Quantification of atopy, lung function and airway hypersensitivity in adults

Component-specific clusters for diagnosis and prediction of allergic airway diseases

BACKGROUND

Previous studies which applied machine learning on multiplex component-resolved diagnostics arrays identified clusters of allergen components which are biologically plausible and reflect the sources of allergenic proteins and their structural homogeneity. Sensitization to different clusters is associated with different clinical outcomes.

OBJECTIVE

To investigate whether within different allergen component sensitization clusters, the internal within-cluster sensitization structure, including the number of c-sIgE responses and their distinct patterns, alters the risk of clinical expression of symptoms.

METHODS

In a previous analysis in a population-based birth cohort, by clustering component-specific (c-s)IgEs, we derived allergen component clusters from infancy to adolescence. In the current analysis, we defined each subject's within-cluster sensitization structure which captured the total number of c-sIgE responses in each cluster and intra-cluster sensitization patterns. Associations between within-cluster sensitization patterns and clinical outcomes (asthma and rhinitis) in early-school age and adolescence were examined using logistic regression and binomial generalized additive models.

RESULTS

Intra-cluster sensitization patterns revealed specific associations with asthma and rhinitis (both contemporaneously and longitudinally) that were previously unseen using binary sensitization to clusters. A more detailed description of the subjects' within-cluster c-sIgE responses in terms of the number of positive c-sIgEs and unique sensitization patterns added new information relevant to allergic diseases, both for diagnostic and prognostic purposes. For example, the increase in the number of within-cluster positive c-sIgEs at age 5 years was correlated with the increase in prevalence of asthma at ages 5 and 16 years, with the correlations being stronger in the prediction context (e.g. for the largest 'Broad' component cluster, contemporaneous: r = .28, p = .012; r = .22, p = .043; longitudinal: r = .36, p = .004; r = .27, p = .04).

CONCLUSION

Among sensitized individuals, a more detailed description of within-cluster c-sIgE responses in terms of the number of positive c-sIgE responses and distinct sensitization patterns, adds potentially important information relevant to allergic diseases.

Understanding the heterogeneity of childhood allergic sensitization and its relationship with asthma

PURPOSE OF REVIEW

To review the current state of knowledge on the relationship between allergic sensitization and asthma; to lay out a roadmap for the development of IgE biomarkers that differentiate, in individual sensitized patients, whether their sensitization is important for current or future asthma symptoms, or has little or no relevance to the disease.

RECENT FINDINGS

The evidence on the relationship between sensitization and asthma suggests that some subtypes of allergic sensitization are not associated with asthma symptoms, whilst others are pathologic. Interaction patterns between IgE antibodies to individual allergenic molecules on component-resolved diagnostics (CRD) multiplex arrays might be hallmarks by which different sensitization subtypes relevant to asthma can be distinguished. These different subtypes of sensitization are associated amongst sensitized individuals at all ages, with different clinical presentations (no disease, asthma as a single disease, and allergic multimorbidity); amongst sensitized preschool children with and without lower airway symptoms, with different risk of subsequent asthma development; and amongst sensitized patients with asthma, with differing levels of asthma severity.

SUMMARY

The use of machine learning-based methodologies on complex CRD data can help us to design better diagnostic tools to help practising physicians differentiate between benign and clinically important sensitization.

Home Dust Allergen Exposure Is Associated with Outcomes among Sensitized Individuals with Chronic Obstructive Pulmonary Disease

Rationale: Environmental exposures have been associated with adverse outcomes in chronic obstructive pulmonary disease (COPD). Approximately one-third of individuals with COPD have allergic sensitization, but it is unknown whether exposure to allergens in the home is associated with outcomes. Objectives: To determine the prevalence and associations of allergen sensitization with exposure to common indoor allergens with symptoms and exacerbation risk in COPD. Methods: Allergen sensitization to five common indoor allergens was assessed in former smokers with COPD. Home settled dust was assessed for presence of corresponding allergens. Sensitization and exposure status was determined and associations evaluated in adjusted models with longitudinal outcomes including symptoms, lung function, and exacerbations. Interactions were assessed between sensitization/exposure status and lung function. Measurements and Main Results: One hundred eighty-three individuals studied were on average 67.3 years of age (SD, 8.22) with average FEV1 of 53.2% (SD, 17.6%). Seventy-seven percent of participants were exposed to at least one tested allergen, and 17% had sensitization with corresponding allergen exposure. After adjustment, sensitization with exposure was associated with lower lung function (β, -8.29; 95% confidence interval [CI], -14.80 to -1.77), higher St. George's Respiratory Questionnaire Total Score (β, 6.71; 95% CI, 0.17 to 13.25), and higher exacerbation risk (odds ratio, 2.31; 95% CI, 1.11 to 4.79). Associations appeared to be more pronounced among individuals with lower lung function. Conclusions: Allergen exposures are common in COPD and associated with adverse outcomes among those with concomitant allergen sensitization. This study establishes allergens as an important home exposure that potentially could be addressed with comprehensive home environmental modification strategies to improve COPD outcomes.

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.

Blood Biomarkers of Sensitization and Asthma

Biomarkers are essential to determine different phenotypes of childhood asthma, and for the prediction of response to treatments. In young preschool children with asthma, aeroallergen sensitization, and blood eosinophil count of 300/μL or greater may identify those who can benefit from the daily use of inhaled corticosteroids (ICS). We propose that every preschool child who is considered for ICS treatment should have these two features measured as a minimum before a decision is made on the commencement of long-term preventive treatment. In practice, IgE-mediated sensitization should be considered as a quantifiable variable, i.e., we should use the titer of sIgE antibodies or the size of skin prick test response. A number of other blood biomarkers may prove useful (e.g., allergen-specific IgG/IgE antibody ratios amongst sensitized individuals, component-resolved diagnostics which measures sIgE response to a large number of allergenic molecules, assessment of immune responses to viruses, level of serum CC16, etc.), but it remains unclear whether these can be translated into clinically useful tests. Going forward, a more integrated approach which takes into account multiple domains of asthma, from the pattern of symptoms and blood biomarkers to genetic risk and lung function measures, is needed if we are to move toward a stratified approach to asthma management.

Approaches to Asthma Diagnosis in Children and Adults

Although the hallmark features of asthma include reversible airflow obstruction, airway eosinophilia, and symptoms of recurrent wheeze associated with breathlessness and cough, it is a heterogeneous disease. The extent of the pathophysiological abnormalities are variable between patients. Despite this, until recently, asthma diagnosis had been made very simplistically predominantly from a clinical history and examination, and often a trial of medication such as short acting bronchodilators. The limitations of this approach have become increasingly apparent with evidence of inappropriate over diagnosis, under diagnosis and misdiagnosis. Although there is no gold standard single test to make a diagnosis of asthma, there are several objective tests that can be used to support the diagnosis including physiological measures such as obstructive spirometry associated with bronchodilator reversibility and airway hyperresponsiveness. In addition, non-invasive tests of airway inflammation such as exhaled nitric oxide or peripheral blood eosinophils are important to identify those with an allergic or eosinophilic phenotype. Diagnostic guidelines reflect the importance of using objective tests to support a diagnosis of asthma, however practical application in the clinic may not be straightforward. The focus of this review is to discuss the need to undertake objective tests in all patients to support asthma diagnosis and not just rely on clinical features. The advantages, challenges and limitations of performing tests of lung function and airway inflammation in the clinic, the difficulties related to training and interpretation of results will be explored, and the utility and relevance of diagnostic tests will be compared in adults and children.

The skin prick test response after allergen immunotherapy in different levels of tIgE children with mite sensitive Asthma/Rhinitis in South China

BACKGROUND

At present, the biomarkers which can predict the clinical efficacy of allergen immunotherapy (AIT) are still much debated. IgE levels are often related to allergic severity. Therefore, this study aimed at relating total IgE (tIgE) levels with the efficacy of AIT assessed by symptoms and drug score and skin prick test (SPT) response.

METHODS

We evaluated 81 allergic children who had received house-dust mite (HDM) subcutaneous immunotherapy for three years. According to the tIgE levels before treatment, all children were divided into high value, medium value and low value group. Each group according to sIgE/tIgE ratio was divided into subgroups. The efficacy of AIT is assessed by symptoms and drug score. By comparing changes in the grade of SPT in each group, the response of AIT are evaluated.

RESULTS

The SPT grade changes to determine efficacy had a high degree of consistency with symptoms and drug score judgment (sensitivity 89.7%, specificity 78.3%, Kappa = 0.670, P < 0.001). Compared to ineffective cases, the effective cases had lower tIgE (P < 0.001) and higher ratio of sIgE/tIgE (P < 0.001). The grades of SPT declined the most in the low value group (low value group vs. medium value group, P < 0.05; low value group vs. high value group, P < 0.001; medium value group vs. high value group, P < 0.05).

CONCLUSIONS

The SPT grade change can be used for efficacy evaluation. Children with lower level of tIgE and higher ratio of sIgE/tIgE that obtain a more satisfactory effect.

Allergy in severe asthma

It is well recognized that atopic sensitization is an important risk factor for asthma, both in adults and in children. However, the role of allergy in severe asthma is still under debate. The term 'Severe Asthma' encompasses a highly heterogeneous group of patients who require treatment on steps 4-5 of GINA guidelines to prevent their asthma from becoming 'uncontrolled', or whose disease remains 'uncontrolled' despite this therapy. Epidemiological studies on emergency room visits and hospital admissions for asthma suggest the important role of allergy in asthma exacerbations. In addition, allergic asthma in childhood is often associated with severe asthma in adulthood. A strong association exists between asthma exacerbations and respiratory viral infections, and interaction between viruses and allergy further increases the risk of asthma exacerbations. Furthermore, fungal allergy has been shown to play an important role in severe asthma. Other contributing factors include smoking, pollution and work-related exposures. The 'Allergy and Asthma Severity' EAACI Task Force examined the current evidence and produced this position document on the role of allergy in severe asthma.

Mechanisms Mediating Pediatric Severe Asthma and Potential Novel Therapies

Although a rare disease, severe therapy-resistant asthma in children is a cause of significant morbidity and results in utilization of approximately 50% of health-care resources for asthma. Improving control for children with severe asthma is, therefore, an urgent unmet clinical need. As a group, children with severe asthma have severe and multiple allergies, steroid resistant airway eosinophilia, and significant structural changes of the airway wall (airway remodeling). Omalizumab is currently the only add-on therapy that is licensed for use in children with severe asthma. However, limitations of its use include ineligibility for approximately one-third of patients because of serum IgE levels outside the recommended range and lack of clinical efficacy in a further one-third. Pediatric severe asthma is thus markedly heterogeneous, but our current understanding of the different mechanisms underpinning various phenotypes is very limited. We know that there are distinctions between the factors that drive pediatric and adult disease since pediatric disease develops in the context of a maturing immune system and during lung growth and development. This review summarizes the current data that give insight into the pathophysiology of pediatric severe asthma and will highlight potential targets for novel therapies. It is apparent that in order to identify novel treatments for pediatric severe asthma, the challenge of undertaking mechanistic studies using age appropriate experimental models and airway samples from children needs to be accepted to allow a targeted approach of personalized medicine to be achieved.

Sensitization pattern affects the asthma risk in Finnish adult population

BACKGROUND

There is a large global variation in the sensitization pattern and its association with allergic diseases. In temperate and tropical urban environments, mite monosensitization can be the predominant cause of allergic airway diseases, whereas in other environments, polysensitization is more typical. Sensitization to mite allergens associates with asthma. However, it is suggested that mite sensitization might play a minor role in Northern Europe. The aim of the study was to analyze how sensitization pattern affects the asthma risk in Finnish adults, with a special focus on mites.

METHODS

A population-based case-control data (N = 523) from Finnish adult asthma patients with one or two matched controls were used. Asthma was diagnosed based on a typical history of asthmatic symptoms and lung function tests. The allergic sensitization was determined based on skin prick test (SPT) of five mites, three molds, and nine other aeroallergens. Information on demographics was obtained by a questionnaire.

RESULTS

The proportion of sensitization to any allergen was 55% in the asthma group and 39% in the control group (P = 0.001, OR 2.06, 95% CI = 1.35-3.14). Sensitization to animal dander, pollen, or Aspergillus fumigatus was associated with asthma. Polysensitization to more than one allergen types and the number of SPT-positive reactions associated with asthma, whereas sensitization to only one allergen type was not associated with asthma.

CONCLUSIONS

The large number of sensitizations to several types of allergens distinguishes subjects with asthma. Mite sensitization had little independent association with asthma in Finland.

Evolution pathways of IgE responses to grass and mite allergens throughout childhood

BACKGROUND

Little is known about longitudinal patterns of the development of IgE to distinct allergen components.

OBJECTIVE

We sought to investigate the evolution of IgE responses to allergenic components of timothy grass and dust mite during childhood.

METHODS

In a population-based birth cohort (n = 1184) we measured IgE responses to 15 components from timothy grass and dust mite in children with available samples at 3 time points (ages 5, 8, and 11 years; n = 235). We designed a nested, 2-stage latent class analysis to identify cross-sectional sensitization patterns at each follow-up and their longitudinal trajectories. We then ascertained the association of longitudinal trajectories with asthma, rhinitis, eczema, and lung function in children with component data for at least 2 time points (n = 534).

RESULTS

Longitudinal latent class analysis revealed 3 grass sensitization trajectories: (1) no/low sensitization; (2) early onset; and (3) late onset. The early-onset trajectory was associated with asthma and diminished lung function, and the late-onset trajectory was associated with rhinitis. Four longitudinal trajectories emerged for mite: (1) no/low sensitization; (2) group 1 allergens; (3) group 2 allergens; and (3) complete mite sensitization. Children in the complete mite sensitization trajectory had the highest odds ratios (ORs) for asthma (OR, 7.15; 95% CI, 3.80-13.44) and were the only group significantly associated with comorbid asthma, rhinitis, and eczema (OR, 5.91; 95% CI, 2.01-17.37). Among children with wheezing, those in the complete mite sensitization trajectory (but not other longitudinal mite trajectories) had significantly higher risk of severe exacerbations (OR, 3.39; 95% CI, 1.62-6.67).

CONCLUSIONS

The nature of developmental longitudinal trajectories of IgE responses differed between grass and mite allergen components, with temporal differences (early vs late onset) dominant in grass and diverging patterns of IgE responses (group 1 allergens, group 2 allergens, or both) in mite. Different longitudinal patterns bear different associations with clinical outcomes, which varied by allergen.

Predicting phenotypes of asthma and eczema with machine learning

Background

There is increasing recognition that asthma and eczema are heterogeneous diseases. We investigated the predictive ability of a spectrum of machine learning methods to disambiguate clinical sub-groups of asthma, wheeze and eczema, using a large heterogeneous set of attributes in an unselected population. The aim was to identify to what extent such heterogeneous information can be combined to reveal specific clinical manifestations.

Methods

The study population comprised a cross-sectional sample of adults, and included representatives of the general population enriched by subjects with asthma. Linear and non-linear machine learning methods, from logistic regression to random forests, were fit on a large attribute set including demographic, clinical and laboratory features, genetic profiles and environmental exposures. Outcome of interest were asthma, wheeze and eczema encoded by different operational definitions. Model validation was performed via bootstrapping.

Results

The study population included 554 adults, 42% male, 38% previous or current smokers. Proportion of asthma, wheeze, and eczema diagnoses was 16.7%, 12.3%, and 21.7%, respectively. Models were fit on 223 non-genetic variables plus 215 single nucleotide polymorphisms. In general, non-linear models achieved higher sensitivity and specificity than other methods, especially for asthma and wheeze, less for eczema, with areas under receiver operating characteristic curve of 84%, 76% and 64%, respectively. Our findings confirm that allergen sensitisation and lung function characterise asthma better in combination than separately. The predictive ability of genetic markers alone is limited. For eczema, new predictors such as bio-impedance were discovered.

Conclusions

More usefully-complex modelling is the key to a better understanding of disease mechanisms and personalised healthcare: further advances are likely with the incorporation of more factors/attributes and longitudinal measures.

EAACI position statement on asthma exacerbations and severe asthma

Asthma exacerbations and severe asthma are linked with high morbidity, significant mortality and high treatment costs. Recurrent asthma exacerbations cause a decline in lung function and, in childhood, are linked to development of persistent asthma. This position paper, from the European Academy of Allergy and Clinical Immunology, highlights the shortcomings of current treatment guidelines for patients suffering from frequent asthma exacerbations and those with difficult‐to‐treat asthma and severe treatment‐resistant asthma. It reviews current evidence that supports a call for increased awareness of (i) the seriousness of asthma exacerbations and (ii) the need for novel treatment strategies in specific forms of severe treatment‐resistant asthma. There is strong evidence linking asthma exacerbations with viral airway infection and underlying deficiencies in innate immunity and evidence of a synergism between viral infection and allergic mechanisms in increasing risk of exacerbations. Nonadherence to prescribed medication has been identified as a common clinical problem amongst adults and children with difficult‐to‐control asthma. Appropriate diagnosis, assessment of adherence and other potentially modifiable factors (such as passive or active smoking, ongoing allergen exposure, psychosocial factors) have to be a priority in clinical assessment of all patients with difficult‐to‐control asthma. Further studies with improved designs and new diagnostic tools are needed to properly characterize (i) the pathophysiology and risk of asthma exacerbations, and (ii) the clinical and pathophysiological heterogeneity of severe asthma.

Pediatric asthma and development of atopy

PURPOSE OF REVIEW

There is ongoing controversy about the relationship between atopy and asthma.

RECENT FINDINGS

In clinical practice, specific IgE and skin test results should not be reported as 'positive' or 'negative', but as the level of IgE and the size of skin test wheal diameter. In assessment of children with severe asthma, these tests are not mutually exclusive but complementary, and both should be carried out and quantified. In the near future, their diagnostic accuracy in children with wheezing may be improved by the measurement of allergen-specific IgG. It is becoming increasingly clear that asthma is not a single disease, but a collection of several diseases with similar/same symptoms. These distinct disease entities (endotypes) may share similar observable characteristics (phenotypes), but arise via different pathophysiological mechanisms. Observable phenotypic features (e.g. sputum inflammatory phenotypes) are not stable in children with asthma. The discovery of novel, latent endotypes of asthma will require integration of a time component to take into account the phenotype instability and longitudinal changes. Not only asthma, but also 'atopy' encompasses a number of different endotypes which differ in their association with asthma.

SUMMARY

Novel endotypes of atopy and asthma which better reflect the unique pathophysiological processes underlying different diseases in the atopy and asthma syndromes can be defined through the fusion of computational thinking and novel mathematical approaches with biomedical science. These novel endotypes may be more relevant for epidemiological, genetic and therapeutic studies.