A biomarker panel (Bioscore) incorporating monocytic surface and soluble TREM-1 has high discriminative value for ventilator-associated pneumonia: a prospective observational study

Ventilator-associated pneumonia: pathobiological heterogeneity and diagnostic challenges

Ventilator-associated pneumonia (VAP) affects up to 20% of critically ill patients and induces significant antibiotic prescription pressure, accounting for half of all antibiotic use in the ICU. VAP significantly increases hospital length of stay and healthcare costs yet is also associated with long-term morbidity and mortality. The diagnosis of VAP continues to present challenges and pitfalls for the currently available clinical, radiological and microbiological diagnostic armamentarium. Biomarkers and artificial intelligence offer an innovative potential direction for ongoing future research. In this Review, we summarise the pathobiological heterogeneity and diagnostic challenges associated with VAP.

Biomarkers in pulmonary infections: a clinical approach

Severe acute respiratory infections, such as community-acquired pneumonia, hospital-acquired pneumonia, and ventilator-associated pneumonia, constitute frequent and lethal pulmonary infections in the intensive care unit (ICU). Despite optimal management with early appropriate empiric antimicrobial therapy and adequate supportive care, mortality remains high, in part attributable to the aging, growing number of comorbidities, and rising rates of multidrug resistance pathogens. Biomarkers have the potential to offer additional information that may further improve the management and outcome of pulmonary infections. Available pathogen-specific biomarkers, for example, Streptococcus pneumoniae urinary antigen test and galactomannan, can be helpful in the microbiologic diagnosis of pulmonary infection in ICU patients, improving the timing and appropriateness of empiric antimicrobial therapy since these tests have a short turnaround time in comparison to classic microbiology. On the other hand, host-response biomarkers, for example, C-reactive protein and procalcitonin, used in conjunction with the clinical data, may be useful in the diagnosis and prediction of pulmonary infections, monitoring the response to treatment, and guiding duration of antimicrobial therapy. The assessment of serial measurements overtime, kinetics of biomarkers, is more informative than a single value. The appropriate utilization of accurate pathogen-specific and host-response biomarkers may benefit clinical decision-making at the bedside and optimize antimicrobial stewardship.

Relationship between low molecular weight heparin calcium therapy and prognosis in severe acute kidney injury in sepsis: Mendelian randomized analysis and retrospective study

Background

Sepsis-associated acute kidney injury (SA-AKI) poses an independent risk for mortality due to the absence of highly sensitive biomarkers and a specific treatment plan.

Objective

Investigate the association between low molecular weight heparin (LMWH) calcium therapy and prognosis in critically ill SA-AKI patients, and assess the causal relationship through Mendelian randomization (MR) analysis.

Methods

A single-center, retrospective, cross-sectional study included 90 SA-AKI patients and 30 septic patients without acute kidney injury (AKI) from the intensive care unit (ICU) of the First Hospital of Lanzhou University. SA-AKI patients were categorized into control or LMWH groups based on LMWH calcium usage. Primary outcome was renal function recovery, with secondary outcomes including 28-day mortality, ICU stay length, number of renal replacement therapy (RRT) recipients, and 90-day survival. MR and related sensitivity analyses explored causal effects.

Results

The combination of heparin-binding protein (HBP), heparanase (HPA), and neutrophil gelatinase-associated lipocalin (NGAL) demonstrated high diagnostic value for SA-AKI. MR analysis suggested a potential causal link between gene-predicted HBP and AKI (OR: 1.369, 95%CI: 1.040-1.801, p = 0.024). In the retrospective study, LMWH-treated patients exhibited improved renal function, reduced levels of HPA, HBP, Syndecan-1, and inflammation, along with enhanced immune function compared to controls. However, LMWH did not impact 28-day mortality, 90-day survival, or ICU stay length.

Conclusion

LMWH could enhance renal function in SA-AKI patients. MR analysis supports this causal link, underscoring the need for further validation in randomized controlled trials.

Hospital-Acquired Pneumonia and Ventilator-Associated Pneumonia: A Literature Review

Hospital-acquired pneumonia (HAP) and its subtype, ventilator-associated pneumonia (VAP), remain two significant causes of morbidity and mortality worldwide, despite the better understanding of pathophysiological mechanisms, etiology, risk factors, preventive methods (bundle of care principles) and supportive care. Prior detection of the risk factors combined with a clear clinical judgement based on clinical scores and dosage of different inflammatory biomarkers (procalcitonin, soluble triggering receptor expressed on myelloid cells type 1, C-reactive protein, mid-regional pro-adrenomedullin, mid-regional pro-atrial natriuretic peptide) represent the cornerstones of a well-established management plan by improving patient's outcome. This review article provides an overview of the newly approved terminology considering nosocomial pneumonia, as well as the risk factors, biomarkers, diagnostic methods and new treatment options that can guide the management of this spectrum of infections.

Game changer or gimmick: inflammatory markers to guide antibiotic treatment decisions in neonatal early-onset sepsis

BACKGROUND

The diagnosis of neonatal early-onset sepsis (EOS) is challenging, and inflammatory markers are widely used to guide decision-making and therapies.

OBJECTIVES

This narrative review presents the current state of knowledge regarding the diagnostic value and potential pitfalls in the interpretation of inflammatory markers for EOS.

SOURCES

PubMed until October 2022 and searched references in identified articles using the search terms: neonatal EOS, biomarker or inflammatory marker, and antibiotic therapy or antibiotic stewardship.

CONTENT

In situations with a high or low probability of sepsis, the measurements of inflammatory markers have no impact on the decision to start or stop antibiotics and are just gimmick, whereas they may be a game changer for neonates with intermediate risk and therefore an unclear situation. There is no single or combination of inflammatory markers that can predict EOS with high probability, allowing us to make decisions regarding the start of antibiotics based only on inflammatory markers. The main reason for the limited accuracy is most probably the numerous noninfectious conditions that influence the levels of inflammatory markers. However, there is evidence that C-reactive protein and procalcitonin have good negative predictive accuracy to rule out sepsis within 24 to 48 hours. Nevertheless, several publications have reported more investigations and prolonged antibiotic treatments with the use of inflammatory markers. Given the limitations of current strategies, using an algorithm with only moderate diagnostic accuracy may have a positive impact, as reported for the EOS calculator and the NeoPInS algorithm.

IMPLICATIONS

As the decision regarding the start of antibiotic therapy is different from the process of stopping antibiotics, the accuracy of inflammatory markers needs to be evaluated separately. Novel machine learning-based algorithms are required to improve accuracy in the diagnosis of EOS. In the future, inflammatory markers included in algorithms may be a game changer reducing bias and noise in the decision-making process.

Evaluation of Five Host Inflammatory Biomarkers in Early Diagnosis of Ventilator-Associated Pneumonia in Critically Ill Children: A Prospective Single Center Cohort Study

Background: Early diagnosis of ventilator-associated pneumonia (VAP) remains a challenge due to subjective clinical criteria and the low discriminative power of diagnostic tests. We assessed whether rapid molecular diagnostics in combination with Clinically Pulmonary Index Score (CPIS) scoring, microbiological surveillance and biomarker measurements of PTX-3, SP-D, s-TREM, PTX-3, IL-1β and IL-8 in the blood or lung could improve the accuracy of VAP diagnosis and follow-up in critically ill children. Methods: A prospective pragmatic study in a Pediatric Intensive Care Unit (PICU) was conducted on ventilated critically ill children divided into two groups: high and low suspicion of VAP according to modified Clinically Pulmonary Index Score (mCPIS). Blood and bronchial samples were collected on days 1, 3, 6 and 12 after event onset. Rapid diagnostics were used for pathogen identification and ELISA for PTX-3, SP-D, s-TREM, IL-1β and IL-8 measurements. Results: Among 20 enrolled patients, 12 had a high suspicion (mCPIS > 6), and 8 had a low suspicion of VAP (mCPIS < 6); 65% were male; and 35% had chronic disease. IL-1β levels at day 1 correlated significantly with the number of mechanical ventilation days (r_s = 0.67, p < 0.001) and the PICU stay (r = 0.66; p < 0.002). No significant differences were found in the levels of the other biomarkers between the two groups. Mortality was recorded in two patients with high VAP suspicion. Conclusions: PTX-3, SP-D, s-TREM, IL-1β and IL-8 biomarkers could not discriminate patients with a high or low suspicion of VAP diagnosis.

Clinical value of serum sTREM-1 and HBP levels in combination with traditional inflammatory markers in diagnosing hospital-acquired pneumonia in elderly

Background

The clinical presentation of hospital-acquired pneumonia (HAP) in older patients is often complex and non-specific, posing a diagnostic challenge. This study evaluates the value of serum soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) and heparin-binding protein (HBP) in combination with traditional inflammatory markers procalcitonin (PCT) and C-reactive protein (CRP) in diagnosing HAP in older patients.

Methods

Thirty-eight elderly male patients with HAP (≥ 80 years old) and 46 age-matched controls, who were hospitalized for other reasons than HAP, were enrolled. The serum sTREM-1, HBP, PCT and CRP levels were measured by ELISA on the first day after enrollment. In addition, routine blood test, blood gas, sputum analysis, clinical pulmonary infection score (CPIS) assessment, and chest X-ray were performed, and the correlations with HAP were analyzed.

Results

The serum sTREM-1 (n = 38, 170.75 ± 158.33 pg/ml), HBP (2.08 ± 0.50), PCT (9.44 ± 17.73) and CRP (79.63 ± 71.37) were all significantly higher in the HAP group, when compared to the control group (P < 0.05). Furthermore, the values were positively correlated with the CPIS. The ROC curve analysis revealed that the AUC for sTREM-1 (0.667) and HBP (0.711) were lower, when compared to that for PCT (AUC = 0.839) and CRP (AUC = 0.840). The combination of PCT and CRP with sTREM-1 (AUC = 0.927) or HBP (AUC = 0.930) had the highest AUC values.

Conclusion

Serum sTREM-1, HBP, PCT and CRP can all be used as diagnostic markers for HAP in the elderly. The combination of traditional inflammatory markers PCT and CRP with novel inflammatory marker sTREM-1 or HBP further improves the diagnostic performance.

Diagnostic and prognostic value of new bioscore in critically ill septic patients

OBJECTIVE

To evaluate the diagnostic and prognostic value of biomarkers and new bioscore in septic patients in intensive care unit (ICU).

MATERIALS AND METHODS

A study was conducted on septic and non-septic patients in ICU. Diagnostic and prognostic values of C-reactive protein (CRP), procalcitonin (PCT), Sequential Organ Failure Assessments (SOFA) score and new bioscore were analysed statistically.

RESULTS

A total of 226 patients were enrolled in the study. In septic patients, PCT, SOFA and bioscore were found significantly increased (p = .007, p = .001 and p = .001, respectively). The AUC value of bioscore was higher than PCT and SOFA in septic patients. SOFA was found to be more significant prognostic marker than bioscore in predicting 28-day mortality. The prognostic value of bioscore and SOFA was similar for predicting 90-day mortality.

CONCLUSIONS

The new bioscore formed by combination of CRP, PCT and SOFA score may be useful in early diagnosis of sepsis.

Biomarkers Predicting Tissue Pharmacokinetics of Antimicrobials in Sepsis: A Review

The pathophysiology of sepsis alters drug pharmacokinetics, resulting in inadequate drug exposure and target-site concentration. Suboptimal exposure leads to treatment failure and the development of antimicrobial resistance. Therefore, we seek to optimize antimicrobial therapy in sepsis by selecting the right drug and the correct dosage. A prerequisite for achieving this goal is characterization and understanding of the mechanisms of pharmacokinetic alterations. However, most infections take place not in blood but in different body compartments. Since tissue pharmacokinetic assessment is not feasible in daily practice, we need to tailor antibiotic treatment according to the specific patient’s pathophysiological processes. The complex pathophysiology of sepsis and the ineffectiveness of current targeted therapies suggest that treatments guided by biomarkers predicting target-site concentration could provide a new therapeutic strategy. Inflammation, endothelial and coagulation activation markers, and blood flow parameters might be indicators of impaired tissue distribution. Moreover, hepatic and renal dysfunction biomarkers can predict not only drug metabolism and clearance but also drug distribution. Identification of the right biomarkers can direct drug dosing and provide timely feedback on its effectiveness. Therefore, this might decrease antibiotic resistance and the mortality of critically ill patients. This article fills the literature gap by characterizing patient biomarkers that might be used to predict unbound plasma-to-tissue drug distribution in critically ill patients. Although all biomarkers must be clinically evaluated with the ultimate goal of combining them in a clinically feasible scoring system, we support the concept that the appropriate biomarkers could be used to direct targeted antibiotic dosing.

Impact of inhalation injury on outcomes in critically ill burns patients: 12-year experience at a regional burns centre

INTRODUCTION

Burns inhalation injury increases the attributable mortality of burns related trauma. However, diagnostic uncertainties around bronchoscopically graded severity, and its effect on outcomes, remain. This study evaluated the impact of different bronchoscopic burns inhalation injury grades on outcomes.

METHODS

A single-centre cohort study of all patients admitted to the London Burns centre intensive care unit (BICU) over 12 years. Demographic data, burn and burns inhalation injury characteristics, and ICU-related parameters were collected retrospectively. The primary outcome was mortality. Secondary outcomes were hospital and ICU lengths of stay. The impact of pneumonia was determined. Univariate and multivariable Cox's proportional hazards regression analyses informed factors predicting mortality.

RESULTS

Burns inhalation injury was diagnosed in 84 of 231 (36%) critically ill burns patients; 20 mild (grade 1), 41 severe (grades 2/3) and 23 unclassified bronchoscopically. Median (IQR) total body surface area burned (TBSA) was 20% (10-40). Mortality was significantly higher in patients with burns inhalation injury vs those without burns inhalation injury (38/84 [45%] vs 35/147 [24%], p < 0.001). Patients with pneumonia had a higher mortality than those without (34/125 [27%] vs 8/71 [11%], p = 0.009). In multivariable analysis, severe burns inhalation injury significantly increased mortality (adjusted HR=2.14, 95%CI: 1.12-4.09, p = 0.022), compared with mild injury (adjusted HR=0.58, 95% CI: 0.18-1.86, p = 0.363). Facial burns (adjusted HR=3.13, 95%CI: 1.69-5.79, p < 0.001), higher TBSA (adjusted HR=1.05, 95%CI: 1.04-1.06, p < 0.001) and older age (adjusted HR=1.04, 95%CI: 1.02-1.07, p < 0.001) also independently predicted mortality, though pneumonia did not.

CONCLUSIONS

Severe burns inhalation injury is a significant risk factor for mortality in critically ill burns patients. However, pneumonia did not increase mortality from burns inhalation injury. This work confirms prior implications of bronchoscopically graded burns inhalation injury. Further study is suggested, through registries, into the diagnostic accuracy and reliability of bronchoscopy in burns related lung injury.

Diagnostic Challenges in Sepsis

Purpose of Review

Sepsis is a leading cause of death worldwide. Groundbreaking international collaborative efforts have culminated in the widely accepted surviving sepsis guidelines, with iterative improvements in management strategies and definitions providing important advances in care for patients. Key to the diagnosis of sepsis is identification of infection, and whilst the diagnostic criteria for sepsis is now clear, the diagnosis of infection remains a challenge and there is often discordance between clinician assessments for infection.

Recent Findings

We review the utility of common biochemical, microbiological and radiological tools employed by clinicians to diagnose infection and explore the difficulty of making a diagnosis of infection in severe inflammatory states through illustrative case reports. Finally, we discuss some of the novel and emerging approaches in diagnosis of infection and sepsis.

Summary

While prompt diagnosis and treatment of sepsis is essential to improve outcomes in sepsis, there remains no single tool to reliably identify or exclude infection. This contributes to unnecessary antimicrobial use that is harmful to individuals and populations. There is therefore a pressing need for novel solutions. Machine learning approaches using multiple diagnostic and clinical inputs may offer a potential solution but as yet these approaches remain experimental.

Serum sTREM-1 and CXCL-16 Levels in Children with Mycoplasma pneumoniae Pneumonia and Their Diagnostic Value

Mycoplasma pneumoniae pneumonia (MPP) is an acute respiratory tract infection caused by Mycoplasma pneumoniae. It is characterized by severe symptoms, long course of disease, many intrapulmonary complications, and poor therapeutic effect. In recent years, the incidence of Mycoplasma infection have been gradually rising trend, and the children's own immune system development is not mature, cases differences, children with mild can only show the upper respiratory tract infection, and critically ill children can lead to lung infection and even lead to multiple organ dysfunction, affect life and health of children. Soluble triggering receptors expressed on myeloid cell-1 (sTREM-1) is a subtype secreted by myeloid cell trigger receptor-1, which is released into blood in large amounts when the body is infected, and is a newly discovered inflammatory indicator in recent years. CXC chemokine 16 (CXCL-16) can recruit lymphocytes by chemotaxis through binding to its receptor CXCR6 to participate in the body's immune regulation. The purpose of this study was to investigate serum sTREM-1 and CXCL-16 levels in children with MPP and to analyze their correlation with the disease and diagnostic value. The results showed that the serum levels of sTREM-1 and CXCL-16 were increased in children with Mycoplasma. Serum levels of sTREM-1 and CXCL-16 were positively correlated with the severity of the disease. sTREM-1 combined with CXCL-16 has an important value in the diagnosis of children with MPP.

Systematic review of studies investigating ventilator associated pneumonia diagnostics in intensive care

Background

Ventilator-associated pneumonia (VAP) is an important diagnosis in critical care. VAP research is complicated by the lack of agreed diagnostic criteria and reference standard test criteria. Our aim was to review which reference standard tests are used to evaluate novel index tests for suspected VAP.

Methods

We conducted a comprehensive search using electronic databases and hand reference checks. The Cochrane Library, MEDLINE, CINHAL, EMBASE, and web of science were searched from 2008 until November 2018. All terms related to VAP diagnostics in the intensive treatment unit were used to conduct the search. We adopted a checklist from the critical appraisal skills programme checklist for diagnostic studies to assess the quality of the included studies.

Results

We identified 2441 records, of which 178 were selected for full-text review. Following methodological examination and quality assessment, 44 studies were included in narrative data synthesis. Thirty-two (72.7%) studies utilised a sole microbiological reference standard; the remaining 12 studies utilised a composite reference standard, nine of which included a mandatory microbiological criterion. Histopathological criteria were optional in four studies but mandatory in none.

Conclusions

Nearly all reference standards for VAP used in diagnostic test research required some microbiological confirmation of infection, with BAL culture being the most common reference standard used.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01560-0.

Host Diagnostic Biomarkers of Infection in the ICU: Where Are We and Where Are We Going?

Purpose of Review

Early identification of infection in the critically ill patient and initiation of appropriate treatment is key to reducing morbidity and mortality. On the other hand, the indiscriminate use of antimicrobials leads to harms, many of which may be exaggerated in the critically ill population. The current method of diagnosing infection in the intensive care unit relies heavily on clinical gestalt; however, this approach is plagued by biases. Therefore, a reliable, independent biomarker holds promise in the accurate determination of infection. We discuss currently used host biomarkers used in the intensive care unit and review new and emerging approaches to biomarker discovery.

Recent Findings

White cell count (including total white cell count, left shift, and the neutrophil-leucocyte ratio), C-reactive protein, and procalcitonin are the most common host diagnostic biomarkers for sepsis used in current clinical practice. However, their utility in the initial diagnosis of infection, and their role in the subsequent decision to commence treatment, remains limited. Novel approaches to biomarker discovery that are currently being investigated include combination biomarkers, host 'sepsis signatures' based on differential gene expression, site-specific biomarkers, biomechanical assays, and incorporation of new and pre-existing host biomarkers into machine learning algorithms.

Summary

To date, no single reliable independent biomarker of infection exists. Whilst new approaches to biomarker discovery hold promise, their clinical utility may be limited if previous mistakes that have afflicted sepsis biomarker research continue to be repeated.

TREM-1 isoforms in bacterial infections: to immune modulation and beyond

The triggering receptor expressed on myeloid cells 1 (TREM-1) is an innate immunity receptor associated with the amplification of inflammation in sterile and non-sterile inflammatory disorders. Since its first description, the two isoforms of the receptor, membrane and soluble (mTREM-1 and sTREM-1, respectively) have been largely explored in the immunopathogenesis of several bacterial diseases and sepsis. The role of the receptor in these scenarios seems to be at least partly dependent on the source/type of bacteria, host and context. As uncontrolled inflammation is a result of several bacterial infections, the inhibition of the receptor has been considered as a promising approach to treat such conditions. Further, sTREM-1 has been explored as a biomarker for diagnosis and/or prognosis of several bacterial diseases. Therefore, this review aims to provide an updated insight into how the receptor influences and is influenced by bacterial infections, highlighting the advances regarding the use/manipulation of TREM-1 isoforms in biomedical research and clinical practice.

Pulmonary infections complicating ARDS

Pulmonary infection is one of the main complications occurring in patients suffering from acute respiratory distress syndrome (ARDS). Besides traditional risk factors, dysregulation of lung immune defenses and microbiota may play an important role in ARDS patients. Prone positioning does not seem to be associated with a higher risk of pulmonary infection. Although bacteria associated with ventilator-associated pneumonia (VAP) in ARDS patients are similar to those in patients without ARDS, atypical pathogens (Aspergillus, herpes simplex virus and cytomegalovirus) may also be responsible for infection in ARDS patients. Diagnosing pulmonary infection in ARDS patients is challenging, and requires a combination of clinical, biological and microbiological criteria. The role of modern tools (e.g., molecular methods, metagenomic sequencing, etc.) remains to be evaluated in this setting. One of the challenges of antimicrobial treatment is antibiotics diffusion into the lungs. Although targeted delivery of antibiotics using nebulization may be interesting, their place in ARDS patients remains to be explored. The use of extracorporeal membrane oxygenation in the most severe patients is associated with a high rate of infection and raises several challenges, diagnostic issues and pharmacokinetics/pharmacodynamics changes being at the top. Prevention of pulmonary infection is a key issue in ARDS patients, but there is no specific measure for these high-risk patients. Reinforcing preventive measures using bundles seems to be the best option.

Biomarkers of sepsis: time for a reappraisal

INTRODUCTION

Sepsis biomarkers can have important diagnostic, therapeutic, and prognostic functions. In a previous review, we identified 3370 references reporting on 178 different biomarkers related to sepsis. In the present review, we evaluate the progress in the research of sepsis biomarkers.

METHODS

Using the same methodology as in our previous review, we searched the PubMed database from 2009 until September 2019 using the terms "Biomarker" AND "Sepsis." There were no restrictions by age or language, and all studies, clinical and experimental, were included.

RESULTS

We retrieved a total of 5367 new references since our previous review. We identified 258 biomarkers, 80 of which were new compared to our previous list. The majority of biomarkers have been evaluated in fewer than 5 studies, with 81 (31%) being assessed in just a single study. Apart from studies of C-reactive protein (CRP) or procalcitonin (PCT), only 26 biomarkers have been assessed in clinical studies with more than 300 participants. Forty biomarkers have been compared to PCT and/or CRP for their diagnostic value; 9 were shown to have a better diagnostic value for sepsis than either or both of these biomarkers. Forty-four biomarkers have been evaluated for a role in answering a specific clinical question rather than for their general diagnostic or prognostic properties in sepsis.

CONCLUSIONS

The number of biomarkers being identified is still increasing although at a slower rate than in the past. Most of the biomarkers have not been well-studied; in particular, the clinical role of these biomarkers needs to be better evaluated.

Procalcitonin in the Assessment of Ventilator Associated Pneumonia: A Systematic Review

BACKGROUND

Ventilator-associated pneumonia (VAP) is one of the most common nosocomial infection, associated with considerable mortality and morbidity in critically ill patients; however, its diagnosis and management remain challenging since clinical assessment is often poorly reliable. The aim of this systematic review was to evaluate the role of PCT in the diagnosis and management of critical ill patients affected by VAP.

METHODS

We performed a systematic review of the evidence published over the last 10 years and currently available in medical literature search databases (Pubmed, Embase, Web of Knowledge, Cochrane Libraries) and searching clinical trial registries. We regarded as predefined outcomes the role of PCT in diagnosis, therapeutic monitoring, antibiotic discontinuation and prognosis. The Open Science Framework Registration number was doi.org/10.17605/OSF.

IO/ZGFKQ RESULTS

761 articles were retrieved and a total of 18 studies (n° of patients = 1774) were selected and analyzed according to inclusion criteria. In this 2020 update, the systematic review showed that currently, conflicting and inconclusive data are available about the role of PCT in the diagnosis of VAP and in the prediction (i) of the efficacy of antibiotic therapy, and (ii) of the clinical outcome. These studies, instead, seem to agree on the utility of PCT in the management of antibiotic therapy discontinuation.

CONCLUSIONS

Currently there is insufficient evidence to support the role of PCT in the routine assessment of patients with VAP. The value of the results published appears to be limited by the deep methodological differences that characterize the various studies available at the present being.

Do we need biomarkers for the follow-up and shortening of antibiotic treatment duration?

PURPOSE OF REVIEW

Clinical and laboratory parameters are useful tools for the diagnosis, follow-up and evaluation of resolution, and to predict outcomes when measured at different time-points onset and serially during follow-up in patients with hospital-acquired pneumonia and/or ventilator-associated pneumonia (HAP/VAP).

RECENT FINDINGS

Both, the 2017 ERS/ESICM/ESCMID/Asociación Latino Americana de Tórax (EEEAG) and the 2016 IDSA/ATS guidelines (IAG) for the management of HAP/VAP recommend using clinical criteria alone, rather than biomarkers for diagnosis. Several studies were conducted to assess the value of serum biomarker concentration and kinetics for predicting the outcome in HAP/VAP, including C-reactive protein and procalcitonin (PCT). Although the EEEAG do not recommend routinely performing biomarker determinations in addition to bedside clinical assessment in patients receiving antibiotic treatment for VAP or HAP to predict adverse outcomes and clinical response, the IAG recommend that routine bedside clinical assessment should be accompanied by measurements of PCT to guide antimicrobial therapy. Additionally, the 2016 Surviving Sepsis Campaign also suggests that PCT levels can be used to support the shortening of antibiotic therapy.

SUMMARY

Current evidence indicate that there is no recommendation to use biomarkers systematically to guide every decision. However, in some circumstances they might add some relevant information to our everyday practice.

Plasma interleukin-6 concentration for the diagnosis of sepsis in critically ill adults

BACKGROUND

The definition of sepsis has evolved over time, along with the clinical and scientific knowledge behind it. For years, sepsis was defined as a systemic inflammatory response syndrome (SIRS) in the presence of a documented or suspected infection. At present, sepsis is defined as a life-threatening organ dysfunction resulting from a dysregulated host response to infection. Even though sepsis is one of the leading causes of mortality in critically ill patients, and the World Health Organization (WHO) recognizes it as a healthcare priority, it still lacks an accurate diagnostic test. Determining the accuracy of interleukin-6 (IL-6) concentrations in plasma, which is proposed as a new biomarker for the diagnosis of sepsis, might be helpful to provide adequate and timely management of critically ill patients, and thus reduce the morbidity and mortality associated with this condition.

OBJECTIVES

To determine the diagnostic accuracy of plasma interleukin-6 (IL-6) concentration for the diagnosis of bacterial sepsis in critically ill adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, and Web of Science on 25 January 2019. We screened references in the included studies to identify additional studies. We did not apply any language restriction to the electronic searches.

SELECTION CRITERIA

We included diagnostic accuracy studies enrolling critically ill adults aged 18 years or older under suspicion of sepsis during their hospitalization, where IL-6 concentrations were evaluated by serological measurement.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the references to identify relevant studies and extracted data. We assessed the methodological quality of studies using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. We estimated a summary receiver operating characteristic (SROC) curve by fitting a hierarchical summary ROC (HSROC) non-linear mixed model. We explored sources of heterogeneity using the HSROC model parameters. We conducted all analyses in the SAS statistical software package and R software.

MAIN RESULTS

We included 23 studies (n = 4192) assessing the accuracy of IL-6 for the diagnosis of sepsis in critically ill adults. Twenty studies that were available as conference proceedings only are awaiting classification. The included participants were heterogeneous in terms of their distribution of age, gender, main diagnosis, setting, country, positivity threshold, sepsis criteria, year of publication, and origin of infection, among other factors. Prevalence of sepsis greatly varied across studies, ranging from 12% to 78%. We considered all studies to be at high risk of bias due to issues related to the index test domain in QUADAS-2. The SROC curve showed a great dispersion in individual studies accuracy estimates (21 studies, 3650 adult patients), therefore the considerable heterogeneity in the collected data prevented us from calculating formal accuracy estimates. Using a fixed prevalence of sepsis of 50% and a fixed specificity of 74%, we found a sensitivity of 66% (95% confidence interval 60 to 72). If we test a cohort 1000 adult patients under suspicion of sepsis with IL-6, we will find that 330 patients would receive appropriate and timely antibiotic therapy, while 130 patients would be wrongly considered to have sepsis. In addition, 370 out of 1000 patients would avoid unnecessary antibiotic therapy, and 170 patients would have been undiagnosed of sepsis. This numerical approach should be interpreted with caution due to the limitations described above.

AUTHORS' CONCLUSIONS

Our evidence assessment of plasma interleukin-6 concentrations for the diagnosis of sepsis in critically ill adults reveals several limitations. High heterogeneity of collected evidence regarding the main diagnosis, setting, country, positivity threshold, sepsis criteria, year of publication, and the origin of infection, among other factors, along with the potential number of misclassifications, remain significant constraints for its implementation. The 20 conference proceedings assessed as studies awaiting classification may alter the conclusions of the review once they are fully published and evaluated. Further studies about the accuracy of interleukin-6 for the diagnosis of sepsis in adults that apply rigorous methodology for conducting diagnostic test accuracy studies are needed. The conclusions of the review will likely change once the 20 studies pending publication are fully published and included.

Biomarkers in Pneumonia-Beyond Procalcitonin

Pneumonia is the leading infectious cause of mortality worldwide and one of the most common lower respiratory tract infections that is contributing significantly to the burden of antibiotic consumption. Due to the complexity of its pathophysiology, it is widely accepted that clinical diagnosis and prognosis are inadequate for the accurate assessment of the severity of the disease. The most challenging task for a physician is the risk stratification of patients with community-acquired pneumonia. Herein, early diagnosis is essential in order to reduce hospitalization and mortality. Procalcitonin and C-reactive protein remain the most widely used biomarkers, while interleukin 6 has been of particular interest in the literature. However, none of them appear to be ideal, and the search for novel biomarkers that will most sufficiently predict the severity and treatment response in pneumonia has lately intensified. Although our insight has significantly increased over the last years, a translational approach with the application of genomics, metabolomics, microbiomics, and proteomics is required to better understand the disease. In this review, we discuss this rapidly evolving area and summarize the application of novel biomarkers that appear to be promising for the accurate diagnosis and risk stratification of pneumonia.

Variations of the lung microbiome and immune response in mechanically ventilated surgical patients

Mechanically ventilated surgical patients have a variety of bacterial flora that are often undetectable by traditional culture methods. The source of infection in many of these patients remains unclear. To address this clinical problem, the microbiome profile and host inflammatory response in bronchoalveolar lavage samples from the surgical intensive care unit were examined relative to clinical pathology diagnoses. The hypothesis was tested that clinical diagnosis of respiratory tract flora were similar to culture positive lavage samples in both microbiome and inflammatory profile. Bronchoalveolar lavage samples were collected in the surgical intensive care unit as standard of care for intubated individuals with a clinical pulmonary infection score of >6 or who were expected to be intubated for >48 hours. Cytokine analysis was conducted with the Bioplex Pro Human Th17 cytokine panel. The microbiome of the samples was sequenced for the 16S rRNA region using the Ion Torrent. Microbiome diversity analysis showed the culture-positive samples had the lowest levels of diversity and culture negative with the highest based upon the Shannon-Wiener index (culture positive: 0.77 ± 0.36, respiratory tract flora: 2.06 ± 0.73, culture negative: 3.97 ± 0.65). Culture-negative samples were not dominated by a single bacterial genera. Lavages classified as respiratory tract flora were more similar to the culture-positive in the microbiome profile. A comparison of cytokine expression between groups showed increased levels of cytokines (IFN-g, IL-17F, IL-1B, IL-31, TNF-a) in culture-positive and respiratory tract flora groups. Culture-positive samples exhibited a more robust immune response and reduced diversity of bacterial genera. Lower cytokine levels in culture-negative samples, despite a greater number of bacterial species, suggest a resident nonpathogenic bacterial community may be indicative of a normal pulmonary environment. Respiratory tract flora samples were most similar to the culture-positive samples and may warrant classification as culture-positive when considering clinical treatment.

Appraisal of systemic inflammation and diagnostic markers in a porcine model of VAP: secondary analysis from a study on novel preventive strategies

Background

We previously evaluated the efficacy of a ventilatory strategy to achieve expiratory flow bias and positive end-expiratory pressure (EFB + PEEP) or the Trendelenburg position (TP) for the prevention of ventilator-associated pneumonia (VAP). These preventive measures were aimed at improving mucus clearance and reducing pulmonary aspiration of bacteria-laden oropharyngeal secretions. This secondary analysis is aimed at evaluating the effects of aforementioned interventions on systemic inflammation and to substantiate the value of clinical parameters and cytokines in the diagnosis of VAP.

Methods

Twenty female pigs were randomized to be positioned in the semirecumbent/prone position, and ventilated with duty cycle 0.33 and without PEEP (control); positioned as in the control group, PEEP 5 cmH₂O, and duty cycle to achieve expiratory flow bias (EFB+PEEP); ventilated as in the control group, but in the Trendelenburg position (Trendelenburg). Following randomization, P. aeruginosa was instilled into the oropharynx. Systemic cytokines and tracheal secretions P. aeruginosa concentration were quantified every 24h. Lung biopsies were collected for microbiological confirmation of VAP.

Results

In the control, EFB + PEEP, and Trendelenburg groups, lung tissue Pseudomonas aeruginosa concentration was 2.4 ± 1.5, 1.9 ± 2.1, and 0.3 ± 0.6 log cfu/mL, respectively (p = 0.020). Whereas, it was 2.4 ± 1.9 and 0.6 ± 0.9 log cfu/mL in animals with or without VAP (p < 0.001). Lower levels of interleukin (IL)-1β (p = 0.021), IL-1RA (p < 0.001), IL-4 (p = 0.005), IL-8 (p = 0.008), and IL-18 (p = 0.050) were found in Trendelenburg animals. VAP increased IL-10 (p = 0.035), tumor necrosis factor-α (p = 0.041), and endotracheal aspirate (ETA) P. aeruginosa concentration (p = 0.024). A model comprising ETA bacterial burden, IL-10, and TNF-α yielded moderate discrimination for the diagnosis of VAP (area of the receiver operating curve 0.82, 95% CI 0.61–1.00).

Conclusions

Our findings demonstrate anti-inflammatory effects associated with the Trendelenburg position. In this reliable model of VAP, ETA culture showed good diagnostic accuracy, whereas systemic IL-10 and TNF-α marginally improved accuracy. Further clinical studies will be necessary to confirm clinical value of the Trendelenburg position as a measure to hinder inflammation during mechanical ventilation and significance of systemic IL-10 and TNF-α in the diagnosis of VAP.

The triggering receptor expressed by myeloid cells-1 activates TLR4-MyD88-NF-κB-dependent signaling to aggravate ventilation-induced lung inflammation and injury in mice

The triggering receptor expressed by myeloid cells-1 (TREM-1) plays an important role in infectious and autoimmune diseases but how it contributes to ventilation-induced lung injury (VILI) and inflammation is unclear. Here, we examine the possibility that TREM-1 activates signaling dependent on Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (Myd88) and nuclear factor (NF)-κB, which leads in turn to VILI. In a mouse model of VILI, which we validated based on lung edema and histopathology as well as cytokine levels, we examine mRNA and protein levels of TREM-1, TLR4, MyD88, NF-κB and its inhibitory protein I-κB in animals subjected to ventilation at normal or high tidal volume. The extent of lung edema, injury and inflammation were higher in the high tidal volume animals, as were the expression levels of all proteins examined. Treatment with TREM-1 agonist aggravated these effects, whereas treatment with TREM-1 antagonist attenuated them. Our results suggest that aggravation of VILI by TREM-1 in mice may be associated with TLR4-MyD88-NF-κB-dependent signaling.

The current status of biomarkers for the diagnosis of nosocomial pneumonias

PURPOSE OF REVIEW

Nosocomial pneumonia is a frequent and severe nosocomial infection divided in two distinct groups: hospital-acquired pneumonia and ventilator-associated pneumonia (VAP). In this context, the VAP is notoriously difficult to diagnose clinically, resulting from the lack of a 'gold standard' method of diagnosis.

RECENT FINDINGS

The use of biomarkers may potentially improve the early diagnosis of infections allowing earlier and better identification and treatment. An exhausting list of biomarkers has been studied and although far from perfect, procalcitonin (PCT) and C-reactive protein (CRP) are the most studied biomarkers used in clinical practice. Data coming from literature suggests the use of PCT for VAP prognosis and as a based algorithm tool for the reduction of duration of pneumonia therapy, as well as, the use of the CRP dynamics to the early prediction of VAP and the response to the antibiotics.

SUMMARY

The evidence for the use of biomarkers to diagnose nosocomial pneumonia as a stand-alone tool is low to moderate. Improved performance for both PCT and CRP can be obtained by using them in association with clinical features or scoring systems but prospective studies are still needed to validate this hypothesis.

Soluble triggering receptor expressed on myeloid cell-1 (sTREM-1): a potential biomarker for the diagnosis of infectious diseases

Sensitive and useful biomarkers for the diagnosis and prognosis of infectious diseases have been widely developed. An example of these biomarkers is triggering receptor expressed on myeloid cell-1 (TREM-1), which is a cell surface receptor expressed on monocytes/macrophages and neutrophils. TREM-1 amplifies inflammation by activating the TREM-1/DAP12 pathway. This pathway is triggered by the interaction of TREM-1 with ligands or stimulation by bacterial lipopolysaccharide. Consequently, pro-inflammatory cytokines and chemokines are secreted. Soluble TREM-1 (sTREM-1) is a special form of TREM-1 that can be directly tested in human body fluids and well-known biomarker for infectious diseases. sTREM-1 level can be potentially used for the early diagnosis and prognosis prediction of some infectious diseases, including infectious pleural effusion, lung infections, sepsis, bacterial meningitis, viral infections (e.g., Crimean Congo hemorrhagic fever and dengue fever), fungal infections (e.g., Aspergillus infection), and burn-related infections. sTREM-1 is a more sensitive and specific biomarker than traditional indices, such as C-reactive protein and procalcitonin levels, for these infectious diseases. Therefore, sTREM-1 is a feasible biomarker for the targeted therapy and rapid and early diagnosis of infectious diseases.

New parameters for childhood ventilator associated pneumonia diagnosis

PURPOSE

Our aim is to determine whether the presence of soluble triggering receptor expressed on myeloid cells-1 (s-TREM-1) of bronchoalveolar lavage fluid (BALF), serum procalcitonin levels (PCT), and Clinical Pulmonary Infection Score (CPIS) have diagnostic value in children with VAP.

METHODS

All children followed in pediatric intensive care unit (PICU) who were mechanically ventilated at least for 48 hr between January 2014 and December 2015 were enrolled into our study. BALF sample was obtained via non-bronchoscopic method from the children with VAP suspicion (case group) and s-TREM-1 levels were measured. Furthermore we calculated CPIS and measured serum PCT levels. Same procedures were applied to the control group who were admitted to PICU without infectious problems and who were not under antimicrobial therapy. First we compared the case group with the control group and then we compared the quantitative culture confirmed and non-confirmed VAP cases among themselves.

RESULTS

Case group (n:58) had significant higher PCT and s-TREM-1 levels compared to control group (n:58). The VAP confirmed cases had higher s-TREM-1, PCT ve CPIS levels compared to non-confirmed VAP cases. s-TREM-1, PCT ve CPIS variables were found to be independent risk factors for VAP. The cutoff values for s-TREM-1, CPIS, and PCT, are 281 pg/ml, 6, and 1.9 ng/ml, respectively. The patients whose s-TREM-1, CPIS, and PCT values above the cutoff levels were found to have higher cumulative VAP rate.

CONCLUSIONS

s-TREM-1 of BALF, serum PCT levels, and CPIS are useful predictors for ventilator-associated pneumonia diagnosis in children. Pediatr Pulmonol. 2017;52:119-128. © 2016 Wiley Periodicals, Inc.

Comparison of soluble urokinase plasminogen activator receptor, soluble triggering receptor expressed on myeloid cells 1, procalcitonin and C-reactive protein in distinguishing concurrent bacterial infection from idiopathic inflammatory myopathy

The aim of the study was to measure the diagnostic values of biomarkers of bacterial infection in idiopathic inflammatory myopathy (IIM) patients. The serum and clinical data of 82 IIM patients with/without bacterial infection were collected. Concentrations of soluble urokinase plasminogen activator receptor (suPAR), soluble triggering receptor expressed on myeloid cells 1 (sTREM-1), procalcitonin (PCT) and C-reactive protein (CRP) were measured in IIM patients and healthy controls. There were no significant differences in serum suPAR and sTREM-1 levels between healthy controls and non-infection IIM patients. Serum levels of suPAR, sTREM-1, PCT and CRP measured in this study were significantly higher in the IIM patient group with concurrent infection than in the non-infection IIM patient group (p < 0.05). The biomarker suPAR showed the highest diagnostic value with sensitivity, specificity, positive predictive value and negative predictive value of 81.6, 77.3, 75.6 and 82.9%, respectively. Combining suPAR negative and CRP negative to rule out bacterial infection in IIM patients provides a very high specificity of 97.4%. Both suPAR and CRP positive to confirm bacterial infection give the specificity of 90.9%. The inflammatory biomarkers suPAR, sTREM-1, PCT and CRP offer diagnostic accuracy in detecting bacterial infection in IIM patients. Particularly, suPAR is the most sensitive and specific biomarker to predict bacterial infection in IIM patients. Combination of suPAR and CRP serum levels provides an even better confirmation of bacterial infection.

Role of C-reactive Protein and Tumor Necrosis Factor-Alpha in Differentiating between Ventilator-Associated Pneumonia and Systemic Inflammatory Response Syndrome without Infectious Etiology

BACKGROUND

Differential diagnosis of systemic inflammatory response syndrome (SIRS) with or without infectious cause is critically important in terms of initiating antimicrobial agents in case of infectious etiology such as ventilator-associated pneumonia (VAP). The aim of this study was to determine the diagnostic and prognostic roles of C-reactive protein (CRP) and tumor necrosis factor-alpha (TNF-α) in differentiating between ventilator-associated pneumonia and SIRS without infectious etiology.

MATERIALS AND METHODS

In this prospective observational study, 91 adult intensive care unit (ICU) patients were enrolled. According to established diagnostic criteria, they were classified into three groups of "non-SIRS non-VAP", "SIRS non-VAP" and "SIRS-VAP". Serum CRP and TNF-α were measured on days 1, 3 and 7 of the study and compared using repeated measures ANOVA.

RESULTS

With respect to diagnosis, there was no significant difference in the values of these biomarkers between groups (P>0.05). There was no statistically significant "time trend" for C-reactive protein and TNF-α (P>0.05). Considering both group effect and Time effect, the changes were not significantly different for CRP (P= 0.86) and TNF-α (P=0.69). In contrast, the clinical score and the clinical pulmonary infection score (CPIS) ≥ 6, had 100% specificity for diagnosing VAP. With respect to prognosis, only an unchanged or decreasing TNF-α from day 1 to day 3 was marginally associated with 28-day survival. However, day 1 and day 3 acute physiology and chronic health evaluation II (APACHE II) scores were highly associated with 28-day survival.

CONCLUSION

Unlike clinical scoring system including CPIS and APACHE II, TNF-α and CRP levels were not useful as diagnostic or prognostic biomarkers for differentiating between SIRS with VAP etiology and SIRS without infectious etiology.

What was old is new again: using the host response to diagnose infectious disease

A century of advances in infectious disease diagnosis and treatment changed the face of medicine. However, challenges continue to develop including multi-drug resistance, globalization that increases pandemic risks and high mortality from severe infections. These challenges can be mitigated through improved diagnostics, focusing on both pathogen discovery and the host response. Here, we review how 'omics' technologies improve sepsis diagnosis, early pathogen identification and personalize therapy. Such host response diagnostics are possible due to the confluence of advanced laboratory techniques (e.g., transcriptomics, metabolomics, proteomics) along with advanced mathematical modeling such as machine learning techniques. The road ahead is promising, but obstacles remain before the impact of such advanced diagnostic modalities is felt at the bedside.

A 2015 Update on Ventilator-Associated Pneumonia: New Insights on Its Prevention, Diagnosis, and Treatment

Ventilator-associated pneumonia (VAP), an infection of the lower respiratory tract which occurs in association with mechanical ventilation, is one of the most common causes of nosocomial infection in the intensive care unit (ICU). VAP causes significant morbidity and mortality in critically ill patients including increased duration of mechanical ventilation, ICU stay and hospitalization. Current knowledge for its prevention, diagnosis and management is therefore important clinically and is the basis for this review. We discuss recent changes in VAP surveillance nomenclature incorporating ventilator-associated conditions and ventilator-associated events, terms recently proposed by the Centers for Disease Control. To the extent possible, we rely predominantly on data from randomized control trials (RCTs) and meta-analyses.

Immune cell expression of GABAA receptors and the effects of diazepam on influenza infection

Benzodiazepines increase vulnerability to infection through α1 subunit dependent Υ-amino-butyric-type-A (GABAA) signalling. Immune cell expression of GABAA receptors and the effect of diazepam on influenza infection was investigated. In patients with pneumonia, α1 GABAA subunits were expressed on alveolar macrophages and blood monocytes. In mice, influenza induced dynamic changes in immune cell GABAA subunit expression: α1 subunits decreased on alveolar macrophage, but increased on monocytes, CD4+ and CD8+ T cells. Following influenza viral infection, diazepam delayed weight loss on day 3 but later increased weight loss. Viral load was unaffected but increased bacterial superinfection was noted on day 10.