Exploring the Utility of Noninvasive Type 2 Inflammatory Markers for Prediction of Severe Asthma Exacerbations in Children and Adolescents

Asthma Phenotypes and Biomarkers

Asthma experienced by both adults and children is a phenotypically heterogeneous condition. Severe asthma, characterized by ongoing symptoms and airway inflammation despite high doses of inhaled and/or systemic corticosteroids, is the focus of research efforts to understand this underlying heterogeneity. Clinical phenotypes in both adult and pediatric asthma have been determined using supervised definition-driven classification and unsupervised data-driven clustering methods. Efforts to understand the underlying inflammatory patterns of severe asthma have led to the seminal discovery of type 2-high versus type 2-low phenotypes and to the development of biologics targeted at type 2-high inflammation to reduce the rates of severe asthma exacerbations. Type 2-high asthma is characterized by upregulation of T helper 2 immune pathways including interleukin (IL)-4, IL-5, and IL-13 along with eosinophilic airway inflammation, sometimes allergic sensitization, and responsiveness to treatment with corticosteroids. Type 2-low asthma is poorly responsive to corticosteroids and is not as well characterized as type 2-high asthma. Type 2-low asthma is limited by being defined as the absence of type 2-high inflammatory markers. Choosing a biologic for the treatment of severe asthma involves the evaluation of a panel of biomarkers such as blood eosinophils, total and specific immunoglobulin E/allergic sensitization, and fractional exhaled nitric oxide. In this review, we focus on the underlying pathobiology of adult and pediatric asthma, discuss the different phenotype-based treatment options for adult and pediatric type 2-high with or without allergic asthma and type 2-low asthma, and describe a clinical phenotyping approach to patients to guide out-patient therapy. Finally, we end with a discussion of whether pediatric asthma exacerbations necessitating admission to an ICU constitute their own high-risk phenotype and/or whether it is a part of other previously defined high-risk subgroups such as difficult-to-control asthma, exacerbation-prone asthma, and severe treatment-resistant asthma.

Clinical and inflammatory features of traffic-related diesel exposure in children with asthma

BACKGROUND

Epidemiologic studies have revealed associations between traffic-related pollutants such as diesel particulate matter (PM) and asthma outcomes in children, but the inflammatory features associated with diesel PM exposure in children with asthma are not understood.

OBJECTIVE

To evaluate symptoms, exacerbations, and lung function measures in children with uncontrolled asthma and their associations with residential proximity to major roadways and to determine associations between diesel PM exposure and systemic inflammatory cytokines, circulating markers of T-cell activation and exhaustion, and metabolomic features using biomarker studies.

METHODS

Children 5 to 17 years of age with physician-diagnosed, uncontrolled asthma despite treatment with an asthma controller medication completed a research visit involving questionnaires, lung function testing, and venipuncture for biomarker studies. Geocoding was performed to quantify residential proximity to major roadways and pollutant exposure.

RESULTS

A total of 447 children with uncontrolled asthma were enrolled. Children living closer to highly trafficked roadways were more disadvantaged and had more exposure to diesel PM, more exacerbations prompting an emergency department visit, and lower lung function measures. Children with the highest diesel PM exposure, compared with children with the lowest diesel PM exposure, also had blunted cytokine secretion and evidence of T-cell exhaustion, including disturbances in several metabolites associated with glutathione formation and oxidative stress.

CONCLUSION

Traffic-related diesel PM exposure in children with poorly controlled asthma is associated with poorer clinical outcomes and unique patterns of inflammation and oxidative stress. These findings argue for continued mitigation efforts to improve traffic-related air quality and health equity in children with asthma.

Distinguishing Childhood Asthma Exacerbations from Stable Asthma: The Utility of Inflammatory White Blood Cell Biomarkers

BACKGROUND

Asthma is a chronic inflammatory condition characterized by episodes of acute asthma exacerbations (AAEs), in addition to chronic airway inflammation, which has a huge impact on both the affected patients and their parents. The main objective of this study was to explore the utility of available white-blood-cell-derived inflammatory markers in diagnosing AAEs and identifying children at risk for severe exacerbations requiring admission to the pediatric intensive care unit (PICU).

METHODS

This study was a retrospective cohort study. The medical records of 128 children diagnosed with asthma exacerbation and 131 children with stable asthma between the ages of 2 and 12 years were reviewed.

RESULTS

A total of 259 participants were enrolled. Children with AAE demonstrated significantly higher white blood cell counts (WBC: 10.0 ± 4.2 × 103/μL vs. 7.1 ± 2.2 × 103/μL, p < 0.001), absolute neutrophil counts (ANC: 7398.5 ± 4600 cells/μL vs. 2634.8 ± 1448 cells/μL, p < 0.001), and neutrophil-to-lymphocyte ratios (NLR: 7.0 ± 6.8 vs. 0.9 ± 0.7, p < 0.001) but significantly lower absolute lymphocyte counts (ALC: 1794.1 ± 1536 × 103/μL vs. 3552.9 ± 1509 × 103/μL, p < 0.001). Interestingly, blood eosinophil count displayed an opposite trend: children with stable asthma had significantly more eosinophils compared to those experiencing an exacerbation (370.1 ± 342.7 cells/mm3 vs. 0.9 ± 1.9 cells/mm3, p < 0.001). Two criteria that are indicative of AAE were identified: NLR values greater than 1.2, with good discriminative ability (area under the curve [AUC] 0.90; 95% confidence interval [CI] 0.85-0.94; sensitivity 82.5%; specificity 79.5%), and ANC values exceeding 3866, with moderate discriminative ability (AUC 0.86; 95% CI 0.81-0.91; sensitivity 75.0%; specificity 82.3%). Moreover, a comparative analysis of these markers (NLR, ANC, PLR, WBC, AEC, and ALC) in patients with AAE did not demonstrate significant differences between those requiring PICU admission and those who did not require it.

CONCLUSIONS

This study contributes two major findings. The first is that NLR, ANC, WBC, and PLR are significantly higher in AAE patients compared to those with stable asthma. The second is that children with stable asthma have higher AEC and ALC levels compared to those with AAE. Furthermore, this study has revealed that the studied markers (NLR, ANC, PLR, WBC, AEC, and ALC) did not differentiate between AAE patients requiring PICU admission and those managed in the general ward, suggesting a need for alternative predictive factors.

New targets for type 2-low asthma

Asthma is characterized by airway obstruction and inflammation, and presents significant diagnostic and treatment challenges. The concept of endotypes has improved understanding of the mechanisms of asthma and has stimulated the development of effective treatment strategies. Sputum profiles may be used to classify asthma into two major inflammatory types: type 2-high (T2H) and type 2-low (T2L) asthma. T2H, characterized by elevated type 2 inflammation, has been extensively studied and several effective biologic treatments have been developed. However, managing T2L is more difficult due to the lack of reliable biomarkers for accurate diagnosis and classification. Additionally, conventional anti-inflammatory therapy does not completely control the symptoms of T2L; therefore, further research is needed to identify effective biologic treatments. This review provides new insights into the clinical characteristics and underlying mechanisms of severe T2L and investigates potential therapeutic approaches to control the disease.

Blood Eosinophils for Prediction of Exacerbation in Preschool Children With Recurrent Wheezing

BACKGROUND

Although clinical features of type 2 inflammation have been associated with poorer longitudinal outcomes in preschool children with recurrent wheezing, it remains difficult to predict which children are at highest risk for poor outcomes during a routine clinical encounter.

OBJECTIVE

We tested the hypothesis that prespecified cut points of blood eosinophil counts would predict exacerbation and treatment response outcomes in preschool children with recurrent wheezing and that prediction could be improved with the addition of a second biomarker.

METHODS

Data from 3 clinical trials of 1,074 preschool children aged 12 to 71 months with recurrent wheezing were merged. The primary outcome was the occurrence of any exacerbation during follow-up. Secondary outcomes included the annualized rate of wheezing exacerbations and the occurrence of any exacerbation requiring hospitalization. Exploratory analyses focused on exacerbation outcomes, offline exhaled nitric oxide concentrations, and caregiver-reported asthma control scores after inhaled corticosteroid treatment initiation.

RESULTS

Each blood eosinophil cut point was associated with increased odds of exacerbation, higher exacerbation rates, and greater hospitalization occurrence in preschool children with recurrent wheezing. However, outcome detection was improved in children with more elevated blood eosinophil counts. Addition of a second biomarker of type 2 inflammation improved outcome detection and was further associated with an improved response to initiation of daily inhaled corticosteroids in exploratory analyses. However, the specificity of blood eosinophils was poor.

CONCLUSIONS

Although validation studies are warranted, blood eosinophil cut points may be useful for clinical assessment and future studies of exacerbation and treatment response in preschool children with recurrent wheezing.

Cluster analysis of plasma cytokines identifies two unique endotypes of children with asthma in the pediatric intensive care unit

Children with life-threatening asthma exacerbations who are admitted to a pediatric intensive care unit (PICU) are a heterogeneous group with poorly studied inflammatory features. We hypothesized that distinct clusters of children with asthma in a PICU would be identified based on differences in plasma cytokine levels and that these clusters would have differing underlying inflammation and asthma outcomes within 1 year. Plasma cytokines and differential gene expression were measured in neutrophils isolated from children admitted to a PICU for asthma. Participants were clustered by differential plasma cytokine abundance. Gene expression differences were compared by cluster and pathway over-representation analysis was performed. We identified two clusters in 69 children with no clinical differences. Cluster 1 (n = 41) had higher cytokines compared to Cluster 2 (n = 28). Cluster 2 had a hazard ratio of 2.71 (95% CI 1.11-6.64) compared to Cluster 1 for time to subsequent exacerbation. Gene expression pathways that differed by cluster included interleukin-10 signaling; nucleotide-binding domain, leucine rich repeat containing receptor (NLR signaling); and toll-like receptor (TLR) signaling. These observations suggest that a subset of children may have a unique pattern of inflammation during PICU hospitalization that might require alternative treatment approaches.

Childhood blood eosinophils and symptoms of allergic disorders: a cross-sectional study in Southern China

PURPOSE

The relationship between childhood blood eosinophils and subtypes of allergic diseases remains understudied. This study aimed to examine the associations between childhood blood eosinophils and subtypes of asthma, rhinitis and dermatitis, as well as the modifying effect of age.

METHODS

We obtained concurrent blood cell counts and serum Immunoglobulin E (IgE) test results in 5026 children (0-13, years) from First Affiliated Hospital of Guangzhou Medical University from 2014 to 2019. Generalized additive models with multivariable adjustments were utilized to model the exposure-response relationship between eosinophils and allergic symptoms. The robustness of the association was assessed in two age categories (<6, 6-13 years).

RESULTS

The association of eosinophils with allergic asthma/rhinitis was positively nonlinear, with a plateau at levels of Q₄ (≥0.51, 10⁹/L). Conversely, exposure-response curves between eosinophils and the risk of non-allergic asthma and rhinitis were negatively linear, and especially, became statistically significant when levels of eosinophils were larger than Q₃ (≥0.30, 10⁹/L). Compared with their counterparts, school-aged children (6-13, years) with a higher level of blood eosinophils (≥0.35, 10⁹/L) were more likely to suffer from allergic asthma [relative excess risk due to interaction (RERI), 2.51; 95% CI, 1.24-3.78], allergic rhinitis (RERI, 2.79; 95% CI, 1.14-4.45) but not allergic dermatitis (RERI not significant).

CONCLUSION

Higher eosinophil counts were associated with the increased risk of allergic subtype symptoms and the decreased risk of non-allergic subtypes in children. Moreover, the associations between eosinophils and allergic asthma/rhinitis were accentuated in the school-aged child. These findings may contribute to providing novel insights for clinical administration relevance of allergic-related symptoms.Key messages:There was a positively nonlinear association between childhood eosinophils and allergic asthma/rhinitis.Age modified the associations between eosinophils and allergy-related outcomes. The associations of eosinophil with allergic asthma/rhinitis accentuated in the school-aged child (6-13, years).

Recent advances in the treatment of childhood asthma: a clinical pharmacology perspective

INTRODUCTION

Childhood asthma is a complex heterogenous inflammatory disease that can pose a large burden on patients and their caregivers. There is a strong need to adapt asthma treatment to the individual patient taking into account underlying inflammatory profiles, moving from a 'one size fits all' approach toward a much-needed personalized approach.

AREAS COVERED

This review article aims to provide an overview of recent advances in the management and treatment of pediatric asthma, including novel insights on the molecular heterogeneity of childhood asthma, the emergence of biologicals to treat severe asthma, and innovative e-health and home monitoring techniques to make asthma management more convenient and accessible.

EXPERT OPINION

Molecular technologies have provided new treatment leads. E-health and home monitoring technologies have helped to gain more insights into disease dynamics and improve adherence to treatment while bringing health care to the patient. However, uncontrolled childhood asthma is still a major unmet clinical need and precision-medicine approaches are still scarce in clinical practice. Advanced omics methods may help researchers or clinicians to more accurately phenotype and treat subtypes of childhood asthma and gain more insight into the complexity of the disease.

T2-low: what do we know?: Past, present, and future of biologic therapies in noneosinophilic asthma

T2-low asthma is an often severe asthma subtype with limited treatment options and biologic therapeutics are lacking. Several monoclonal antibodies (mAbs) targeting non-T2 cytokines were previously reported to be ineffective in asthma. These trials often investigated heterogeneous asthma populations and negative outcomes could be related to unsuitable study cohorts. More tailored approaches in selecting participants based on specific biomarkers have been beneficial in treating severe T2-high asthma. Similarly, mAbs previously deemed ineffective bear the potential to be useful when administered to the correct target population. Here, we review individual clinical trials conducted between 2005 and 2021 and assess the suitability of the selected cohorts, whether study end points were met, and whether outcome measures were appropriate to investigate the effectiveness of the respective drug. We discuss potential target groups within the T2-low asthma population and suggest biomarkers that may predict a treatment response. Furthermore, we assess whether biomarker-guided approaches or subgroup analyses were associated with more positive study outcomes. The mAbs directed against alarmins intervene early in the inflammatory cascade and are the first mAbs found to have efficacy in T2-low asthma. Several randomized controlled trials performed predefined subgroup analyses that included T2-low asthma. Subgroup analyses were associated with positive outcomes and were able to reveal a stronger response in at least 1 subgroup. A better understanding of T2-low subgroups and specific biomarkers is necessary to identify the most responsive target population for a given mAb.

Considering biomarkers in asthma disease severity

Amongst patients with asthma, reliance on the type/dose of prescribed medication and symptom control does not adequately capture those at risk of adverse outcomes, and we need biomarkers for risk and treatment stratification which are consistently accurate, readily quantifiable and reproducible. The majority of patients with severe asthma, regardless of age, have predominant type-2 (T2) inflammation mediated disease, making airway/blood eosinophils, FeNO, periostin and/or allergic sensitization potentially important biomarkers for severe disease. In both adult and pediatric asthma, there is scope to improve prediction of severe attacks by using a composite T2 biomarkers of blood eosinophils and FeNO. Technological advances in component-resolved diagnostics (CRD) microarray technologies coupled with the development of interpretation software offer a possibility to use CRD as biomarkers of asthma severity amongst sensitized asthmatics. Genetic predisposition and polygenic risk scores of relevant traits (e.g., lung function, host immune responses, biomarkers of exposure from the indoor and outdoor environment, infection and microbial dysbiosis) may also contribute to prediction algorithms. We challenge the idea that asthma can be accurately defined in an individual patient by a discrete and static "endotype" (e.g., T2-high asthma). As we traverse the new era of molecular endotyping in asthma, we need to understand how relevant mechanisms impact patient outcomes, and in parallel develop new tools and approaches to stratify therapies and define individual patient trajectories.

Severe acute asthma at the pediatric intensive care unit: can we link the clinical phenotypes to immunological endotypes?

INTRODUCTION

The clinical phenotype of severe acute asthma at the pediatric intensive care unit (PICU) is highly heterogeneous. However, current treatment is still based on a 'one-size-fits-all approach'.

AREAS COVERED

We aim to give a comprehensive description of the clinical characteristics of pediatric patients with severe acute asthma admitted to the PICU and available immunological biomarkers, providing the first steps toward precision medicine for this patient population. A literature search was performed using PubMed for relevant studies on severe acute (pediatric) asthma.

EXPERT OPINION

Omics technologies should be used to investigate the relationship between cellular molecules and pathways, and their clinical phenotypes. Inflammatory phenotypes might guide bedside decisions regarding the use of corticosteroids, neutrophil modifiers and/or type of beta-agonist. A next step toward precision medicine should be inclusion of these patients in clinical trials on biologics.

Pediatric Asthma Exacerbation in Children with Suspected and Confirmed Coronavirus Disease 2019 (COVID-19): An Observational Study from Saudi Arabia

Background

Most asthma exacerbations are caused by viral respiratory infections such as rhinovirus, coronaviruses, influenza viruses, and many others. While there have been data about the impact of COVID-19 on adult asthma, much remains unknown about the impact of COVID-19 on childhood asthma.

Methods

This retrospective cohort study included all pediatric patients aged 2 to 12 years who were admitted to Abha Maternity and Children Hospital for acute asthma exacerbation between June 1, 2020, and May 31, 2021, and underwent testing for SARS-CoV-2 using nasopharyngeal real-time polymerase chain reaction.

Results

Sixty children hospitalized with the diagnosis of asthma were included in the study. Out of these patients, 10 (16.7%) were diagnosed with COVID-19. The enrolled patients were between 2 and 12 years, with a median age of five years (interquartile range, 3.8), and 58% were males (35/60). Cough, shortness of breath, and hypoxia were the most common presenting symptoms and signs. Severe asthma was more prevalent among positive COVID-19 compared with negative COVID-19 patients (60 vs 20%; P= 0.016). In addition, chronic asthma for more than five years was more prevalent among positive COVID-19 than negative COVID-19 patients (60 vs 40%, P= 0.305). Fifty-five percent of the enrolled patients had eosinophilic asthma using a 300cells/μL threshold. None of the children required invasive respiratory support (ventilation through an endotracheal tube or tracheostomy), but 12 patients (21.7%) required respiratory support via high-flow nasal cannula. The total days of hospitalization in either PICU or pediatric general ward did not differ between the two groups. All patients were discharged, and there were no reports of serious morbidity or mortality.

Conclusion

Eosinophilic asthma was the most prevalent asthma phenotype in the study group. Furthermore, there was no difference in the presenting symptoms of an asthma flare-up, laboratory indicators, and hospitalization outcomes (critical care admission and hospital stay) between asthmatics with and without a COVID-19 diagnosis.

Childhood asthma and cardiovascular morbidity and mortality in adulthood: The Busselton Health Study

BACKGROUND

Long-term childhood asthma studies that investigate adult outcomes other than respiratory morbidity are lacking. This study examines the associations of childhood asthma and the occurrence of cardiovascular disease (CVD) events and mortality in adulthood.

METHODS

A cohort of 4430 school children (aged 17 years) who attended the Busselton Health Study between 1967 and 1983 were analyzed. Self-reported history of doctor-diagnosed asthma was determined based on the questionnaire. Subsequent CVD events (hospital admissions or death) up to 2014 were identified using the Western Australia Data Linkage System. Cox regression models were used to investigate the impact of childhood asthma on CVD events and mortality in adulthood. A subgroup of 2153 participants who re-attended a survey in young adulthood was also analyzed.

RESULTS

A total of 462 (10%) of the cohort had childhood asthma. During follow-up, 867 participants experienced a CVD event and 22 participants died from CVD. Childhood asthma was not associated with the risk of CVD events in adulthood (HR, 1.12; 95% CI: 0.91-1.39; p = .2833) and this persisted after adjustment for confounders. Childhood asthma was not associated with coronary heart disease events (HR, 0.72; 95% CI: 0.40-1.30; p = .2761), heart failure events (HR, 0.55; 95% CI: 0.07-4.13; p = .5604) or CVD mortality (HR, 0.91; 95% CI: 0.21-3.89; p = .8987) in adulthood.

CONCLUSION

Childhood asthma is not associated with the risk of CVD events and mortality in adulthood.

Treating severe asthma: Targeting the IL-5 pathway

Severe asthma is a heterogeneous disease with different phenotypes based on clinical, functional or inflammatory parameters. In particular, the eosinophilic phenotype is associated with type 2 inflammation and increased levels of interleukin (IL)-4, IL-5 and IL-13). Monoclonal antibodies that target the eosinophilic inflammatory pathways (IL-5R and IL-5), namely mepolizumab, reslizumab, and benralizumab, are effective and safe for severe eosinophilic asthma. Eosinophils threshold represents the most indicative biomarker for response to treatment with all three monoclonal antibodies. Improvement in asthma symptoms scores, lung function, the number of exacerbations, history of late-onset asthma, chronic rhinosinusitis with nasal polyposis, low oral corticosteroids use and low body mass index represent predictive clinical markers of response. Novel Omics studies are emerging with proteomics data and exhaled breath analyses. These may prove useful as biomarkers of response and non-response biologics. Moreover, future biomarker studies need to be undertaken in paediatric patients affected by severe asthma. The choice of appropriate biologic therapy for severe asthma remains challenging. The importance of finding biomarkers that can predict response continuous an open issue that needs to be further explored. This review describes the clinical effects of targeting the IL-5 pathway in severe asthma in adult and paediatric patients, focusing on predictors of response and non-response.

T2-"Low" Asthma: Overview and Management Strategies

Although the term "asthma" has been applied to all patients with airway lability and variable chest symptoms for centuries, phenotypes of asthma with distinct clinical and molecular features that may warrant different treatment approaches are well recognized. Patients with type 2 (T2)-"high" asthma are characterized by upregulation of T2 immune pathways (ie, IL-4 and IL-13 gene sets) and eosinophilic airway inflammation, whereas these features are absent in patients with T2-"low" asthma and may contribute to poor responsiveness to corticosteroid treatment. This review details definitions and clinical features of T2-"low" asthma, potential mechanisms and metabolic aspects, pediatric considerations, and potential treatment approaches. Priority research questions for T2-"low" asthma are also discussed.

Biomarkers for Severe Asthma: Lessons From Longitudinal Cohort Studies

Severe asthma (SA) is a heterogeneous disease characterized by uncontrolled symptoms, frequent exacerbations, and lung function decline. The discovery of phenotypes and endotypes of SA significantly improves our understanding of its pathophysiology and allows the advent of biologics blocking multiple molecular targets. The advances have mainly been made in type 2-high asthma associated with elevated type 2 inflammatory biomarkers such as immunoglobulin E (IgE), interleukins (IL)-4, IL-5, and IL-13. Previous clinical trials have demonstrated that type 2 biomarkers, including blood/sputum eosinophils and the fraction of exhaled nitric oxide (FeNO), were correlated to severe airway inflammation, persistent symptoms, frequent exacerbations, and the clinical efficacy of these biomarkers in predicting treatment outcomes of type 2-targeting biologics. However, it is well known that type 2 inflammation is partially attributable to the pathogenesis of SA. Although some recent studies have suggested that type 2-low and mixed phenotypes of asthma are important contributors to the heterogeneity of SA, many questions about these non-type 2 asthma phenotypes remain to be solved. Consequently, many efforts to investigate and find novel biomarkers for SA have also made in their methods. Many cross-sectional experimental studies in large-scale cohorts and randomized clinical trials have proved their value in understanding SA. More recently, real-world cohort studies have been in the limelight for SA research, which is unbiased and expected to give us an answer to the unmet needs of the heterogeneity of SA.

The Predictive Role of Biomarkers and Genetics in Childhood Asthma Exacerbations

Asthma exacerbations are associated with significant childhood morbidity and mortality. Recurrent asthma attacks contribute to progressive loss of lung function and can sometimes be fatal or near-fatal, even in mild asthma. Exacerbation prevention becomes a primary target in the management of all asthmatic patients. Our work reviews current advances on exacerbation predictive factors, focusing on the role of non-invasive biomarkers and genetics in order to identify subjects at higher risk of asthma attacks. Easy-to-perform tests are necessary in children; therefore, interest has increased on samples like exhaled breath condensate, urine and saliva. The variability of biomarker levels suggests the use of seriate measurements and composite markers. Genetic predisposition to childhood asthma onset has been largely investigated. Recent studies highlighted the influence of single nucleotide polymorphisms even on exacerbation susceptibility, through involvement of both intrinsic mechanisms and gene-environment interaction. The role of molecular and genetic aspects in exacerbation prediction supports an individual-shaped approach, in which follow-up planning and therapy optimization take into account not only the severity degree, but also the risk of recurrent exacerbations. Further efforts should be made to improve and validate the application of biomarkers and genomics in clinical settings.

Blood eosinophil count as predictor of asthma exacerbation. A meta-analysis

BACKGROUND

Evidence about the association of high blood eosinophil count with asthma exacerbation is inconsistent and unclear. The objective of this meta-analysis was to determine whether elevated blood eosinophil count predicts asthma exacerbation.

METHODS

We searched MEDLINE, EMBASE, and additional databases, without any language restriction. We also checked the reference lists of the included studies and of relevant systematic reviews. The main outcome was the occurrence of asthma exacerbation. We calculated global pooled odds ratios (ORs) and their 95% confidence intervals (CIs) and performed predefined subgroup analyses. We appraised the quality of the studies using Newcastle-Ottawa Scale, examined the heterogeneity between studies, assessed publication bias, and carried out sensitivity analyses.

RESULTS

Among 1567 retrieved publications, 23 observational studies comprising 155,772 participants met the inclusion criteria. High blood eosinophil count was associated with higher odds of asthma exacerbation [OR: 1.31 (95% CI: 1.16, 1.49)], specifically with asthma-related outpatient visits [OR: 1.46 (95% CI: 1.25, 1.70)] and emergency department visits [OR: 1.63 (95% CI: 1.29, 2.07)]. A significant association was observed starting from an eosinophils' cutoff value of 200 cells/μl. The association was observed for cohort studies [OR: 1.30 (95%CI: 1.13, 1.49)], North American studies [OR: 1.43 (95%CI: 1.31, 1.57)], Asian populations [OR: 1.67 (95%CI: 1.34, 2.08)], children [OR: 1.38 (95%CI: 1.22, 1.56)], and studies that adjusted for inhaled corticosteroids therapy [OR: 1.42 (95%CI: 1.28, 1.56)].

CONCLUSIONS

Blood eosinophil counts ≥ 200 cells/µL are associated with asthma exacerbation. Blood eosinophil count is a modifiable factor that could be addressed in asthma management strategies.

Identification and treatment of T2-low asthma in the era of biologics

Currently, and based on the development of relevant biologic therapies, T2-high is the most well-defined endotype of asthma. Although much progress has been made in elucidating T2-high inflammation pathways, no specific clinically applicable biomarkers for T2-low asthma have been identified. The therapeutic approach of T2-low asthma is a problem urgently needing resolution, firstly because these patients have poor response to steroids, and secondly because they are not candidates for the newer targeted biologic agents. Thus, there is an unmet need for the identification of biomarkers that can help the diagnosis and endotyping of T2-low asthma. Ongoing investigation is focusing on neutrophilic airway inflammation mediators as therapeutic targets, including interleukin (IL)-8, IL-17, IL-1, IL-6, IL-23 and tumour necrosis factor-α; molecules that target restoration of corticosteroid sensitivity, mainly mitogen-activated protein kinase inhibitors, tyrosine kinase inhibitors and phosphatidylinositol 3-kinase inhibitors; phosphodiesterase (PDE)3 inhibitors that act as bronchodilators and PDE4 inhibitors that have an anti-inflammatory effect; and airway smooth muscle mass attenuation therapies, mainly for patients with paucigranulocytic inflammation. This article aims to review the evidence for noneosinophilic inflammation being a target for therapy in asthma; discuss current and potential future therapeutic approaches, such as novel molecules and biologic agents; and assess clinical trials of licensed drugs in the treatment of T2-low asthma.

Performance of Eosinophil Cationic Protein as a Biomarker in Asthmatic Children

BACKGROUND

Although blood eosinophils are a frequently used marker of type 2 inflammation in children with asthma, their sensitivity is relatively poor. Additional markers of type 2 inflammation are needed.

OBJECTIVE

We hypothesized that plasma concentrations of eosinophil cationic protein (ECP), a marker of eosinophil activation, would be useful for detection of type 2 inflammation and would predict poorer asthma outcomes over 1 year.

METHODS

Children and adolescents 6 through 17 years (N = 256) with confirmed asthma completed a baseline visit and a follow-up visit at 12 months. A subset also underwent systemic corticosteroid responsiveness testing with intramuscular triamcinolone. Outcome measures at 12 months included uncontrolled asthma, lung function, and asthma exacerbations treated with systemic corticosteroids.

RESULTS

Plasma ECP concentrations ranged from 0.03 to 413.61 ng/mL (median, 6.95 ng/mL) and were consistently associated with other markers of type 2 inflammation. At baseline, children in the highest ECP tertile had poorer asthma control, more airflow limitation, and more exacerbations, but also had greater symptom improvement with intramuscular triamcinolone. At 12 months, associations between the highest ECP tertile and exacerbations, but not lung function or asthma control, persisted after covariate adjustment. However, the sensitivity of ECP was modest and was not markedly different from that of blood eosinophil counts.

CONCLUSION

Plasma ECP concentrations may be a useful marker of type 2 inflammation in children and may help identify those children at highest risk for recurrent exacerbations who could benefit from corticosteroid treatment. However, additional markers may be needed to improve sensitivity for outcome detection.

Asthma phenotypes and endotypes in childhood

Asthma is a very heterogeneous disease and since early childhood many classifications have been proposed according to phenotype and endotype. The phenotype includes the clinical features of asthma such as age of onset, triggers, comorbidities, response to treatment and evolution over time. The endotype is more difficult to define, includes the underlying immunopathological mechanisms of the disease and requires reliable biomarkers. A deep knowledge of phenotype and endotype of the patient may guide a tailored therapeutic approach. In this review the main phenotypes and endotypes of asthma acknowledged in children will be discussed.

Measuring inflammation in paediatric severe asthma: biomarkers in clinical practice

Severe asthma in children is a highly heterogeneous disorder, encompassing different clinical characteristics (phenotypes) and immunopathological pathways (endotypes). Research is focusing on the identification of noninvasive biomarkers able to predict treatment response and assist in designing personalised therapies for severe asthma. Blood and sputum eosinophils, serum IgE and exhaled nitric oxide fraction mostly reflect type 2 airway inflammation in children. However, in the absence of available point-of-care biomarkers, the diagnosis of non-type 2 asthma is still reached by exclusion. In this review, we present the most recent evidence on biomarkers for severe asthma and discuss their implementation in clinical practice. We address the methods for guiding treatment decisions and patient identification, focusing on the paediatric age group.

KEY POINTS

Severe asthma in children is a highly heterogeneous disorder, encompassing different clinical characteristics (phenotypes) and immunopathological pathways (endotypes).Research is focusing on the identification of noninvasive biomarkers able to predict treatment response and assist in designing personalised therapies for severe asthma.Blood and sputum eosinophils, serum IgE and exhaled nitric oxide fraction mostly reflect type 2 airway inflammation in children. However, knowledge regarding non-type 2 inflammation and related biomarkers is still lacking.

EDUCATIONAL AIMS

To summarise the most recent evidence on biomarkers for severe asthma in children.To discuss their implementation in clinical practice through guiding patient identification and treatment decisions.

The Journal of Allergy and Clinical Immunology: In Practice 2019 Highlights

This article provides highlights of the clinically impactful original studies and reviews published in The Journal of Allergy and Clinical Immunology: In Practice in 2019 on the subjects of anaphylaxis, asthma, dermatitis, drug allergy, food allergy, immunodeficiency, immunotherapy, rhinitis/sinusitis, and urticaria/angioedema/mast cell disorders. Within each topic, practical aspects of diagnosis and management are emphasized. Treatments discussed include lifestyle modifications, allergen avoidance therapy, positive and negative effects of pharmacologic therapy, and various forms of immunologic and desensitization management. We designed this review to help readers consolidate and use this extensive and practical knowledge for the benefit of their patients.

Opening the Window of Immune Opportunity: Treating Childhood Asthma

Asthma is an increasingly common childhood disease and although most patients can control their symptoms with medication, a proportion experience life-threatening symptoms. The advent of novel biologic therapies represents a giant leap forward for asthma treatment, but efficacy is rarely tested in children. Recent mechanistic work in mice suggests that early life is a key period for immune development and, therefore, allergen sensitization. Although children with severe asthma experience significant comorbidities and are at increased risk for serious diseases such as chronic obstructive pulmonary disease as adults, no specific investigation into tailored treatment for young children with severe asthma exists. Here, we propose how new information regarding early life immunity could be used to inform modified treatments for children.