An Update on Sepsis Biomarkers

N-terminal pro-brain natriuretic peptide is an independent predictor of mortality in patients with sepsis

This study aims to evaluate the role of cardiac enzymes N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiac troponin-I (CTnI) as predictors of outcomes in patients with sepsis.78 cases with a diagnosis of sepsis were enrolled over a 2-year period. Baseline demographic, Acute Physiology and Chronic Health Evaluation-II (APACHE-II), Simplified Acute Physiology Score-II (SAPS-II), hematologic and biochemical parameters were noted. Serum NT-proBNP and CTnI were evaluated at 24 and 72 hours of admission along with echocardiography. Patients were prospectively followed up until death or discharge.Mean APACHE-II score was 19.8±9.6 and SAPS-II was 44.8±17.2. Survival rate in the study was 47.5% (36 of 78 patients). NT-proBNP was significantly higher in non-survivors with values over 4300 pg/mL at 24 hours and 5229 pg/mL at 72 hours associated with poor outcomes (p<0.05). CTnI was higher among non-survivors than in survivors, but the difference was not significant. APACHE-II score combined with NT-proBNP predicted a poor outcome in 51.2% cases compared with 14.6% cases with APACHE-II alone (p<0.05), while SAPS-II combined with NT-proBNP predicted a poor outcome in 53.6% cases as compared with 9.6% cases with SAPS-II alone (p<0.05). SAPS-II greater than 45 and NT-proBNP values at 72 hours were independent predictors of mortality in patients with sepsis.NT-proBNP is an independent predictor of mortality in patients with sepsis and its combination with APACHE-II and SAPS-II improves the predictive values of the scoring systems.

The Effects of a Meldonium Pre-Treatment on the Course of the Faecal-Induced Sepsis in Rats

Sepsis is a life-threatening condition caused by the dysregulated and overwhelming response to infection, accompanied by an exaggerated pro-inflammatory state and lipid metabolism disturbance leading to sequential organ failure. Meldonium is an anti-ischemic and anti-inflammatory agent which negatively interferes with lipid metabolism by shifting energy production from fatty acid oxidation to glycolysis, as a less oxygen-demanding pathway. Thus, we investigated the effects of a four-week meldonium pre-treatment on faecal-induced sepsis in Sprague-Dawley male rats. Surprisingly, under septic conditions, meldonium increased animal mortality rate compared with the meldonium non-treated group. However, analysis of the tissue oxidative status did not provide support for the detrimental effects of meldonium, nor did the analysis of the tissue inflammatory status showing anti-inflammatory, anti-apoptotic, and anti-necrotic effects of meldonium. After performing tissue lipidomic analysis, we concluded that the potential cause of the meldonium harmful effect is to be found in the overall decreased lipid metabolism. The present study underlines the importance of uninterrupted energy production in sepsis, closely drawing attention to the possible harmful effects of lipid-mobilization impairment caused by certain therapeutics. This could lead to the much-needed revision of the existing guidelines in the clinical treatment of sepsis while paving the way for discovering new therapeutic approaches.

Proadrenomedullin in Sepsis and Septic Shock: A Role in the Emergency Department

Sepsis and septic shock represent a leading cause of mortality in the Emergency Department (ED) and in the Intensive Care Unit (ICU). For these life-threating conditions, different diagnostic and prognostic biomarkers have been studied. Proadrenomedullin (MR-proADM) is a biomarker that can predict organ damage and the risk of imminent death in patients with septic shock, as shown by a large amount of data in the literature. The aim of our narrative review is to evaluate the role of MR-proADM in the context of Emergency Medicine and to summarize the current knowledge of MR-proADM as a serum indicator that is useful in the Emergency Department (ED) to determine an early diagnosis and to predict the long-term mortality of patients with sepsis and septic shock. We performed an electronic literature review to investigate the role of MR-proADM in sepsis and septic shock in the context of ED. We searched papers on PubMed^®, Cochrane^®, UptoDate^®, and Web of Science^® that had been published in the last 10 years. Data extracted from this literature review are not conclusive, but they show that MR-proADM may be helpful as a prognostic biomarker to stratify the mortality risk in cases of sepsis and septic shock with different degrees of organ damage, guiding emergency physicians in the diagnosis and the succeeding therapeutic workup. Sepsis and septic shock are conditions of high complexity and have a high risk of mortality. In the ED, early diagnosis is crucial in order to provide an early treatment and to improve patient survival. Diagnosis and prognosis are often the result of a combination of several tests. In our opinion, testing for MR-proADM directly in the ED could contribute to improving the prognostic assessment of patients, facilitating the subsequent clinical management and intensive treatment by the emergency physicians, but more studies are needed to confirm these results.

Biomarker-Guided Individualization of Antibiotic Therapy

Treatment failure of antibiotic therapy due to insufficient efficacy or occurrence of toxicity is a major clinical challenge, and is expected to become even more urgent with the global rise of antibiotic resistance. Strategies to optimize treatment in individual patients are therefore of crucial importance. Currently, therapeutic drug monitoring plays an important role in optimizing antibiotic exposure to reduce treatment failure and toxicity. Biomarker-based strategies may be a powerful tool to further quantify and monitor antibiotic treatment response, and reduce variation in treatment response between patients. Host response biomarkers, such as CRP, procalcitonin, IL-6, and presepsin, could potentially carry significant information to be utilized for treatment individualization. To achieve this, the complex interactions among immune system, pathogen, drug, and biomarker need to be better understood and characterized. The purpose of this tutorial is to discuss the use and evidence of currently available biomarker-based approaches to inform antibiotic treatment. To this end, we also included a discussion on how treatment response biomarker data from preclinical, healthy volunteer, and patient-based studies can be further characterized using pharmacometric and system pharmacology based modeling approaches. As an illustrative example of how such modeling strategies can be used, we describe a case study in which we quantitatively characterize procalcitonin dynamics in relation to antibiotic treatments in patients with sepsis.

Tumor necrosis factor-α small interfering RNA alveolar epithelial cell-targeting nanoparticles reduce lung injury in C57BL/6J mice with sepsis

Background

The role of tumor necrosis factor (TNF)-α small interfering (si)RNA alveolar epithelial cell (AEC)-targeting nanoparticles in lung injury is unclear.

Methods

Sixty C57BL/6J mice with sepsis were divided into normal, control, sham, 25 mg/kg, 50 mg/kg, and 100 mg/kg siRNA AEC-targeting nanoparticles groups (n = 10 per group). The wet:dry lung weight ratio, and hematoxylin and eosin staining, western blotting, and enzyme-linked immunosorbent assays for inflammatory factors were conducted to compare differences among groups.

Results

The wet:dry ratio was significantly lower in control and sham groups than other groups. TNF-α siRNA AEC-targeting nanoparticles significantly reduced the number of eosinophils, with significantly lower numbers in the 50 mg/kg group than in 25 mg/kg and 100 mg/kg groups. The nanoparticles also significantly reduced the expression of TNF-α, B-cell lymphoma-2, caspase 3, interleukin (IL)-1β, and IL-6, with TNF-α expression being significantly lower in the 50 mg/kg group than in 25 mg/kg and 100 mg/kg groups.

Conclusion

TNF-α siRNA AEC-targeting nanoparticles appear to be effective at improving lung injury-related sepsis, and 50 mg/kg may be a preferred dose option for administration.

A new tool for sepsis screening in the Emergency Department

OBJECTIVES

In this study, we developed and evaluated the diagnostic accuracy of the Sepsis Index for early sepsis screening in the Emergency Department (ED).

METHODS

Sepsis Index is based on the combination of monocyte distribution width (MDW) and mean monocyte volume (MMV). Sepsis Index≥1 was selected to define sepsis. We tested its diagnostic accuracy in an ED population stratified in four groups: controls, Systemic Inflammatory Response Syndrome (SIRS), infection, and sepsis, according to Sepsis-2 criteria.

RESULTS

Patients with sepsis displayed higher median Sepsis Index value than patients without sepsis. At the receiver operating characterictis (ROC) curve analysis for the prediction of sepsis, the area under the curve (AUC) of MDW and Sepsis Index were similar: 0.966 (95%CI 0.947-0.984), and 0.964 (95%CI 0.942-0.985), respectively. Sepsis Index showed increased specificity than MDW (94.7 vs. 90.6%), without any decrease in sensitivity (92.0%). Additionally, LR+ increased from 9.8 (MDW) to 17.4 (Sepsis Index), without any substantial change in LR- (respectively 0.09 vs. 0.08). Finally, PPV increased from 0.286 (MDW) to 0.420 (Sepsis Index).

CONCLUSIONS

Sepsis Index improves the diagnostic accuracy of MDW alone for sepsis screening.

Intravital Imaging of Pulmonary Immune Response in Inflammation and Infection

Intravital microscopy (IVM) is a unique imaging method providing insights in cellular functions and interactions in real-time, without the need for tissue extraction from the body. IVM of the lungs has specific challenges such as restricted organ accessibility, respiratory movements, and limited penetration depth. Various surgical approaches and microscopic setups have been adapted in order to overcome these challenges. Among others, these include the development of suction stabilized lung windows and the use of more advanced optical techniques. Consequently, lung IVM has uncovered mechanisms of leukocyte recruitment and function in several models of pulmonary inflammation and infection. This review focuses on bacterial pneumonia, aspiration pneumonia, sepsis-induced acute lung Injury, and cystic fibrosis, as examples of lung inflammation and infection. In addition, critical details of intravital imaging techniques of the lungs are discussed.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Monocyte distribution width as a biomarker of sepsis in the intensive care unit: A pilot study

BACKGROUND

Monocyte distribution width has been recently proposed as a sepsis biomarker in the emergency department. The aim of this study was to assess the role of monocyte distribution width as a diagnostic biomarker of sepsis in the intensive care unit.

METHODS

In this prospective observational study, we included all consecutive patients admitted to the intensive care unit of the University Hospital "P. Giaccone" of Palermo. Patients were classified into three groups according to Sepsis-3 criteria: (1) patients without sepsis; (2) patients developing sepsis during their hospital stay; (3) patients admitted with sepsis. Monocyte distribution width was measured at admission (groups 1, 2, 3) and daily until the developing of sepsis (group 2) or the end of hospitalization (group 1).

RESULTS

Monocyte distribution width was significantly higher in group 3 than group 1 and group 2 (30.9 [25.6-36.0] vs. 20.3 [18.3-23.6] and 21.4 [19.4-25.2]). Among patients belonging to group 2, monocyte distribution width values, measured at the day when sepsis was clinically diagnosed, were significantly higher than those found at admission: 29.4 (26.7-36.0) vs. 21.4 (19.4-25.2), P = 0.001.

CONCLUSION

Monocyte distribution width could represent a reliable biomarker of sepsis in the intensive care unit.

Lymphocyte expression of EZH2 is associated with mortality and secondary infectious complications in sepsis

Recent studies have shown that epigenetic factors may affect immune responses. We previously reported that histone methyltransferase enhancer of zeste homolog 2 (EZH2) was involved in the innate inflammatory responses both in animal model of sepsis and in septic patients. In this study, we prospectively evaluated EZH2 expression kinetics in peripheral CD4+ and CD8+ T cells and HLA-DR expression in CD14+ cells from 48 patients with sepsis and 48 healthy controls. Results showed higher level of EZH2 in CD4+ T cells and CD8+ T cells in sepsis patients than in controls. Meanwhile, EZH2 expression was correlated with CD27 status on T cells. Mean fluorescence intensity (MFI) of EZH2 in CD8+ T cells on day 1 independently predicted death in septic patients. Also, the combination of CD8+ T cell EZH2 expression with APACHEII and SOFA score could enhance the prognostic predictive ability. Moreover, multivariate logistic regression analysis showed that increased expression (proportion and MFI) of EZH2 in CD4+ and CD8+ lymphocytes on day 3 were independently associated with nosocomial infection in septic patients. Additionally, spearman correlation analysis indicated that the levels of EZH2 in CD4+ T cells and CD8+ T cells correlated to CD14+ cells-expressing HLA-DR in patients with sepsis at each time point. Overall, these findings suggest that EZH2 in CD4+ T cells or/and CD8+ T cells may be a novel biomarker for predicting adverse outcomes (mortality and secondary infectious complications) in patients with sepsis.

Identification of Potential Biomarkers and Immune Features of Sepsis Using Bioinformatics Analysis

Sepsis remains a major global concern and is associated with high mortality and morbidity despite improvements in its management. Markers currently in use have shortcomings such as a lack of specificity and failures in the early detection of sepsis. In this study, we aimed to identify key genes involved in the molecular mechanisms of sepsis and search for potential new biomarkers and treatment targets for sepsis using bioinformatics analyses. Three datasets (GSE95233, GSE57065, and GSE28750) associated with sepsis were downloaded from the public functional genomics data repository Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified using R packages (Affy and limma). Functional enrichment of the DEGs was analyzed with the DAVID database. Protein-protein interaction networks were derived using the STRING database and visualized using Cytoscape software. Potential biomarker genes were analyzed using receiver operating characteristic (ROC) curves in the R package (pROC). The three datasets included 156 whole blood RNA samples from 89 sepsis patients and 67 healthy controls. Between the two groups, 568 DEGs were identified, among which 315 were upregulated and 253 were downregulated in the septic group. These genes were enriched for pathways mainly involved in the innate immune response, T-cell biology, antigen presentation, and natural killer cell function. ROC analyses identified nine genes—LRG1, ELANE, TP53, LCK, TBX21, ZAP70, CD247, ITK, and FYN—as potential new biomarkers for sepsis. Real-time PCR confirmed that the expression of seven of these genes was in accordance with the microarray results. This study revealed imbalanced immune responses at the transcriptomic level during early sepsis and identified nine genes as potential biomarkers for sepsis.

Reference interval of monocyte distribution width (MDW) in healthy blood donors

BACKGROUND

The aim of the study was to accurately establish the reference interval (RI) of monocyte distribution width (MDW) in healthy blood donors by the direct method using different statistical approaches.

METHODS

MDW was measured in 486 subjects. RI of MDW was calculated by the non-parametric method, the robust method and, the Harrell-Davis bootstrap method and using different tests to identify potential outliers (Dixon-Reed and Tukey).

RESULTS

Lower and upper reference limits of the RI calculated by the non-parametric method were, 16.22 (90%CI 15.78-16.47) - 23.15 (90%CI 22.80-24.10) (without outlier removal), and 16.44 (90%CI 16.21-16.67) - 22.99 (90%CI 22.33-23.22) (after outlier removal). The RIs based on the robust method were, respectively, 16.29-22.98 (without) and 16.50-22.67 (with outlier removal). Finally, the RIs calculated by the Harrell-Davis bootstrap method, without or after outlier removal, were 16.19-23.24 and 16.43-22.93. Thus, the RIs obtained by the three calculation methods were very similar. Additionally, no RI partition was done since no significant gender or age association was found.

CONCLUSIONS

Our results support the use of a unique RI of MDW, independently of sex and age.