Phenotypes of Recurrent Wheezing in Preschool Children: Identification by Latent Class Analysis and Utility in Prediction of Future Exacerbation

Dysfunctional neutrophil type 1 interferon responses in preschool children with recurrent wheezing and IL-4-mediated aeroallergen sensitization

Background

The innate mechanisms associated with viral exacerbations in preschool children with recurrent wheezing are not understood.

Objective

We sought to assess differential gene expression in blood neutrophils from preschool children with recurrent wheezing, stratified by aeroallergen sensitization, at baseline and after exposure to polyinosinic:polycytidylic acid (poly(I:C)) and also to examine whether poly(I:C)-stimulated blood neutrophils influenced airway epithelial gene expression.

Methods

Blood neutrophils were purified and cultured overnight with poly(I:C) and underwent next-generation sequencing with Reactome pathway analysis. Primary human small airway epithelial cells were treated with poly(I:C)-treated neutrophil culture supernatants and were analyzed for type 1 interferon gene expression with a targeted array. Symptoms and exacerbations were assessed in participants over 12 months.

Results

A total of 436 genes were differently expressed in neutrophils from children with versus without aeroallergen sensitization at baseline, with significant downregulation of type 1 interferons. These type 1 interferons were significantly upregulated in sensitized children after poly(I:C) stimulation. Confirmatory experiments demonstrated similar upregulation of type 1 interferons in IL-4-treated neutrophils stimulated with poly(I:C). Poly(I:C)-treated neutrophil supernatants from children with aeroallergen sensitization also induced a type 1 interferon response in epithelial cells. Children with aeroallergen sensitization also had higher symptom scores during exacerbations, and these symptom differences persisted for 3 days after prednisolone treatment.

Conclusions

Type 1 interferon responses are dysregulated in preschool children with aeroallergen sensitization, which is in turn associated with exacerbation severity. Given the importance of type 1 interferon signaling in viral resolution, additional studies of neutrophil type 1 interferon responses are needed in this population.

Emergency management and asthma risk in young Medicaid-enrolled children with recurrent wheeze

OBJECTIVES

To describe clinical characteristics of young children presenting to the emergency department (ED) for early recurrent wheeze, and determine factors associated with subsequent persistent wheeze and risk for early childhood asthma.

METHODS

Retrospective cohort study of Medicaid-enrolled children 0-3 years old with an index ED visit for wheeze (e.g. bronchiolitis, reactive airway disease) from 2009 to 2013, and at least one prior documented episode of wheeze at an ED or primary care visit. The primary outcome was persistent wheeze between 4 and 6 years of age. Demographics and clinical characteristics were collected from the index ED visit. Logistic regression was used to estimate the association between potential risk factors and subsequent persistent wheeze.

RESULTS

During the study period, 41,710 children presented to the ED for recurrent wheeze. Mean age was 1.3 years; 59% were male, 42% Black, and 6% Hispanic. At index ED visits, the most common diagnosis was acute bronchiolitis (40%); 77% of children received an oral corticosteroid prescription. Between 4 and 6 years of age, 11,708 (28%) children had persistent wheeze. A greater number of wheezing episodes was associated with an increased odds of ED treatment with asthma medications. Subsequent persistent wheeze was associated with male sex, Black race, atopy, prescription for bronchodilators or corticosteroids, and greater number of visits for wheeze.

CONCLUSIONS

Young children with persistent wheeze are at risk for childhood asthma. Thus, identification of risk factors associated with persistent wheeze in young children with recurrent wheeze might aid in early detection of asthma and initiation of preventative therapies.

Clinical Predictors of Severe Exacerbations in Pediatric Patients With Recurrent Wheezing

Introduction Wheezing is common in preschool-aged children, affecting about half of all children within their first six years of life. Children who have recurrent wheezing experience disease-related morbidity, including increased emergency visits and hospitalizations. Early-life lower respiratory tract viral infections are linked to recurrent wheezing and eventual asthma onset. Identifying high-risk children is crucial, with the frequency and severity of wheezing episodes being good predictors of long-term outcomes. Aim To identify predictors of severe exacerbations in children with recurrent wheezing. Methods We conducted a retrospective cohort study involving 168 pediatric patients with recurrent wheezing followed up at our outpatient clinic. The outcome of interest was the occurrence of a severe exacerbation, defined as any exacerbation requiring hospitalization and the need for supplemental oxygenation or ventilatory support. Results The median age of the first wheezing exacerbation was five months, with a predominance of the male gender. Approximately two-thirds of the patients had a family history of atopy. Comorbid allergic rhinitis and atopic dermatitis were present in 15.4% and 16.7% of patients, respectively. Twenty percent of patients had a severe wheezing exacerbation as the first form of presentation, and 30% presented at least one severe exacerbation from the first presentation to the last follow-up. Patients with severe exacerbations were younger at the first episode (median age 4 months, IQR 2-7, versus 7 months, IQR 4-12, p=0.027) and more frequently had a family history of atopy (71.7% versus 55.6%, p=0.050). In this cohort, patients who initially presented with a severe episode are at increased risk of incident severe exacerbations during follow-up, HR 2.24 (95%CI 1.01-4.95). Conclusions We know that the severity of exacerbations in children with recurrent wheezing correlates with the long-term outcomes of the disease. Therefore, preventing severe exacerbations can positively impact the prognosis of these patients. In this analysis, we found independent predictors of severe exacerbations to be the first clinical episode before the age of three months and a family history of atopy. We also found that patients whose initial presentation was severe have a higher risk of new severe exacerbations. Therefore, these subgroups of patients should be closely monitored by pediatricians.

Phenotypes of cough in children: A latent class analysis

INTRODUCTION

Distinguishing phenotypes among children with cough helps understand underlying causes. Using a statistical data-driven approach, we aimed to identify and validate cough phenotypes based on measurable traits, physician diagnoses, and prognosis.

METHODS

We used data from the Swiss Paediatric Airway Cohort and included 531 children aged 5-16 years seen in outpatient clinics since 2017. We included children with any parent-reported cough (i.e. cough without a cold, cough at night, cough more than other children, or cough longer than 4 weeks) without current wheeze. We applied latent class analysis to identify phenotypes using nine symptoms and characteristics and selected the best model using the Akaike information criterion. We assigned children to the most likely phenotype and compared the resulting groups for parental atopy history, comorbidities, spirometry, fractional exhaled nitric oxide (FeNO), skin prick tests and specific IgE, physician diagnoses, and 1-year prognosis.

RESULTS

We identified four cough phenotypes: non-specific cough (26%); non-allergic infectious and night cough with snoring and otitis (4%); chronic allergic dry night cough with snoring (9%); and allergic non-infectious cough with rhino-conjunctivitis (61%). Children with the allergic phenotype often had family or personal history of atopy and asthma diagnosis. FeNO was highest for the allergic phenotype [median 17.9 parts per billion (ppb)] and lowest for the non-allergic infectious phenotype [median 7.0 parts per billion (ppb)]. Positive allergy test results differed across phenotypes (p < .001) and were most common among the allergic (70%) and least common among the non-specific cough (31%) phenotypes. Subsequent wheeze was more common among the allergic than the non-specific phenotype.

CONCLUSION

We identified four clinically relevant cough phenotypes with different prognoses. Although we excluded children with current wheeze, most children with cough belonged to allergy-related phenotypes.

Functional immunophenotyping of blood neutrophils identifies novel endotypes of viral response in preschool children with recurrent wheezing

BACKGROUND

Preschool children with recurrent wheezing are heterogeneous, with differing responses to respiratory viral infections. Although neutrophils are crucial for host defense, their function has not been studied in this population.

OBJECTIVE

We performed functional immunophenotyping on isolated blood neutrophils from 52 preschool children with recurrent wheezing (aeroallergen sensitization, n = 16; no sensitization, n = 36).

METHODS

Blood neutrophils were purified and cultured overnight with polyinosinic:polycytidylic acid [poly(I:C)] as a viral analog stimulus. Neutrophils underwent next-generation sequencing with Reactome pathway analysis and were analyzed for cytokine secretion, apoptosis, myeloperoxidase, and extracellular DNA release. CD14+ monocytes were also exposed to neutrophil culture supernatant and analyzed for markers of M1 and M2 activation.

RESULTS

A total of 495 genes, related largely to the innate immune system and neutrophil degranulation, were differently expressed in children with versus without aeroallergen sensitization. Functional experiments identified more neutrophil degranulation and extracellular trap formation (ie, more myeloperoxidase and extracellular DNA) and less neutrophil proinflammatory cytokine secretion in children with aeroallergen sensitization. Neutrophils also shifted CD14+ monocytes to a more anti-inflammatory (ie, M2) phenotype in sensitized children and a more proinflammatory (ie, M1) phenotype in nonsensitized children. Although both groups experienced viral exacerbations, annualized exacerbation rates prompting unscheduled health care were also higher in children without aeroallergen sensitization after enrollment.

CONCLUSIONS

Systemic neutrophil responses to viral infection differ by allergic phenotype and may be less effective in preschool children without allergic inflammation. Further studies of neutrophil function are needed in this population, which often has less favorable therapeutic responses to inhaled corticosteroids and other therapies directed at type 2-high inflammation.

Limited clinical role of blood eosinophil levels in early life atopic disease: A mother-child cohort study

BACKGROUND

Blood eosinophil count is a well-established biomarker of atopic diseases in older children and adults. However, its predictive role for atopic diseases in preschool children is not well established.

OBJECTIVE

To investigate the association between blood eosinophil count in children and development of atopic diseases up to age 6 years.

METHODS

We investigated blood eosinophil count at age 18 months and 6 years in relation to recurrent wheeze/asthma, atopic dermatitis, allergic rhinitis, and allergic sensitization during the first 6 years of life in the two Copenhagen Prospective Studies on Asthma in Childhood cohorts (n = 1111). Blood eosinophil count was investigated in association with remission of existing atopic disease, current atopic disease, and later development of atopic disease.

RESULTS

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis, while blood eosinophil count at age 6 years was associated with increased occurrence of current wheezing/asthma (OR = 1.1; 1.04-1.16, p = .0005), atopic dermatitis (OR = 1.06; 1.01-1.1, p = .02), and allergic rhinitis (OR = 1.11; 1.05-1.18, p = .0002). Blood eosinophil count at 18 months did not predict persistence or development of recurrent wheeze/asthma or atopic dermatitis at age 6 years.

CONCLUSION

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis and did not predict persistence or development of disease. This implies a limited clinical role of blood eosinophil levels in early-life atopic disease and questions the clinical value of blood eosinophil counts measured in toddlers as a predictive biomarker for subsequent atopic disease in early childhood.

Composite predictive models for asthma exacerbations or asthma deterioration in pediatric asthmatic patients: A systematic review of the literature

A variety of factors have shown to be useful in predicting which children are at high risk for future asthma exacerbations, some of them combined into composite predictive models. The objective of the present review was to systematically identify all the available published composite predictive models developed for predicting which children are at high risk for future asthma exacerbations or asthma deterioration. A systematic search of the literature was performed to identify studies in which a composite predictive model developed for predicting which children are at high risk for future asthma exacerbations or asthma deterioration was described. Methodological quality assessment was performed using accepted criteria for prediction rules and prognostic models. A total of 18 articles, describing a total of 17 composite predictive models were identified and included in the review. The number of predictors included in the models ranged from 2-149. Upon analyzing the content of the models, use of healthcare services for asthma and prescribed or dispensed asthma medications were the most frequently used items (in 8/17, 47.0% of the models). Seven (41.2%) models fulfilled all the quality criteria considered in our evaluation. The identified models may help clinicians dealing with asthmatic children to identify which children are at a higher risk for future asthma exacerbations or asthma deterioration, therefore targeting and/or reinforcing specific interventions for these children in an attempt to prevent exacerbations or deterioration of the disease.

Social determinants of health influence preschool and caregiver experiences during symptoms and exacerbations of wheezing

BACKGROUND

Social determinants of health have been inadequately studied in preschool children with wheezing and their caregivers but may influence the care received.

OBJECTIVE

To evaluate the symptom and exacerbation experiences of wheezing preschool children and their caregivers, stratified by risk of social vulnerability, over 1 year of longitudinal follow-up.

METHODS

A total of 79 caregivers and their preschool children with recurrent wheezing and at least 1 exacerbation in the previous year were stratified by a composite measure of social vulnerability into "low" (N = 19), "intermediate" (N = 27), and "high" (N = 33) risk groups. Outcome measures at the follow-up visits included child respiratory symptom scores, asthma control, caregiver-reported outcome measures of mental and social health, exacerbations, and health care utilization. The severity of exacerbations reflected by symptom scores and albuterol use and exacerbation-related caregiver quality of life were also assessed.

RESULTS

Preschool children at high risk of social vulnerability had greater day-to-day symptom severity and more severe symptoms during acute exacerbations. High-risk caregivers were also distinguished by lower general life satisfaction at all visits and lower global and emotional quality of life during acute exacerbations which did not improve with exacerbation resolution. Rates of exacerbation or emergency department visits did not differ, but intermediate- and high-risk families were significantly less likely to seek unscheduled outpatient care.

CONCLUSION

Social determinants of health influence wheezing outcomes in preschool children and their caregivers. These findings argue for routine assessment of social determinants of health during medical encounters and tailored interventions in high-risk families to promote health equity and improve respiratory outcomes.

Impact of Adjunct Corticosteroid Therapy on Quality of Life for Children With Suspected Pneumonia

OBJECTIVE

To determine the association between adjunct corticosteroid therapy and quality of life (QoL) outcomes in children with signs and symptoms of lower respiratory tract infection and clinical suspicion for community-acquired pneumonia (CAP) in the emergency department (ED).

METHODS

Secondary analysis from a prospective cohort study of children aged 3 months to 18 years with signs and symptoms of LRTI and a chest radiograph for suspected CAP in the ED, excluding children with recent (within 14 days) systemic corticosteroid use. The primary exposure was receipt of corticosteroids during the ED visit. Outcomes were QoL measures and unplanned visits. Multivariable regression was used to evaluate the association between corticosteroid therapy and outcomes.

RESULTS

Of 898 children, 162 (18%) received corticosteroids. Children who received corticosteroids were more frequently boys (62%), Black (45%), had history of asthma (58%), previous pneumonia (16%), presence of wheeze (74%), and more severe illness at presentation (6%). Ninety-six percent were treated for asthma as defined by report of asthma or receipt of ß-agonist in the ED. Receipt of corticosteroids was not associated with QoL measures: days of activity missed (adjusted incident rate ratio [aIRR], 0.84; 95% confidence interval [CI], 0.63-1.11) and days of work missed (aIRR, 0.88; 95% CI, 0.60-1.27). There was a statistically significant interaction between age (>2 years) and corticosteroids receipt; the patients had fewer days of activity missed (aIRR, 0.62; 95% CI, 0.46-0.83), with no effect on children 2 years or younger (aIRR, 0.83; 95% CI, 0.54-1.27). Corticosteroid treatment was not associated with unplanned visit (odds ratio, 1.37; 95% CI, 0.69-2.75).

CONCLUSIONS

In this cohort of children with suspected CAP, receipt of corticosteroids was associated with asthma history and was not associated with missed days of activity or work, except in a subset of children aged older than 2 years.

Phenotype and endotype based treatment of preschool wheeze

INTRODUCTION

Preschool wheeze (PSW) is a significant public health issue, with a high presentation rate to emergency departments, recurrent symptoms, and severe exacerbations. A heterogenous condition, PSW comprises several phenotypes that may relate to a range of pathobiological mechanisms. However, treating PSW remains largely generalized to inhaled corticosteroids and a short acting beta agonist, guided by symptom-based labels that often do not reflect underlying pathways of disease.

AREAS COVERED

We review the observable features and characteristics used to ascribe phenotypes in children with PSW and available pathobiological evidence to identify possible endotypes. These are considered in the context of treatment options and future research directions. The role of machine learning (ML) and modern analytical techniques to identify patterns of disease that distinguish phenotypes is also explored.

EXPERT OPINION

Distinct clusters (phenotypes) of severe PSW are characterized by different underlying mechanisms, some shared and some unique. ML-based methodologies applied to clinical, biomarker, and environmental data can help design tools to differentiate children with PSW that continues into adulthood, from those in whom wheezing resolves, identifying mechanisms underpinning persistence and resolution. This may help identify novel therapeutic targets, inform mechanistic studies, and serve as a foundation for stratification in future interventional therapeutic trials.

Clinical features and later prognosis of replicable early-life wheeze clusters from two birth cohorts 12 years apart

BACKGROUND

Clustering techniques can define the heterogeneity of asthma and wheezing. Defining early-life wheezing clusters and associated asthma risk could potentially inform patient management strategies. Clustering models that yield replicable cluster groups will have greater validity and clinical utility. This study sought to identify early-life wheezing clusters that are translatable into clinical practice and assess their stability over time in two whole-population birth cohorts established a decade apart from the same geographical location.

METHODS

Nonparametric K-means cluster analysis was performed separately on two birth cohorts from the Isle of Wight, UK; the Isle of Wight Birth Cohort (IOWBC) and Food Allergy and Intolerance Research Cohort (FAIR), using clinically defining variables in wheezing subjects in the first 3-4 years. Associations of resulting clusters with potential early-life risk factors and 10-year asthma outcomes were further assessed.

RESULTS

Five clusters were identified in both cohorts: (1) infantile-onset-transient-non-atopic-wheeze, (2) infantile-onset-persistent-non-atopic-wheeze, (3) infantile-onset-atopic-wheeze, (4) early-childhood-onset-non-atopic-wheeze, and (5) early-childhood-onset-atopic-wheeze. Two atopic wheezing clusters (3 and 5) were associated with greatest early-life wheeze frequency, highest wheeze persistence, and asthma prevalence at 10 years. Cluster 1 was commonest but had lowest early-life wheeze frequency and asthma prevalence at 10 years. Cluster 2, characterized by limited atopy but recurrent infantile respiratory infections and ongoing early-life wheezing, had high 10-year asthma prevalence only in IOWBC.

CONCLUSIONS

Early-life wheeze comprises several disease clusters (two more severe and three mild-moderate) with differing relationships to later childhood asthma, which can be replicated over time supporting their potential validity and clinical utility.

Poorer Caregiver Mental and Social Health Is Associated With Worse Respiratory Outcomes in Preschool Children With Recurrent Wheezing

BACKGROUND

Mental and social health in caregivers of preschool children has been inadequately studied, but it may influence respiratory symptom recognition and management.

OBJECTIVE

To identify preschool caregivers at highest risk for poor mental and social health outcomes on the basis of patient-reported outcome measures.

METHODS

Female caregivers 18 to 50 years old (N = 129) with a preschool child aged 12 to 59 months with recurrent wheezing and at least 1 exacerbation in the previous year completed 8 validated patient-reported outcome measures of mental and social health. k-means cluster analysis was performed using the T score for each instrument. Caregiver/child dyads were followed for 6 months. Primary outcomes included caregiver quality of life and wheezing episodes in their preschool children.

RESULTS

Three clusters of caregivers were identified: low risk (n = 38), moderate risk (n = 56), and high risk (n = 35). The high-risk cluster had the lowest life satisfaction, meaning and purpose, and emotional support and the highest social isolation, depression, anger, perceived stress, and anxiety that persisted for more than 6 months. This cluster had the poorest quality of life and marked disparities in social determinants of health. Preschool children from caregivers in the high-risk cluster had more frequent respiratory symptoms and a higher occurrence of any wheezing episode, but a lower outpatient physician utilization for wheezing management.

CONCLUSIONS

Caregiver mental and social health is associated with respiratory outcomes in preschool children. Routine assessment of mental and social health in caregivers is warranted to promote health equity and improve wheezing outcomes in preschool children.

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.

Bronchial Remodeling-based Latent Class Analysis Predicts Exacerbations in Severe Preschool Wheezers

Rationale: Children with preschool wheezing represent a very heterogeneous population with wide variability regarding their clinical, inflammatory, obstructive, and/or remodeling patterns. We hypothesized that assessing bronchial remodeling would help clinicians to better characterize severe preschool wheezers. Objectives: The main objective was to identify bronchial remodeling-based latent classes of severe preschool wheezers. Secondary objectives were to compare cross-sectional and longitudinal clinical and biological data between classes and to assess the safety of bronchoscopy. Methods: This double-center prospective study (NCT02806466) included severe preschool wheezers (1-5 yr old) requiring fiberoptic bronchoscopy. Bronchial remodeling parameters (i.e., epithelial integrity, reticular basement membrane [RBM] thickness, mucus gland, fibrosis and bronchial smooth muscle [BSM] areas, the density of blood vessels, and RBM-BSM distance) were assessed and evaluated by latent class analysis. An independent cohort of severe preschool wheezers (NCT04558671) was used to validate our results. Measurements and Main Results: Fiberoptic bronchoscopy procedures were well tolerated. A two-class model was identified: Class BR1 was characterized by increased RBM thickness, normalized BSM area, the density of blood vessels, decreased mucus gland area, fibrosis, and RBM-BSM distance compared with Class BR2. No significant differences were found between classes in the year before fiberoptic bronchoscopy. By contrast, Class BR1 was associated with a shorter time to first exacerbation and an increased risk of both frequent (3 or more) and severe exacerbations during the year after bronchoscopy in the two cohorts. Conclusions: Assessing bronchial remodeling identified severe preschool wheezers at risk of frequent and severe subsequent exacerbations with a favorable benefit to risk ratio.

Standardization of Reporting Obstructive Airway Disease in Children: A National Delphi Process

BACKGROUND

Pediatric pulmonologists report asthma and obstructive bronchitis in medical records in a variety of ways, and there is no consensus for standardized reporting.

OBJECTIVE

We investigated which diagnostic labels and features pediatric pulmonologists use to describe obstructive airway disease in children and aimed to reach consensus for standardized reporting.

METHODS

We obtained electronic health records from 562 children participating in the Swiss Pediatric Airway Cohort from 2017 to 2018. We reviewed the diagnosis section of the letters written by pediatric pulmonologists to referring physicians and extracted the terms used to describe the diagnosis. We grouped these terms into diagnostic labels (eg, asthma) and features (eg, triggers) using qualitative thematic framework analysis. We also assessed how frequently the different terms were used. Results were fed into a modified Delphi process to reach consensus on standardized reporting.

RESULTS

Pediatric pulmonologists used 123 different terms to describe the diagnosis, which we grouped into 6 diagnostic labels and 17 features. Consensus from the Delphi process resulted in the following recommendations: (i) to use the diagnostic label "asthma" for children older than 5 years and "obstructive bronchitis" or "suspected asthma" for children younger than 5 years; (ii) to accompany the diagnosis with relevant features: diagnostic certainty, triggers, symptom control, risk of exacerbation, atopy, treatment adherence, and symptom perception.

CONCLUSION

We found great heterogeneity in the reporting of obstructive airway disease among pediatric pulmonologists. The proposed standardized reporting will simplify communication among physicians and improve quality of research based on electronic health records.

Probability of successful inhaled corticosteroids cessation in preschool wheezers: a predictive score

Nearly all asthma predictive tools estimate the future risk of asthma development. However, there is no tool to predict the probability of successful ICS cessation at an early age. Therefore, we aimed to determine the predictors of successful ICS cessation in preschool wheezers, and developed a simple predictive tool for clinical practice. This was a retrospective cohort study involving preschool wheezers who had undergone an ICS therapeutic trial during 2015-2020 at the University Hospital, Southern, Thailand. A predictive scoring system was developed using a nomogram to estimate the probability of successful ICS cessation. We calculated area under ROC curve and used a calibration plot for assessing the tool's performance. A total of 131 medical records were eligible for analysis. Most of the participants were male (68.9%). More than half of the preschool wheezers had successful ICS cessation after an initial therapeutic trial regimen. The predictors of less successful ICS cessation were perinatal oxygen use [OR 0.10 (0.01, 0.70), P = 0.02], allergic rhinitis [OR 0.20 (0.08, 0.56), P = 0.002], blood eosinophil count > 500 cell/mm³ [OR 0.20 (0.06, 0.67), P = 0.008], and previous ICS use > 6 months [OR 0.30 (0.09, 0.72), P = 0.009].

CONCLUSIONS

Predictors of less successful ICS cessation were the following: perinatal oxygen use, allergic rhinitis, blood eosinophil count > 500 cell/mm³, and previous ICS use > 6 months. A simple predictive score developed in this study may help general practitioners to be more confident in making a decision regarding the discontinuation of ICS after initial therapeutic trials.

WHAT IS KNOWN

• Early allergic sensitization is associated with reduced chances of inhaled corticosteroid cessation at school age. • Prolonged ICS is associated with the emergence of adverse effect and discontinuing too early can result in recurrence symptoms.

WHAT IS NEW

• Requirement of oxygen support within 7 days after birth in term neonate is a postnatal factor associated with less successful ICS cessation. • We propose a simple predictive tool with easily available clinical parameters (perinatal oxygen use, allergic rhinitis, blood eosinophil count, parental asthma history, and duration of previous ICS use) to determine the timing of inhalational corticosteroid cessation in preschool wheezers.

Modeling Wheezing Spells Identifies Phenotypes with Different Outcomes and Genetic Associates

Rationale: Longitudinal modeling of current wheezing identified similar phenotypes, but their characteristics often differ between studies. Objectives: We propose that a more comprehensive description of wheeze may better describe trajectories than binary information on the presence/absence of wheezing. Methods: We derived six multidimensional variables of wheezing spells from birth to adolescence (including duration, temporal sequencing, and the extent of persistence/recurrence). We applied partition-around-medoids clustering on these variables to derive phenotypes in five birth cohorts. We investigated within- and between-phenotype differences compared with binary latent class analysis models and ascertained associations of these phenotypes with asthma and lung function and with polymorphisms in asthma loci 17q12-21 and CDHR3 (cadherin-related family member 3). Measurements and Main Results: Analysis among 7,719 participants with complete data identified five spell-based wheeze phenotypes with a high degree of certainty: never (54.1%), early-transient (ETW) (23.7%), late-onset (LOW) (6.9%), persistent (PEW) (8.3%), and a novel phenotype, intermittent wheeze (INT) (6.9%). FEV₁/FVC was lower in PEW and INT compared with ETW and LOW and declined from age 8 years to adulthood in INT. 17q12-21 and CDHR3 polymorphisms were associated with higher odds of PEW and INT, but not ETW or LOW. Latent class analysis- and spell-based phenotypes appeared similar, but within-phenotype individual trajectories and phenotype allocation differed substantially. The spell-based approach was much more robust in dealing with missing data, and the derived clusters were more stable and internally homogeneous. Conclusions: Modeling of spell variables identified a novel intermittent wheeze phenotype associated with lung function decline to early adulthood. Using multidimensional spell variables may better capture wheeze development and provide a more robust input for phenotype derivation.

Current strategies for phenotyping and managing asthma in preschool children

PURPOSE OF REVIEW

Half of all children will experience an episode of wheezing by 6 years. Recurrent preschool wheezing is associated with early lung function loss and has a lifelong impact on airway health, so deciding which children should be treated to prevent exacerbations while also avoiding irreversible health consequences is crucial. The purpose of this review is to provide a practical approach to the pediatric patient under 5 years of age with asthma, with particular attention to the recent enhanced identification of wheeze phenotypes.

RECENT FINDINGS

Here, we note the difficulty of defining 'asthma' for this age group and advocate that it be determined by the set of respiratory symptoms presented, without assumptions about the underlying mechanisms of the disease. In addition, we propose a forward-looking approach, what treatment to apply to particular phenotypes, which child should be treated, and, if so, which treatment strategy to choose. No clear recommendation exists for the management of nonallergic preschool wheezing, a substantial clinical and research gap.

SUMMARY

We recommend an empathetic approach to parent anxiety and considering objective markers: timing, severity, and frequency of symptoms, along with an assessment of other biomarkers, including viral etiology, aeroallergen sensitization, and blood eosinophils, that contribute to successful decision-making.

Asthma and Allergy: Unravelling a Tangled Relationship with a Focus on New Biomarkers and Treatment

Asthma is a major driver of health care costs across ages. Despite widely disseminated asthma-treatment guidelines and a growing variety of effective therapeutic options, most patients still experience symptoms and/or refractoriness to standard of care treatments. As a result, most patients undergo a further intensification of therapy to optimize symptom control with a subsequent increased risk of side effects. Raising awareness about the relevance of evaluating aeroallergen sensitizations in asthmatic patients is a key step in better informing clinical practice while new molecular tools, such as the component resolved diagnosis, may be of help in refining the relationship between sensitization and therapeutic recommendations. In addition, patient care should benefit from reliable, easy-to-measure and clinically accessible biomarkers that are able to predict outcome and disease monitoring. To attain a personalized asthma management and to guide adequate treatment decisions, it is of paramount importance to expand clinicians' knowledge about the tangled relationship between asthma and allergy from a molecular perspective. Our review explores the relevance of allergen testing along the asthma patient's journey, with a special focus on recurrent wheezing children. Here, we also discuss the unresolved issues regarding currently available biomarkers and summarize the evidence supporting the eosinophil-derived neurotoxin as promising biomarker.

Viral Induced Effects on a Vulnerable Epithelium; Lessons Learned From Paediatric Asthma and Eosinophilic Oesophagitis

The epithelium is integral to the protection of many different biological systems and for the maintenance of biochemical homeostasis. Emerging evidence suggests that particular children have epithelial vulnerabilities leading to dysregulated barrier function and integrity, that resultantly contributes to disease pathogenesis. These epithelial vulnerabilities likely develop in utero or in early life due to various genetic, epigenetic and environmental factors. Although various epithelia are uniquely structured with specific function, prevalent allergic-type epithelial diseases in children potentially have common or parallel disease processes. These include inflammation and immune response dysregulation stemming from atypical epithelial barrier function and integrity. Two diseases where aetiology and pathogenesis are potentially linked to epithelial vulnerabilities include Paediatric Asthma and Eosinophilic Oesophagitis (EoE). For example, rhinovirus C (RV-C) is a known risk factor for paediatric asthma development and is known to disrupt respiratory epithelial barrier function causing acute inflammation. In addition, EoE, a prevalent atopic condition of the oesophageal epithelium, is characterised by similar innate immune and epithelial responses to viral injury. This review examines the current literature and identifies the gaps in the field defining viral-induced effects on a vulnerable respiratory epithelium and resulting chronic inflammation, drawing from knowledge generated in acute wheezing illness, paediatric asthma and EoE. Besides highlighting the importance of epithelial structure and barrier function in allergic disease pathogenesis regardless of specific epithelial sub-types, this review focuses on the importance of examining other parallel allergic-type disease processes that may uncover commonalities driving disease pathogenesis. This in turn may be beneficial in the development of common therapeutics for current clinical management and disease prevention in the future.

Identifying wheezing phenotypes in a pediatric Turkish cohort

OBJECTIVE

Characterization of wheezing phenotypes in children might help to identify the underlying mechanisms through which asthma occurs. In our study, we aimed to describe wheezing phenotypes in Turkish children and to identify risk factors according to phenotypes.

METHODS

651 wheezy children were evaluated and 5 wheezing phenotypes were described according to age of onset, atopy and persistence at 6 years of age and risk factors were identified.

RESULTS

Distribution of wheezing phenotypes was transient early wheeze (TEW)(34.9%) non-atopic wheeze (NAW) (18%), atopic wheeze (AW) (22.3%), intermediate onset wheeze (IOW) (11.1%), late onset wheeze (LOW) (11.7%). LOW, AW, and IOW were associated with, father's, sibling's and family's atopy (p:0.001) whereas LOW and AW were associated with mother's asthma and atopy as well as family's asthma (p < 0.05). Atopic dermatitis and allergic rhinitis were common of patients with LOW, AW, and IOW (p < 0.05). İnfection was the major trigger for TEW and NAW whereas multiple triggers were common of AW, LOW, and IOW. Allergens were mostly associated with AW, IOW and LOW. Aeroallergen-specific IgE positivity was mostly with AW, IOW, and LOW phenotype. Skin prick tests showed multiple allergen sensitivity in IOW, LOW groups and mostly single allergen in AW phenotype. Modified asthma predictive index (mAPI) positivity was high in all groups except TEW and NAW.

CONCLUSIONS

With this study we classified five wheeze phenotypes and found that atopy and family's atopy history, maternal asthma were strongly associated with AW, LOW, and IOW phenotypes which were usually effected by allergens or multiple triggers.

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.

Novel Treatment-Refractory Preschool Wheeze Phenotypes Identified by Cluster Analysis of Lung Lavage Constituents

BACKGROUND

Preschool children with treatment-refractory wheeze often require unscheduled acute care. Current guidelines advise treatment of persistent wheeze with inhaled corticosteroids. Alternative treatments targeting structural abnormalities and specific inflammatory patterns could be more effective.

OBJECTIVE

To apply unsupervised analysis of lung lavage (bronchoalveolar lavage [BAL]) variables to identify clusters of preschool children with treatment-refractory wheeze.

METHODS

A total of 155 children 6 years or younger underwent bronchoscopy with BAL for evaluation of airway structure, inflammatory markers, and pathogens. Variables were screened with factor analysis and sorted into clusters by Ward's method, and membership was confirmed by discriminant analysis.

RESULTS

The model was repeatable in a 48-case validation sample and accurately classified 86% of cases. Cluster 1 (n = 60) had early-onset wheeze, 85% with structural abnormalities, mostly tracheamalacia, with low total IgE and agranulocytic BAL. Cluster 2 (n = 42) had later-onset wheeze, the highest prevalence of gastroesophageal reflux, little atopy, and two-third had increased BAL lipid-laden macrophages. Cluster 3 (n = 46) had mid-onset wheeze, low total IgE, and two-third had BAL viral transcripts, predominately human rhinovirus, with BAL neutrophilia. Cluster 4 (n = 7) was older, with high total IgE, blood eosinophilia, and mixed BAL eosinophils and neutrophils.

CONCLUSIONS

Preschool children with recurrent wheeze refractory to inhaled corticosteroid treatment include 4 clusters: airway malacia, gastroesophageal reflux, indolent human rhinovirus bronchoalveolitis, and type-2^high inflammation. The results support the risk and cost of invasive bronchoscopy to diagnose causes of treatment-refractory wheeze and develop novel therapies targeting airway malacia, human rhinovirus infection, and BAL neutrophilia in preschool children.

Predicting Severe Asthma Exacerbations in Children: Blueprint for Today and Tomorrow

Severe asthma exacerbations are the primary cause of morbidity and mortality in children with asthma. Accurate prediction of children at risk for severe exacerbations, defined as those requiring systemic corticosteroids, emergency department visit, and/or hospitalization, would considerably reduce health care utilization and improve symptoms and quality of life. Substantial progress has been made in identifying high-risk exacerbation-prone children. Known risk factors for exacerbations include demographic characteristics (ie, low income, minority race/ethnicity), poor asthma control, environmental exposures (ie, aeroallergen exposure/sensitization, concomitant viral infection), inflammatory biomarkers, genetic polymorphisms, and markers from other "omic" technologies. The strongest risk factor for a future severe exacerbation remains having had one in the previous year. Combining risk factors into composite scores and use of advanced predictive analytic techniques such as machine learning are recent methods used to achieve stronger prediction of severe exacerbations. However, these methods are limited in prediction efficiency and are currently unable to predict children at risk for impending (within days) severe exacerbations. Thus, we provide a commentary on strategies that have potential to allow for accurate and reliable prediction of children at risk for impending exacerbations. These approaches include implementation of passive, real-time monitoring of impending exacerbation predictors, use of population health strategies, prediction of severe exacerbation responders versus nonresponders to conventional exacerbation management, and considerations for preschool-age children who can be especially high risk. Rigorous prediction and prevention of severe asthma exacerbations is needed to advance asthma management and improve the associated morbidity and mortality.

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.

Which Wheezing Preschoolers Should be Treated for Asthma?

Wheezing disorders in children younger than 5 years are common, but lack of clarity remains about which children should be treated to prevent symptoms and acute episodes. The aim of this review was to discuss a practical approach to deciding which children younger than 5 years with asthma should be treated, and if so, with which strategy. The importance of having a clear definition of "asthma" for this age group, determined by a collection of presenting respiratory symptoms, without assumptions about underlying mechanisms is addressed. Subsequent consideration should be given to timing, severity, and frequency of symptoms, together with assessment of objective biomarkers, including aeroallergen sensitization and blood eosinophils, to inform whether or not a preschooler with recurrent wheezing requires treatment. Numerous unanswered questions remain about the optimal management of nonallergic preschool wheezing and asthma, and areas of specific unmet need and future directions for research are highlighted.

Hospitalization, Asthma Phenotypes, and Readmission Rates in Pre-school Asthma

Objective: Children with pre-school asthma suffer disproportionally more often from severe asthma exacerbations with emergency visits and hospital admissions compared to school children. Despite this high disease burden, there are only a few reports looking at this particular severe asthma cohort. Similarly, there is little real-life research on the distribution of asthma phenotypes and personalized treatment at discharge in this age group. Patients and Methods: Retrospective analysis of the electronic charts of all children aged 1-5 years with asthma hospitalizations (ICD J45) at the Frankfurt University between 2008 and 2017. An acute severe asthma exacerbation was defined as dyspnea, oxygen demand, and/or systemic steroid therapy. Age, gender, duration of hospitalization, asthma phenotype, treatment, and readmission rate were analyzed. Results: Of 572 patients, 205 met the definition of acute severe asthma. The phenotypic characterization showed 56.1% had allergic asthma, 15.2% eosinophilic asthma and 28.7% non-allergic asthma. Of these patients, 71.7% were discharged with inhaled corticosteroids (ICS) or ICS + long-acting-beta-agonists (LABA), 15.1% with leukotriene antagonists (LTRA) and 7.3% salbutamol on demand. The rate of emergency presentations (emergency department and readmission) within 12 months after discharge was high (n = 42; 20.5%). No phenotype tailored treatment was detectable. Neither the number of eosinophils (>300/μl) nor the treatment at discharge had an effect on emergency visits and readmission rate. Conclusion: Despite protective therapy with ICS, ICS + LABA, or LTRA, the readmission rate was high. Thus, current care and treatment strategies should be reevaluated continuously, in order to better control asthma in pre-school children and prevent hospitalization.

Impact of pneumococcal vaccine response on asthma exacerbation frequency in young children

INTRODUCTION

Chronic asthma is a heterogeneous disease, and increased eosinophils have been shown to predict increased asthma exacerbations, especially in adults. Recent recommendations suggest the need for supplemental PPV-23 vaccination in older children with chronic asthma.

METHODS

To investigate differences in preschool asthma, our case-cohort study comprised of 127 children, mean age 47 months (32-65), with a history of asthma exacerbations requiring more than three courses of systemic steroid bursts and more than six antibiotics courses in the previous year.

RESULTS

At baseline, mean antibody titer response to Streptococcus pneumoniae was decreased at 2.6 ± 2 out of 14 serotypes, despite prior complete pneumococcal conjugate vaccine (PCV) vaccinations. All children were readministered pneumococcal vaccinations with PCV-13 booster and/or PPSV-23. Mean postvaccination pneumococcal vaccine (PV) titer response was 16 ± 5 out of 23 serotypes. After contacting 91 parents/caretakers, 75 responded with less frequency of corticosteroids and antibiotic use for asthma exacerbations after PV. This group had baseline eosinophil counts of 211 ± 36/µL, while those without improvement were significantly higher at 371 ± 123/µL,*P < .05. There were no significant differences (P > .05) between the two groups from other baseline measures including demography or atopic status.

CONCLUSIONS

This subset of children with exacerbation-prone asthma had poor antibody titer response to Streptococcus pneumoniae, even with prior complete PCV-13 immunization. Identification of low antibody responses to PV serotypes may provide a targeted therapeutic approach to reduce wheezing exacerbations in a precise asthma phenotype in children.

Prevention and treatment of recurrent viral-induced wheezing in the preschool child

OBJECTIVE

To summarize the recent evidence in the treatment of viral-induced wheezing in the infant and preschool aged child.

DATA SOURCES

Published literature obtained through PubMed database searches.

STUDY SELECTIONS

Studies relevant to phenotypes and treatment of wheezing illnesses in infants and preschool children were included.

RESULTS

Recurrent wheezing in preschool children is common and is frequently triggered by viral respiratory tract infections. Certain phenotypes may respond to treatments differently, depending on the risk factors identified. Inhaled corticosteroids, administered continuously or intermittently, reduce the risk of virus-induced wheezing episodes. The use of leukotriene modifying agents may have a role in wheezing episodes in a select group of preschool children. Early administration of azithromycin reduces the risk of severe lower respiratory tract illnesses in children. The effect of oral corticosteroids on wheezing episodes in young children varies by degree of episode severity.

CONCLUSION

Recurrent viral-induced wheezing illnesses has been the focus of many clinical trials, which now provide an increasingly robust evidence base for management. Additional research is needed to define optimal strategies, to best match therapies to specific phenotypes and endotypes, and will eventually begin to include therapies directed specifically at the viral triggers.

Preschool Wheezing: Trajectories and Long-Term Treatment

Wheezing is very common in infancy affecting one in three children during the first 3 years of life. Several wheeze phenotypes have been identified and most rely on temporal pattern of symptoms. Assessing the risk of asthma development is difficult. Factors predisposing to onset and persistence of wheezing such as breastfeeding, atopy, indoor allergen exposure, environmental tobacco smoke and viral infections are analyzed. Inhaled corticosteroids are recommended as first choice of controller treatment in all preschool children irrespective of phenotype, but they are particularly beneficial in terms of fewer exacerbations in atopic children. Other therapeutic options include the addition of montelukast or the intermittent use of inhaled corticosteroids. Overuse of inhaled steroids must be avoided. Therefore, adherence to treatment and correct administration of the medications need to be checked at every visit.

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.

Exacerbation-Prone Asthma

Patients who are prone to exacerbations of asthma experience significant costs in terms of missed work and school, acute care visits, and hospitalizations. Exacerbations are largely driven by environmental exposures including pollutants, stress, and viral and bacterial pathogens. These exposures are most likely to induce acute severe "asthma attacks" in high-risk patients. These personal risk factors for exacerbations can vary with the phenotype of asthma and age of the patient. In children, allergic sensitization is a strong risk factor, especially for those children who develop sensitization early in life. Airway inflammation is an important risk factor, and biomarkers are under evaluation for utility in detecting eosinophilic and type 2 inflammation and neutrophilic inflammation as indicators of risk for recurrent exacerbations. Insights into inflammatory mechanisms have led to new approaches to prevent exacerbations using mAb-based biologics that target specific type 2 pathways. Challenges remain in developing an evidence base to support precision interventions with these effective yet expensive therapies, and in determining whether these treatments will be safe and effective in young children. Unfortunately, there has been less progress in developing treatments for acute exacerbations. Hopefully, greater understanding of mechanisms relating airway viruses, bacteria, mucin production, and neutrophilic inflammatory responses will lead to additional treatment options for patients experiencing acute exacerbations.

The risk of preschool asthma at 2-4 years is not associated with leukocyte telomere length at birth or at 1 year of age

Background

Exposure to prenatal stress is associated with offspring allergic-disease development, and oxidative stress may mediate this relationship.

Objective

We aimed to evaluate whether leukocyte telomere length (LTL) shortening, a marker for exposure to oxidative stress, in early life is associated with increased risk of asthma development during the preschool period.

Methods

We assessed the follow-up clinical data of a subgroup from a birth cohort whose LTLs had been measured from cord-blood and 1-year peripheral-blood samples. We examined whether the LTLs would be associated with asthma development at the age of 2–4 years.

Results

The data of 84 subjects were analyzed. LTLs were measured from the cord-blood and 1-year peripheral blood of 75 and 79 subjects, respectively. Among them, 14 subjects (16.7%) developed bronchial asthma between 2–4 years old. Prenatally stressed subjects had marginally increased odds of developing asthma (p = 0.097). There was no significant difference in the odds of preschool-asthma development between the groups with shorter and longer cord-blood LTLs (odds ratio [OR], 0.651; 95% confidence interval [CI], 0.184–2.306) or in the odds between the groups with shorter and longer 1-year peripheral-blood LTLs (OR, 0.448; 95% CI, 0.135–1.483). Finally, subjects with both higher prenatal stress and shorter LTLs did not have significantly higher odds of preschool-asthma development (for cord-blood: OR, 1.242; 95% CI, 0.353–4.368; for 1-year peripheral-blood: OR, 1.451; 95% CI, 0.428–4.919).

Conclusion

There was no significant association between early life LTLs and higher risk of bronchial-asthma development during the preschool years.

EAACI Guidelines on Allergen Immunotherapy: House dust mite-driven allergic asthma

Allergen immunotherapy (AIT) has been in use for the treatment of allergic disease for more than 100 years. Asthma treatment relies mainly on corticosteroids and other controllers recommended to achieve and maintain asthma control, prevent exacerbations, and improve quality of life. AIT is underused in asthma, both in children and in adults. Notably, patients with allergic asthma not adequately controlled on pharmacotherapy (including biologics) represent an unmet health need. The European Academy of Allergy and Clinical Immunology has developed a clinical practice guideline providing evidence-based recommendations for the use of house dust mites (HDM) AIT as add-on treatment for HDM-driven allergic asthma. This guideline was developed by a multi-disciplinary working group using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. HDM AIT was separately evaluated by route of administration and children and adults: subcutaneous (SCIT) and sublingual AIT (SLIT), drops, and tablets. Recommendations were formulated for each. The important prerequisites for successful treatment with HDM AIT are (a) selection of patients most likely to respond to AIT and (b) use of allergen extracts and desensitization protocols of proven efficacy. To date, only AIT with HDM SLIT-tablet has demonstrated a robust effect in adults for critical end points (exacerbations, asthma control, and safety). Thus, it is recommended as an add-on to regular asthma therapy for adults with controlled or partially controlled HDM-driven allergic asthma (conditional recommendation, moderate-quality evidence). HDM SCIT is recommended for adults and children, and SLIT drops are recommended for children with controlled HDM-driven allergic asthma as the add-on to regular asthma therapy to decrease symptoms and medication needs (conditional recommendation, low-quality evidence).