Neutrophil gelatinase-associated lipocalin after off pump versus on pump coronary artery surgery

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

RATIONALE & OBJECTIVE

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

STUDY DESIGN

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

SETTING & STUDY POPULATIONS

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

SELECTION CRITERIA FOR STUDIES

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

DATA EXTRACTION

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

ANALYTICAL APPROACH

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

RESULTS

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

LIMITATIONS

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

CONCLUSIONS

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

Effect of goal-directed therapy on post-operative neutrophil gelatinase-associated lipocalin profile in patients undergoing on-pump coronary artery surgery

Purpose

Neutrophil gelatinase-associated lipocalin (NGAL) is an early biomarker of acute kidney injury (AKI). Goal-directed therapy (GDT) in on-pump coronary artery bypass grafting (CABG) has been associated with lower post-operative NGAL levels in recent studies. The present study aimed at comparing plasma (P) and urinary (U)-NGAL levels following the use of GDT versus conventional haemodynamic therapy (CT) in patients undergoing on-pump CABG.

Methods

A prospective randomised controlled study conducted in a single university hospital. A total of 54 patients in the GDT group and 56 patients in CT group after exclusions.

Results

U-NGAL was significantly lower immediately post-surgery (T ₁) in GDT group (25.11 ± 1.5 versus 27.80 ± 1.7 μg/L; p < 0.001) and at 4 h (T ₂) (38.19 ± 23.6 versus 52.30 ± 28.3 μg/L; p = 0.006) and at 24 h post-operatively (T ₃) (34.85 ± 14 versus 39.7 ± 11.1 μg/L; p = 0.047). P-NGAL was comparable between groups at T ₁ but lower in the GDT group at T ₂ (92.81 ± 4.8 versus 94.77 ± 4.5 μg/L; p = 0.03) and T ₃ (67.44 ± 3.7 versus 75.96 ± 5.3 μg/L; p < 0.001). U-NGAL levels correlated well with the peak post-operative creatinine as compared to P-NGAL. On-pump patients manifest neutrophil activation, accounting for comparable levels of P-NGAL in the two groups at T ₁. GDT-based haemodynamic management resulted in lower U-NGAL levels at T ₁, T ₂ and T ₃ and lower P-NGAL levels at T ₂ and T ₃.

Conclusions

Haemodynamic optimisation with GDT prevents further renal insult initiated with the inflammatory activation with cardiopulmonary bypass (CPB), as evidenced by lower post-operative U-NGAL levels.

The origin of plasma neutrophil gelatinase-associated lipocalin in cardiac surgery

Background

Acute kidney injury (AKI) is common after heart surgery. Neutrophil gelatinase-associated lipocalin (NGAL) is produced in injured kidney. NGAL has been used as an early plasma biomarker for AKI in patients undergoing heart surgery. Neutrophils contain all isoforms (25-kDa, 45-kDa and 145-kDa) but the kidney produces almost exclusively the 25-kDa isoform of NGAL. We investigated first, whether there is association between NGAL and neutrophil activation, and second whether activated neutrophils are a significant source of circulating NGAL in plasma in patients undergoing cardiac surgery.

Methods

Two separate patient cohorts were studied: 1) the “kinetic cohort” (n = 29) and 2) the “FINNAKI cohort” (n = 306). As NGAL is strictly co-localized with lactoferrin in neutrophils, NGAL and lactoferrin were measured with enzyme-linked immunosorbent assay in all patients. In sixty-one patients of the “FINNAKI cohort” Western blot was used to separate NGAL isoforms according to their molecular size. Mann-Whitney U, Kruskal-Wallis H, Pearson’s and Spearman’s tests were used as appropriate.

Results

There was strong intraoperative association between NGAL and lactoferrin at all four time-points in the “kinetic cohort”. In the “FINNAKI cohort”, NGAL and lactoferrin concentrations correlated preoperatively (R = 0.59, p < 0.001) and at admission to the intensive care unit (R = 0.69, p < 0.001). At admission to intensive care unit, concentrations of NGAL and lactoferrin were higher in AKI than in non-AKI patients (NGAL: p < 0.001; lactoferrin: p < 0.029). In Western blot analyses, neutrophil specific 45-kDa isoform (median 41% [IQR 33.3–53.1]) and mostly neutrophil derived 145-kDa isoform (median 53.5% [IQR 44.0–64.9%]) together represented over 90% of total NGAL in plasma. Potentially kidney derived NGAL isoform (25-kDa) accounted for only 0.9% (IQR 0.3 – 3.0%) of total NGAL in plasma. There were no statistically significant differences in the distribution of NGAL isomers between AKI and non-AKI patients.

Conclusions

Plasma NGAL during cardiac surgery is associated with neutrophil activation. Based on molecular size, the majority of circulating NGAL is derived from neutrophils. Neutrophil activation is a confounding factor when interpreting increased plasma NGAL in cardiac surgery.

The time course of calprotectin liberation from human neutrophil granulocytes after Escherichia coli and endotoxin challenge

Plasma calprotectin has previously been reported as a biomarker for sepsis. The aim of the present study was to elucidate the kinetics of calprotectin release from neutrophils exposed to Escherichia coli and endotoxin. Whole blood samples were exposed to E. coli bacteria or endotoxin in vitro. Blood samples were collected after 0, 1, 2, 3 and 4 h and plasma calprotectin was analysed by particle enhanced turbidimetric immunoassay while TNF-α, IL-6, neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) were analyzed by ELISA. When neutrophils were exposed to either E. coli or endotoxin, calprotectin levels began to increase within a couple of hours after the challenge. Calprotectin increases early in response to bacterial challenge. Given the logistic advantages of the calprotectin analysis, this may be of interest for early diagnosis of bacterial infections.

Plasma Biomarkers in Predicting Renal Recovery from Acute Kidney Injury in Critically Ill Patients

BACKGROUND

Numerous studies have suggested a possible role for acute kidney injury (AKI) biomarkers in predicting renal recovery both before and after renal replacement therapy (RRT). However, definitions for recovery and whether to include patients dying but free of RRT may influence results.

OBJECTIVES

To validate plasma neutrophil gelatinase-associated lipocalin (pNGAL) as a useful biomarker for predicting or improving the ability of clinical predictors alone to predict recovery following AKI, including in our model plasma B-type natriuretic peptide (pBNP) to account for cardiovascular events.

METHODS

We analyzed 69 patients enrolled in the Acute Renal Failure Trial Network study. pNGAL and pBNP were measured on days 2, 7, and 14. We analyzed their predictive ability for subsequent recovery, defined as alive and independent from dialysis in 60 days. In sensitivity analyses, we explored changes in results with alternative definitions of recovery.

RESULTS

Twenty-nine patients (42%) recovered from AKI. Neither pNGAL nor pBNP, alone or in combination, was accurate predictors of renal recovery-the best area under the receiver-operating characteristics curve (AUC) was for pNGAL using the largest relative change (AUC 0.59, 95% CI 0.45-0.74). The best clinical model achieved superior performance to biomarkers (AUC 0.69, 95% CI 0.56-0.81). The AUC was greatest (0.75, 95% CI 0.60-0.91) when pNGAL + pBNP on day 14 were added to the clinical model but this increase did not achieve statistical significance. However, integrated discrimination improvement analysis showed that the addition of pNGAL and pBNP on day 14 to the clinical model significantly improved the prediction of renal recovery (p = 0.008).

CONCLUSIONS

pNGAL and pBNP can improve the accuracy of clinical parameters in predicting AKI recovery and a full model using biomarkers together with age achieved adequate discrimination.

Differences in acute kidney injury ascertainment for clinical and preclinical studies

Background

Acute kidney injury (AKI) is a common clinical condition directly associated with adverse outcomes. Several AKI biomarkers have been discovered, but their use in clinical and preclinical studies has not been well examined. This study aims to investigate the differences between clinical and preclinical studies on AKI biomarkers.

Methods

We performed a systematic review of clinical and preclinical interventional studies that considered AKI biomarkers in enrollment criteria and/or outcome assessment and described the main differences according to their setting, the inclusion of biomarkers in the definition of AKI and the use of biomarkers as primary or secondary end points.

Results

In the 151 included studies (76 clinical, 75 preclinical), clinical studies have prevalently focused on cardiac surgery (38.1%) and contrast-associated AKI (17.1%), while the majority of preclinical studies have focused on ether ischemia-reperfusion injury or drug-induced AKI (42.6% each). A total of 57.8% of clinical studies defined AKI using the standard criteria and only 19.7% of these studies used AKI biomarkers in the definition of renal injury. Conversely, the majority of preclinical studies defined AKI according to the increase in serum creatinine and blood urea nitrogen, and 32% included biomarkers in that definition. The percentage of both clinical and preclinical studies with biomarkers as a primary end point has not significantly increased in the last 10 years; however, preclinical studies are more likely to use AKI biomarkers as a primary end point compared with clinical studies [odds ratio 2.31 (95% confidence interval 1.17-4.59); P  =  0.016].

Conclusion

Differences between clinical and preclinical studies are evident and may affect the translation of preclinical findings in the clinical setting.

The impact of hydrocortisone treatment on neutrophil gelatinase-associated lipocalin release in porcine endotoxemic shock

Background

A key feature of sepsis is systemic inflammatory activation that could be counteracted by steroids. In this experimental model of systemic inflammation, we sought to investigate whether septic neutrophil activation, evaluated by the plasma levels of neutrophil gelatinase-associated protein (NGAL), is modulated by the timing of hydrocortisone treatment.

Methods

Sixteen anesthetized pigs were allocated to one of four equally sized groups. Three of these groups received endotoxin at 2 μg × kg⁻¹ × h⁻¹ for 6 h so as to induce endotoxemic shock. Hydrocortisone (5 mg × kg⁻¹) was administered intravenously before endotoxemic challenge, or at the onset of endotoxemic shock. Endotoxemic pigs not receiving hydrocortisone and non-endotoxemic pigs served as control groups. Physiologic variables, hematology, and biochemistry, including plasma NGAL, were measured repeatedly.

Results

Hydrocortisone treatment prior to endotoxemia attenuated some inflammatory, hematological, circulatory, and metabolic manifestations of shock (i.e., higher white blood cell count, higher mean arterial pressure, lower heart rate and mean pulmonary arterial pressure, higher left ventricular stroke work index, higher base excess). Endotoxemic shock increased plasma NGAL (p < 0.001). In pigs given hydrocortisone before the endotoxin infusion, plasma NGAL was lower as compared to those given hydrocortisone at endotoxemic shock (p < 0.05). Plasma NGAL levels correlated inversely to neutrophil granulocyte counts (rho = −0.65) but not to urine output (rho = −0.10) at the end of the experiment.

Conclusions

The increase in plasma NGAL is counteracted by hydrocortisone administration prior to endotoxemia; concomitantly, this treatment was associated with less expressed circulatory derangement. Urine NGAL did not differ between the groups, suggesting that the NGAL response was not primarily related to kidney injury.

Urinary neutrophil gelatinase-associated lipocalin in critically ill surgical cancer patients

BACKGROUND AND AIMS

Neutrophil gelatinase-associated lipocalin (N-GAL) is an early biomarker of acute kidney injury (AKI) due to various etiologies. On the other hand, N-GAL is also elevated in patients with acute inflammatory conditions and in several solid neoplasms. The goal of this study was to assess the efficacy of N-GAL as a predictor of AKI and mortality in oncological surgical patients postoperatively in the intensive care unit (ICU).

METHODS

This was a prospective cohort observation study on adult cancer patients submitted to elective or emergency surgeries and admitted in the ICU. Urinary N-GAL was measured at the first 2 h after admission. AKI incidence and other complications were assessed, including hospital mortality.

RESULTS

A total of 22 patients were assessed (77% male, age 52.8 years, Acute Physiology and Chronic Health Evaluation II [APACHE II] 17.3) in whom the most frequent site of cancer was the gastrointestinal tract. AKI incidence was 13.6%. Urinary N-GAL was a predictor of AKI (22.0 ng/ml in patients without AKI vs. 239.1 ng/ml in patients with AKI, P < 0.001). Multivariate analysis showed that the main predictors of AKI were age, APACHE II, and N-GAL. N-GAL was also higher, although not statistically significant in patients who died in the hospital.

CONCLUSIONS

In oncological postoperative patients admitted to the ICU, urinary N-GAL was an independent predictor of AKI; moreover, its level was higher in the deceased patients.