Changes in eosinophil count during bacterial infection: revisiting an old marker to assess the efficacy of antimicrobial therapy

Normalization of eosinophil count is predictive of oxygen weaning over the course of COVID-19 infection among hospitalized adults during the first wave of 2020 pandemic

Background

Understanding COVID-19 outcomes remains a challenge. While numerous biomarkers have been proposed for severity at admission, limited exploration exists for markers during the infection course, especially for the requirement of oxygen therapy. This study investigates the potential of eosinophil count normalization as a predictor for oxygen weaning during the initial wave of the pandemic.

Methods

A retrospective study was conducted between March and April 2020 (first wave) among adults admitted directly to a medicine ward. Biological abnormalities, including lymphocyte count, eosinophil count, and C-reactive protein (CRP), were gathered daily during the first week of admission according to oxygen level. In case of worsening, oxygen level was censored at 15 L/min. The primary aim was to assess whether eosinophil count normalization predicts a subsequent decrease in oxygen requirements.

Results

Overall, 132 patients were admitted, with a mean age of 59.0 ± 16.3 years. Of the patients, 72% required oxygen, and 20.5% were admitted to the intensive care unit after a median delay of 48 hours. The median CRP at admission was 79 (26-130) mg/L, whereas the eosinophil count was 10 (0-60)/mm3. Eosinophil count normalization (≥100/mm3) by day 2 correlated significantly with decreased oxygen needs (<2 L) with hazard ratio (HR) = 3.7 [1.1-12.9] (p = 0.04). Likewise, CRP < 80 mg/L was associated with reduced oxygen requirements (p < 0.001). Predictors, including underlying chronic respiratory disease, exhibited a trend toward a negative association (p = 0.06).

Conclusion

The study highlights the relationship between eosinophil count and CRP, with implications for predicting oxygen weaning during COVID-19. Further research is warranted to explore the relevance of these biomarkers in other respiratory infections.

Association between low eosinophil count and acute bacterial infection, a prospective study in hospitalized older adults

BACKGROUND

The incidence of sepsis increases significantly with age, including a high incidence of bacterial infection in the old adults. Eosinopenia and the CIBLE score have been proposed in critically ill adults and in internal medicine wards. This study aimed to assess whether a low eosinophil count was associated with acute bacterial infection among hospitalized older adults, and to find the most efficient eosinophil count cut-off to differentiate acute bacterial infection from other inflammatory states.

METHODS

This was a prospective study from July 2020 to July 2022 in geriatric wards of the University Paul Brousse Hospital (Villejuif, France) including patients aged of 75 y/o or over suffering from fever or biological inflammation. Acute bacterial infection was assessed using biological identification and/or clinical and radiological data.

RESULTS

A total of 156 patients were included. Eighty-two (53%) patients suffered from acute bacterial infection (mean age (SD) 88.7 (5.9)). Low eosinophil count was independently associated with acute bacterial infection: OR [CI95%] 3.03 [1.04-9.37] and 6.08 [2.42-16.5] for eosinophil count 0-0.07 G/L and 0.07-0.172 G/L respectively (vs. eosinophil count > 0.172 G/L). Specificity and sensitivity for eosinophil count < 0.01 G/L and CIBLE score were 84%-49% and 72%-62%, respectively with equivalent AUCs (0.66 and 0.67).

CONCLUSION

Eosinophil count < 0.01 G/L is a simple, routinely used and inexpensive tool which can easily participate in antibiotic decisions for older adults. Further studies are needed to assess clinical benefits.

TRIAL REGISTRATION

The study was registered at Clinical trial.gov (NCT04363138-23/04/2020).

Bordetella spp. block eosinophil recruitment to suppress the generation of early mucosal protection

Bordetella spp. are respiratory pathogens equipped with immune evasion mechanisms. We previously characterized a Bordetella bronchiseptica mutant (RB50ΔbtrS) that fails to suppress host responses, leading to rapid clearance and long-lasting immunity against reinfection. This work revealed eosinophils as an exclusive requirement for RB50ΔbtrS clearance. We also show that RB50ΔbtrS promotes eosinophil-mediated B/T cell recruitment and inducible bronchus-associated lymphoid tissue (iBALT) formation, with eosinophils being present throughout iBALT for Th17 and immunoglobulin A (IgA) responses. Finally, we provide evidence that XCL1 is critical for iBALT formation but not maintenance, proposing a novel role for eosinophils as facilitators of adaptive immunity against B. bronchiseptica. RB50ΔbtrS being incapable of suppressing eosinophil effector functions illuminates active, bacterial targeting of eosinophils to achieve successful persistence and reinfection. Overall, our discoveries contribute to understanding cellular mechanisms for use in future vaccines and therapies against Bordetella spp. and extension to other mucosal pathogens.

Changes in Inflammatory Markers in Patients Treated for Buruli Ulcer and Their Ability to Predict Paradoxical Reactions

Mycobacterium ulcerans causes Buruli ulcer, the third most frequent mycobacterial disease after tuberculosis and leprosy. Transient clinical deteriorations, known as paradoxical reactions (PRs), occur in some patients during or after antibiotic treatment. We investigated the clinical and biological features of PRs in a prospective cohort of 41 patients with Buruli ulcer from Benin. Neutrophil counts decreased from baseline to day 90, and interleukin 6 (IL-6), granulocyte colony-stimulating factor, and vascular endothelial growth factor were the cytokines displaying a significant monthly decrease relative to baseline. PRs occurred in 10 (24%) patients. The baseline biological and clinical characteristics of the patients presenting with PRs did not differ significantly from those of the other patients. However, the patients with PRs had significantly higher IL-6 and tumor necrosis factor alpha (TNF-α) concentrations on days 30, 60, and 90 after the start of antibiotic treatment. The absence of a decrease in IL-6 and TNF-α levels during treatment should alert clinicians to the possibility of PR onset.

Changes in leukocytes and CRP in different stages of major depression

Background

We recently reported increased levels of neutrophils, monocytes and C-reactive protein (CRP) correlated with symptom severity in acute schizophrenia. Here, we investigated if a similar pattern of innate immune system activation occurs in major depression (MD).

Methods

We assessed differential blood counts, CRP, depression symptoms (HAMD-21) and psychosocial functioning (GAF) in controls (n = 129) and patients with first (FEMD: n = 82) or recurrent (RMD: n = 47) disease episodes of MD at baseline (T0; hospital admission) and after 6-weeks treatment (T6).

Results

Considering smoking, BMI and gender as covariates, neutrophils (FEMD: p = 0.034, RMD: p = 0.034) and CRP (FEMD: p < 0.001, RMD: p = 0.021) were higher, and eosinophils (FEMD: p = 0.005, RMD: p = 0.004) lower in patients versus controls at T0. Baseline lymphocyte counts were elevated in RMD (p = 0.003) but not FEMD. Results were confirmed by analyses of nonsmokers. At follow-up, eosinophils rose significantly in FEMD (p = 0.011) but no significant changes were observed in RMD. Improvement in HAMD-21 correlated with T0–T6 changes of neutrophil counts in FEMD (r = 0.364, p = 0.024). Compared with our previous schizophrenia study, raised baseline neutrophil and reduced eosinophil counts in MD had smaller effect sizes and treatment had a weaker association with T0-T6 changes in neutrophils. In addition, lymphocytes were elevated at T0 in recurrent MD but not in schizophrenia patients.

Conclusions

These findings suggest that innate immunity may be involved in early stages of MD, and adaptive immunity may be involved in chronic disease. Thus, further studies may lead to new disease stage-dependent MD treatment strategies targeting different aspects of immune system activation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02429-7.

Eosinophil Cell Count Predicts Mortality in the Intensive Care Unit after Return of Spontaneous Circulation

BACKGROUND

Eosinophils constitute 1%-5% of peripheral blood leukocytes, less in the presence of acute infections (referred to as eosinopenia). Studies indicate that eosinopenia can be used as a prognostic predictor for chronic obstructive pulmonary disease exacerbation, sepsis, or acute myocardial infarction disease. There are only a few studies about predicting mortality in emergency departments and intensive care units (ICUs). Prognostic studies about patients in ICUs are generally carried out using different scoring systems. We aimed to analyze if the eosinophil count can estimate the prognosis among non-traumatic patients who underwent cardiopulmonary resuscitation and were hospitalized in ICU thereafter.

METHODS

The data were evaluated of 865 non-traumatic adult patients (>18 years of age) who were admitted with cardiopulmonary arrest or developed cardiopulmonary arrest during clinical follow-ups. Admission venous blood sample tests, complete blood count, and biochemical laboratory results were recorded. Arterial blood gas results were also evaluated. The mean results of the recorded laboratory results were compared between the surviving and non-surviving patients groups.

RESULTS

There was a significant difference between the two groups in regard to platelet, eosinophil count, pH, PaO₂, SaO₂, and HCO₃^- (P<0.001 for all). In the multiple linear regression analysis, eosinophil counts were found to be an independent factor (odds ratio=0.03, 95% confidence interval 0.33-0.56, P<0.001) associated with the mortality after cardiopulmonary resuscitation.

CONCLUSION

Because admission eosinophil counts can be measured easily, they are inexpensive biomarkers that can be used for predicting the prognosis among the patients who have return of spontaneous circulation and are treated in ICUs.

Eosinopenia as a biomarker for antibiotic use in COPD exacerbations: protocol for a retrospective hospital-based cohort study

INTRODUCTION

The acute exacerbation of chronic obstructive pulmonary disease (AECOPD) has a seriously negative impact on patients' healths condition and disease progression. Bacterial infection is closely related to AECOPD, and antibiotics are frequently used in clinical practice. The lack of specific biomarkers for rational antibiotics use always leads to antibiotics abuse in chronic obstructive pulmonary disease (COPD) flare-ups. Eosinopenia has been considered to be related to increased bacterial load of potentially pathogenic organisms at the onset of COPD exacerbations. Therefore, this study aims to investigate whether eosinopenia could be used as a reference for the use of antibiotics in AECOPD.

METHODS AND ANALYSIS

In this study, a hospital-based retrospective cohort design will be adopted to analyse the clinical data of inpatients who are primarily diagnosed with AECOPD in West China Hospital of Sichuan University from 1 January 2010 to 31 December 2020. Relevant data will be extracted from the Clinical Big Data Platform for Scientific Research in West China Hospital, including demographic characteristics, blood eosinophil count, procalcitonin, C reactive protein, microbial cultivation, antibiotics use, length of hospital stay, non-invasive ventilation use, intensive care unit transfer and mortality, etc. The collected data will be described and inferred by corresponding statistical methods according to the data type and their distributions. Multiple binary logistic regression models will be used to analyse the relationship between blood eosinophil count and bacterial infection. The antibiotics use, and patient morbidity and mortality will be compared between patients with or without eosinopenia.

ETHICS AND DISSEMINATION

This study has been approved by the Biomedical Ethics Review Board of West China Hospital of Sichuan University (Approval No. 2020-1056). And the research results will be published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ChiCTR2000039379.

Clinicopathological Characteristics Related to Etiologies of Erythema Nodosum: A 10-Year Retrospective Study

Background

Erythema nodosum (EN) is the most common panniculitis associated with a wide variety of conditions. Updated studies regarding the clinicopathological manifestations related to etiologies of EN and its prognosis are limited.

Objective

We aimed to explore the clinicopathological features in relation to the etiologies of EN and determine characteristics of disease recurrence and its predictive factors.

Methods

A total of 169 patients with biopsy-proven EN or septal panniculitis from January 2008 to September 2018 were retrospectively reviewed. Patients were classified as either idiopathic or secondary EN. Patients’ general information, clinical manifestations, investigations, and recurrence of EN were recorded. The details on histopathological findings were reviewed by a blinded dermatopathologist.

Results

The mean age at diagnosis of EN was 40.6 ± 17.3 years. The majority of patients (85.2%) were female. Idiopathic EN was found in 62.7% of patients. Tuberculosis (23.8%) and drugs (23.8%) were the leading causes of secondary EN. In univariate logistic regression analysis, lesions on upper extremities (p = 0.018), fever (p = 0.003), clinical lymphadenopathy (p < 0.001) favored secondary EN. Histopathologically, the presence of focal peripheral lobular panniculitis with eosinophils was linked to idiopathic EN (p = 0.03). However, multivariable logistic regression analysis failed to demonstrate factors associated with secondary EN. Recurrence was found in 46.6% of patients with no identifiable predictive factors.

Conclusion

Although no clinical risk factors were associated with the etiology of EN, the histopathological presence of eosinophils in focal peripheral lobular panniculitis suggested idiopathic EN.

A Comprehensive Analysis of the Stability of Blood Eosinophil Levels

Rationale: Blood eosinophil counts are used to inform diagnosis/management of eosinophilic asthma. Objectives: Examine blood eosinophil variability and identify factors affecting eosinophil levels to inform clinical interpretation. Methods:Post hoc analysis to understand eosinophil variability using data from four randomized controlled asthma trials. We examined 1) influence of intrinsic/extrinsic factors (comorbidities, medication, and patient history) using baseline data (n = 2,612); 2) monthly variation using placebo-treated patient data (n = 713); 3) stability of eosinophil classification (<150, 150-299, and ⩾300 cells/μl) in placebo-treated patients with monthly measurements over a 1-year period (n = 751); and 4) impact of technical factors (laboratory-to-laboratory differences and time from collection to analysis). Results: Of intrinsic/extrinsic factors examined, nasal polyps increased eosinophil levels by 38%, whereas current smoking decreased levels by 23%. Substantial seasonal differences in eosinophil counts were observed, with differences of ∼20% between July and January. Eosinophil levels between 150 and 299 cells/μl were least stable, with 44% of patients remaining in the same classification for seven of 10 measurements versus 59% and 66% of patients in the <150 and ⩾300 cells/μl subgroups, respectively. Measurements at different laboratories showed high association (Spearman's correlation coefficient, R = 0.89); however, eosinophil counts were reduced, with longer time from collection to analysis, and variability increased with increasing eosinophil counts. Conclusions: Several intrinsic, extrinsic, and technical factors may influence, and should be considered in, clinical interpretation of eosinophil counts. Additionally, a single measurement may not be sufficient when using eosinophil counts for diagnosis/management of eosinophilic asthma.

Persistent eosinopenia is associated with in-hospital mortality among older patients: unexpected prognostic value of a revisited biomarker

Introduction

Infection is one of the major causes of mortality and morbidity in older adults. Available biomarkers are not associated with prognosis in older patients. This study aimed to analyze the value of eosinopenia (eosinophil count< 100/mm³) as a prognosis marker among older patients with suspected or confirmed bacterial infection.

Methods

A retrospective study was performed from 1 January to 31 December 2018 among patients in a geriatrics ward suffering from a bacterial infection treated with antibiotics. Biomarker data including the eosinophil count, neutrophil count and C-reactive protein (CRP) were collected within 4 days after patient diagnosis. Persistent eosinopenia was defined as a consistent eosinophil count< 100/mm³ between Day 2 and Day 4. The association of biomarkers with 30-day hospital mortality in a multivariate analysis was assessed and their predictive ability using the area under the ROC curve (AUC) was compared.

Results

Our study included 197 patients with a mean age of 90 ± 6 years. A total of 36 patients (18%) died during their stay in hospital. The patients who died were more likely to have persistent eosinopenia in comparison to survivors (78% versus 34%, p < 0.001). In the multivariate analysis, persistent eosinopenia was associated with in-hospital mortality with an adjusted HR of 8.90 (95%CI 3.46–22.9). The AUC for eosinophil count, CRP and neutrophil count between Day 2 and Day 4 were 0.7650, 0.7130, and 0.698, respectively.

Conclusion

Persistent eosinopenia within 4 days of diagnosis of bacterial infection appeared to be a predictor of in-hospital mortality in older patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-021-02515-0.

Eosinophils and Bacteria, the Beginning of a Story

Eosinophils are granulocytes primarily associated with TH2 responses to parasites or immune hyper-reactive states, such as asthma, allergies, or eosinophilic esophagitis. However, it does not make sense from an evolutionary standpoint to maintain a cell type that is only specific for parasitic infections and that otherwise is somehow harmful to the host. In recent years, there has been a shift in the perception of these cells. Eosinophils have recently been recognized as regulators of immune homeostasis and suppressors of over-reactive pro-inflammatory responses by secreting specific molecules that dampen the immune response. Their role during parasitic infections has been well investigated, and their versatility during immune responses to helminths includes antigen presentation as well as modulation of T cell responses. Although it is known that eosinophils can present antigens during viral infections, there are still many mechanistic aspects of the involvement of eosinophils during viral infections that remain to be elucidated. However, are eosinophils able to respond to bacterial infections? Recent literature indicates that Helicobacter pylori triggers TH2 responses mediated by eosinophils; this promotes anti-inflammatory responses that might be involved in the long-term persistent infection caused by this pathogen. Apparently and on the contrary, in the respiratory tract, eosinophils promote TH17 pro-inflammatory responses during Bordetella bronchiseptica infection, and they are, in fact, critical for early clearance of bacteria from the respiratory tract. However, eosinophils are also intertwined with microbiota, and up to now, it is not clear if microbiota regulates eosinophils or vice versa, or how this connection influences immune responses. In this review, we highlight the current knowledge of eosinophils as regulators of pro and anti-inflammatory responses in the context of both infection and naïve conditions. We propose questions and future directions that might open novel research avenues in the future.

Eosinophils as Major Player in Type 2 Inflammation: Autoimmunity and Beyond

Eosinophils are a subset of differentiated granulocytes which circulate in peripheral blood and home in several body tissues. Along with their traditional relevance in helminth immunity and allergy, eosinophils have been progressively attributed important roles in a number of homeostatic and pathologic situations. This review aims at summarizing available evidence about eosinophils functions in homeostasis, infections, allergic and autoimmune disorders, and solid and hematological cancers.Their structural and biological features have been described, along with their physiological behavior. This includes their chemokines, cytokines, granular contents, and extracellular traps. Besides, pathogenic- and eosinophilic-mediated disorders have also been addressed, with the aim of highlighting their role in Th2-driven inflammation. In allergy, eosinophils are implicated in the pathogenesis of atopic dermatitis, allergic rhinitis, and asthma. They are also fundamentally involved in autoimmune disorders such as eosinophilic esophagitis, eosinophilic gastroenteritis, acute and chronic eosinophilic pneumonia, and eosinophilic granulomatosis with polyangiitis. In infections, eosinophils are involved in protection not only from parasites but also from fungi, viruses, and bacteria. In solid cancers, local eosinophilic infiltration is variably associated with an improved or worsened prognosis, depending on the histotype. In hematologic neoplasms, eosinophilia can be the consequence of a dysregulated cytokine production or the result of mutations affecting the myeloid lineage.Recent experimental evidence was thoroughly reviewed, with findings which elicit a complex role for eosinophils, in a tight balance between host defense and tissue damage. Eventually, emerging evidence about eosinophils in COVID-19 infection was also discussed.

Silent existence of eosinopenia in sepsis: a systematic review and meta-analysis

BACKGROUND

Sepsis is a life-threatening and time-critical medical emergency; therefore, the early diagnosis of sepsis is essential to timely treatment and favorable outcomes for patients susceptible to sepsis. Eosinopenia has been identified as a potential biomarker of sepsis in the past decade. However, its clinical application progress is slow and its recognition is low. Recent studies have again focused on the potential association between Eosinopenia and severe infections. This study analyzed the efficacy of Eosinopenia as a biomarker for diagnosis of sepsis and its correlation with pathophysiology of sepsis.

METHOD

The protocol for this meta-analysis is available in PROSPERO (CRD42020197664). We searched PubMed, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials CENTRAL databases to identify studies that met the inclusion criteria. Two authors performed data extraction independently. The pooled outcomes were calculated by TP (true positive), FP (false positive), FN (false negative), TN (true negative) by using bivariate meta-analysis model in STATA 14.0 software. Meanwhile, possible mechanisms of sepsis induced Eosinopenia was also analyzed.

RESULTS

Seven studies were included in the present study with a total number of 3842 subjects. The incidence of Eosinopenia based on the enrolled studies varied from 23.2 to 92.7%. For diagnosis of sepsis, the pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio of Eosinopenia were 0.66 (95%CI [0.53-0.77]), 0.68 (95%CI [0.56-0.79]), 2.09 (95%CI [1.44-3.02]), 0.49 (95%CI [0.34-0.71]) and 4.23 (95%CI [2.15-8.31]), respectively. The area under the summary receiver operator characteristic curve (SROC) was 0.73 (95%CI [0.68-0.76]). Meta-regression analysis revealed that no single parameter accounted for the heterogeneity of pooled outcomes. For each subgroup of different eosinopenia cutoff values (50, 40, ≤25, 100), the sensitivity was 0.61, 0.79, 0.57, 0.54, and the specificity was 0.61, 0.75, 0.83, 0.51, respectively.

CONCLUSIONS

Our findings suggested that Eosinopenia has a high incidence in sepsis but has no superiority in comparison with conventional biomarkers for diagnosis of sepsis. However, eosinopenia can still be used in clinical diagnosis for sepsis as a simple, convenient, fast and inexpensive biomarker. Therefore, further large clinical trials are still needed to re-evaluate eosinopenia as a biomarker of sepsis.

Eosinopenia <100/μL as a marker of active COVID-19: An observational prospective study

Objectives

To analyse the diagnostic performance of eosinopenia, alone or combined with polymorphonuclear neutrophils (PMN) and/or lymphocytes, as a marker of active COVID-19 in patients hospitalized for suspicion of SARS-CoV-2 infection.

Methods

A prospective observational study including patients hospitalized for suspicion of COVID-19 in a COVID unit was performed from 20th March to 5th April 2020, in Perpignan, France. Patients for which there was a doubt upon diagnosis, who were recently under oral corticosteroids, had myeloid malignancy or human immunodeficient virus infection were excluded. SARS-CoV-2 detection was performed using an RT-PCR assay, from nasopharyngeal swab specimens. Complete blood count were performed for all patients.

Results

One-hundred and twenty-one patient were included: 57 patients were diagnosed with COVID-19, 64 patients were not. Eosinophil count was lower in the COVID-19 group (median: 0/μL versus 70/μL, p < 0.0001). To diagnose COVID-19, eosinopenia had a sensitivity of 89.5% and a specificity of 78.1% while lymphopenia's were 73.7% and 62.5% respectively. Using area under curve (AUC) of receiving operating characteristics (ROC) curves, eosinophil's optimal cut-off level was 10/μL, sensitivity and specificity were 86%, and 79.7% respectively. Regarding the eosinophil/PMN ratio, the optimal cut-off level was 3.344, sensitivity and specificity were 87.7% and 73.4% respectively. The AUC of lymphocyte/PMN ratio was significantly lower than eosinophil/PMN ratio's (0.621 versus 0.846, p = 0.0003).

Conclusion

Eosinopenia – <10/μL – and eosinophil/PMN ratio are useful, low-cost, reproducible tools to help diagnose COVID-19, during an epidemic period, in a population of hospitalized patients admitted for suspicion of COVID-19.

Eosinopenia as predictor of infection in patients admitted to an internal medicine ward: a cross-sectional study

Supplemental Digital Content is available in the text

Background:

The identification of infection in an internal medicine ward is crucial but not always straightforward. Eosinopenia has been proposed as a marker of infection, but specific cutoffs for prediction are not established yet. We aim to assess whether there is difference in eosinophil count between infected and noninfected patients and, if so, the best cutoffs to differentiate them.

Methods:

Cross-sectional, observational study with analysis of all patients admitted to an Internal Medicine Department during 2 consecutive months. Clinical, laboratory and imaging data were analyzed. Infection at hospital admission was defined in the presence of either a microbiological isolation or suggestive clinical, laboratory, and/or imaging findings. Use of antibiotics in the 8 days before hospital admission, presence of immunosuppression, hematologic neoplasms, parasite, or fungal infections were exclusion criteria. In case of multiple hospital admissions, only the first admission was considered.

Sensitivity and specificity values for eosinophils, leukocytes, neutrophils, and C-reactive protein were determined by receiver operating characteristic curve. Statistical analysis was performed with IBM SPSS Statistics® v25 and MedCalc Statistical Software® v19.2.3.

Results:

A total of 323 hospitalization episodes were evaluated, each corresponding to a different patient. One hundred fifteen patients were excluded. A total of 208 patients were included, 62.0% (n = 129) of them infected at admission. Ten patients had multiple infections.

Infected patients had fewer eosinophils than uninfected patients (15.8 ± 42 vs 71.1 ± 159 cell/mm³; P < .001). An eosinophil count at admission ≤69 cell/mm³ had a sensitivity of 89.1% and specificity of 54.4% (area under the curve 0.752; 95% confidence interval 0.682–0.822) for the presence of infection. Eosinophil count of >77 cells/mm³ had a negative likelihood ratio of 0.16.

Conclusions:

Eosinophil count was significantly lower in infected than in uninfected patients. The cutoff 69 cells/mm³ was the most accurate in predicting infection. Eosinophil count >77 cells/mm³ was a good predictor of absence of infection.

Safety of Eosinophil-Depleting Therapy for Severe, Eosinophilic Asthma: Focus on Benralizumab

Eosinophils play a pivotal role in the inflammatory pathology of asthma and have been the target of new biologic treatments for patients with eosinophilic asthma. Given the central role of interleukin (IL)-5 in the eosinophil lifecycle, several therapies directed against the IL-5 pathway have been developed, including the anti-IL-5 antibodies mepolizumab and reslizumab and the IL-5 receptor α (IL-5Rα)-directed cytolytic antibody benralizumab. Eosinophil-depleting therapies represent a relatively new class of asthma treatment, and it is important to understand their long-term efficacy and safety. Eosinophils have been associated with host protection and tumor growth, raising potential concerns about the consequences of long-term therapies that deplete eosinophils. However, evidence for these associations in humans is conflicting and largely indirect or based on mouse models. Substantial prospective clinical trial and postmarketing data have accrued, providing insight into the potential risks associated with eosinophil depletion. In this review, we explore the current safety profile of eosinophil-reducing therapies, with particular attention to the potential risks of malignancies and severe infections and a focus on benralizumab. Benralizumab is an IL-5Rα-directed cytolytic monoclonal antibody that targets and efficiently depletes blood and tissue eosinophils through antibody-dependent cell-mediated cytotoxicity. Benralizumab is intended to treat patients with severe, uncontrolled asthma with eosinophilic inflammation. The integrated analyses of benralizumab safety data from the phase III SIROCCO and CALIMA trials and subsequent BORA extension trial for patients with asthma, and the phase III GALATHEA and TERRANOVA trials for patients with chronic obstructive pulmonary disease, form the principal basis for this review.

Eosinophil count (EC) as a diagnostic and prognostic marker for infection in the internal medicine department setting

INTRODUCTION

Eosinopenia has been previously investigated as a marker to differentiate infectious from non-infectious diagnoses and as a prognostic marker. Most previous studies were conducted in intensive care unit patients. Our study focuses on the value of eosinopenia in patients admitted to the Internal Medicine department.

METHODS

We retrospectively analyzed 271 consecutive patients with infection and 31 patients presenting with fever or inflammatory syndrome and a non-infectious diagnosis. We evaluated and compared the following markers for differentiating infectious from non-infectious diagnoses: eosinophil count [EC], CRP, WBC and neutrophil-to-lymphocyte count ratio [NLCR]. We also evaluated the value of eosinopenia as a monitoring parameter in patients with infections.

RESULTS

Eosinopenia at admission was found in 71% of patients with infection compared to 32% in the non-infection group. EC and NLCR were moderate markers for discriminating infection from non-infection, with an area under the receiver operating characteristic curve of 0.789 and 0.718 respectively. Significant eosinopenia (≤ 10/µL) had a high specificity (90%) for diagnosing infections. High EC at admission (> 400/µL) was rare in the infection group (1.5%), but not uncommon in the non-infection group (25.8%). Persistent eosinopenia was noted in non-survivors, compared to the rapid normalization of EC in survivors.

CONCLUSIONS

Among patients presenting with fever and/or high inflammatory markers a low EC is supportive of infection, while a high EC may suggest non-infectious diagnoses. The persistence/ resolution of eosinopenia may be a useful monitoring parameter to predict response to therapy.

Eosinopenia as a marker of diagnosis and prognostic to distinguish bacterial from aseptic meningitis in pediatrics

Procalcitonin (PCT) has proven its efficacy to distinguish bacterial from aseptic meningitis in children. Nevertheless, its use in routine is limited by its cost and availability, especially in low- and middle-income countries. It is now acknowledged that eosinopenia is a marker of infection and/or severity of the systemic inflammatory response. Although no study ever demonstrated that eosinopenia could differentiate bacterial from viral infection, we decided to conduct a study concerning meningitis in children. This bicentric and retrospective study was conducted between January 2012 and October 2018, in children hospitalized for meningitis. The white blood cell was systematically gathered at the admission to evaluate the eosinophil count. Characteristic data were compared between 2 groups: documented bacterial meningitis (DBP) and aseptic meningitis which includes documented viral meningitis (DVM) and non-documented meningitis (ND). Among 190 patients admitted for meningitis, 151 were analyzed, including DBM (n = 45), DVM (n = 73), and ND (n = 33) meningitis. Groups were comparable. Mean age was 33 ± 48 months with a sex ratio of 1.6. Mean of eosinophil count was 15 ± 34/mm³ in the DBM group versus 132 ± 167/mm³ for the aseptic meningitis group (p < 0.0001). Best threshold for the diagnosis of bacterial meningitis was an eosinophil count < 5/mm³ with a sensitivity of 80% and specificity of 73% and a likelihood ratio of 2.9. Eosinopenia seems to be a reliable and non-invasive marker of bacterial meningitis in pediatrics. The absence of extra cost makes it very interesting in low- and middle-income countries or when usual biomarkers such as PCT are unavailable.

Development of bone regeneration strategies using human periosteum-derived osteoblasts and oxygen-releasing microparticles in mandibular osteomyelitis model of miniature pig

Hypoxia and limited vascularization inhibit bone growth and recovery after surgical debridement to treat osteomyelitis. Similarly, despite significant efforts to create functional tissue-engineered organs, clinical success is often hindered by insufficient oxygen diffusion and poor vascularization. To overcome these shortcomings, we previously used the oxygen carrier perfluorooctane (PFO) to develop PFO emulsion-loaded hollow microparticles (PFO-HPs). PFO-HPs act as a local oxygen source that increase cell viability and maintains the osteogenic differentiation potency of human periosteum-derived cells (hPDCs) under hypoxic conditions. In the present study, we used a miniature pig model of mandibular osteomyelitis to investigate bone regeneration using hPDCs seeded on PFO-HPs (hPDCs/PFO-HP) or hPDCs seeded on phosphate-buffered saline (PBS)-HPs (hPDCs/PBS-HP). Osteomyelitis is characterized by a series of microbial invasion, vascular disruption, bony necrosis, and sequestrum formation due to impaired host defense response. Sequential plain radiography, computed tomography (CT), and 3D reconstructed CT images revealed new bone formation was more advanced in defects that had been implanted with the hPDCs/PFO-HPs than in defects implanted with the hPDCs/PBS-HP. Thus, PFO-HPs are a promising tissue engineering approach to repair challenging bone defects and regenerate structurally organized bone tissue with 3D architecture.

White blood cell count and eosinopenia as valuable tools for the diagnosis of bacterial infections in the ED

Identifying an infection may be difficult in the ED. Neutrophilic leukocytosis is often used in the diagnosis of infection despite its lack of specificity in situations of stress. Our objective was to study the value of each parameter of the WBC count, in particular eosinopenia, to diagnose bacterial infections in the ED. We conducted a retrospective and observational study over a period of 6 months. All patients with one of the following diagnoses were eligible: pneumonia (9.9%), pyelonephritis (26.2%), prostatitis (8.4%), appendicitis (26.2%), cholecystitis (8.4%), and diverticular sigmoiditis (5%). A total of 466 infected patients were included for statistical analysis, and a control group of 466 uninfected patients was randomly selected in the same period of time. All leukocyte count parameters were significantly modified (p < 0.001) in the infected group compared with the control group. Neutrophils and total leukocytes remain the two most suitable parameters for the diagnosis of infections in the ED. Eosinopenia represented the most efficient parameter of the WBC count for the diagnosis of urinary and biliary tract infections. Deep eosinopenia presented a specificity of 94% for the diagnosis of infection. Any modification of the WBC count associated with an elevation of CRP (> 40 mg/L) or fever (> 38.5 °C) showed a high specificity for the diagnosis of infection. A careful analysis of the WBC count remains a valuable tool for the diagnosis of infection in the ED.

[Eosinopenia in 2018]

Since 1893, eosinopenia is a biological test to help a diagnosis of bacterial infection. Several publications have confirmed this hypothesis, particularly in the intensive care, pneumology and pediatric units. The value of this marker has been identified in vascular cerebral diseases and coronary bypass. Its contribution seems as relevant as procalcitonin, without extra cost. The diagnostic performance of this test was reinforced by a composite score (CIBLE score) that may improve its value in daily routine. Finally, monitoring eosinopenia appears to be a reliable mortality marker.

Eosinophils from Physiology to Disease: A Comprehensive Review

Despite being the second least represented granulocyte subpopulation in the circulating blood, eosinophils are receiving a growing interest from the scientific community, due to their complex pathophysiological role in a broad range of local and systemic inflammatory diseases as well as in cancer and thrombosis. Eosinophils are crucial for the control of parasitic infections, but increasing evidence suggests that they are also involved in vital defensive tasks against bacterial and viral pathogens including HIV. On the other side of the coin, eosinophil potential to provide a strong defensive response against invading microbes through the release of a large array of compounds can prove toxic to the host tissues and dysregulate haemostasis. Increasing knowledge of eosinophil biological behaviour is leading to major changes in established paradigms for the classification and diagnosis of several allergic and autoimmune diseases and has paved the way to a "golden age" of eosinophil-targeted agents. In this review, we provide a comprehensive update on the pathophysiological role of eosinophils in host defence, inflammation, and cancer and discuss potential clinical implications in light of recent therapeutic advances.

Pitfalls in studies of eosinopenia and neutrophil-to-lymphocyte count ratio

There is a number of publications evaluating the eosinophil count and the neutrophil-to-lymphocyte count ratio for diagnosis, prognosis or monitoring of patients. Of special interest is the use of these parameters for discrimination between the different causes of fever (e.g. bacterial versus viral vs. non-infectious causes of fever) and for monitoring the efficacy of therapy and predict the course of the patient. However, pitfalls in previous study designs prevent applicability to clinical practice. Here, we provide a short review of the relevant literature and summarize important factors that should be taken into account when designing studies, with special attention to the selection of a proper and clinically meaningful study population and the effects of the stress response and of corticosteroids.