Causes of variability in latent phenotypes of childhood wheeze

Identification of eczema clusters and their association with filaggrin and atopic comorbidities: analysis of five birth cohorts

BACKGROUND

Longitudinal modelling of the presence/absence of current eczema through childhood has identified similar phenotypes, but their characteristics often differ between studies.

OBJECTIVES

To demonstrate that a more comprehensive description of longitudinal pattern of symptoms may better describe trajectories than binary information on eczema presence.

METHODS

We derived six multidimensional variables of eczema spells from birth to 18 years of age (including duration, temporal sequencing and the extent of persistence/recurrence). Spells were defined as consecutive observations of eczema separated by no eczema across 5 epochs in five birth cohorts: infancy (first year); early childhood (age 2-3 years); preschool/early school age (4-5 years); middle childhood (8-10 years); adolescence (14-18 years). We applied Partitioning Around Medoids clustering on these variables to derive clusters of the temporal patterns of eczema. We then investigated the stability of the clusters, within-cluster homogeneity and associated risk factors, including FLG mutations.

RESULTS

Analysis of 7464 participants with complete data identified five clusters: (i) no eczema (51.0%); (ii) early transient eczema (21.6%); (iii) late-onset eczema (LOE; 8.1%); (iv) intermittent eczema (INT; 7.5%); and (v) persistent eczema (PE; 11.8%). There was very-high agreement between the assignment of individual children into clusters when using complete or imputed (n = 15 848) data (adjusted Rand index = 0.99; i.e. the clusters were very stable). Within-individual symptom patterns across clusters confirmed within-cluster homogeneity, with consistent patterns of symptoms among participants within each cluster and no overlap between the clusters. Clusters were characterized by differences in associations with risk factors (e.g. parental eczema was associated with all clusters apart from LOE; sensitization to inhalant allergens was associated with all clusters, with the highest risk in the PE cluster). All clusters apart from LOE were associated with FLG mutations. Of note, the strongest association was for PE [relative risk ratio (RRR) 2.70, 95% confidence interval (CI) 2.24-3.26; P < 0.001] followed by INT (RRR 2.29, 95% CI 1.82-2.88; P < 0.001).

CONCLUSIONS

Clustering of multidimensional variables identified stable clusters with different genetic architectures. Using multidimensional variables may capture eczema development and derive stable and internally homogeneous clusters. However, deriving homogeneous symptom clusters does not necessarily mean that these are underpinned by completely unique mechanisms.

Understanding progression from pre-school wheezing to school-age asthma: Can modern data approaches help?

Preschool wheezing and childhood asthma create a heavy disease burden which is only exacerbated by the complexity of the conditions. Preschool wheezing exhibits both "curricular" and "aetiological" heterogeneity: that is, heterogeneity across patients both in the time-course of its development and in its underpinning pathological mechanisms. Since these are not fully understood, but clinical presentations across patients may nonetheless be similar, current diagnostic labels are imprecise-not mapping cleanly onto underlying disease mechanisms-and prognoses uncertain. These uncertainties also make a identifying new targets for therapeutic intervention difficult. In the past few decades, carefully designed birth cohort studies have collected "big data" on a large scale, incorporating not only a wealth of longitudinal clinical data, but also detailed information from modalities as varied as imaging, multiomics, and blood biomarkers. The profusion of big data has seen the proliferation of what we term "modern data approaches" (MDAs)-grouping together machine learning, artificial intelligence, and data science-to make sense and make use of this data. In this review, we survey applications of MDAs (with an emphasis on machine learning) in childhood wheeze and asthma, highlighting the extent of their successes in providing tools for prognosis, unpicking the curricular heterogeneity of these conditions, clarifying the limitations of current diagnostic criteria, and indicating directions of research for uncovering the etiology of the diseases underlying these conditions. Specifically, we focus on the trajectories of childhood wheeze phenotypes. Further, we provide an explainer of the nature and potential use of MDAs and emphasize the scope of what we can hope to achieve with them.

Current state and prospects of artificial intelligence in allergy

The field of medicine is witnessing an exponential growth of interest in artificial intelligence (AI), which enables new research questions and the analysis of larger and new types of data. Nevertheless, applications that go beyond proof of concepts and deliver clinical value remain rare, especially in the field of allergy. This narrative review provides a fundamental understanding of the core concepts of AI and critically discusses its limitations and open challenges, such as data availability and bias, along with potential directions to surmount them. We provide a conceptual framework to structure AI applications within this field and discuss forefront case examples. Most of these applications of AI and machine learning in allergy concern supervised learning and unsupervised clustering, with a strong emphasis on diagnosis and subtyping. A perspective is shared on guidelines for good AI practice to guide readers in applying it effectively and safely, along with prospects of field advancement and initiatives to increase clinical impact. We anticipate that AI can further deepen our knowledge of disease mechanisms and contribute to precision medicine in allergy.

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.

A meta-analysis of genome-wide association studies of childhood wheezing phenotypes identifies ANXA1 as a susceptibility locus for persistent wheezing

Background

Many genes associated with asthma explain only a fraction of its heritability. Most genome-wide association studies (GWASs) used a broad definition of 'doctor-diagnosed asthma', thereby diluting genetic signals by not considering asthma heterogeneity. The objective of our study was to identify genetic associates of childhood wheezing phenotypes.

Methods

We conducted a novel multivariate GWAS meta-analysis of wheezing phenotypes jointly derived using unbiased analysis of data collected from birth to 18 years in 9568 individuals from five UK birth cohorts.

Results

Forty-four independent SNPs were associated with early-onset persistent, 25 with pre-school remitting, 33 with mid-childhood remitting, and 32 with late-onset wheeze. We identified a novel locus on chr9q21.13 (close to annexin 1 [ANXA1], p<6.7 × 10-9), associated exclusively with early-onset persistent wheeze. We identified rs75260654 as the most likely causative single nucleotide polymorphism (SNP) using Promoter Capture Hi-C loops, and then showed that the risk allele (T) confers a reduction in ANXA1 expression. Finally, in a murine model of house dust mite (HDM)-induced allergic airway disease, we demonstrated that anxa1 protein expression increased and anxa1 mRNA was significantly induced in lung tissue following HDM exposure. Using anxa1-/- deficient mice, we showed that loss of anxa1 results in heightened airway hyperreactivity and Th2 inflammation upon allergen challenge.

Conclusions

Targeting this pathway in persistent disease may represent an exciting therapeutic prospect.

Funding

UK Medical Research Council Programme Grant MR/S025340/1 and the Wellcome Trust Strategic Award (108818/15/Z) provided most of the funding for this study.

Early childhood wheezing phenotypes and determinants in a South African birth cohort: longitudinal analysis of the Drakenstein Child Health Study

BACKGROUND

Developmental trajectories of childhood wheezing in low-income and middle-income countries (LMICs) have not been well described. We aimed to derive longitudinal wheeze phenotypes from birth to 5 years in a South African birth cohort and compare those with phenotypes derived from a UK cohort.

METHODS

We used data from the Drakenstein Child Health Study (DCHS), a longitudinal birth cohort study in a peri-urban area outside Cape Town, South Africa. Pregnant women (aged ≥18 years) were enrolled during their second trimester at two public health clinics. We followed up children from birth to 5 years to derive six multidimensional indicators of wheezing (including duration, temporal sequencing, persistence, and recurrence) and applied Partition Around Medoids clustering to derive wheeze phenotypes. We compared phenotypes with a UK cohort (the Avon Longitudinal Study of Parents and Children [ALSPAC]). We investigated associations of phenotypes with early-life exposures, including all-cause lower respiratory tract infection (LRTI) and virus-specific LRTI (respiratory syncytial virus, rhinovirus, adenovirus, influenza, and parainfluenza virus) up to age 5 years. We investigated the association of phenotypes with lung function at 6 weeks and 5 years.

FINDINGS

Between March 5, 2012, and March 31, 2015, we enrolled 1137 mothers and there were 1143 livebirths. Four wheeze phenotypes were identified among 950 children with complete data: never (480 children [50%]), early transient (215 children [23%]), late onset (104 children [11%]), and recurrent (151 children [16%]). Multivariate adjusted analysis indicated that LRTI and respiratory syncytial virus-LRTI, but not other respiratory viruses, were associated with increased risk of recurrent wheeze (odds ratio [OR] 2·79 [95% CI 2·05-3·81] for all LTRIs; OR 2·59 [1·30-5·15] for respiratory syncytial virus-LRTIs). Maternal smoking (1·88 [1·12-3·02]), higher socioeconomic status (2·46 [1·23-4·91]), intimate partner violence (2·01 [1·23-3·29]), and male sex (2·47 [1·50-4·04]) were also associated with recurrent wheeze. LRTI and respiratory syncytial virus-LRTI were also associated with early transient and late onset clusters. Wheezing illness architecture differed between DCHS and ALSPAC; children included in ALSPAC in the early transient cluster wheezed for a longer period before remission and late-onset wheezing started at an older age, and no persistent phenotype was identified in DCHS. At 5 years, airway resistance was higher in children with early or recurrent wheeze compared with children who had never wheezed. Airway resistance increased from 6 weeks to 5 years among children with recurrent wheeze.

INTERPRETATION

Effective strategies to reduce maternal smoking and psychosocial stressors and new preventive interventions for respiratory syncytial virus are urgently needed to optimise child health in LMICs.

FUNDING

UK Medical Research Council; The Bill & Melinda Gates Foundation; National Institutes of Health Human Heredity and Health in Africa; South African Medical Research Council; Wellcome Trust.

Evolution of Eczema, Wheeze, and Rhinitis from Infancy to Early Adulthood: Four Birth Cohort Studies

Rationale: The relationship between eczema, wheeze or asthma, and rhinitis is complex, and epidemiology and mechanisms of their comorbidities is unclear. Objectives: To investigate within-individual patterns of morbidity of eczema, wheeze, and rhinitis from birth to adolescence/early adulthood. Methods: We investigated onset, progression, and resolution of eczema, wheeze, and rhinitis using descriptive statistics, sequence mining, and latent Markov modeling in four population-based birth cohorts. We used logistic regression to ascertain if early-life eczema or wheeze, or genetic factors (filaggrin [FLG] mutations and 17q21 variants), increase the risk of multimorbidity. Measurements and Main Results: Single conditions, although the most prevalent, were observed significantly less frequently than by chance. There was considerable variation in the timing of onset/remission/persistence/intermittence. Multimorbidity of eczema+wheeze+rhinitis was rare but significantly overrepresented (three to six times more often than by chance). Although infantile eczema was associated with subsequent multimorbidity, most children with eczema (75.4%) did not progress to any multimorbidity pattern. FLG mutations and rs7216389 were not associated with persistence of eczema/wheeze as single conditions, but both increased the risk of multimorbidity (FLG by 2- to 3-fold, rs7216389 risk variant by 1.4- to 1.7-fold). Latent Markov modeling revealed five latent states (no disease/low risk, mainly eczema, mainly wheeze, mainly rhinitis, multimorbidity). The most likely transition to multimorbidity was from eczema state (0.21). However, although this was one of the highest transition probabilities, only one-fifth of those with eczema transitioned to multimorbidity. Conclusions: Atopic diseases fit a multimorbidity framework, with no evidence for sequential atopic march progression. The highest transition to multimorbidity was from eczema, but most children with eczema (more than three-quarters) had no comorbidities.

Early-life residential exposure to moisture damage is associated with persistent wheezing in a Finnish birth cohort

BACKGROUND AND AIMS

Moisture damage increases the risk for respiratory disorders in childhood. Our aim was to determine whether early age residential exposure to inspector-observed moisture damage or mold is associated with different wheezing phenotypes later in childhood.

METHODS

Building inspections were performed by civil engineers, in a standardized manner, in the children's homes-mostly single family and row houses (N = 344)-in the first year of life. The children were followed up with repeated questionnaires until the age of 6 years and wheezing phenotypes-never/infrequent, transient, intermediate, late onset, and persistent-were defined using latent class analyses. The multinomial logistic regression model was used for statistical analysis.

RESULTS

A total of 63% (n = 218) had infrequent or no wheeze, 23% (n = 80) had transient and 9.6% (n = 21) had a persistent wheeze. Due to the low prevalence, results for intermediate (3.8%, n = 13) and late-onset wheeze (3.5%, n = 12) were not further evaluated. Most consistent associations were observed with the persistent wheeze phenotype with an adjusted odds ratio (95% confidence intervals) 2.04 (0.67-6.18) for minor moisture damage with or without mold spots (present in 23.8% of homes) and 3.68 (1.04-13.05) for major damage or any moisture damage with visible mold in a child's main living areas (present in 13.4% of homes). Early-age moisture damage or mold in the kitchen was associated with transient wheezing.

CONCLUSION

At an early age, residential exposure to moisture damage or mold, can be dose-dependently associated especially with persistent wheezing phenotype later in childhood.

Enigma variations: The multi-faceted problems of pre-school wheeze

Numerous publications on wheezing disorders in children younger than 6 years have appeared in the medical literature over the last decades with the aim of shedding light on the mechanistic pathways (endotypes) and treatment. Nevertheless, there is yet no consensus as to the appropriate way to manage preschool wheeze mainly because of the lack of a clear definition of "preschool asthma" and the paucity of scientific evidence concerning its underlying endotypes. A symptom-based approach is inadequate since the human airway can respond to external stimuli with a limited range of symptoms and signs, including cough and wheeze, and these manifestations represent the final expression of many clinical entities with potentially different pathophysiologies requiring different individualized treatments. Hence, new studies challenge the symptom-based approach and promote the importance of managing the wheezy child based on the "airway phenotype." This will enable the clinician to identify not only the child with a serious underlying pathology (e.g., a structural airway disorder or immunodeficiency) who is in need of prompt and specific treatment but also increase the specificity of treatment for the child with symptoms suggestive of an "asthma" syndrome. In the latter case, focus should be given to the identification of treatable traits. This review summarizes the current understanding in management of preschool wheezing and highlights the unmet need for further research.

Pathogens and Pathogenesis in Wheezing Diseases in Children Under 6

Few studies have comprehensively assessed the roles of cytokine production in wheezing pathogenesis. Therefore, we undertook this study to determine the association between wheezing episodes and cytokines, and to provide further information on this topic. Firstly, we retrospectively collected I176 children, including 122 subjects with first wheezing and 54 subjects with recurrent wheezing, to analyze the etiology and clinical characteristics of children with wheezing diseases. Then, we collected 52 children with wheezing diseases and 25 normal controls to detect the expression of interferon-γ (IFN-γ), interleukin-4 (IL-4), IFN-γ/IL-4, IL-17A, IL-17E, IgE, matrix metalloproteinase-3 (MMP-3), and MMP-9 in serum or plasma. The results showed that boys under 3 years old with history of allergies were more likely to develop wheezing diseases. In our cohort, M. pneumoniae caused a greater proportion of wheezing in children than expected. The expression of IgE [18.80 (13.65-31.00) vs. 17.9 (10.15-21.60)], IL-4 [24.00 (24.00-48.00) vs. 23.00 (9.50-27.00)], IFN-γ [70.59 (41.63-116.46) vs. 49.83 (29.58-81.74)], MMP3 [53.40 (20.02-128.2) vs. 30.90 (13.80-50.95)], MMP9 [148.10 (99.30-276.10) vs. 122.10 (82.20-162.35)], IL-17A [80.55 (54.46-113.08) vs. 61.11 (29.43-93.87)], and IL-17E [1.75 (0.66-2.77) vs. 1.19 (0.488-2.1615)] were significantly increased in the wheezing group (p<0.05) compared to normal controls, while the level of IFN-γ/IL-4 had no significant difference between the two groups (1.24 ± 1.88 vs 0.68 ± 0.74, p>0.05). There was altered cytokine production in children with wheezing diseases which was quite similar to asthma pathogenesis. Sex, age, pathogen infection, and inflammation in our study were also risk factors for wheezing diseases.

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.

Wheezing trajectories from childhood to adulthood in a population-based cohort

BACKGROUND

Wheezing may lead to asthma and reduced pulmonary function in later life. The study aims to identify wheezing trajectories and investigate their relation with pulmonary function and asthma-related outcomes at 22 years of age.

METHODS

Individuals from a population-based cohort in Brazil (1993 Pelotas Birth Cohort) with post-bronchodilator pulmonary function data at 22 years (3350) were included in the study. From parentally reported (4 and 11 years) and self-reported (15, 18 and 22 years) history of wheezing in the last 12 months, we used a group-based trajectory modelling approach to derive wheezing trajectories.

RESULTS

Four trajectories were identified: never/infrequent, transient-early, late-onset and persistent wheeze. After adjustments, wheezing trajectories remained associated with lower post-bronchodilator values of pulmonary function. Individuals in the persistent wheeze trajectory had a markedly poorer pulmonary function and also showed greater odds of asthma-related outcomes compared to other trajectories groups. Those following this trajectory had on average -109 ml (95% CI: -188; -35), -1.80 percentage points (95% CI: -2.73; -0.87) and -316 ml/s (95% CI: -482; -150) lower FEV₁, FEV₁/FVC ratio and FEF_25-75% respectively; higher odds of self-reported medical diagnosis of allergy (OR 6.18; 95% CI: 3.59; 10.61) and asthma (OR 12.88; 95% CI: 8.91; 18.61) and asthma medication use (OR 9.42; 95% CI: 5.27; 16.87) compared to the never/infrequent group.

CONCLUSIONS

Wheezing trajectories, especially the persistent wheeze trajectory, were related to lower pulmonary function values and increased risk of asthma and allergy diagnosis in early adulthood.

Viral wheezing in early childhood as a risk factor for asthma in young adulthood: A prospective long-term cohort study

Background and Aims

There is an increased risk of asthma after viral wheezing episodes in early childhood, but unfortunately, prospective longitudinal data until adulthood are mostly lacking. The aim of this cohort study was to evaluate the risk of asthma in young adulthood after hospitalization for viral wheezing episodes in early childhood.

Methods

The original cohort comprised 100 individuals aged <24 months who were hospitalized for viral wheezing episodes in 1992-1993. After the index episode, data on a diagnosis of asthma 1 year later and at median ages of 4.0, 7.2, and 12.3 years were recorded in follow-up visits. Forty-nine individuals attended the latest follow-up visit at the age of 17-20 years. Current asthma was diagnosed based on symptoms at the time of the last follow-up, use of inhaled corticosteroids and peak expiratory flow monitoring.

Results

A total of 26 (53%) of the 49 cohort individuals had asthma at a mean age of 18.8 years. In multivariate analyses, a diagnosis of asthma 1 year after index hospitalization and at ages 4.0, 7.2, and 12.3 years were significant risk factors for current asthma (adjusted odds ratios [aORs] of 7.13, 8.86, 8.05, and 21.16, respectively). Atopic dermatitis in infancy (aOR: 4.20) and eosinophilia on admission (5.18) were also significant predictive factors for asthma.

Conclusion

Over half (26/49) of the participants who had been hospitalized for viral wheezing episodes in early childhood had asthma in young adulthood. An asthma diagnosis at any age during childhood, as well as eosinophilia in early childhood, were independent significant predictive factors for asthma.

High Insulin in Early Childhood Is Associated with Subsequent Asthma Risk Independent of Body Mass Index

BACKGROUND

Asthma and obesity are major, interconnected public health challenges that usually have their origins in childhood, and for which the relationship is strengthened among those with insulin resistance.

OBJECTIVE

To determine whether high insulin in early life confers increased longitudinal risk for asthma independent of body mass index.

METHODS

The study used data from the Tucson Children's Respiratory Study (TCRS) and the Avon Longitudinal Study of Parents and Children (ALSPAC). Nonfasting insulin was measured in TCRS participants at age 6 years and fasting insulin in ALSPAC participants at age 8 years. Physician-diagnosed active asthma was determined at baseline and at subsequent assessments up to age 36 years in TCRS and 17 years in ALSPAC.

RESULTS

In TCRS, high insulin (upper quartile) at age 6 years was associated with increased odds of having active asthma from ages 8 to 36 years compared with low insulin (odds ratio,1.98; 95% CI, 1.28-3.05; P = .002). Similarly, in ALSPAC, high insulin was associated with a significantly higher risk of active asthma from ages 11 to 17 years compared with low insulin (odds ratio, 1.59; 95% CI, 1.12-2.27; P = .009). These findings were independent of baseline body mass index in both cohorts, and were not related to other demographic and asthma risk factors nor other tested markers of systemic inflammation and metabolic syndrome.

CONCLUSIONS

In 2 separate birth cohorts, higher blood insulin level in early childhood was associated with increased risk of active asthma through adolescence and adulthood, independent of body mass index. High insulin indicates a novel mechanism for asthma development, which may be a target for intervention.

Modelling trajectories of parentally reported and physician-confirmed atopic dermatitis in a birth cohort study

BACKGROUND

In a population-based birth cohort, we aimed to identify longitudinal trajectories of atopic dermatitis (AD) during childhood using data from different sources (validated questionnaires and healthcare records). We investigated the impact of different AD definitions on such trajectories and their relationships with various risk factors.

METHODS

Of the 1184 children born into the study, 1083 had information on current AD for at least three follow-ups from birth to age 11 years and were included in the analysis for parentally reported AD (PRAD). Data were transcribed from healthcare records for 916 of 1184 children for the analysis of doctor-diagnosed AD (DDAD). We also derived a composite definition of AD (CDAD) (at least two of the following: PRAD, DDAD, current use of AD treatment). Using latent class analysis (LCA), we determined longitudinal profiles of AD using the three definitions. Filaggrin (FLG) genotype data were available for 803 white participants.

RESULTS

For PRAD, LCA identified four AD classes ('no AD', 'persistent', 'early-onset remitting' and 'late-onset'). For DDAD and CDAD, the optimal number of phenotypes was three ('no AD', 'persistent' and 'early-onset remitting'). Although AD classes at population level appeared similar in different models, a considerable proportion of children (n = 485, 45%) moved between classes. The association with FLG genotype, atopic diseases and early-life risk factors was inconsistent across different definitions, but the association with oral food challenge-confirmed peanut allergy was similar, with a nine- to 11-fold increase among children in the persistent AD class. In a CDAD model, compared with the early-onset remitting class, those with persistent AD were significantly more likely to have (at age 3 years) moderate/severe AD, polysensitization and current wheeze, and were less likely to have been breastfed.

CONCLUSIONS

Standardized composite definitions of AD may help to define AD cases with more precision and identify more consistent long-term trajectories.

Wheeze trajectories: Determinants and outcomes in the CHILD Cohort Study

BACKGROUND

Wheezing in early life is associated with asthma in adulthood; however, the determinants of wheezing trajectories and their associations with asthma and lung function in childhood remain poorly understood.

OBJECTIVE

In the CHILD Cohort Study, we aimed to identify wheezing trajectories and examine the associations between these trajectories, risk factors, and clinical outcomes at age 5 years.

METHODS

Wheeze data were collected at 8 time points from 3 months to 5 years of age. We used group-based trajectory models to derive wheeze trajectories among 3154 children. Associations with risk factors and clinical outcomes were analyzed by weighted regression models.

RESULTS

We identified 4 trajectories: a never/infrequent trajectory, transient wheeze, intermediate-onset (preschool) wheeze, and persistent wheeze. Higher body mass index was a common risk factor for all wheeze trajectories compared with that in the never/infrequent group. The unique predictors for specific wheeze trajectories included male sex, lower respiratory tract infections, and day care attendance for transient wheeze; paternal history of asthma, atopic sensitization, and child genetic risk score of asthma for intermediate wheeze; and maternal asthma for persistent wheeze. Blood eosinophil counts were higher in children with the intermediate wheeze trajectory than in those children with the other trajectories at the ages of 1 and 5 years. All wheeze trajectories were associated with decreased lung function and increased risk of asthma at age 5 years.

CONCLUSIONS

We identified 4 distinct trajectories in children from 3 months to 5 years of age, reflecting different phenotypes of early childhood wheeze. These trajectories were characterized by different biologic and physiologic traits and risk factors.

Four subtypes of childhood allergic rhinitis identified by latent class analysis

BACKGROUND

Childhood allergic rhinitis (AR) is clinically heterogenous. We aimed to identify distinct phenotypes among children with AR using data-driven techniques and to ascertain their association with patterns of symptoms, allergic sensitization, and comorbidities.

METHODS

We recruited 510 children with physician-diagnosed AR, of whom 205 (40%) had asthma. Latent class analysis (LCA) was performed to identify latent structure within the data set using 17 variables (allergic conjunctivitis, eczema, asthma, family history of asthma, family history of allergic rhinitis, skin sensitization to 8 common allergens, tonsillectomy, adenoidectomy).

RESULTS

A four-class solution was selected as the optimal model based on statistical fit. We labeled latent classes as: (1) AR with grass mono-sensitization and conjunctivitis (n = 361, 70.8%); (2) AR with house dust mite sensitization and asthma (n = 75, 14.7%); (3) AR with pet and grass polysensitization and conjunctivitis (n = 35, 6.9%); and (4) AR among children with tonsils and adenoids removed (n = 39, 7.6%). Perennial AR was significantly more common among children in Class 2 (OR 5.83, 95% CI 3.42-9.94, p < .001) and Class 3 (OR 2.88, 95% CI 1.36-6.13, p = .006). Mild and intermittent AR symptoms were significantly more common in children in Class 2 compared to those in Class 1. AR was more severe in Class 1 compared to other 3 classes, indicating that upper respiratory symptoms are more severe among children with isolated seasonal rhinitis, than in those with rhinitis and coexisting asthma.

CONCLUSION

We have identified 4 phenotypes in school-age children with AR, which were associated with different patterns of clinical symptoms and comorbidities.

Recurrent Severe Preschool Wheeze: From Pre-Specified Diagnostic Labels to Underlying Endotypes

Rationale: Preschool wheezing is heterogeneous, but the underlying mechanisms are poorly understood.

Objectives: To investigate lower airway inflammation and infection in preschool children with different clinical diagnoses undergoing elective bronchoscopy and BAL.

Methods: We recruited 136 children aged 1–5 years (105 with recurrent severe wheeze [RSW]; 31 with nonwheezing respiratory disease [NWRD]). Children with RSW were assigned as having episodic viral wheeze (EVW) or multiple-trigger wheeze (MTW). We compared lower airway inflammation and infection in different clinical diagnoses and undertook data-driven analyses to determine clusters of pathophysiological features, and we investigated their relationships with prespecified diagnostic labels.

Measurements and Main Results: Blood eosinophil counts and percentages and allergic sensitization were significantly higher in children with RSW than in children with a NWRD. Blood neutrophil counts and percentages, BAL eosinophil and neutrophil percentages, and positive bacterial culture and virus detection rates were similar between groups. However, pathogen distribution differed significantly, with higher detection of rhinovirus in children with RSW and higher detection of Moraxella in sensitized children with RSW. Children with EVW and children with MTW did not differ in terms of blood or BAL-sample inflammation, or bacteria or virus detection. The Partition around Medoids algorithm revealed four clusters of pathophysiological features: 1) atopic (17.9%), 2) nonatopic with a low infection rate and high use of inhaled corticosteroids (31.3%), 3) nonatopic with a high infection rate (23.1%), and 4) nonatopic with a low infection rate and no use of inhaled corticosteroids (27.6%). Cluster allocation differed significantly between the RSW and NWRD groups (RSW was evenly distributed across clusters, and 60% of the NWRD group was assigned to cluster 4; P < 0.001). There was no difference in cluster membership between the EVW and MTW groups. Cluster 1 was dominated by Moraxella detection (P = 0.04), and cluster 3 was dominated by Haemophilus or Staphylococcus or Streptococcus detection (P = 0.02).

Conclusions: We identified four clusters of severe preschool wheeze, which were distinguished by using sensitization, peripheral eosinophilia, lower airway neutrophilia, and bacteriology.

Characterization of Asthma Trajectories from Infancy to Young Adulthood

BACKGROUND

Development of asthma is complicated by the multidimensional nature of the disease.

OBJECTIVE

To identify and characterize trajectories of asthma from infancy to young adulthood, and their associations with lung function and inflammatory and respiratory markers in adolescence and young adulthood.

METHODS

A latent class analysis was performed in a population-based cohort (N = 4089). Parental and self-reported symptoms of asthma were used to investigate asthma development. We characterized background factors, allergic comorbidity, and IgE sensitization and investigated associations with asthma markers.

RESULTS

A 4-class solution of asthma trajectories was identified: never/infrequent (n = 3291 [80.4%]), early-onset transient (n = 307 [7.5%]), adolescent-onset (n = 261 [6.4%]), and persistent asthma (n = 230 [5.6%]). Uncontrolled asthma was equally prevalent in the adolescent-onset and persistent asthma trajectory groups, at both age 16 (41.7% vs 42.4%; P = .90) and 24 years (53.7% vs 52.4%; P = .81). The persistent asthma trajectory group had a higher proportion of eosinophil counts greater than or equal to 0.3 (10⁹ cells/L) at age 24 years compared with the adolescent-onset trajectory group (31.0% vs 18.5%; P < .01).

CONCLUSIONS

The adolescent-onset and persistent asthma trajectory groups had equal burdens of asthma control in adolescence and young adulthood. However, the persistent asthma trajectory group showed more signs of type 2 inflammation than the adolescent-onset trajectory group. This unbiased approach highlights the need of identifying patients with adolescent asthma to optimize care, because they suffer the same lack of asthma control as those with persistent asthma.

Childhood wheeze trajectory-specific risk factors: A systematic review and meta-analysis

BACKGROUND

There is growing interest in the use of latent trajectory methodology to identify wheeze patterns in heterogeneous populations of children. This study systematically reviewed and meta-analyzed childhood wheeze trajectory studies to identify childhood wheeze trajectory group-specific risk factors among children from birth through to adolescence.

METHODS

We included studies that used latent trajectory methodology to identify wheeze trajectories and associated risk factors. We searched PubMed, EMBASE, and Google Scholar from 2000 through September 30, 2019, for relevant studies. The study was conducted according to the PRISMA recommendations.

RESULTS

Thirteen cohort studies conducted in eleven high-income countries were included in our meta-analysis with the length of follow-up ranging from 3 to 18 years. Five distinct latent wheeze trajectory groups were identified: Never/Infrequent, Early-Transient, Early-Persistent, Intermediate-Onset, and Late-Onset. We found moderate-to-strong evidence that family history of asthma predicted persistent childhood wheezing among male children but with lower risk among first-born children. There was weak-to-moderate evidence for childhood atopy, male sex, short duration of breastfeeding, tobacco exposure, daycare attendance, and having siblings as risk factors for Early-Transient wheezing; except for breastfeeding, these factors were also associated with intermediate and Late-Onset wheezing with varying effect sizes in high-risk vs general population cohorts.

CONCLUSIONS

Our findings confirm the consistency of wheeze trajectory groups defined by onset, peak prevalence, and duration; we also suggest a common nomenclature for future trajectory studies. With the exception of the relationship between a family history of asthma and persistent childhood wheezing, commonly suspected wheeze risk factors (childhood atopy, male sex, short duration of breastfeeding, tobacco exposure, daycare attendance, and having siblings) are not trajectory-specific and have varying effects in high-risk vs general population cohorts. Delineation of time-varying risk factor effects may be critical to the specificity of wheeze trajectory group prediction to better inform prognosis and targeted early preventive intervention among at-risk children.

Atopic phenotypes and their implication in the atopic march

INTRODUCTION

Eczema, allergic rhinitis, and asthma are traditionally considered atopic (or allergic) diseases. They are complex, multifactorial, and are caused by a variety of different mechanisms, which result in multiple heterogeneous clinical phenotypes. Atopic march is usually interpreted as the sequential development of symptoms from eczema in infancy, to asthma, and then allergic rhinitis. Areas covered: The authors reviewed the evidence on the multimorbidity of eczema, asthma, and rhinitis, and the implication of results of data-driven analyses on the concept framework of atopic march. A literature search was conducted in the PubMed and Web of Science for peer-reviewed articles published until July 2020. Application of Bayesian machine learning framework to rich phenotypic data from birth cohorts demonstrated that the postulated linear progression of symptoms (atopic march) does not capture the heterogeneity of allergic phenotypes. Expert opinion: Eczema, wheeze, and rhinitis co-exist more often than would be expected by chance, but their relationship can be best understood in a multimorbidity framework, rather than through atopic march sequence. The observation of their co-occurrence does not imply any specific relationship between them, and certainly not a progressive or causal one. It is unlikely that a sngle mechanism such as allergic sensitization underpins different multimorbidity manifestations.

Distinguishing Wheezing Phenotypes from Infancy to Adolescence. A Pooled Analysis of Five Birth Cohorts

Rationale: Pooling data from multiple cohorts and extending the time frame across childhood should minimize study-specific effects, enabling better characterization of childhood wheezing.

Objectives: To analyze wheezing patterns from early childhood to adolescence using combined data from five birth cohorts.

Methods: We used latent class analysis to derive wheeze phenotypes among 7,719 participants from five birth cohorts with complete report of wheeze at five time periods. We tested the associations of derived phenotypes with late asthma outcomes and lung function, and investigated the uncertainty in phenotype assignment.

Results: We identified five phenotypes: never/infrequent wheeze (52.1%), early onset preschool remitting (23.9%), early onset midchildhood remitting (9%), persistent (7.9%), and late-onset wheeze (7.1%). Compared with the never/infrequent wheeze, all phenotypes had higher odds of asthma and lower forced expiratory volume in 1 second and forced expiratory volume in 1 second/forced vital capacity in adolescence. The association with asthma was strongest for persistent wheeze (adjusted odds ratio, 56.54; 95% confidence interval, 43.75–73.06). We observed considerable within-class heterogeneity at the individual level, with 913 (12%) children having low membership probability (<0.60) of any phenotype. Class membership certainty was highest in persistent and never/infrequent, and lowest in late-onset wheeze (with 51% of participants having membership probabilities <0.80). Individual wheezing patterns were particularly heterogeneous in late-onset wheeze, whereas many children assigned to early onset preschool remitting class reported wheezing at later time points.

Conclusions: All wheeze phenotypes had significantly diminished lung function in school-age children, suggesting that the notion that early life episodic wheeze has a benign prognosis may not be true for a proportion of transient wheezers. We observed considerable within-phenotype heterogeneity in individual wheezing patterns.

Characterisation of pulmonary function trajectories: results from a Brazilian cohort

BACKGROUND

Pulmonary function (PF) trajectories are determined by different exposures throughout the life course. The aim of this study was to investigate characteristics related to PF trajectories from 15 to 22 years in a Brazilian cohort.

METHODS

A birth cohort study (1993 Pelotas Birth Cohort) was conducted with spirometry at 15, 18 and 22 years. PF trajectories were built based on z-score of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and their ratio using a group-based trajectory model. Associations with exposures reported from perinatal to 22 years were described.

RESULTS

Three trajectories, low (LT), average (AT) and high (HT) were identified in 2917 individuals. Wealthiest individuals belonged to the HT of FEV1 (p=0.023). Lower maternal pregestational body mass index (BMI) (22.4±0.2; p<0.001 and 22.1±0.14; p<0.001) and lower birth weight (3164.8±25.4; p=0.029 and 3132.3±19.4; p=0.005) were related to the LT of FEV1 and FVC. Mother's smoking exposure during pregnancy (37.7%; p=0.002), active smoking at ages 18 and 22 years (20.1% and 25.8%; p<0.001) and family history of asthma (44.8%; p<0.001) were related to the LT of FEV1/FVC. Wheezing, asthma and hospitalisations due to respiratory diseases in childhood were related to the LT of both FEV1 and FEV1/FVC. Higher BMIs were related to the HT of FEV1 and FVC at all ages.

CONCLUSIONS

PF trajectories were mainly related to income, pregestational BMI, birth weight, hospitalisation due to respiratory diseases in childhood, participant's BMI, report of wheezing, medical diagnosis and family history of asthma, gestational exposure to tobacco and current smoking status in adolescence and young adult age.

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.

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.

Does understanding endotypes translate to better asthma management options for all?

Despite the development of novel treatments, improvement in the design of delivery devices, and new technologies for monitoring and improving adherence, the burden of asthma is not decreasing. Predicting an individual patient's response to asthma drugs remains challenging, and the provision of personalized treatment remains elusive. Although biomarkers, such as allergic sensitization and blood eosinophilia, might be important predictors of response to inhaled corticosteroids in preschool children, these relatively cheap and available investigations are seldom used in clinical practice to select patients for corticosteroid prescription. However, for the majority of patients, response to different treatments cannot be accurately predicted. One of the key factors preventing further advances is the reductionist view of asthma as a single disease, which is forcing patients with different asthma subtypes into a single group for empiric treatment. This inevitably results in treatment failures and, for some, an unacceptable risk/benefit ratio. The approach to asthma today is an example of the traditional symptom (diagnosis)-based, one-size-fits-all approach rather than a stratified approach, and our guidelines-driven management based on a unitary diagnosis might not be the optimal way to deliver care. The only way to deliver stratified medicine and find a cure is through the understanding of asthma endotypes. We propose that the way to discover endotypes, biomarkers, and personalized treatments is through the iterative process based on interpretation of big data analytics from birth and patient cohorts, responses to treatments in randomized controlled trials, and in vitro mechanistic studies using human samples and experimental animal models, with technological and methodological advances at its core.