokine-based model yielded decent performance in both the screening (C-statistic: 0.87, Brier 0.10) and validation cohorts (C-statistic: 0.86, Brier 0.11). Decision curve analysis revealed that the cytokine-based model had a superior net benefit over both the clinical factor-based model and the established plasma biomarker-based model for predicting severe acute kidney injury. In addition, elevated concentrations of each cytokine were associated with longer mechanical ventilation times, intensive care unit stays, and hospital stays. They strongly predicted the risk of composite events (defined as treatment with renal replacement therapy and/or in-hospital death) (OR of the fourth versus the first quartile [95% CI]: interferon-γ, 27.78 [3.61-213.84], interleukin-16, 38.07 [4.98-291.07], and MIP-1α, 9.13 [2.84-29.33]). Conclusions Our study developed and validated a promising blood cytokine-based model for predicting severe acute kidney injury after cardiac surgery and identified prognostic biomarkers for assisting in outcome risk stratification.

The need for disruptive innovation in acute kidney injury

Acute kidney injury (AKI) is a threatening medical condition associated with poor outcomes at different settings. The development of standardized diagnostic criteria and new biomarkers addressed significant clinical impacts of AKI and the need for an early AKI detection, respectively. There have been some breakthroughs in understanding the pathogenesis of AKI through basic research; however, treatments against AKI aside from renal replacement therapy (RRT) have not shown adequate successful results. Biomarkers that could identify good responders to certain treatment are expected to facilitate translation of basic research findings. Most patients with severe AKI treated with RRT died due to multiple-organ failure, not renal dysfunction. Hence, it is essential to identify other organ dysfunctions induced by AKI as organ crosstalk. Also, a multidisciplinary approach of critical care nephrology is needed to evaluate a complex organ crosstalk in AKI. For disruptive innovation for AKI, we further explore these new aspects of AKI, which previously were considered outside the scope of nephrology.

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.

Increased Urinary Liver-Type Fatty Acid-Binding Protein Level Predicts Major Adverse Cardiovascular Events in Patients With Hypertension

BACKGROUND

Urinary liver-type fatty acid-binding protein (L-FABP) has been known as a potential biomarker for acute kidney injury. It has also been suggested to have an effective predictive value for cardiovascular mortality in patients with diabetes or critically ill condition. Therefore, this study aimed to examine the ability of urinary L-FABP in predicting mid-term cardiovascular morbidity and mortality in patients with hypertension.

METHODS

Urinary L-FABP levels in stable outpatients without diabetes who were treated with antihypertensive drugs were measured, and a 5-year follow-up was planned. The primary end-point was a combination of acute heart failure requiring hospitalization, myocardial infarction, stroke, and cardiovascular death. The secondary end-point was kidney disease progression defined as a relative decline in the estimated glomerular filtration rate of ≥30% from the baseline.

RESULTS

A total of 197 patients were recruited. Primary and secondary end-points occurred in 24 (12.2%) and 42 (21.3%) patients, respectively, during a median follow-up of 5.7 years. Patients with urinary L-FABP levels higher than the upper limit (8.4 µg/g creatinine) were more likely to reach the primary (30.43% vs. 9.77%; P = 0.003) and secondary end-points (56.52% vs. 16.67%; P < 0.001) than those with urinary L-FABP levels within the normal limits. Urinary L-FABP level was independently associated with both primary (hazard ratio (HR) 1.21; P = 0.03) and secondary end-points (HR 1.19; P = 0.02).

CONCLUSIONS

This study demonstrated that increased urinary L-FABP levels may predict adverse cardiovascular events and renal dysfunction progression even among stable nondiabetic patients with hypertension.

Perioperative acute kidney injury: Stratification and risk reduction strategies

Perioperative acute kidney injury (AKI) is associated with increased morbidity and mortality. Patient comorbidities, the type of surgery, timing of surgery, and exposure to nephrotoxins are important contributors for developing acute kidney injury. Urgent or emergent surgery, cardiac, and organ transplantation procedures are associated with a higher risk of acute kidney injury. Nephrotoxic drugs, contrast dye, and diuretics can worsen preexisting kidney dysfunction or act as an additive and/or synergistic insult to perioperative injury. A history of preoperative chronic kidney disease is the main risk factor for developing AKI, conferring as much as a 10-fold risk. However, beyond the preoperative renal function, the development of AKI is a complex phenomenon that involves a combination of patient-related and surgery-related factors.

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.

Combining Serum Cystatin C and Urinary N-Acetyl-Beta-D-Glucosaminidase Improves the Precision for Acute Kidney Injury Diagnosis after Resection of Intracranial Space-Occupying Lesions

BACKGROUND

Postoperative acute kidney injury (AKI) is frequent and associated with adverse outcomes. Unfortunately, the early diagnosis of AKI remains a challenge. Combining functional and tubular damage biomarkers may provide better precision for AKI detection. However, the diagnostic accuracy of this combination for AKI after neurosurgery is unclear. Serum cystatin C (sCysC) and urinary albumin/creatinine ratio (uACR) are considered functional biomarkers, while urinary N-acetyl-β-D-glucosaminidase (uNAG) represents tubular damage. We aimed to assess the performances of these clinical available biomarkers and their combinations for AKI prediction after resection of intracranial space-occupying lesions.

METHODS

A prospective study was conducted, enrolling adults undergoing resection of intracranial space-occupying lesions and admitted to the neurosurgical intensive care unit. The discriminative abilities of postoperative sCysC, uNAG, uACR, and their combinations in predicting AKI were compared using the area under the receiver operating characteristic curve (AUC-ROC), continuous net reclassification index (cNRI), and incremental discrimination improvement (IDI).

RESULTS

Of 605 enrolled patients, AKI occurred in 67 patients. The cutoff values of sCysC, uNAG, and uACR to predict postoperative AKI were 0.72 mg/L, 19.98 U/g creatinine, and 44.21 mg/g creatinine, respectively. For predicting AKI, the composite of sCysC and uNAG (AUC-ROC = 0.785) outperformed either individual biomarkers or the other two panels (uNAG plus uACR or sCysC plus uACR). Adding this panel to the predictive model improved the AUC-ROC to 0.808. Moreover, this combination significantly improved risk reclassification over the clinical model alone, with cNRI (0.633) and IDI (0.076). Superior performance of this panel was further confirmed with bootstrap internal validation.

CONCLUSIONS

Combination of functional and tubular damage biomarkers improves the predictive accuracy for AKI after resection of intracranial space-occupying lesions.

N-acety-b-D-glucosaminidase: A potential biomarker for early detection of acute kidney injury in acute chest pain

AIM

Acute kidney injury (AKI) is often underdiagnosed due to several limitations of the renal marker creatinine. Tubular urinary biomarkers may substantially contribute to diagnose AKI early. For early detection of AKI, we evaluated for the first time N-acetyl-β-d-glucosaminidase (NAG), Kidney-injury-molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) in acute chest pain.

METHODS

We included 402 chest pain patients aged 18 to 95 years seen in the emergency department. From 311 subjects, blood and urine samples were collected.

RESULTS

Thirty-three patients developed an AKI and showed a significant increase in all three tubular markers compared to patients without AKI (each P < .001). According to receiver operating characteristic (ROC) analysis, combining NAG and creatinine showed a significantly increased area under the curve (AUC) compared to creatinine alone (AUC: 0.75 vs 0.87; P < .001). KIM-1, NGAL and cystatin C showed no significant differences in AUC compared to creatinine. In 120 individuals with blood and urine sampling before contrast media exposure, ROC analysis showed a significantly improved diagnostic performance for the combination of both (AUC: 0.83 vs creatinine AUC: 0.66; P = .004). AKI occurrence showed no dependency from CM volume. NAG presented as an independent AKI predictor beside creatinine, age, the diagnosis of myocardial infarction and mean arterial pressure. Regarding the prognostic value for renal replacement therapy, the combination of NAG and creatinine showed a significantly lager AUC than creatinine (AUC: 0.95 vs AUC: 0.85; P < .001).

CONCLUSION

NAG presented as a promising marker of impending AKI and the necessity of renal replacement therapy.

Acute kidney injury after cardiac surgery: prevalence, impact and management challenges

Acute kidney injury (AKI) is a major medical problem that is of particular concern after cardiac surgery. Perioperative AKI is independently associated with an increase in short-term morbidity, costs of treatment, and long-term mortality. In this review, we explore the definition of cardiac surgery-associated acute kidney injury (CSA-AKI) and identify diverse mechanisms and risk factors contributing to the renal insult. Current theories of the pathophysiology of CSA-AKI and description of its clinical course will be addressed in this review. Data on the most promising renal protective strategies in cardiac surgery, from well-designed studies, will be scrutinized. Furthermore, diagnostic tools such as novel biomarkers of AKI and their potential utility will be discussed.

Kidney Tubular Damage and Functional Biomarkers in Acute Kidney Injury Following Cardiac Surgery

Background

Cardiac surgery–associated acute kidney injury (AKI) is associated with increased morbidity and mortality. We examined the utility of combining biomarkers of kidney function loss (serum cystatin C) and kidney tubular damage (urine neutrophil gelatinase-associated lipocalin [NGAL] and Kidney Injury Molecule-1 [KIM-1]) for the prediction of post–cardiac surgery AKI.

Methods

Single-center prospective cohort study of 106 adults undergoing coronary artery bypass grafting and/or valve surgery with cardiopulmonary bypass (CPB). Primary outcome was postoperative in-hospital AKI defined by serum creatinine (SCr)–Kidney Disease: Improving Global Outcomes criteria. Biomarkers were measured preoperatively, 6 hours after CPB and on postoperative days (PODs) 1 to 4.

Results

A total of 23 subjects (21.7%) developed AKI. After adjusting for preoperative left ventricular ejection fraction, body mass index >30 kg/m², and estimated glomerular filtration rate (eGFR) <60 ml/min per 1.73 m², the combination of peak serum cystatin C and peak urine KIM-1/creatinine (Cr) (6 hours post-CPB to POD 1) above optimal cutoff significantly associated with postoperative AKI (odds ratio [OR]: 5.32; 95% confidence interval [CI]: 1.31–21.67; P = 0.020). This biomarker combination significantly improved the performance of the clinical model for the prediction of postoperative AKI (area under the curve [AUC]: 0.77, 95% CI: 0.65–0.90 for the clinical model alone versus 0.83, 95% CI: 0.73–0.93 for the clinical model with the addition of biomarker data, P = 0.049).

Conclusions

Combining biomarkers of postoperative kidney function loss and postoperative kidney tubular damage significantly improved prediction of in-hospital AKI following cardiac surgery. Future large, multicenter studies are warranted to assess whether panels of biomarkers reflecting distinct pathobiology can be used to guide interventions and improve short- and long-term outcomes in patients undergoing cardiac surgery.

A Novel Biomarker for Acute Kidney Injury, Vanin-1, for Obstructive Nephropathy: A Prospective Cohort Pilot Study

Background: Vanin-1 is a novel acute kidney injury (AKI) biomarker that has not been clinically investigated as a biomarker for obstructive nephropathy. This study investigated the diagnostic value of vanin-1 as a biomarker for adult obstructive nephropathy by comparing it to existing AKI biomarkers. Methods: A total of 49 patients, 21 controls, and 28 hydronephrosis (HN) cases were assessed. AKI biomarkers in bladder (BL) urine and renal pelvic (RP) urine in the HN group were compared to each BL marker in the control group. In a subgroup of cases receiving interventions for obstructive nephropathy, the BL values of each biomarker were assessed after the intervention. Results: RP vanin-1 levels were significantly higher while BL vanin-1 levels were marginally higher in the HN group than in the control group. The area under the receiver operating characteristics curve values for RP and BL vanin-1 were 0.9778 and 0.6386, respectively. In multivariate analyses, BL vanin-1 and N-acetyl-β-D-glucosaminidase (NAG), but not kidney injury molecule-1 (KIM-1) or neutrophil gelatinase-associated lipocalin (NGAL), were independent factors for predicting the presence of HN. In cases receiving interventions, vanin-1 decreased significantly from 1 week after the intervention in cases of moderate to severe obstructive nephropathy compared to RP values at baseline. Conclusion: Urinary vanin-1 is a useful biomarker to detect and monitor the clinical course of obstructive nephropathy.

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

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

The Accuracy of Urinary TIMP-2 and IGFBP7 for the Diagnosis of Cardiac Surgery-Associated Acute Kidney Injury: A Systematic Review and Meta-Analysis

Background:

Tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) are recent promising markers for identification of cardiac surgery-associated acute kidney injury (CSA-AKI). The aim of this study was systematically and quantitatively to evaluate the accuracy of urinary TIMP-2 and IGFBP7 for the diagnosis of CSA-AKI.

Methods:

Three databases including PubMed, ISI web of knowledge, and Embase were systematically searched from inception to March 2018. Two investigators conducted the processes of literature search study selection, data extraction, and quality evaluation independently. Meta-DiSc and STATA were used for all statistical analyses.

Results:

A total of 8 studies comprising 552 patients were included in this meta-analysis. Pooled sensitivity and specificity with corresponding 95% confidence intervals (CIs) were 0.79 (95% CI, 0.71-0.86, I 2 = 74.2%) and 0.76 (95% CI, 0.72-0.80, I 2 = 80.8%), respectively. Pooled positive likelihood ratio (LR), negative LR, and diagnostic odds ratio were 3.49 (95% CI, 2.44-5.00, I 2 = 61.5%), 0.31(95% CI, 0.19-0.51, I 2 = 51.8%), and 14.89 (95% CI, 7.31-30.32, I 2 = 27.9%), respectively. The area under curve estimated by summary receiver operating characteristic was 0.868 (standard error [SE] 0.032) with a Q* value of 0.799 (SE 0.032). Sensitivity analysis demonstrated that one study notably affected the stability of pooled results. One of the subgroups investigated—AKI threshold—could account for partial heterogeneity.

Conclusion:

Urinary TIMP-2 and IGFBP7 is a helpful biomarker for early diagnosis of CSA-AKI. And, the potential of this biomarker with a broader spectrum of clinical settings may be the focus of future studies.

The Japanese clinical practice guideline for acute kidney injury 2016

Acute kidney injury (AKI) is a syndrome which has a broad range of etiologic factors depending on different clinical settings. Because AKI has significant impacts on prognosis in any clinical settings, early detection and intervention is necessary to improve the outcomes of AKI patients. This clinical guideline for AKI was developed by a multidisciplinary approach with nephrology, intensive care medicine, blood purification, and pediatrics. Of note, clinical practice for AKI management which was widely performed in Japan was also evaluated with comprehensive literature search.

Early diagnosis of acute kidney injury in aged patients undergoing percutaneous coronary intervention

In aged patients, acute kidney injury (AKI) is a common clinical complication after percutaneous coronary intervention (PCI), highlighting the need for timely and certain diagnosis of this disease. A single centre, nested case-control study was conducted, which assessed the usefulness of urinary liver-type fatty acid-binding protein (uL-FABP), neutrophil gelatinase-associated lipocalin (uNGAL), and kidney injury molecule-1 (uKIM-1) for early detection of AKI. One hundred and thirty-two patients at or over 60 years old undergoing PCI were included. Serum creatinine (SCr) was measured before PCI, 24 and 48 h after PCI; uL-FABP, uNGAL, and uKIM-1 were measured before PCI, 6, 24, and 48 h after PCI. We identified 16 AKI patients and selected 32 control patients matched by admission time (<1 week), age (±5 years), and gender. In the receiver operating characteristic (ROC) curve analysis, the areas under the curve (AUCs) for the relative measurements of uL-FABP, uNGAL, and uKIM-1 were 0.809, 0.867, and 0.512 at 6 h after PCI, and 0.888, 0.840, and 0.676 at 24 h after PCI, respectively. AUC for the combination of uL-FABP and uNGAL was 0.899 at 6 h after PCI, and 0.917 at 24 h after PCI. Thus, measurement of uL-FABP and uNGAL levels at 6 and 24 h after PCI may be useful in detecting AKI in aged patients. Measurement of uKIM-1 levels provides inferior predictive power for early diagnosis of AKI.

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

Background

The early prediction of acute kidney injury (AKI) can facilitate timely intervention and prevent complications. We aimed to understand the predictive value of urinary liver-type fatty-acid binding protein (L-FABP) levels on admission to medical (non-surgical) cardiac intensive care units (CICUs) for AKI, both independently and in combination with serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels.

Methods

We prospectively investigated the predictive value of L-FABP and NT-proBNP for AKI in a large, heterogeneous cohort of patients treated in medical CICUs. Baseline urinary L-FABP and serum NT-proBNP were measured on admission. AKI was diagnosed according to the Kidney Disease: Improving Global Outcomes criteria. We studied 1273 patients (mean age, 68 years), among whom 46% had acute coronary syndromes, 38% had acute decompensated heart failure, 5% had arrhythmia, 3% had pulmonary hypertension, 2% had acute aortic syndrome, 2% had infective endocarditis, and 1% had Takotsubo cardiomyopathy.

Results

Urinary L-FABP levels correlated with serum NT-proBNP levels (r = 0.17, p < 0.0001). AKI occurred in 224 patients (17.6%), including 48 patients with stage 2 or 3 disease. Patients who developed AKI had higher one-week and 6-month mortality than those who did not develop AKI (p = 0.0002 and p = 0.003, respectively). In the multivariate logistic analysis, both L-FABP (p < 0.0001) and NT-proBNP (p = 0.006) were independently associated with the development of AKI. Adding L-FABP and NT-proBNP to a baseline model that included established risk factors further improved reclassification (p < 0.001) and discrimination (p < 0.01) beyond that of the baseline model or any single biomarker individually.

Conclusions

Urinary L-FABP and serum NT-proBNP levels on admission are independent predictors of AKI, and when used in combination, improve early prediction of AKI in patients hospitalized at medical CICUs.

The Japanese Clinical Practice Guideline for acute kidney injury 2016

Acute kidney injury (AKI) is a syndrome which has a broad range of etiologic factors depending on different clinical settings. Because AKI has significant impacts on prognosis in any clinical settings, early detection and intervention are necessary to improve the outcomes of AKI patients. This clinical guideline for AKI was developed by a multidisciplinary approach with nephrology, intensive care medicine, blood purification, and pediatrics. Of note, clinical practice for AKI management which was widely performed in Japan was also evaluated with comprehensive literature search.

Renal Angina Is a Sensitive, but Nonspecific Identifier of Postcardiac Surgery Acute Kidney Injury

OBJECTIVES

Acute kidney injury (AKI) is a common complication of cardiac surgery, and early detection is difficult. This study was performed to determine the sensitivity, specificity, positive predictive value, negative predictive value, and statistical performance of renal angina (RA) as an early predictor of AKI in an adult cardiac surgical patient population.

DESIGN

Retrospective, nonrandomized, observational study.

SETTING

A single, university-affiliated, quaternary medical center.

PARTICIPANTS

The study comprised 324 consecutive patients undergoing coronary artery bypass grafting or cardiac valvular surgery from February 1 through July 30, 2014.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred-seven patients at moderate or high risk of developing postoperative renal injury were identified, 82 of whom met criteria for RA. The occurrence of RA was found to have an 80.9% sensitivity and 30.8% specificity for the prediction of AKI using Acute Kidney Injury Network criteria and 89.3% sensitivity and 27.8% specificity when paired with the Risk, Injury, Failure, Loss, End Stage Renal Disease criteria. A receiver operating characteristic area under the curve analysis revealed a nonsignificant predictive ability of 55.8% (95% confidence interval 0.47-0.65) when RA was paired with Acute Kidney Injury Network criteria; however, the receiver operating characteristic area under the curve was significant when paired with Risk, Injury, Failure, Loss, End Stage Renal Disease criteria, with a predictive ability of 0.586 (0.509-0.662).

CONCLUSIONS

RA is a sensitive, but nonspecific, predictor of postcardiac surgery AKI, with clinical utility most suited as a screening tool.

Urinary biomarkers predict advanced acute kidney injury after cardiovascular surgery

BACKGROUND

Acute kidney injury (AKI) after cardiovascular surgery is a serious complication. Little is known about the ability of novel biomarkers in combination with clinical risk scores for prediction of advanced AKI.

METHODS

In this prospectively conducted multicenter study, urine samples were collected from 149 adults at 0, 3, 6, 12 and 24 h after cardiovascular surgery. We measured urinary hemojuvelin (uHJV), kidney injury molecule-1 (uKIM-1), neutrophil gelatinase-associated lipocalin (uNGAL), α-glutathione S-transferase (uα-GST) and π-glutathione S-transferase (uπ-GST). The primary outcome was advanced AKI, under the definition of Kidney Disease: Improving Global Outcomes (KDIGO) stage 2, 3 and composite outcomes were KDIGO stage 2, 3 or 90-day mortality after hospital discharge.

RESULTS

Patients with advanced AKI had significantly higher levels of uHJV and uKIM-1 at 3, 6 and 12 h after surgery. When normalized by urinary creatinine level, uKIM-1 in combination with uHJV at 3 h post-surgery had a high predictive ability for advanced AKI and composite outcome (AUC = 0.898 and 0.905, respectively). The combination of this biomarker panel (normalized uKIM-1, uHJV at 3 h post-operation) and Liano's score was superior in predicting advanced AKI (AUC = 0.931, category-free net reclassification improvement of 1.149, and p <  0.001).

CONCLUSIONS

When added to Liano's score, normalized uHJV and uKIM-1 levels at 3 h after cardiovascular surgery enhanced the identification of patients at higher risk of progression to advanced AKI and composite outcomes.

TIMP-2*IGFBP7 (Nephrocheck®) Measurements at Intensive Care Unit Admission After Cardiac Surgery are Predictive for Acute Kidney Injury Within 48 Hours

BACKGROUND/AIMS

Acute kidney injury (AKI) is a postoperative complication after cardiac surgery with a high impact on mortality and morbidity. Nephrocheck® [TIMP-2*IGFBP7] determines markers of tubular stress, which occurs prior to tubular damage. It is unknown at which time-point [TIMP-2*IGFBP7] measurement should be performed to ideally predict AKI. We investigated the association of [TIMP-2*IGFBP7] at various time-points with the incidence of AKI in patients undergoing elective cardiac surgery including cardio-pulmonary bypass.

METHODS

In a prospective cohort study, serial blood and urine samples were collected from 150 patients: pre-operative, at ICU-admission, 24h and 48h post-surgery. AKI was defined as Serum-Creatinine rise >0.3 mg/dl within 48hrs. Urinary [TIMP-2*IGFBP7] was measured at pre-operative, ICU-admission and 24h post-surgery; medical staff was kept blinded to these results.

RESULTS

A total of 35 patients (23.5%) experienced AKI, with a higher incidence in those with high [TIMP-2*IGFBP7] values at ICU admission (57.1% vs. 10.1%, p<0.001). In logistic regression [TIMP-2*IGFBP7] at ICU admission was independently associated with the occurrence of AKI (Odds Ratio 11.83; p<0.001, C-statistic= 0.74) after adjustment for EuroSCORE II and CBP-time.

CONCLUSIONS

Early detection of elevated [TIMP-2*IGFBP7] at ICU admission was strongly predictive for postoperative AKI and appeared to be more precise as compared to subsequent measurements.

The ischemic/nephrotoxic acute kidney injury and the use of renal biomarkers in clinical practice

The term Acute Renal Failure (ARF) has been replaced by the term Acute Kidney Injury (AKI). AKI indicates an abrupt (within 24-48h) decrease in Glomerular Filtraton Rate, due to renal damage, that causes fluid and metabolic waste retention and alteration of electrolyte and acid-base balance. The renal biomarkers of AKI are substances or processes that are indicators of normal or impaired function of the kidney. The most used renal biomarker is still serum creatinine that is inadequate for several reasons, one of which is its inability to differentiate between hemodynamic changes of renal function ("prerenal azotemia") from intrinsic renal failure or obstructive nephropathy. Cystatin C is no better in this respect. After the description of the pathophysiology of "prerenal azotemia" and of Acute Kidney Injury (AKI) due to ischemia or nephrotoxicity, the renal biomarkers are listed and described: urinary NAG, urinary and serum KIM-1, serum and urinary NGAL, urinary IL-18, urinary L-FABP, serum Midkine, urinary IGFBP7 and TIMP2, urinary α-GST and π-GST, urinary ɣGT and AP, urinary β₂M, urinary RBP, serum and urinary miRNA. All have been shown to appear much earlier than the rise of serum Creatinine. Some of them have been demonstrated to predict the clinical outcomes of AKI, such as the need for initiation of dialysis and mortality.

Evaluation of clinically available renal biomarkers in critically ill adults: a prospective multicenter observational study

BACKGROUND

Although serum cystatin C (sCysC), urinary N-acetyl-β-D-glucosaminidase (uNAG), and urinary albumin/creatinine ratio (uACR) are clinically available, their optimal combination for acute kidney injury (AKI) detection and prognosis prediction remains unclear. We aimed to assess the discriminative abilities of these biomarkers and their possible combinations for AKI detection and intensive care unit (ICU) mortality prediction in critically ill adults.

METHODS

A multicenter, prospective observational study was conducted in mixed medical-surgical ICUs at three tertiary care hospitals. One thousand eighty-four adult critically ill patients admitted to the ICUs were studied. We assessed the use of individual biomarkers (sCysC, uNAG, and uACR) measured at ICU admission and their combinations with regard to AKI detection and prognosis prediction.

RESULTS

AUC-ROCs for sCysC, uNAG, and uACR were calculated for total AKI (0.738, 0.650, and 0.683, respectively), severe AKI (0.839, 0.706, and 0.771, respectively), and ICU mortality (0.727, 0.793, and 0.777, respectively). The panel of sCysC plus uNAG detected total and severe AKI with significantly higher accuracy than either individual biomarkers or the other two panels (uNAG plus uACR or sCysC plus uACR). For detecting total AKI, severe AKI, and ICU mortality at ICU admission, this panel yielded AUC-ROCs of 0.756, 0.863, and 0.811, respectively; positive predictive values of 0.71, 0.31, and 0.17, respectively; and negative predictive values of 0.81, 0.97, and 0.98, respectively. Moreover, this panel significantly contributed to the accuracy of the clinical models for AKI detection and ICU mortality prediction, as measured by the AUC-ROC, continuous net reclassification index, and incremental discrimination improvement index. The comparable performance of this panel was further confirmed with bootstrap internal validation.

CONCLUSIONS

The combination of a functional marker (sCysC) and a tubular damage marker (uNAG) revealed significantly superior discriminative performance for AKI detection and yielded additional prognostic information on ICU mortality.

Methodological issues in current practice may lead to bias in the development of biomarker combinations for predicting acute kidney injury

Individual biomarkers of renal injury are only modestly predictive of acute kidney injury (AKI). Using multiple biomarkers has the potential to improve predictive capacity. In this systematic review, statistical methods of articles developing biomarker combinations to predict acute kidney injury were assessed. We identified and described three potential sources of bias (resubstitution bias, model selection bias and bias due to center differences) that may compromise the development of biomarker combinations. Fifteen studies reported developing kidney injury biomarker combinations for the prediction of AKI after cardiac surgery (8 articles), in the intensive care unit (4 articles) or other settings (3 articles). All studies were susceptible to at least one source of bias and did not account for or acknowledge the bias. Inadequate reporting often hindered our assessment of the articles. We then evaluated, when possible (7 articles), the performance of published biomarker combinations in the TRIBE-AKI cardiac surgery cohort. Predictive performance was markedly attenuated in six out of seven cases. Thus, deficiencies in analysis and reporting are avoidable and care should be taken to provide accurate estimates of risk prediction model performance. Hence, rigorous design, analysis and reporting of biomarker combination studies are essential to realizing the promise of biomarkers in clinical practice.

Meta-analysis for outcomes of acute kidney injury after cardiac surgery

This study aimed to investigate the outcomes of acute kidney injury (AKI) after cardiac surgery by the meta-analysis.Electronic databases PubMed and Embase were searched for relative studies from December 2008 to June 2015. For eligible studies, the R software was conducted to meta-analyze outcomes of AKI patients (AKI group) and none-AKI patients after cardiac surgery (NO AKI group). The chi-square-based Q test and I statistic were used for heterogeneity analysis. P < 0.1 or I > 50% revealed significant heterogeneity among studies, and then a random effects model was used; otherwise a fixed effect model was performed. Egger's test was performed for publication bias assessment. Subgroup analysis was performed by stratifying AKI definitions and study type.Totally 17 studies with 9656 subjects (2331 in the AKI group and 7325 in the NO AKI group) were enrolled. Significantly higher renal replacement therapy (RRT) (OR=23.67, 95%CI: 12.58-44.55), mortality (OR = 6.27, 95%CI: 3.58-11.00), serum creatinine (SMD = 1.42, 95%CI: 1.01-1.83), and hospital length of stay (LOS) (SMD = 0.45, 95%CI: 0.02-0.88) were shown in the AKI group compared with patients in the NO AKI group. Subgroup analysis showed that results of only 3 subgroups were reversed indicating that the definition of AKI did not affect its outcomes. Publication bias was only found among studies involving mortality and serum creatinine, but the 2 outcomes were not reversed after correction.This meta-analysis confirmed the worse outcomes of AKI in patients after cardiac surgery, including higher RRT rates, mortality, and longer hospital LOS than those of NO AKI patients.