Comparison of Plasma and Urine Biomarker Performance in Acute Kidney Injury

Cardiopulmonary bypass associated acute kidney injury: better understanding and better prevention

Cardiopulmonary bypass (CPB) is a common technique in cardiac surgery but is associated with acute kidney injury (AKI), which carries considerable morbidity and mortality. In this review, we explore the range and definition of CPB-associated AKI and discuss the possible impact of different disease recognition methods on research outcomes. Furthermore, we introduce the specialized equipment and procedural intricacies associated with CPB surgeries. Based on recent research, we discuss the potential pathogenesis of AKI that may result from CPB, including compromised perfusion and oxygenation, inflammatory activation, oxidative stress, coagulopathy, hemolysis, and endothelial damage. Finally, we explore current interventions aimed at preventing and attenuating renal impairment related to CPB, and presenting these measures from three perspectives: (1) avoiding CPB to eliminate the fundamental impact on renal function; (2) optimizing CPB by adjusting equipment parameters, optimizing surgical procedures, or using improved materials to mitigate kidney damage; (3) employing pharmacological or interventional measures targeting pathogenic factors.

Identification of a substrate of the renal tubular transporters for detecting drug-induced early acute kidney injury

Early identification of drug-induced acute kidney injury (AKI) is essential to prevent renal damage. The renal tubules are typically the first to exhibit damage, frequently accompanied by changes in renal tubular transporters. With this in mind, we have identified an endogenous substrate of the renal tubular transporters that may serve as a biomarker for early detection of drug-induced AKI. Using gentamicin- and vancomycin-induced AKI models, we found that traumatic acid (TA), an end metabolite, was rapidly increased in both AKI models. TA, a highly albumin-bound compound (96% to 100%), could not be filtered by the glomerulus and was predominantly eliminated by renal tubules via the OAT1, OAT3, OATP4C1, and P-gp transporters. Importantly, there is a correlation between elevated serum TA levels and reduced OAT1 and OAT3 levels. A clinical study showed that serum TA levels rose before an increase in serum creatinine in 13 out of 20 AKI patients in an intensive care unit setting. In addition, there was a notable rise in TA levels in the serum of individuals suffering from nephrotic syndrome, chronic renal failure, and acute renal failure. These results indicate that the decrease in renal tubular transporter expression during drug-induced AKI leads to an increase in the serum TA level, and the change in TA may serve as a monitor for renal tubular injury. Acute kidney injury (AKI) has a high clinical incidence, and if patients do not receive timely treatment and intervention, it can lead to severe consequences. During AKI, tubular damage is often the primary issue. Endogenous biomarkers of tubular damage are critical for the early diagnosis and treatment of AKI. However, there is currently a lack of reliable endogenous biomarkers for diagnosing tubular damage in clinical practice. Tubular secretion is primarily mediated by renal tubular transporters (channels), which are also impaired during tubular damage. Therefore, we aim to identify endogenous biomarkers of tubular damage from the perspective of renal tubular transporters, providing support for the early detection and intervention of AKI. TA is a substrate of multiple channels, including OAT1, OAT3, OATP4C1, and P-gp, and is primarily secreted by the renal tubules. In the early stages of rat AKI induced by GEN and VCA, serum TA levels are significantly elevated, occurring earlier than the rise in serum creatinine (SCr). Thus, TA is expected to become a potential endogenous biomarker for the early diagnosis of tubular damage.

Serum albumin and white matter hyperintensities

People living with HIV and those diagnosed with alcohol use disorders (AUD) relative to healthy individuals commonly have low levels of serum albumin, substantiated as an independent predictor of cardiovascular events. White matter hyperintensities (WMH)-a neuroimaging feature of cerebral small vessel disease-are also related to cardiovascular disease. Despite consensus regarding associations between high levels of urine albumin and WMH prevalence, and low serum albumin levels and impaired cognitive functioning, relations between serum albumin and WMH burdens have rarely been evaluated. Here, a sample including 160 individuals with AUD, 142 living with HIV, and 102 healthy controls was used to test the hypothesis that serum albumin would be inversely related to WMH volumes and directly related to cognitive performance in the two diagnostic groups. Although serum albumin and periventricular WMH volumes showed an inverse relationship in both AUD and HIV groups, this relationship persisted only in the HIV group after consideration of traditional cardiovascular (i.e., age, sex, body mass index (BMI), nicotine use, hypertension, diabetes), study-relevant (i.e., race, socioeconomic status, hepatitis C virus status), and disease-specific (i.e., CD4 nadir, HIV viral load, HIV duration) factors. Further, serum albumin contributed more significantly than periventricular WMH volume to variance in performance on a verbal learning and memory composite score in the HIV group only. Relations in both HIV and AUD groups between albumin and hematological red blood cell markers (e.g., hemoglobin, hematocrit) suggest that in this sample, serum albumin reflects hematological abnormalities. Albumin, a simple serum biomarker available in most clinical settings, may therefore help identify periventricular WMH burden and performance levels in specific cognitive domains in people living with HIV. Whether serum albumin contributes mechanistically to periventricular WMH in HIV will require additional investigation.

Acute and Chronic Kidney Disease Worsen Outcomes in Experimental Sepsis

Key Points

Acute kidney disease (AKD) and CKD are common conditions associated with high rates of incident infection, and poor outcomes once infection have been established. We successfully modeled AKD and CKD in rodents and then administered a cecal slurry solution to create peritonitis and tracked sepsis severity, end organ injury, and inflammatory changes. Our results indicate that AKD mice are more susceptible to infection than CKD mice, developing an aggravated inflammatory response and suggests that this condition predisposes to disparate infection risk.

Background

Infection is a leading cause of morbidity in individuals with acute kidney disease (AKD) and CKD. However, there is significant difficulty in modeling infection into an animal host with preexisting kidney disease. We report a novel method of peritoneal infection induced via cecal slurry (CS) inoculation deployed into mice with experimental aristolochic acid–induced AKD and CKD.

Methods

AKD, CKD, and paired control mice were injected with sham, low, or higher doses of donor–recipient matched CS solution. Animal survival, sepsis severity, and change in GFR were tracked longitudinally throughout the study. Histology for kidney injury, flow cytometry, plasma cytokines, and evidence of indirect organ injury from sepsis were also assessed.

Results

Infected AKD mice experienced significantly heightened sepsis severity, with 100% mortality by 24 hours after high CS doses versus no mortality in control mice. In addition, AKD mice receiving lower CS doses developed dramatically increased proinflammatory cytokines and persistent cytopenias. Infected CKD mice also had worse outcomes than paired CKD controls, although less severe than in AKD mice. Interestingly, animals with AKD had worse outcomes than mice with CKD after any CS dose or time point after inoculation, despite higher baseline kidney function and less uremic sequela.

Conclusions

These data confirm that acute bacterial infection can be modeled in animals with established kidney disease and suggest that the clinical state of kidney disease (AKD versus CKD) may influence host susceptibility to infection more than the degree of kidney failure alone.

Development and validation of a machine learning model to predict the use of renal replacement therapy in 14,374 patients with COVID-19

PURPOSE

To develop a model to predict the use of renal replacement therapy (RRT) in COVID-19 patients.

MATERIALS AND METHODS

Retrospective analysis of multicenter cohort of intensive care unit (ICU) admissions of Brazil involving COVID-19 critically adult patients, requiring ventilatory support, admitted to 126 Brazilian ICUs, from February 2020 to December 2021 (development) and January to May 2022 (validation). No interventions were performed.

RESULTS

Eight machine learning models' classifications were evaluated. Models were developed using an 80/20 testing/train split ratio and cross-validation. Thirteen candidate predictors were selected using the Recursive Feature Elimination (RFE) algorithm. Discrimination and calibration were assessed. Temporal validation was performed using data from 2022. Of 14,374 COVID-19 patients with initial respiratory support, 1924 (13%) required RRT. RRT patients were older (65 [53-75] vs. 55 [42-68]), had more comorbidities (Charlson's Comorbidity Index 1.0 [0.00-2.00] vs 0.0 [0.00-1.00]), had higher severity (SAPS-3 median: 61 [51-74] vs 48 [41-58]), and had higher in-hospital mortality (71% vs 22%) compared to non-RRT. Risk factors for RRT, such as Creatinine, Glasgow Coma Scale, Urea, Invasive Mechanical Ventilation, Age, Chronic Kidney Disease, Platelets count, Vasopressors, Noninvasive Ventilation, Hypertension, Diabetes, modified frailty index (mFI) and Gender, were identified. The best discrimination and calibration were found in the Random Forest (AUC [95%CI]: 0.78 [0.75-0.81] and Brier's Score: 0.09 [95%CI: 0.08-0.10]). The final model (Random Forest) showed comparable performance in the temporal validation (AUC [95%CI]: 0.79 [0.75-0.84] and Brier's Score, 0.08 [95%CI: 0.08-0.1]).

CONCLUSIONS

An early ML model using easily available clinical and laboratory data accurately predicted the use of RRT in critically ill patients with COVID-19. Our study demonstrates that using ML techniques is feasible to provide early prediction of use of RRT in COVID-19 patients.

Serum albumin and white matter hyperintensities

Urine albumin, high in kidney disease, predicts cardiovascular incidents and CNS white matter hyperintensity (WMH) burdens. Serum albumin - a more general biomarker which can be low in several disorders - including kidney and liver disease, malnutrition, and inflammation - also predicts cardiovascular events and is associated with cognitive impairment in several clinical populations; relations between serum albumin and WMH prevalence, however, have rarely been evaluated. In a sample of 160 individuals with alcohol use disorder (AUD), 142 infected with HIV, and 102 healthy controls, the hypothesis was tested that lower serum albumin levels would predict larger WMH volumes and worse cognitive performance irrespective of diagnosis. After considering traditional cardiovascular risk factors (e.g., age, sex, body mass index (BMI), nicotine use, hypertension, diabetes) and study-relevant variables (i.e., primary diagnoses, race, socioeconomic status, hepatitis C virus status), serum albumin survived false discovery rate (FDR)-correction in contributing variance to larger periventricular but not deep WMH volumes. This relationship was salient in the AUD and HIV groups, but not the control group. In secondary analyses, serum albumin and periventricular WMH along with age, sex, diagnoses, BMI, and hypertension were considered for hierarchical contribution to variance in performance in 4 cognitive domains. Albumin survived FDR-correction for significantly contributing to visual and verbal learning and memory performance after accounting for diagnosis. Relations between albumin and markers of liver integrity [e.g., aspartate transaminase (AST)] and blood status (e.g., hemoglobin, red blood cell count, red cell distribution width) suggest that in this sample, albumin reflects both liver dysfunction and hematological abnormalities. The current results suggest that albumin, a simple serum biomarker available in most clinical settings, can predict variance in periventricular WMH volumes and performance in visual and verbal learning and memory cognitive domains. Whether serum albumin contributes mechanistically to periventricular WMH prevalence will require additional investigation.

Urinary Cytokines as Potential Biomarkers of Mild Cognitive Impairment and Alzheimer's Disease: A Pilot Study

Background

Alzheimer's disease (AD) is the most common form of dementia, accounting for 80% of all cases. Mild cognitive impairment (MCI) is a transitional state between normal aging and AD. Early detection is crucial, as irreversible brain damage occurs before symptoms manifest.

Objective

This study aimed to identify potential biomarkers for early detection of AD by analyzing urinary cytokine concentrations. We investigated 37 cytokines in AD, MCI, and cognitively normal individuals (NC), assessing their associations with AD development.

Methods

Urinary cytokine concentrations were measured in AD (n = 25), MCI (n = 25), and NC (n = 26) patients. IL6ST and MMP-2 levels were compared between AD and NC, while TNFRSF8, IL6ST, and IL-19 were assessed in AD versus MCI. Diagnostic models distinguished AD from NC, and in-silico analysis explored molecular mechanisms related to AD.

Results

Significant perturbations in IL6ST and MMP-2 concentrations were observed in AD urine compared to NC, suggesting their potential as biomarkers. TNFRSF8, IL6ST, and IL-19 differed significantly between AD and MCI, implicating them in disease progression. Diagnostic models exhibited promising performance (AUC: 0.59-0.79, sensitivity: 0.72-0.80, specificity: 0.56-0.78) in distinguishing AD from NC. In-silico analysis revealed molecular insights, including relevant non-coding RNAs, microRNAs, and transcription factors.

Conclusion

This study establishes significant associations between urinary cytokine concentrations and AD and MCI. IL6ST, MMP-2, TNFRSF8, IL6ST, and IL-19 emerge as potential biomarkers for early detection of AD. In-silico analysis enhances understanding of molecular mechanisms in AD. Further validation and exploration of these biomarkers in larger cohorts are warranted to assess their clinical utility.

Renal Biomarkers in Cardiovascular Patients with Acute Kidney Injury: A Case Report and Literature Review

Biomarkers have become important tools in the diagnosis and management of cardiorenal syndrome (CRS), a complex condition characterized by dysfunction in both the cardiovascular and renal systems. Biomarkers can help identify the presence and severity of CRS, predict its progression and outcomes, and facilitate personalized treatment options. Several biomarkers, including natriuretic peptides, troponins, and inflammatory markers, have been extensively studied in CRS, and have shown promising results in improving diagnosis and prognosis. In addition, emerging biomarkers, such as kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin, offer potential for early detection and intervention of CRS. However, the use of biomarkers in CRS is still in its infancy, and further research is needed to establish their utility in routine clinical practice. This review highlights the role of biomarkers in the diagnosis, prognosis, and management of CRS, and discusses their potential as valuable clinical tools for personalized medicine in the future.

Urine Complement Factor Ba Is Associated with AKI in Critically Ill Children

Key Points

Complement activation, specifically factor B, is implicated in AKI pathogenesis in animal models. Urine Ba (an activation fragment of factor B) was significantly higher in critically ill children with stage 3 AKI and sepsis-AKI. If larger studies show similar association between urine Ba and AKI severity, clinical trials of factor B inhibition are warranted.

Background:

Critically ill children with AKI have high morbidity and mortality rates and lack treatment options. Complement activation is implicated in AKI pathogenesis, which could be treated with complement-targeted therapeutics. We assessed for an association between urine Ba, an activation fragment of the alternative complement pathway, and AKI in a large cohort of critically ill children.

Methods:

A biorepository of children requiring mechanical ventilation was leveraged. AKI was based on pediatric version of the RIFLE criteria—stage 1: 25% decreased eGFR or urine output (UOP) <0.5ml/kg per hour for 8 hours; stage 2: 50% decreased eGFR or UOP <0.5 ml/kg per hour for 16 hours; stage 3: 75% decreased eGFR or UOP <0.3ml/kg per hour for 24 hours or anuric for 12 hours. ELISAs were performed to quantitate urine Ba values. Log Ba was used in ANOVA with pairwise comparison by the Tukey method. Logistic regression was performed to test the association between urine Ba and AKI diagnosis.

Results:

Seventy-three patients were included, of which 56 had AKI: 26 (46%) stage 1, 16 (29%) stage 2, and 14 (25%) stage 3. Ba was significantly higher in patients with stage 3 AKI compared with all other stages. Ba was higher in sepsis-associated AKI compared with non–sepsis-associated AKI. Multivariate analysis included urine Ba, urine IL-18, urine NGAL, sepsis, and Pediatric Risk of Mortality Scores-II (an estimate of illness severity) and showed a significant association between urine Ba and AKI (odds ratio 1.57, 95% confidence interval, 1.13 to 2.20; P 0.007).

Conclusion:

Urine Ba is significantly increased in patients with AKI compared with patients without AKI. In patients with similar illness severity, a doubling of urine Ba level was associated with a 57% increase in AKI diagnosis of any stage. Further studies are needed to study complement inhibition in treatment or prevention of AKI in critically ill children.

Assessment of Renal Function in Head and Neck Cancer Patients Treated with Cisplatin: Different Biomarkers and Acute Kidney Injury Classifications

Cisplatin is associated with dose-limiting nephrotoxicity, and the timely detection of acute kidney injury (AKI) can affect morbimortality. Therefore, this study aimed to investigate the tools for monitoring renal function in AKI. This was a retrospective, cohort study. Cisplatin-treated patients with head and neck cancer were included. Nephrotoxicity was assessed using serum creatinine, estimated creatinine clearance, serum electrolytic alterations, and plasma kidney injury molecule-1 (KIM-1). The toxicity severity was classified according to Common Terminology Criteria for Adverse Events (CTCAE), and AKI was classified by Risk, Injury, Failure, Loss, and End-stage kidney disease (RIFLE) and Acute Kidney Injury Network (AKIN). A total of 81 participants were included, of whom only 32 did not have AKI. Almost 90% of participants had a decreased estimated glomerular filtration rate five (D5) days after chemotherapy. The AKI estimate differs between AKIN and RIFLE; more participants were diagnosed by the RIFLE at D5, 19.5% versus 2.4% by AKIN, and fifteen had a discordance between these classifications. All laboratory markers showed significant changes on D5. KIM-1 appeared a possible biomarker when considering CTCAE or AKIN classifications (p < 0.05 on D5), but not when RIFLE classification was used (p = 0.0780). Further studies may seek to understand the profiles of different biomarkers together.

Utility of plasma NGAL for the diagnosis of AKI following cardiac surgery requiring cardiopulmonary bypass: a systematic review and meta-analysis

The objective of this study was to assess the diagnostic value of plasma neutrophil gelatinase-associated lipocalin (pNGAL) for the early diagnosis of acute kidney injury (AKI) in adult patients following cardiac surgery requiring cardiopulmonary bypass (CPB). Electronic databases and other resources were systematically searched for relevant studies. Risk of bias was assessed using the Quality Assessment for Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Studies were assigned to a sub-group based on the timing of the pNGAL sample in relation to the cessation of CPB. These were < 4 h, 4–8 h, 12 h or 24 h post-cessation of CPB. Summary values for sensitivity and specificity were estimated using the hierarchical summary receiver operator characteristic (ROC) curve model. A random-effects meta-analysis of each pair of sensitivity and specificity estimates from each included study was performed. In total, 3131 patients from 16 studies were included. When taken at 4–8 h following CPB, pNGAL had superior performance for the diagnosis of AKI in the defined population when compared to earlier and later time points. Prediction regions and confidence intervals, however, demonstrated significant variability in pooled estimates of sensitivity and specificity. This is likely due to population and study design heterogeneity, lack of standardisation of assays and thresholds, and inability to distinguish the different molecular forms of NGAL. In conclusion, the diagnostic utility of pNGAL in this clinical setting is inconclusive and large individual studies of representative populations of cardiac surgery patients using assays that specifically detect NGAL in its monomeric form are required.

Biomarkers for assessing acute kidney injury for people who are being considered for admission to critical care: a systematic review and cost-effectiveness analysis

BACKGROUND

Acute kidney injury is a serious complication that occurs in the context of an acute critical illness or during a postoperative period. Earlier detection of acute kidney injury may facilitate strategies to preserve renal function, prevent further disease progression and reduce mortality. Acute kidney injury diagnosis relies on a rise in serum creatinine levels and/or fall in urine output; however, creatinine is an imperfect marker of kidney function. There is interest in the performance of novel biomarkers used in conjunction with existing clinical assessment, such as NephroCheck^® (Astute Medical, Inc., San Diego, CA, USA), ARCHITECT^® urine neutrophil gelatinase-associated lipocalin (NGAL) (Abbott Laboratories, Abbott Park, IL, USA), and urine and plasma BioPorto NGAL (BioPorto Diagnostics A/S, Hellerup, Denmark) immunoassays. If reliable, these biomarkers may enable earlier identification of acute kidney injury and enhance management of those with a modifiable disease course.

OBJECTIVE

The objective was to evaluate the role of biomarkers for assessing acute kidney injury in critically ill patients who are considered for admission to critical care.

DATA SOURCES

Major electronic databases, conference abstracts and ongoing studies were searched up to June 2019, with no date restrictions. MEDLINE, EMBASE, Health Technology Assessment Database, Cumulative Index to Nursing and Allied Health Literature, Cochrane Central Register of Controlled Trials, Web of Science, World Health Organization Global Index Medicus, EU Clinical Trials Register, International Clinical Trials Registry Platform and ClinicalTrials.gov were searched.

REVIEW METHODS

A systematic review and meta-analysis were conducted to evaluate the performance of novel biomarkers for the detection of acute kidney injury and prediction of other relevant clinical outcomes. Random-effects models were adopted to combine evidence. A decision tree was developed to evaluate costs and quality-adjusted life-years accrued as a result of changes in short-term outcomes (up to 90 days), and a Markov model was used to extrapolate results over a lifetime time horizon.

RESULTS

A total of 56 studies (17,967 participants), mainly prospective cohort studies, were selected for inclusion. No studies addressing the clinical impact of the use of biomarkers on patient outcomes, compared with standard care, were identified. The main sources of bias across studies were a lack of information on blinding and the optimal threshold for NGAL. For prediction studies, the reporting of statistical details was limited. Although the meta-analyses results showed the potential ability of these biomarkers to detect and predict acute kidney injury, there were limited data to establish any causal link with longer-term health outcomes and there were considerable clinical differences across studies. Cost-effectiveness results were highly uncertain, largely speculative and should be interpreted with caution in the light of the limited evidence base. To illustrate the current uncertainty, 15 scenario analyses were undertaken. Incremental quality-adjusted life-years were very low across all scenarios, ranging from positive to negative increments. Incremental costs were also small, in general, with some scenarios generating cost savings with tests dominant over standard care (cost savings with quality-adjusted life-year gains). However, other scenarios generated results whereby the candidate tests were more costly with fewer quality-adjusted life-years, and were thus dominated by standard care. Therefore, it was not possible to determine a plausible base-case incremental cost-effectiveness ratio for the tests, compared with standard care.

LIMITATIONS

Clinical effectiveness and cost-effectiveness results were hampered by the considerable heterogeneity across identified studies. Economic model predictions should also be interpreted cautiously because of the unknown impact of NGAL-guided treatment, and uncertain causal links between changes in acute kidney injury status and changes in health outcomes.

CONCLUSIONS

Current evidence is insufficient to make a full appraisal of the role and economic value of these biomarkers and to determine whether or not they provide cost-effective improvements in the clinical outcomes of acute kidney injury patients.

FUTURE WORK

Future studies should evaluate the targeted use of biomarkers among specific patient populations and the clinical impact of their routine use on patient outcomes and management.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42019147039.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Evidence Synthesis programme and will be published in full in Health Technology Assessment; Vol. 26, No. 7. See the NIHR Journals Library website for further project information.

Neutrophil Gelatinase-Associated Lipocalin Acts as a Robust Early Diagnostic Marker for Renal Replacement Therapy in Patients with Russell's Viper Bite-Induced Acute Kidney Injuries

Snakebite-induced acute kidney injury (AKI) is frequently observed in patients following bites from vipers such as Russell's viper (Daboia russelii) in India. Currently, the levels of serum creatinine are mainly used as a marker to determine the necessity for renal replacement therapy (RRT) (haemodialysis) in severe cases of AKI. However, it takes up to 48 h to ascertain a distinct change in creatinine levels compared to its baseline level upon admission. The time lost between admission and the 48 h timepoint significantly affects the clinical management of snakebite victims. Moreover, early diagnosis of AKI and decision on the necessity for RRT in snakebite victims is critical in saving lives, reducing long-term complications, and minimising treatment costs arising from expensive haemodialysis. Neutrophil gelatinase-associated lipocalin (NGAL) has been recently studied as a robust early marker for AKI in non-snakebite patients. However, its suitability for clinical use in snakebite victims has not been rigorously established. Here, we demonstrate the clinical significance of plasma NGAL as a robust marker for RRT following AKI using a large cohort (309) of Russell's viper victims without any pre-existing health conditions. NGAL levels upon admission are positively correlated with creatinine levels at 48 h in different stages of AKI. Overall, NGAL acts as a robust early marker to ascertain the need for RRT following Russell's viper bites. The quantification of NGAL can be recommended as a routine test in hospitals that treat snakebites to decide on RRT at early time points instead of waiting for 48 h to confirm the increase in creatinine levels. The diagnostic use of NGAL in Russell's viper victims with pre-existing comorbidities and for other vipers should be evaluated in future studies.

Evaluating kidney function using a point-of-care creatinine test in Ugandan children with severe malaria: a prospective cohort study

Background

Acute kidney injury (AKI) disproportionately affects individuals in low-and middle-income countries (LMIC). However, LMIC—particularly countries in sub-Saharan Africa— are under-represented in global AKI research. A critical barrier in diagnosing AKI is access to reliable serum creatinine results. We evaluated the utility of a point-of-care test to measure creatinine and diagnose AKI in Ugandan children with malaria.

Methods

Paired admission creatinine was assessed in 539 Ugandan children 6 months to 4 years of age hospitalized with severe malaria based on blood smear or rapid diagnostic test. Creatinine levels were measured using isotope dilution mass spectrometry (IDMS)-traceable methods. The reference creatinine was measured using the modified Jaffe method by a certified laboratory and the point-of-care testing was conducted using an i-STAT blood analyzer (i-STAT1, with and without adjustment for the partial pressure of carbon dioxide). AKI was defined and staged using the Kidney Disease: Improving Global Outcomes criteria.

Results

The mean age of children was 2.1 years, and 21.6% of children were stunted. Mortality was 7.6% in-hospital. Over the entire range of measured creatinine values (<0.20mg/dL-8.4mg/dL), the correlation between the reference creatinine and adjusted and unadjusted point-of-care creatinine was high with R² values of 0.95 and 0.93 respectively; however, the correlation was significantly lower in children with creatinine values <1mg/dL (R² of 0.44 between the reference and adjusted and unadjusted i-STAT creatinine). The prevalence of AKI was 45.5% using the reference creatinine, and 27.1 and 32.3% using the unadjusted and adjusted point-of-care creatinine values, respectively. There was a step-wise increase in mortality across AKI stages, and all methods were strongly associated with mortality (p<0.0001 for all). AKI defined using the reference creatinine measure was the most sensitive to predict mortality with a sensitivity of 85.4% compared to 70.7 and 63.4% with the adjusted and unadjusted point-of-care creatinine values, respectively.

Conclusions

Point-of-care assessment of creatinine in lean Ugandan children <4 years of age underestimated creatinine and AKI compared to the clinical reference. Additional studies are needed to evaluate other biomarkers of AKI in LMIC to ensure equitable access to AKI diagnostics globally.

Diagnostic Value of Multiple Serum Biomarkers for Vancomycin-Induced Kidney Injury

Acute kidney injury (AKI) is a major contributor to in-hospital morbidity and mortality. Vancomycin, one of the most commonly used antibiotics in a clinical setting, is associated with AKI, with its incidence ranging up to 43%. Despite the high demand, few studies have investigated serum biomarkers to detect vancomycin-induced kidney injury (VIKI). Here, we evaluated the diagnostic value of nine candidate serum biomarkers for VIKI. A total of 23,182 cases referred for vancomycin concentration measurement from January 2018 to December 2019 were screened and 28 subjects with confirmed VIKI were enrolled (VIKI group). Age- and sex- matched control group consisted of 21 subjects who underwent vancomycin therapy without developing VIKI (non-VIKI group), and 23 healthy controls (HC group). The serum concentrations of clusterin, retinol binding protein 4 (RBP4), interleukin-18 (IL-18), tumor necrosis factor receptor 1 (TNF-R1), C-X-C motif chemokine ligand 10 (CXCL10), neutrophil gelatinase-associated lipocalin (NGAL), osteopontin, trefoil factor-3 (TFF3), and cystatin C were compared among the three groups, and their correlations with estimated glomerular filtration rate (eGFR) and diagnostic values for VIKI were assessed. All of the biomarkers except clusterin and RBP4 exhibited significant elevation in the VIKI group. Serum TFF3, cystatin C, TNF-R1, and osteopontin demonstrated an excellent diagnostic value for VIKI (TFF3, area under the curve (AUC) 0.932; cystatin C, AUC 0.917; TNF-R1, AUC 0.866; osteopontin, AUC 0.787); and except osteopontin, a strong negative correlation with eGFR (TFF3, r = −0.71; cystatin C, r = −0.70; TNF-R1, r = −0.60). IL-18, CXCL10, and NGAL showed weak correlation with eGFR and moderate diagnostic value for VIKI. This study tested multiple serum biomarkers for VIKI and showed that serum TFF3, cystatin C, TNF-R1, and osteopontin could efficiently discriminate VIKI patients. Further studies are warranted to clarify the diagnostic value of these biomarkers in VIKI.

Malaria-Associated Acute Kidney Injury in African Children: Prevalence, Pathophysiology, Impact, and Management Challenges

Acute kidney injury (AKI) is emerging as a complication of increasing clinical importance associated with substantial morbidity and mortality in African children with severe malaria. Using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria to define AKI, an estimated 24–59% of African children with severe malaria have AKI with most AKI community-acquired. AKI is a risk factor for mortality in pediatric severe malaria with a stepwise increase in mortality across AKI stages. AKI is also a risk factor for post-discharge mortality and is associated with increased long-term risk of neurocognitive impairment and behavioral problems in survivors. Following injury, the kidney undergoes a process of recovery and repair. AKI is an established risk factor for chronic kidney disease and hypertension in survivors and is associated with an increased risk of chronic kidney disease in severe malaria survivors. The magnitude of the risk and contribution of malaria-associated AKI to chronic kidney disease in malaria-endemic areas remains undetermined. Pathways associated with AKI pathogenesis in the context of pediatric severe malaria are not well understood, but there is emerging evidence that immune activation, endothelial dysfunction, and hemolysis-mediated oxidative stress all directly contribute to kidney injury. In this review, we outline the KDIGO bundle of care and highlight how this could be applied in the context of severe malaria to improve kidney perfusion, reduce AKI progression, and improve survival. With increased recognition that AKI in severe malaria is associated with substantial post-discharge morbidity and long-term risk of chronic kidney disease, there is a need to increase AKI recognition through enhanced access to creatinine-based and next-generation biomarker diagnostics. Long-term studies to assess severe malaria-associated AKI’s impact on long-term health in malaria-endemic areas are urgently needed.

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.

Urinary vanin-1 for predicting acute pyelonephritis in young children with urinary tract infection: a pilot study

BACKGROUND

Vanin-1, an epithelial glycosylphosphatidylolinositol (GPI)-anchored pantetheinase, is a valuable marker of renal injury.

PURPOSE

The aim of this study was to assess the predictive value of vanin-1 in acute pyelonephritis (APN) in comparison to the conventional serum inflammatory markers in children aged 1-24 months with the first episode of urinary tract infection (UTI).

MATERIAL AND METHODS

Urinary vanin-1, vanin-1/Cr ratio, WBC, CRP, PCT were analysed in 58 children with febrile UTI and in 18 children with non-febrile UTI. Febrile UTI group was divided into APN subgroup (n = 29) and non-APN subgroup (n = 29), based on the results of Tc-99m-ethylenedicysteine scan.

RESULTS

The mean vanin-1 level was higher in the APN group compared to the non-febrile UTI group (p = 0.02) and did not differ between APN and non-APN subgroup. In univariate analysis, vanin-1 (p = 0.042), CRP (p < 0.001), PCT (p < 0.001), and WBC (p = 0.022), were associated with APN, but only vanin-1 (p = 0.048) and CRP (p = 0.002) were independent markers of APN. In ROC analysis, vanin-1, with its best cut-off value of 16.53 ng/mL, had worse diagnostic profile (AUC 0.629, sensitivity 58,6%, specificity 63.8%) than CRP, PCT and WBC (AUC: 0.937; 0.880; 0.667, respectively).

CONCLUSIONS

Vanin-1 is not useful for predicting APN, since its diagnostic value is inferior to other conventional serum inflammatory markers.

Pulmonary and renal tolerance of cisplatin-based regimens combining intravenous and endotracheal routes for lung cancer treatment in mice

Despite recent advances, platinum-based chemotherapy (partially composed of cisplatin, CIS) remains the backbone of non-small-cell lung cancer treatment. As CIS presents a cumulative and dose-limiting nephrotoxicity, it is currently administered with an interruption phase of 3-4 weeks between treatment cycles. During these periods, the patient recovers from the treatment side effects but so does the tumour. Our strategy is to increase the treatment frequency by delivering a cisplatin controlled-release dry powder for inhalation (CIS-DPI) formulation during these off-cycles to expose the tumour environment for longer to CIS, increasing its effectiveness. This is promising as long as the pulmonary and renal toxicities remain acceptable. The aim of the present investigation was to evaluate the pulmonary and renal tolerance of CIS-DPI (three times per cycle) and CIS using the intravenous (IV) route (CIS-IV) (one time per cycle) as monotherapies and to optimize their combination in terms of dose and schedule. At the maximum tolerated dose (MTD), combining CIS-DPI and CIS-IV impaired the pulmonary and the renal tolerance. Therefore, pulmonary tolerance was improved when the CIS-IV dose was decreased by 25% (to 1.5 mg/kg) while maintaining the MTD for CIS-DPI. In addition to this dose adjustment, a delay of 24 h between CIS-DPI and CIS-IV administrations limited the acute kidney injury.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The Marker of Tubular Injury, Kidney Injury Molecule-1 (KIM-1), in Acute Kidney Injury Complicating Acute Pancreatitis: A Preliminary Study

Acute pancreatitis (AP) may be associated with severe inflammation and hypovolemia leading to organ complications including acute kidney injury (AKI). According to current guidelines, AKI diagnosis is based on dynamic increase in serum creatinine, however, creatinine increase may be influenced by nonrenal factor and appears late following kidney injury. Kidney injury molecule-1 (KIM-1) is a promising marker of renal tubular injury and it has not been studied in AP. Our aim was to assess if urinary KIM-1 may be used to diagnose AKI complicating the early stage of AP. We recruited 69 patients with mild to severe AP admitted to a secondary care hospital during the first 24 h from initial symptoms of AP. KIM-1 was measured in urine samples collected on the day of admission and two subsequent days of hospital stay. AKI was diagnosed based on creatinine increase according to Kidney Disease: Improving Global Outcomes 2012 guidelines. Urinary KIM-1 on study days 1 to 3 was not significantly higher in 10 patients who developed AKI as compared to those without AKI and did not correlate with serum creatinine or urea. On days 2 and 3, urinary KIM-1 correlated positively with urinary liver-type fatty acid-binding protein, another marker of tubular injury. On days 2 and 3, urinary KIM-1 was higher among patients with systemic inflammatory response syndrome, and several correlations between KIM-1 and inflammatory markers (procalcitonin, urokinase-type plasminogen activator receptor, C-reactive protein) were observed on days 1 to 3. With a limited number of patients, our study cannot exclude the diagnostic utility of KIM-1 in AP, however, our results do not support it. We hypothesize that the increase of KIM-1 in AKI complicating AP lasts a short time, and it may only be observed with more frequent monitoring of the marker. Moreover, urinary KIM-1 concentrations in AP are associated with inflammation severity.

Biological variation in kidney injury and kidney function biomarkers among farmers in Lamphun province, Thailand

Frequent and long-term exposure to pesticides can induce acute kidney injury and subsequent chronic kidney diseases. In this study, we aimed to investigate the correlation between kidney injury, kidney function biomarkers, and pesticide use in farmers from the Pasang district, Lamphun province, Thailand. A cross-sectional study was performed in 59 farmers occupationally exposed to various types of pesticides. The levels of urinary neutrophil gelatinase-associated lipocalin (uNGAL), serum creatinine (sCr), urinary microalbumin-to-creatinine ratio (ACR), serum cystatin C (sCys-C), estimated glomerular filtration rate (eGFR), and exposure intensity index (EII) were evaluated. Spearman's correlation and a linear regression analysis were carried out to investigate the association between age, pesticide use, EII, kidney injury markers, and kidney function biomarkers. The most common pesticide used in this study area was glyphosate, followed by paraquat and iprodione. Urinary NGAL levels showed a significant correlation with sCys-C levels, EII, and eGFR Cr-Cys. In addition, the sCr levels were associated with glyphosate use (B = 0.08) and EII (B = 0.01). In conclusion, occupation exposure to pesticides is likely to be linked to kidney injury and dysfunction. Pesticide mix status, pesticide application method, equipment repair status, and personal protective equipment (PPE) use are all involved in changes in kidney markers.

Biomarkers for Diagnosis and Prediction of Outcomes in Contrast-Induced Nephropathy

Background

Serum creatinine is suboptimal as a biomarker in the early diagnosis of contrast-induced nephropathy (CIN). In this study, we investigated a panel of novel biomarkers in the early diagnosis of CIN and in assessing patient outcomes.

Methods

This single-centre, nested, prospective case-controlled study included 30 patients with CIN and 60 matched controls. Serum and urine samples were collected before contrast administration and at 24 hours, 48 hours, and ≥5 days after contrast administration. Concentrations of NGAL, cystatin C, β₂M, IL18, IL10, KIM1, and TNFα were determined using Luminex and ELISA assays. Outcomes were biomarker diagnostic discrimination performance for CIN and mortality after generation of area under receiver operating characteristic curves (AUROCs).

Results

Median serum levels for 24 h cystatin C (p < 0.01) and 48 h β₂M levels (p < 0.001) and baseline urine NGAL (p=0.02) were higher in CIN patients compared to controls with AUROCs of 0.75, 0.78, and 0.74, respectively, for the early diagnosis of CIN. Serum β₂M levels were higher in CIN patients at all time points. Elevated baseline serum concentrations of IL18 (p < 0.001), β₂M (p=0.04), TNFα (p < 0.001), and baseline urine KIM (p=0.01) and 24 h urine NGAL (p=0.02) were significantly associated with mortality. Baseline serum concentrations of IL18, β₂M, and TNFα showed the best discrimination performance for mortality with AUROCs, all >0.80. Baseline NGAL was superior for excluding patients at risk for CIN, with positive and negative predictive ranges of 0.50–0.55 and 0.81–0.88, respectively. Cystatin C (p=0.003) and β₂M (p=0.03) at 24 h independently predicted CIN risk. β₂M predicted increased mortality of 40% at baseline and 50% at 24 hours.

Conclusion

Serum cystatin C at 24 h was the best biomarker for CIN diagnosis, while baseline levels of serum IL18, β₂M, and TNFα were best for predicting prognosis.

Prognostic value of serum and urine kidney injury molecule-1 in infants with urinary tract infection

Introduction

Kidney injury molecule-1 (KIM-1) is an important diagnostic and prognostic marker in acute kidney injury and chronic kidney disease of various aetiologies. The aim of the study was to evaluate the usefulness of serum KIM-1 (sKIM-1) and urine KIM-1 (uKIM-1) for predicting febrile and non-febrile urinary tract infection (UTI) in infants.

Material and methods

A prospective study included 101 children divided into three groups: febrile UTI 49 children, non-febrile UTI 22 children, and healthy controls 30 children. The following laboratory tests were performed: sKIM-1, uKIM-1, white blood count (WBC), C-reactive protein (CRP), and procalcitonin (PCT).

Results

Median levels of sKIM-1 were significantly higher in the febrile and non-febrile UTI group compared to the healthy controls (both p < 0.05). Mean levels of uKIM-1 were significantly lower in the febrile UTI group compared to the non-febrile UTI group and healthy controls (p < 0.001 and p < 0.0001, respectively). Univariate logistic regression analysis has demonstrated a positive association of sKIM-1 with febrile and non-febrile UTI (both p < 0.05), and negative association uKIM-1 with febrile UTI (p < 0.0001). Receiver operating curve (ROC) analysis showed good diagnostic profiles of uKIM-1 with a best cut-off value of 2.4 ng/ml and sKIM-1 with a best cut-off value of 3.88 ng/ml for predicting febrile UTI (area under the curve [AUC] 0.82 and 0.67, sensitivity 73% and 63%, specificity 86% and 80%, respectively).

Conclusions

sKIM-1 can be useful for predicting febrile UTI. We do not recommended use of uKIM-1 as a marker of febrile UTI because of its negative association with febrile UTI. Both markers are not useful for predicting non-febrile UTI.

A novel urinary biomarker predicts 1-year mortality after discharge from intensive care

Rationale

The urinary proteome reflects molecular drivers of disease.

Objectives

To construct a urinary proteomic biomarker predicting 1-year post-ICU mortality.

Methods

In 1243 patients, the urinary proteome was measured on ICU admission, using capillary electrophoresis coupled with mass spectrometry along with clinical variables, circulating biomarkers (BNP, hsTnT, active ADM, and NGAL), and urinary albumin. Methods included support vector modeling to construct the classifier, Cox regression, the integrated discrimination (IDI), and net reclassification (NRI) improvement, and area under the curve (AUC) to assess predictive accuracy, and Proteasix and protein-proteome interactome analyses.

Measurements and main results

In the discovery (deaths/survivors, 70/299) and test (175/699) datasets, the new classifier ACM128, mainly consisting of collagen fragments, yielding AUCs of 0.755 (95% CI, 0.708–0.798) and 0.688 (0.656–0.719), respectively. While accounting for study site and clinical risk factors, hazard ratios in 1243 patients were 2.41 (2.00–2.91) for ACM128 (+ 1 SD), 1.24 (1.16–1.32) for the Charlson Comorbidity Index (+ 1 point), and ≥ 1.19 (P ≤ 0.022) for other biomarkers (+ 1 SD). ACM128 improved (P ≤ 0.0001) IDI (≥ + 0.50), NRI (≥ + 53.7), and AUC (≥ + 0.037) over and beyond clinical risk indicators and other biomarkers. Interactome mapping, using parental proteins derived from sequenced peptides included in ACM128 and in silico predicted proteases, including/excluding urinary collagen fragments (63/35 peptides), revealed as top molecular pathways protein digestion and absorption, lysosomal activity, and apoptosis.

Conclusions

The urinary proteomic classifier ACM128 predicts the 1-year post-ICU mortality over and beyond clinical risk factors and other biomarkers and revealed molecular pathways potentially contributing to a fatal outcome.

The Clinical Utility and Assessment of Renal Biomarkers in Acute Kidney Injury After Abdominal Endovascular Aneurysm Repair. A Systematic Review

The widespread adoption of endovascular aneurysm repair (EVAR) for abdominal aortic aneurysms (AAA) is due to the obvious advantages of the procedure compared to the traditional open repair. However, these advantages have to be weighed against the increased risk of renal dysfunction with EVAR. The evaluation of the perioperative renal function after EVAR has been hampered by the lack of sensitive and specific biochemical markers of acute kidney injury (AKI). The purpose of this study was to summarize all novel renal biomarkers and to evaluate their clinical utility for the assessment of the kidney function after EVAR. A systematic review of the current literature, as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines, was performed to identify relevant studies with novel renal biomarkers and EVAR. Pubmed and Scopus databases were systemically searched. Studies reporting on thoracic endovascular aortic repair (TEVAR), case reports, case series, letters to the editor, and systematic reviews were excluded. Neutrophil-Gelatinase-Associated Lipocalin, Cystatin C, Liver-type fatty-acid-binding protein were the most common among the eligible studies while Interleukin-18, Retinol binding protein, N-acetyle-b-D-glucosaminidase and microalbumin have a sparse appearance in the literature. These biomarkers have been assessed in plasma as well as urine samples with each sample material having its own advantages and drawbacks. Which of these biomarkers has the most potential for assessing postoperative renal failure after EVAR, remains to be proved. The few studies presented in the literature show the potential clinical utility of these biomarkers, but larger studies with longer follow-up are required to determine the precise relationship between these biomarkers and postoperative acute kidney injury.

Cardiovascular Risk Assessment for Noncardiac Surgery: Are We Ready for Biomarkers?

Biomarkers aided perioperative cardiac assessment is a relatively new concept. Cardiac biomarkers with historical significance (aspartate transaminase, dehydrogenase, creatinine kinase and myoglobin) have paved the way for traditional biomarkers (cardiac troponin, C-reactive protein, lipoprotein). Contemporary biomarkers like natriuretic peptides (BNP and ProBNP) are validated risk markers in both acute and chronic cardiac diseases and are showing remarkable promise in predicting serious cardiovascular complications after non-cardiac surgery. This review is intended to provide a critical overview of traditional and contemporary biomarkers for perioperative cardiovascular assessment and management. This review also discusses the potential utility of newer biomarkers like galectin-3, sST-2, GDF-15, TNF-alpha, MiRNAs and many others that can predict inflammation, cardiac remodeling, injury and endogenous stress and need further investigations to establish their clinical utility. Though promising, biomarker led perioperative care is still in infancy and it has not been determined that it can improve clinical outcomes.

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.

Twenty-four hour pharmacokinetic relationships for intravenous vancomycin and novel urinary biomarkers of acute kidney injury in a rat model

OBJECTIVES

To identify the pharmacokinetic (PK) and toxicodynamic (TD) relationship for vancomycin-induced kidney injury.

METHODS

Male Sprague-Dawley rats received intravenous (iv) vancomycin. Doses ranging from 150 mg/kg/day to 400 mg/kg/day were administered as a single or twice-daily injection over 24 h (total protocol duration). Controls received iv saline. Plasma was sampled with up to eight samples in 24 h per rat. Twenty-four hour urine was collected and assayed for kidney injury molecule 1 (KIM-1), osteopontin and clusterin. Vancomycin in plasma was quantified via LC-MS/MS. PK analyses were conducted using Pmetrics for R. PK exposures during the first 24 h (i.e. AUC0-24h, Cmax 0-24h and Cmin 0-24h) were calculated. PK/TD relationships were assessed with Spearman's rank coefficient (rs) and the best-fit mathematical model.

RESULTS

PK/TD data were generated from 45 vancomycin-treated and 5 control rats. A two-compartment model fit the data well (Bayesian: observed versus predicted R2 = 0.97). Exposure-response relationships were found between AUC0-24h versus KIM-1 and osteopontin (R2 = 0.61 and 0.66) and Cmax 0-24h versus KIM-1 and osteopontin (R2 = 0.50 and 0.56) using a four-parameter Hill fit. Conversely, Cmin 0-24h was less predictive of KIM-1 and osteopontin (R2 = 0.46 and 0.53). A vancomycin AUC0-24h of 482.2 corresponded to a 90% of maximal rise in KIM-1.

CONCLUSIONS

Vancomycin-induced kidney injury as defined by urinary biomarkers is driven by vancomycin AUC or Cmax rather than Cmin. Further, an identified PK/TD target AUC0-24h of 482.2 mg·h/L may have direct relevance to human outcomes.

Predictive value of plasma neutrophil gelatinase-associated lipocalin in acute charcoal-burning carbon monoxide poisoning

This study aimed to assess the feasibility of using the plasma neutrophil gelatinase-associated lipocalin (NGAL) level at the time of presentation in the emergency department (ED) to predict acute kidney injury (AKI) and the long-term neurological outcomes of acute charcoal-burning carbon monoxide (CO) poisoning. This retrospective study included 260 patients who suffered acute charcoal-burning CO poisoning. The median plasma NGAL concentration at the time of presentation in the ED after acute charcoal-burning CO poisoning was 78 (54–115) ng/ml. The NGAL level was an independent predictor of AKI development and could be used to stratify the severity of AKI. However, the area under the receiver operating characteristic curve (AUC) of the predictive model for AKI that included both the plasma NGAL level and clinical parameters was comparable to that of the predictive model including only the clinical parameters. The plasma NGAL level at the time of presentation in the ED was an independent factor predicting long-term neurological outcomes in patients who did not develop AKI. In these patients, the plasma NGAL level significantly improved the predictive accuracy of the model when used in combination with clinical parameters. In contrast, the plasma NGAL level was not associated with long-term neurological outcomes in patients who developed AKI. Measurement of the plasma NGAL level at the time ED presentation might improve the prediction of long-term neurological outcomes in patients who do not develop AKI after acute charcoal-burning CO poisoning. However, it might not offer additional benefit for AKI prediction compared to previously used markers.

Assessment of lipid peroxidation and artificial neural network models in early Alzheimer Disease diagnosis

OBJECTIVE

Lipid peroxidation constitutes a molecular mechanism involved in early Alzheimer Disease (AD) stages, and artificial neural network (ANN) analysis is a promising non-linear regression model, characterized by its high flexibility and utility in clinical diagnosis. ANN simulates neuron learning procedures and it could provide good diagnostic performances in this complex and heterogeneous disease compared with linear regression analysis.

DESIGN AND METHODS

In our study, a new set of lipid peroxidation compounds were determined in urine and plasma samples from patients diagnosed with early Alzheimer Disease (n = 70) and healthy controls (n = 26) by means of ultra-performance liquid chromatography coupled with tandem mass-spectrometry. Then, a model based on ANN was developed to classify groups of participants.

RESULTS

The diagnostic performances obtained using an ANN model for each biological matrix were compared with the corresponding linear regression model based on partial least squares (PLS), and with the non-linear (radial and polynomial) support vector machine (SVM) models. Better accuracy, in terms of receiver operating characteristic-area under curve (ROC-AUC), was obtained for the ANN models (ROC-AUC 0.882 in plasma and 0.839 in urine) than for PLS and SVM models.

CONCLUSION

Lipid peroxidation and ANN constitute a useful approach to establish a reliable diagnosis when the prognosis is complex, multidimensional and non-linear.

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

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

A scrutiny of circulating microRNA biomarkers for drug-induced tubular and glomerular injury in rats

Drug-induced acute kidney injury (AKI) is a frequent cause of adverse drug reaction. Serum creatinine (CRE) and blood urea nitrogen (BUN) are widely used as standard biomarkers for kidney injury; however, the sensitivity and specificity are considered to be low. In recent years, circulating microRNA (miRNAs) have been attracting considerable attention as novel biomarkers for organ injury, but there are currently no established miRNA biomarkers for drug-induced AKI. The present study aimed to identify plasma miRNAs that may enable early and specific detection of drug-induced tubular and glomerular injury through next-generation sequencing analysis. Six-week old male Sprague-Dawley (SD) rats were intravenously administered cisplatin (CSP, 6 mg/kg) and gentamicin (GEN, 120 mg/kg) to induce tubular injury. To create glomerular injury models, puromycin (PUR, 120 mg/kg) and doxorubicin (DOX, 7.5 mg/kg) were intravenously administered, and these models were always accompanied by tubular damage. Small RNA-sequencing was performed to analyze time-dependent changes in the plasma miRNA profiles. The cluster analyses showed that there were distinct plasma miRNA profiles according to the types of injury, and the changes reflected the progress of renal damages. In the differential analysis, miR-3473 was specifically up-regulated in the glomerular injury models. miR-143-3p and miR-122-5p were commonly down-regulated in all models, and the changes were earlier than the traditional biomarkers, such as plasma CRE and BUN. These data indicated that changes in the specific miRNAs in plasma may enable the early and sensitive detection of tubular and glomerular injuries. The present study suggests the potential utility of plasma miRNAs in the early and type-specific detection of drug-induced AKI.

Prognostic Significance of Serum NGAL and Troponin I against Acute Kidney Injury in Egyptian ICU Patients after Open Heart Surgery: A Pilot Study

Background

Acute kidney injury (AKI) is a common complication following cardiac surgery and percutaneous coronary interventions, with an estimated incidence rate around 30%, depicted by long-term intensive care unit stay and culminating renal dysfunction over time, triggering either perpetual renal damage evolving to chronic kidney disease/end-stage renal disease transitions or high vulnerability for sudden death after surgery. The classical diagnosis of AKI is based on a sharp rise in serum creatinine that takes at least 48 h to be visible and is associated with multiple nonrenal factors.

Objective

We aimed to evaluate the predictive performance of both neutrophil gelatinase-associated lipocalin (NGAL) and Klotho for AKI in patients who underwent cardiothoracic surgery using cardiopulmonary bypass (CPB).

Results

Out of the 182 patients included in the study, 65 had AKI and 117 had non-AKI according to the Kidney Disease: Improving Global Outcomes criteria relying on serum creatinine levels. Baseline serum NGAL was 103.5 ± 41.69 μg/L in the AKI group compared to 79.12 ± 48.02 μg/L in the non-AKI group (p < 0.01) and then manifested a peak-fall-rise pattern until 48 h of CPB, with a more remarkable change in the AKI than in the non-AKI group. ROC curve analysis for all measured biomarkers after 2 h of CPB showed that serum NGAL (0.819, > 75% cutoff, 83.5% accuracy) came after serum creatinine (0.864, > 140% cutoff, 85% accuracy), and troponin I was poorer than both (0.606, > 5.5% cutoff, 60% accuracy). Furthermore, multivariate analysis showed that preoperative serum NGAL, preoperative eGFR ≤60 mL/min/1.73 m², and arterial hypertension were possible risk factors for AKI with adverse outcomes.

Conclusions

Our study suggests the role of preoperative serum NGAL as a prognostic tool for renal consequences after cardiac surgery. Besides, postoperative serum NGAL is a sensitive marker for AKI, but is less specific than serum creatinine. Troponin I is considered to be a risk confirmatory tool and may help in the prediction of AKI. However, its diagnostic utility is restricted due to age-dependent cutoff values and poor standardization and harmonization because of interassay variations.

Novel renal markers for the assessment of renal integrity in patients undergoing knee arthroplasty - a pilot study

Background

The feasibility of novel kidney injury biomarkers in consecutive patients having total knee arthroplasty with local infiltration analgesia was evaluated.

Methods

We enrolled 30 patients scheduled for elective unilateral total knee arthroplasty. Paired plasma and urine samples were taken before surgery and at 4 h, 24 h and 48 h after surgery to measure creatinine, cystatin C, neutrophil gelatinase associated lipocalin, kidney injury molecule-1, interleukin-18 and liver-type fatty acid-binding protein.

Results

At baseline, 13 subjects had normal kidney function, 15 had mild and two had moderate kidney failure evaluated by calculated glomerular filtration rate. None of the subjects had all measured novel renal markers below proposed cut-off concentrations. Altogether 28/30 subjects had one (n = 3), two (n = 7) or three (n = 18) plasma neutrophil gelatinase associated lipocalin values above normal. In seven of these 28 subjects plasma creatinine, calculated glomerular filtration rate and plasma cystatin C were within the reference values. Five subjects had a low urine output, < 0.5 mL/h, indicating transient acute kidney injury, four of these had high plasma neutrophil gelatinase associated lipocalin and one high plasma cystatin C.

Conclusions

In the present study plasma neutrophil gelatinase associated lipocalin was elevated in most subjects with total knee arthroplasty and local infiltration analgesia as a marker of possible renal proximal tubular injury. Five subjects had transient low urine output, but none developed renal deterioration requiring treatment.

Diagnosis of cardiac surgery-associated acute kidney injury from functional to damage biomarkers

PURPOSE OF REVIEW

Acute kidney injury (AKI) occurs in up to 30% after cardiac surgery and is associated with adverse outcome. Currently, cardiac surgery-associated acute kidney injury (CSA-AKI) is diagnosed by Kidney Disease: Improving Global Outcomes criteria based on creatinine and urine output. To detect and treat AKI earlier, various biomarkers have been evaluated. This review addresses the current position of the two damage biomarkers neutrophil gelatinase-associated lipocalin (NGAL) and [TIMP-2] [IGFBP7] in clinical practice.

RECENT FINDINGS

We present an updated review on the use of blood and urinary NGAL in CSA-AKI. NGAL is a good predictor, and performs better in children than adults. There is a large variation in predictive ability, possibly caused by diversity of AKI definitions used, different time of measurement of NGAL, and lack of specificity of NGAL assays.Similarly, there are conflicting data on the predictive ability of urinary [TIMP-2] [IGFBP7] for CSA-AKI.Recently, both for NGAL and for urinary [TIMP-2] [IGFBP7], a set of actions, based on pretest assessment of risk for CSA-AKI and biomarker test results, was developed. These scores should be evaluated in prospective trials.

SUMMARY

NGAL and urinary [TIMP-2] [IGFBP7], in combination with pretest assessment, are promising tools for early detection and treatment in CSA-AKI.

Association of Elevated Urinary miR-126, miR-155, and miR-29b with Diabetic Kidney Disease

Effective diabetic kidney disease (DKD) biomarkers remain elusive, and urinary miRNAs represent a potential source of novel noninvasive disease sentinels. We profiled 754 miRNAs in pooled urine samples from DKD patients (n = 20), detecting significantly increased miR-126, miR-155, and miR-29b compared with controls (n = 20). These results were confirmed in an independent cohort of 89 DKD patients, 62 diabetic patients without DKD, and 41 controls: miR-126 (2.8-fold increase; P < 0.0001), miR-155 (1.8-fold increase; P < 0.001), and miR-29b (4.6-fold increase; P = 0.024). Combined receiver operating characteristic curve analysis resulted in an area under the curve of 0.8. A relative quantification threshold equivalent to 80% sensitivity for each miRNA gave a positive signal for 48% of DKD patients compared with 3.6% of diabetic patients without DKD. Laser-capture microdissection of renal biopsy specimens, followed by quantitative RT-PCR, detected miR-155 in glomeruli and proximal and distal tubules, whereas miR-126 and miR-29b were most abundant in glomerular extracts. Subsequent experiments showed miR-126 and miR-29b enrichment in glomerular endothelial cells (GEnCs) compared with podocytes, proximal tubular epithelial cells, and fibroblasts. Significantly increased miR-126 and miR-29b were detected in GEnC conditioned medium in response to tumor necrosis factor-α and transforming growth factor-β1, respectively. Our data reveal an altered urinary miRNA profile associated with DKD and link these variations to miRNA release from GEnCs.

Renal haemodynamics and oxygenation during and after cardiac surgery and cardiopulmonary bypass

Acute kidney injury (AKI) is a common complication following cardiac surgery performed on cardiopulmonary bypass (CPB) and has important implications for prognosis. The aetiology of cardiac surgery-associated AKI is complex, but renal hypoxia, particularly in the medulla, is thought to play at least some role. There is strong evidence from studies in experimental animals, clinical observations and computational models that medullary ischaemia and hypoxia occur during CPB. There are no validated methods to monitor or improve renal oxygenation during CPB, and thus possibly decrease the risk of AKI. Attempts to reduce the incidence of AKI by early transfusion to ameliorate intra-operative anaemia, refinement of protocols for cooling and rewarming on bypass, optimization of pump flow and arterial pressure, or the use of pulsatile flow, have not been successful to date. This may in part reflect the complexity of renal oxygenation, which may limit the effectiveness of individual interventions. We propose a multi-disciplinary pathway for translation comprising three components. Firstly, large-animal models of CPB to continuously monitor both whole kidney and regional kidney perfusion and oxygenation. Secondly, computational models to obtain information that can be used to interpret the data and develop rational interventions. Thirdly, clinically feasible non-invasive methods to continuously monitor renal oxygenation in the operating theatre and to identify patients at risk of AKI. In this review, we outline the recent progress on each of these fronts.

Risk Assessment

Purpose of Review

The central question of preoperative assessment is not “What can be done?” but “What should be done and how?” Predicting a patient’s risk of unwanted outcomes is vital to answering this question. This review discusses risk prediction tools currently available and anticipates future developments.

Recent Findings

Simple, parsimonious risk scales and scores are being replaced by complex risk prediction models as high-capacity information systems become ubiquitous. The accuracy of risk estimation will be further increased by improved assessment of physical fitness, frailty, and incorporation of existing and novel biomarkers. However, the limitations of risk prediction for individual patient care must be recognized.

Summary

Risk prediction is transforming from clinical estimation to statistical science. Predictions should be used within the context of a patient’s baseline risk (life expectancy independent of surgery), personal circumstances, quality of life, their expectations and values, and consideration of outcomes that are meaningful for the patient.

Biomarkers for predicting outcomes in chronic kidney disease

PURPOSE OF REVIEW

Current biomarkers for chronic kidney disease (CKD) are limited by lack of sensitivity and inability to prognosticate CKD progression. Significant recent research has better characterized novel biomarker candidates that are associated with CKD progression and cardiovascular mortality in CKD. This review discusses the most significant advances within the past year.

RECENT FINDINGS

We discuss biomarkers for outcomes in CKD under two categories: emerging (defined as having been validated in an independent cohort), which include serum cystatin C, serum β-trace protein, β2-microglobulin, soluble urokinase-type plasminogen activator receptor, soluble tumor necrosis factor receptors 1/2, urinary monocyte chemotactic protein-1, neutrophil gelatin-associated lipocalin, kidney injury molecule-1, and fibroblast growth factor-23; and novel (which have shown associations in smaller observational studies but have not been validated yet), which include indoxyl sulfate, p-cresyl sulfate, trimethylamine-N-oxide, IL-18, Klotho, markers of endothelial dysfunction, vimentin, and procollagen type III N-terminal propeptide. Further, we also discuss future directions for biomarker research including unbiased -omics approaches.

SUMMARY

There are a number of promising biomarkers that can better prognosticate outcomes in and progression of CKD. Further research is warranted to examine whether these biomarkers validate independently as well, and if their incorporation improves clinical practice or trial enrollment.

Candidate Urine Peptide Biomarkers for IgA Nephropathy: Where Are We Now?

Early detection, prognosis, and management of IgA nephropathy (IgAN) remain a challenge. Histological examination of renal tissue still comprises the only way to confirm an IgAN diagnosis. It is of great importance to establish noninvasive diagnostic, prognostic, and predictive biomarkers that would improve the clinical care and outcome of patients suffering from IgAN. This review summarises the findings from previous mass spectrometry- (MS-) based studies dedicated to the discovery of urinary peptide profiles specific to IgAN. There is a substantial number of urinary peptides that have been discovered to date, which show promise as biomarkers of IgAN; however, all of them require further, rigorous validation in well-planned studies, involving a large number of subjects who represent diverse and numerous populations.

MicroRNAs associated with the development of kidney diseases in humans and animals

Mature microRNAs (miRNAs) are single-stranded RNAs with approximately 18-25 bases, and their sequences are highly conserved among animals. miRNAs act as posttranscriptional regulators by binding mRNAs, and their main function involves the degradation of their target mRNAs. Recent studies revealed altered expression of miRNAs in the kidneys during the progression of acute kidney injury (AKI) and chronic kidney disease (CKD) in humans and experimental rodent models by using high-throughput screening techniques including microarray and small RNA sequencing. Particularly, miR-21 seems to be strongly associated with renal pathogenesis both in the glomerulus and tubulointerstitium. Furthermore, abundant evidence has been gathered showing the involvement of miRNAs in renal fibrosis. Because of the complex morphofunctional organization of the mammalian kidneys, it is crucial both to determine the exact localization of the kidney cells that express the miRNAs, which has been addressed mainly using in situ hybridization methods, and to identify precisely which mRNAs are bound and degraded by these miRNAs, which has been studied mostly through in vitro analysis. To discover novel biomarker candidates, miRNA levels in urine supernatant, sediment, and exosomal fraction were comprehensively investigated in different types of kidney disease, including drug-induced AKI, ischemia-induced AKI, diabetic nephropathy, lupus nephritis, and IgA nephropathy. Recent studies also demonstrated the therapeutic effect of miRNA and/or anti-miRNA administrations. The intent of this review is to illustrate the state-of-the-art research in the field of miRNAs associated with renal pathogenesis, especially focusing on AKI and CKD in humans and animal models.

Neutrophil Gelatinase-associated Lipocalin as a Predictor of Acute Kidney Injury in Patients during Treatment with Colistimethate Sodium

Background

The emergence of multidrug-resistant, Gram-negative bacteria has resulted in reconsideration of colistimethate sodium (CMS) as a last resort for treatment of such infections. However, acute kidney injury (AKI) may represent a major limiting adverse effect of use of CMS. Early AKI detection in CMS-treated patients can help prevent progression to acute failure and reduce the need of renal replacement therapy. We hypothesized that plasma neutrophil gelatinase-associated lipocalin (NGAL) may be an early biomarker of AKI in CMS-treated patients.

Materials and Methods

This prospective cohort study included patients aged ≥20 years who received intravenous CMS between March 2014 and November 2015. AKI was defined according to Kidney Disease: Improving Global Outcomes criteria. The primary endpoint was the difference between the average time to AKI onset based on serum creatinine and empirically derived plasma NGAL levels.

Results

Among 109 CMS-treated patients, 23 patients (mean age, 61.3 ± 16.1 years; men, 65.2%) were evaluated. Thirteen (56.5%) patients fulfilled the AKI criteria. The mean time to AKI onset based on serum creatinine after CMS initiation was 78.15 ± 30.49 hours. AKI was detected approximately 22 hours earlier using plasma NGAL than when using serum creatinine as an indicator of AKI (P = 0.035). The baseline plasma NGAL level was 264.0 ± 167.3 ng/mL and 192.7 ± 65.3 ng/mL in patients with and without AKI, respectively (P = 0.218). The area under the curve for plasma NGAL level at 56 hours was 0.796 (95% confidence interval, 0.609–0.983; P = 0.017), with a sensitivity and specificity of 69.2% and 90.0%, respectively (cutoff value, 285 ng/mL).

Conclusion

NGAL level was found to be a strong predictor of AKI. This study provides additional evidence of the utility of NGAL for AKI in patients with treated CMS. Plasma NGAL represent sensitive and specific predictive early biomarkers for AKI in patient treated CMS.

Relationships of kidney injury molecule-1 with renal function and cardiovascular risk factors in the general population

BACKGROUND

Kidney injury molecule-1 (KIM-1) has been associated with kidney damage in patients with preexisting renal disease. However, little is known about the relationships of KIM-1 with renal function and cardiovascular risk factors in healthy individuals from the general population.

METHODS

Healthy individuals aged 25-41years were enrolled in a population-based study. Main exclusion criteria were a BMI >35kg/m², preexisting kidney disease or established cardiovascular disease. KIM-1 was measured from frozen plasma samples using a high-sensitivity assay. Multivariable linear regression models were constructed to assess the relationships of KIM-1 with renal function and various cardiovascular risk factors.

RESULTS

We included 2060 individuals (47% men, median (interquartile range) age: 37 (31-40) years) in this analysis. Median KIM-1 levels were 82.5 (IQR 59.4-112.7) pg/ml. We found no significant relationship of KIM-1 with creatinine (adjusted β-coefficient (95% confidence interval) 0.0005 (-0.002; 0.003), p=0.61) and cystatin C (-0.02 (-0.21; 0.17), p=0.84). There were significant linear relationships of log-transformed KIM-1 with systolic blood pressure (adjusted β-coefficient (95% confidence interval) 0.07 (0.04; 0.09), p<0.0001), diastolic blood pressure (0.04 (0.02; 0.07), p=0.001), low-density lipoprotein cholesterol (0.09 (0.06; 0.11), p<0.0001), high-density lipoprotein cholesterol (0.07 (0.05; 0.1), p<0.0001), high-sensitivity C-reactive protein (0.05 (0.03; 0.07), p<0.0001), age (0.09 (0.07; 0.11), p<0.0001), BMI (0.04 (0.01; 0.06), p=0.005) and current smoking (0.12 (0.07; 0.17), p<0.0001).

CONCLUSION

Among healthy adults from the general population, plasma levels of KIM-1 were not associated with renal function but were independently related to multiple cardiovascular risk factors.

Group analysis identifies differentially elevated biomarkers with distinct outcomes for advanced acute kidney injury in cardiac surgery

AIM

To investigate early postoperative biomarkers for risk discrimination of advanced acute kidney injury (AKI).

MATERIALS & METHODS

Postoperative plasma biomarkers including NGAL, h-FABP, CK-MB, hsTNT, NT-proBNP, IL-6, IL-10 and VEGF were analyzed using group-based method among 426 patients with AKI after cardiac surgery.

RESULTS

Six patient groups with distinct biomarker patterns were identified. Individual biomarker displayed significant difference across the groups. The groups showed better discrimination for advanced AKI than any single biomarker either with or without adjusting for clinical variables. Average concentration of a single biomarker within each group, mortality and risk of a secondary outcome all demonstrated an approximately U-shaped relationship with proportion of advanced AKI within each group.

CONCLUSION

The group-based analysis revealed that the order of the patient groups with an increasing likelihood of advanced AKI had a nonlinear relationship with average concentration of an individual biomarker, mortality and risk of other outcomes.

Evaluation of the renal function using serum Cystatin C following open and endovascular aortic aneurysm repair

Objectives

Controversies regarding renal function impairment after open and endovascular aortic aneurysm repair still exist. The purpose of this study was to evaluate the renal function following open repair and endovascular aneurysm repair using Cystatin C.

Methods

This prospective, observational case–control study was conducted in tertiary referral centre over 3 years, starting from 2012. In total, 60 patients operated due to infrarenal AAA either by means of open repair (30 patients) or endovascular aneurysm repair (30 patients) were included in the study. Biochemical markers of renal function (sCr, urea, potassium) were recorded pre-operatively and at these specific time points, immediately after the operation and at discharge, home (third postoperative day, endovascular aneurysm repair group) or from intensive care unit (third postoperative day, open repair group). Multivariate and propensity score adjustments were used to control for the baseline differences between the groups.

Results

Creatinine levels in serum remained unchanged during the hospital stay in both groups without significant differences at any time point. Cystatin C levels in endovascular aneurysm repair patients significantly increased postoperatively and restored to values comparable to baseline at the discharge (0.865 ± 0.319 vs. *0.962 ± 0.353 vs. 0.921 ± 0.322, * p < 0.001). Cystatin C levels in patients treated with the open surgery was decreasing over time but not statistically significant comparing to Cystatin C values at the admission. However, decrease in Cystatin C serum levels in patients treated with conventional surgery resulted in statistically significant lower values compared to endovascular aneurysm repair patients both postoperatively and at the time of discharge (0.760 ± 0.225 vs. 0.962 ± 0.353, p < 0.05; 0.750 vs. 0.156, p < 0.05). Both multivariate linear regression models and propensity score adjustment confirm that, even after correction for previously observed intergroup differences, type of surgery, i.e. endovascular aneurysm repair is independently associated with the higher levels of Cystatin C both postoperatively and at the discharge.

Conclusions

Dynamics of Cystatin C levels have been proven as a more vulnerable marker of renal dysfunction. Endovascular aneurysm repair is associated with higher levels of kidney injury markers.

Cardiac surgery related cardio-renal syndrome assessed by conventional and novel biomarkers - under or overestimated diagnosis?

INTRODUCTION

Serum creatinine is a 'gold standard' criterion of recognizing and staging of acute kidney injury (AKI) despite it being a suboptimal, delayed indicator. The interpretation of increased values of biomarkers imposes great difficulty regarding cardiac surgery procedures performed with cardiopulmonary bypass and may lead to under- or overestimated diagnosis. The aim of this study was to evaluate the clinical utility of the sole serum creatinine or urine neutrophil gelatinase-associated lipocalin (NGAL) concentration used for identification of patients with AKI after cardiac surgery.

MATERIAL AND METHODS

A prospective observational study was conducted on a group of 88 adult patients undergoing a coronary artery bypass grafting procedure. Serum creatinine was evaluated on the day of the operation, and 24 and 48 h post-operatively. Urinary NGAL concentration was measured: immediately after and one hour after cardiopulmonary bypass, and 24 h from the beginning of the operation. We assessed features of kidney injury and 30-day and 5-year mortality.

RESULTS

Patients in the AKI group diagnosed with creatinine level and urine output criteria presented more advanced age (p = 0.01), higher body mass index (p = 0.01) and preoperative myocardial infarction (p = 0.02). Elevation of NGAL level was observed in 5 of 13 cases with AKI, based on creatinine criteria and 4 of 75 cases without AKI. Within 5 years after the surgical procedure the recurrence of renal failure was 36% in the AKI group (with perioperative NGAL elevation in 2 cases only).

CONCLUSIONS

In the cardiac surgery patients the diagnosis of AKI based on sole serum creatinine or urine NGAL concentration confirmed transient kidney injury. However, the clinical implications of these findings are insufficient for prediction of clinical outcome.