Fraction of exhaled nitric oxide and wheezing phenotypes in preschool children

Assessment of bronchodilator response in preschoolers: A systematic review

BACKGROUND

Several techniques can be used to assess bronchodilator response (BDR) in preschool-aged children, including spirometry, respiratory oscillometry, the interrupter technique, and specific airway resistance. However, there has not been a systematic comparison of BDR thresholds across studies yet.

METHODS

A systematic review was performed on all studies up to May 2023 measuring a bronchodilator effect in children 2-6 years old using one of these techniques (PROSPERO CRD42021264659). Studies were identified using MEDLINE, Cochrane, EMBASE, CINAHL via EBSCO, Web of Science databases, and reference lists of relevant manuscripts.

RESULTS

Of 1224 screened studies, 43 were included. Over 85% were from predominantly European ancestry populations, and only 22 studies (51.2%) calculated a BDR cutoff based on a healthy control group. Five studies included triplicate testing with a placebo to account for the within-subject intrasession repeatability. A relative BDR was most consistently reported by the included studies (95%) but varied widely across all techniques. Various statistical methods were used to define a BDR, with six studies using receiver operating characteristic analyses to measure the discriminative power to distinguish healthy from wheezy and asthmatic children.

CONCLUSION

A BDR in 2- to 6-year-olds cannot be universally defined based on the reviewed literature due to inconsistent methodology and cutoff calculations. Further studies incorporating robust methods using either distribution-based or clinical anchor-based approaches to define BDR are required.

Early Prediction of Asthma

The clinical manifestations of asthma in children are highly variable, are associated with different molecular and cellular mechanisms, and are characterized by common symptoms that may diversify in frequency and intensity throughout life. It is a disease that generally begins in the first five years of life, and it is essential to promptly identify patients at high risk of developing asthma by using different prediction models. The aim of this review regarding the early prediction of asthma is to summarize predictive factors for the course of asthma, including lung function, allergic comorbidity, and relevant data from the patient's medical history, among other factors. This review also highlights the epigenetic factors that are involved, such as DNA methylation and asthma risk, microRNA expression, and histone modification. The different tools that have been developed in recent years for use in asthma prediction, including machine learning approaches, are presented and compared. In this review, emphasis is placed on molecular mechanisms and biomarkers that can be used as predictors of asthma in children.

Exhaled nitric oxide in asthma: from diagnosis to management

PURPOSE OF REVIEW

Exhaled nitric oxide (FENO) is a noninvasive marker of eosinophilic airway inflammation, therefore, highly informative in asthma. Although FENO measurement is a potentially accessible tool to many physicians, recommendations regarding its clinical utility in diagnosing or tailoring treatment have not reached the expected diffusion. More recently FENO emerged as a biomarker for type-2 asthma phenotyping and a predictor of response to biologics.

RECENT FINDINGS

The physiological discoveries and relevant acquisitions in clinical practice regarding FENO in asthma are presented. The FENO story draw a wavy path, characterized by promising findings, exciting confirmations and periods of low visibility. FENO emerged as a tool to increase the probability of asthma diagnosis. FENO predicts response to inhaled glucocorticoids (ICS), favoring the development of tailored treatment strategies and unrevealing nonadherence to ICS in difficult-to-treat or uncontrolled asthma. Finally, FENO was associated with a more severe phenotype and became a consolidated biomarker of type-2 inflammation.

SUMMARY

FENO demonstrated to be a noninvasive and very reproducible test, encompassing many applications in the field of asthma management. Its routinely use, according to international guidelines, may improve the quality of patient assistance, from difficult-to-treat cases to biologic monitoring.

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.

Application of exhaled nitric oxide (FeNO) in pediatric asthma

PURPOSE OF REVIEW

Fractional concentration of Nitric Oxide in the exhaled air (FeNO) is a moderately good biomarker of type-2 airway inflammation, and its measurement is feasible also in children. The available evidence is still not enough to support the routine use of FeNO to diagnose or manage asthma in every patient in clinical practice. However, its role in identifying asthma with eosinophilic inflammation is of particular interest in the management of severe asthma.

RECENT FINDINGS

In healthy subjects, FeNO levels increase with age and height, particularly in males, and are also influenced by ethnicity. FeNO measurement can support asthma diagnosis and help in predicting asthma development later in life in young children with recurrent wheezing. FeNO-guided asthma management is effective in reducing asthma exacerbations but may result in a higher daily dose of inhaled corticosteroids. FeNO can also be used as a marker to evaluate adherence to asthma treatment and predict response to different biologicals, especially Omalizumab and Dupilumab.

SUMMARY

This review outlines recent data on the application of FeNO in childhood-onset asthma diagnosis and management, as well as in phenotyping subjects with severe asthma who may benefit from monoclonal antibodies administration.

Asthma predictive index as a useful diagnostic tool in preschool children: a cross-sectional study in Korea

BACKGROUND

It is challenging to diagnose asthma in preschool children. The asthma predictive index (API) has been used to predict asthma and decide whether to initiate treatment in preschool children.

PURPOSE

This study aimed to investigate the association between questionnaire-based current asthma with API, pulmonary function, airway hyperreactivity (AHR), fractional expiratory nitric oxide (FeNO), and atopic sensitization in preschool children.

METHODS

We performed a population-based cross-sectional study in 916 preschool children aged 4-6 years. We defined current asthma as the presence of both physician-diagnosed asthma and at least one wheezing episode within the previous 12 months using a modified International Study of Asthma and Allergies in Childhood questionnaire. Clinical and laboratory parameters were compared between groups according to the presence of current asthma.

RESULTS

The prevalence of current asthma was 3.9% in the study population. Children with current asthma showed a higher rate of positive bronchodilator response and loose and stringent API scores than children without current asthma. The stringent API was associated with current asthma with 72.2% sensitivity and 82.0% specificity. The diagnostic accuracy of the stringent API for current asthma was 0.771. However, no intergroup differences in spirometry results, methacholine provocation test results, FeNO level, or atopic sensitization rate were observed.

CONCLUSION

The questionnaire-based diagnosis of current asthma is associated with API, but not with spirometry, AHR, FeNO, or atopic sensitization in preschool children.

Fractional Exhaled Nitric Oxide (FENO) in the management of asthma: a position paper of the Italian Respiratory Society (SIP/IRS) and Italian Society of Allergy, Asthma and Clinical Immunology (SIAAIC)

Asthma prevalence in Italy is on the rise and is estimated to be over 6% of the general population. The diagnosis of asthma can be challenging and elusive, especially in children and the last two decades has brought evidences that asthma is not a single disease but consists of various phenotypes. Symptoms can be underestimated by the patient or underreported to the clinician and physical signs can be scanty. Usual objective measures, like spirometry, are necessary but sometimes not significant. Despite proper treatment, asthma can be a very severe condition (even leading to death), however new drugs have recently become available which can be very effective in its control. Since asthma is currently thought to be caused by inflammation, a direct measure of the latter can be of paramount importance. For this purpose, the measurement of Fractional Exhaled Nitric Oxide (FE_NO) has been used since the early years of the current century as a non-invasive, easy-to-assess tool useful for diagnosing and managing asthma. This SIP-IRS/SIAAIC Position Paper is a narrative review which summarizes the evidence behind the usefulness of FE_NO in the diagnosis, management and phenotypization of asthma.

Nitric Oxide and Biological Mediators in Pediatric Chronic Rhinosinusitis and Asthma

BACKGROUND

In the context of the so-called unified airway theory, chronic rhinosinusitis (CRS) and asthma may coexist. The inflammation underlying these conditions can be studied through the aid of biomarkers. Main body: We described the main biological mediators that have been studied in pediatric CRS and asthma, and, according to the available literature, we reported their potential role in the diagnosis and management of these conditions. As for CRS, we discussed the studies that investigated nasal nitric oxide (nNO), pendrin, and periostin. As for asthma, we discussed the role of fractional exhaled nitric oxide (feNO), the role of periostin, and that of biological mediators measured in exhaled breath condensate (EBC) and exhaled air (volatile organic compounds, VOCs).

CONCLUSION

Among non-invasive biomarkers, nNO seems the most informative in CRS and feNO in asthma. Other biological mediators seem promising, but further studies are needed before they can be applied in clinical practice.

The Role of FeNO in Predicting Asthma

Asthma-like symptoms like wheezing and dyspnea affect 1 in every 3 preschool children. An easily available biomarker that predicts later asthma or unfavorable lung growth in these children may be helpful in targeting the right child with the right drugs and avoiding exposure to potentially harmful drugs in others. The fraction of exhaled nitric oxide (FeNO) has been suggested as a marker of eosinophilic inflammation. FeNO can be measured in a standardized way from the age of 4 but several methods have been developed to measure FeNO also in younger children. Several studies have assessed the predictive value of FeNO in preschool wheezing children for asthma later in life. These studies have shown that FeNO may be helpful in defining different preschool wheezing phenotypes, and in assessing the risk of later asthma or impaired lung growth. However, data are conflicting on the added value over clinical parameters. In two studies in school children, high FeNO was predictive for asthma development during follow up and also predicted lower lung function growth. In school children with respiratory symptoms suggestive of asthma, particularly in atopic children, FeNO has diagnostic value for an asthma diagnosis, mostly for ruling in asthma. There are not enough data to assess if FeNO has a predictive value for lung development in school children.

Exhaled biomarkers in childhood asthma: old and new approaches

Background

Asthma is a chronic condition usually characterized by underlying inflammation. The study of asthmatic inflammation is of the utmost importance for both diagnostic and monitoring purposes. The gold standard for investigating airway inflammation is bronchoscopy, with bronchoalveolar lavage and bronchial biopsy, but the invasiveness of such procedures limits their use in children. For this reason, in the last decades there has been a growing interest for the development of noninvasive methods.

Main body

In the present review, we describe the most important non-invasive methods for the study of airway inflammation in children, focusing on the measure of the fractional exhaled nitric oxide (feNO), on the measure of the exhaled breath temperature (EBT) and on the analysis of both exhaled breath condensate (EBC) and exhaled air (Volatile Organic Compounds, VOCs), using targeted and untargeted approaches. We summarize what is currently known on the topic of exhaled biomarkers in childhood asthma, with a special emphasis on emerging approaches, underlining the role of exhaled biomarkers in the diagnosis, management and treatment of asthma, and their potential for the development of personalized treatments.

Conclusion

Among non-invasive methods to study asthma, exhaled breath analysis remains one of the most interesting approaches, feNO and “-omic” sciences seem promising for the purpose of characterizing biomarkers of this disease.

Expression and Regulation of Thymic Stromal Lymphopoietin and Thymic Stromal Lymphopoietin Receptor Heterocomplex in the Innate-Adaptive Immunity of Pediatric Asthma

Asthma is a chronic inflammatory disease affecting the airway, and it is characterized by a wheezing breathing sound, variable airflow obstruction and the presence of inflammatory cells in the submucosa of the bronchi. Viral infection, pollutants and sensitivity to aeroallergens damage the epithelium from childhood, which causes asthma. The pathogenesis of asthma includes pathways of innate stimulation by environmental microbes and irritant pathogens. Damaged epithelial cells produce thymic stromal lymphopoietin (TSLP) and stimulate myeloid dendritic cell maturation through the thymic stromal lymphopoietin receptor (TSLPR) heterocomplex. TSLP-activated myeloid dendritic cells promote naive CD4⁺ T cells to differentiate into T helper type 2 (Th2) phenotype CD4⁺ T cells. Re-exposure to allergens or environmental stimuli causes an adaptive immune response. TSLP-activated dendritic cells expressing the OX40 ligand (OX40L; CD252) trigger naive CD4⁺ T cells to differentiate into inflammatory Th2 effector cells secreting the cytokines interleukin-4, 5, 9, and 13 (IL-4, IL-5, IL-9 and IL-13), and the dendritic cells (DCs) promote the proliferation of allergen-specific Th2 memory cells. Allergen presentation by Th2 cells through its interaction with their receptors in the presence of major histocompatibility complex (MHC) class II on B cells and through costimulation involving CD40 and CD40L interactions results in immunoglobulin class switching from IgM to IgE. DCs and other blood cell subsets express the TSLPR heterocomplex. The regulatory mechanism of the TSLPR heterocomplex on these different cell subsets remains unclear. The TSLPR heterocomplex is composed of the IL-7Rα chain and TSLPR chain. Moreover, two isoforms of TSLP, short isoform TSLP (sfTSLP) and long isoform TSLP (lfTSLP), have roles in atopic and allergic development. Identifying and clarifying the regulation of TSLPR and IL-7Rα in pediatric asthma are still difficult, because the type of blood cell and the expression for each blood cell in different stages of atopic diseases are poorly understood. We believe that further integrated assessments of the regulation mechanism of the TSLP–TSLPR heterocomplex axis in vitro and in vivo can provide a faster and earlier diagnosis of pediatric asthma and promote the development of more effective preventive strategies at the onset of allergies.

Recurrent wheeze and its relationship with lung function and airway inflammation in preschool children: a cross-sectional study in South Korea

BACKGROUND

Relationship between recurrent wheeze and airway function and inflammation in preschool children is not fully known.

OBJECTIVE

To investigate the relationship between recurrent wheeze and airway inflammation, lung function, airway hyper-reactivity (AHR) and atopy in preschool children.

DESIGN

Observational study, comparing forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC) and mid-forced expiratory flow (FEF_25%-75%), dose-response slope (DRS), exhaled nitric oxide (eNO) and atopic sensitisation between children with recurrent wheeze and those without.

SETTING

Population-based, cross-sectional study in Seoul and the Gyeonggi province of Korea conducted as a government-funded programme to perform standardised measurement of the prevalence of allergic diseases, and related factors, in preschool children.

PARTICIPANTS

900 children aged 4-6 years. PRIMARY AND SECONDARY OUTCOME MEASURES: eNO, FEV₁/FVC, FEF_25%-75%, DRS, atopic sensitisation and allergic diseases.

METHODS

Children completed the modified International Study of Asthma and Allergies in Childhood questionnaire and underwent eNO assessments, spirometry, methacholine bronchial provocation tests and skin prick tests. Recurrent wheeze was defined as having a lifetime wheeze of more than three episodes, based on the questionnaire. The frequency of hospitalisation and emergency room visits was also obtained by means of the questionnaire. 'Current' wheeze was defined as having symptoms or treatments within the past 12 months.

RESULTS

The prevalence of recurrent wheeze was 13.4%. Children with recurrent wheeze showed a higher prevalence of lifetime or current allergic rhinitis (p=0.01 and p=0.002, respectively) and lifetime atopic dermatitis (p=0.007). Children with recurrent wheeze showed lower FEV₁/FVC (p=0.033) and FEF_25%-75% (p=0.004), and higher eNO levels (p=0.013) than those without recurrent wheeze. However, the DRS, prevalence of atopic sensitisation and serum IgE levels were not significantly different between the two groups.

CONCLUSIONS

Recurrent wheeze in preschool children may be associated with airway inflammation and diminished airway function, but not with AHR or atopy.

Current and future management of the young child with early onset wheezing

PURPOSE OF REVIEW

In this review, we discuss current thinking in relation to available guidelines for the care of preschool-aged children with recurrent wheezing, while highlighting the gaps in our knowledge and discussing changes that could occur over the next 5 years.

RECENT FINDINGS

The Asthma Predictive Index as well as allergen-specific IgE, peripheral eosinophil count and exhaled nitric oxide are perhaps underutilized sources of information that can assist in predicting progression to asthma and response to therapies. Inhaled corticosteroids and leukotriene receptor antagonists decrease impairment and exacerbation frequency in wheezing children but are not disease modifying. Macrolides may be useful during acute wheezing episodes for preventing progression to more severe symptoms. Monoclonal antibodies targeting IgE and TH2 cytokines have been successful in trials of adults and older children with asthma, but trials in younger children are needed.

SUMMARY

Establishing the phenotype and endotype of young wheezing children can be useful for prognostication of future asthma risk as well as for selection of the most appropriate treatment. Primary asthma prevention strategies are needed during the critical developmental window in early life prior to the onset of irrecoverable loss of lung function.

Identification of infants and preschool children at risk for asthma: predictive scores and biomarkers

PURPOSE OF REVIEW

Predictive asthma scores and biomarkers are important tools that help many physicians in the identification of infants and preschool children at high risk for asthma. Our objective was to review recent data regarding this subject.

RECENT FINDINGS

Recently, two new predictive asthma scores were developed with some innovative features, such as the definition of scales of asthma risk. In a systematic review, 12 asthma-predictive models were identified with heterogeneous performance. Prospective studies have shown that elevated fractional concentration of nitric oxide (FeNO) is a strong risk factor for latter asthma among early wheezers, and a predictive asthma score with FeNO values has been proposed. Plasma cytokines and exhaled volatile organic compounds were also identified as potential asthma predictors.

SUMMARY

Predictive scores are simple, practical, and inexpensive tools to identify children at high risk for asthma at school age. Whereas some scores are better at identifying asthmatic children, others are better at excluding the diagnosis of asthma. Although promising, clear evidence for FeNO as a robust asthma predictor in comparison to clinical scores is still lacking. Specific IgE and eosinophil counts remain the most consistent biomarkers for the identification of children at risk for asthma, and further studies are necessary to clarify the role of other biomarkers.

Exhaled nitric oxide in school children: Searching for the lost variability

OBJECTIVE

The factors - including asthma and rhinoconjunctivitis - which influence FeNO values in a general population of school children have been studied in order to know to what extent the variability of those values can be explained.

METHODS

FeNO was measured in a population of 240 school children aged 6-12 years by means of a Niox-Mino™ device in a standardised way. Parents filled in an ISAAC-validated questionnaire of symptoms and environmental factors. Diagnoses were checked against clinical records. Height and weight were measured. A multivariate regression analysis including all variables in the questionnaire was performed, which was followed by two Xi stepwise tests in order to build a predictive model which included the main variables influencing FeNO values.

RESULTS

Among the 240 children, 10 suffered from asthma, 16 from rhinoconjunctivitis and 15 from both conditions. FeNO values (GM±GSD) in children with rhinoconjunctivitis (19.61±1.20ppb), with asthma (18.62±1.32ppb), and with both conditions (17.62±1.19ppb) tended to be significantly higher than control children (11.42±1.04ppb), p=0.0016, p=0.08 and p=0.01, respectively. The different predictive models were able to explain only 20-27% of FeNO variability.

CONCLUSIONS

The proportion of FeNO inter-individual variability which can be explained by individual (including suffering from asthma or rhinoconjunctivitis), family, and environmental factors is very low (20-27%). This could have implications on the usefulness of FeNO as a diagnostic tool in asthma.

Associations of wheezing phenotypes with late asthma outcomes in the Avon Longitudinal Study of Parents and Children: A population-based birth cohort

Background

Variable patterns of childhood wheezing might indicate differences in the cause and prognosis of respiratory illnesses. Better understanding of these patterns could facilitate identification of modifiable factors related to development of asthma.

Objectives

We characterized childhood wheezing phenotypes from infancy to adolescence and their associations with asthma outcomes.

Methods

Latent class analysis was used to derive phenotypes based on patterns of wheezing recorded at up to 14 time points from birth to 16½ years among 12,303 participants from the Avon Longitudinal Study of Parents and Children. Measures of lung function (FEV₁, forced vital capacity [FVC], and forced expiratory flow between 25% and 75% [FEF_25-75]) and fraction of exhaled nitric oxide (Feno) were made at 14 to 15 years of age.

Results

Six wheezing phenotypes were identified: never/infrequent, preschool-onset remitting, midchildhood-onset remitting, school age–onset persisting, late childhood–onset persisting, and continuous wheeze. The 3 persistent phenotypes were associated with bronchodilator reversibility of 12% or greater (BDR) from baseline (odds ratio [OR] range, 2.14-3.34), a Feno value of 35 ppb or greater (OR range, 3.82-6.24), and lung function decrements (mean range of differences: −0.22 to −0.27 SD units (SDU) for FEV₁/FVC ratio and −0.21 to −0.33 SDU for FEF_25-75) compared with never/infrequent wheeze. Midchildhood-onset (4½ years) remitting wheeze was associated with BDR (OR, 1.77; 95% CI, 1.11-2.82), a Feno value of 35 ppb or greater (OR, 1.72; 95% CI, 1.14-2.59), FEV₁/FVC ratio decrements (OR, −0.22 SDU; 95% CI, −0.36 to −0.08 SDU), and FEF_25-75 decrements (OR, −0.16 SDU; 95% CI, −0.30 to −0.01 SDU). Preschool-onset (18 months) remitting wheeze was only associated with FEV₁/FVC ratio decrements (OR, −0.15 SDU; 95% CI, −0.25 to −0.05 SDU) and FEF_25-75 decrements (OR, −0.14 SDU; 95% CI, −0.24 to −0.04 SDU). The persisting phenotypes showed evidence of sex stratification during adolescence.

Conclusions

Early childhood–onset wheezing that persists into adolescence represents the clearest target group for interventions to maximize lung function outcomes.

Exhaled nitric oxide as a diagnostic tool for wheezing in preschool children: A diagnostic accuracy study

BACKGROUND

Airways inflammation may precede pulmonary dysfunction in wheezing individuals. The fraction of exhaled nitric oxide (FENO) has been described as a useful method for wheezing diagnosis in children, however, its application requires evidence. This study aimed to determine the accuracy of FENO in identifying wheezing in preschoolers.

METHODS

A cross-sectional study was carried out with children from 3 to 5 years old, from Brazilian day care centers and public schools. They were evaluated by FENO measurement through the single breath method, and by ATS-DLD-78-C questionnaire that is used as a gold standard to phenotype wheezing patterns.

RESULTS

The sample consisted of 243 non-wheezing children, 118 non-recurrent wheezing and 62 recurrent wheezing. The means of FENO and confidence intervals of 95%, were 5.4 (CI 95%, 5.2-5.6); 7.5 (CI 95%, 6.9-8.2) and 11.2 (CI 95%, 9.6-12.7), respectively. The sensitivity, specificity, positive and negative predictive FENO values in the 6 parts per billion (ppb) cut-off point that best diagnosed wheezing of non-wheezing children, were: 65.5%, 84.3%, 75.6% and 76.7%, respectively, with an area under the curve (AUC) = 0.77. At 10 ppb, the best cut-off points for differentiating recurrent wheezing of non-recurrent wheezing were: 56.4%, 81.3%, 61.4%, 78.0%, respectively, with an AUC = 0.69. The post-test probability for each FENO cut-off points was increased by 33% for wheezing and 20% for recurrent wheezing diagnosis when associated with clinical examination.

CONCLUSION

FENO can provide a reliable and accurate method to discriminate the presence and type of wheezing in preschoolers with 92% of acceptable in this study population.

Biomarkers to predict asthma in wheezing preschool children

Wheezing in preschool children is a very common symptom. An adequate prediction of asthma in these children is difficult and cannot be reliably assessed with conventional clinical tools. The study of potential predictive biomarkers in various media, ranging from invasive sampling (e.g. bronchoscopy) to non-invasive sampling (lung function testing and exhaled breath analysis), was comprehensively reviewed. The evolution in biomarker discovery has resulted in an 'omics' approach, in which hundreds of biomarkers in the field of genomics, proteomics, metabolomics, and 'breath-omics' can be simultaneously studied. First, results on gene expression and exhaled breath profiles in predicting an early asthma diagnosis are promising. However, many hurdles need to be overcome before clinical implementation is possible. To reliably predict asthma in a wheezing child, probably a holistic approach is needed, combining clinical information with blood sampling, lung function tests, and potentially exhaled breath analysis. The further development of predictive, non-invasive biomarkers may eventually improve an early asthma diagnosis in wheezing preschool children and assist clinicians in early treatment decision-making.

Exhaled nitric oxide as a better diagnostic indicator for evaluating wheeze and airway hyperresponsiveness in preschool children

OBJECTIVE

Fractional concentration of exhaled nitric oxide (FeNO) is a known marker of airway inflammation. The aims of this study were to evaluate FeNO, impulse oscillometry (IOS), and spirometry in preschool children and to investigate their relationship with wheeze and airway hyperresponsiveness (AHR).

METHODS

We performed a population-based, cross-sectional study with 561 children aged 5-6 years. A total of 544 children completed a modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and eligible for the study. We measured FeNO, spirometry, methacholine bronchial provocation, and IOS. AHR was defined as the induction of a 20% decrease in FEV(1)(PC(20)) by a methacholine concentration ≤8.0 mg/dL.

RESULTS

Children who had wheeze or AHR had higher FeNO levels than children without these symptoms. However, neither IOS nor spirometry parameters showed significant differences between children with wheeze or AHR and those without. FeNO was associated with AHR, whereas IOS or spirometry parameters showed no association. Mean FeNO levels were positively correlated with a dose-response slope for methacholine, but neither IOS nor spirometry parameters showed significant correlations.

CONCLUSIONS

FeNO is a more sensitive measurement of AHR and wheeze than spirometry or IOS in preschool children.

Clinical application of exhaled nitric oxide measurements in a korean population

Nitric oxide (NO) is a biologic mediator of various physiologic functions. Recent evidence suggests the clinical utility of fractional exhaled NO (FeNO) as a biomarker for assessing asthma and other respiratory diseases. FeNO methodologies have been recently standardized by international research groups and subsequently validated in several Korean population studies. Normal ranges for FeNO have been reported for various ethnic groups, and the clinical utility has been widely evaluated in asthma and various respiratory diseases. Based on current evidence including most of Korean population data, this position paper aims to introduce the methodological considerations, and provide the guidance for the proper clinical application of FeNO measurements in Korean populations.

Revisiting the role of exhaled nitric oxide in asthma

PURPOSE OF REVIEW

This review focuses on the most recent studies investigating fractional nitric oxide concentration in exhaled breath (FeNO) as a useful biomarker for identifying specific phenotypes in asthma and as a tool for asthma diagnosis, monitoring and clinical decision-making.

RECENT FINDINGS

On the basis of the current literature, it has been highlighted that FeNO is a clinically relevant marker in various clinical aspects of asthma: FeNO is a predictor for developing asthma in persistent rhinitis or in infants with respiratory symptoms; FeNO contributes to identification of asthma phenotypes in both children and adults, also in relation to severity; FeNO is useful in monitoring the effectiveness of inhaled corticosteroids (including compliance) and biologic treatments like omalizumab; FeNO, in conjunction with symptom registration and lung function measurements, contributes to asthma diagnosis and optimizes asthma management.

SUMMARY

FeNO provides further information in distinguishing different phenotypes in asthma, allowing a much more appropriate control of the disease, especially in patients with difficult/severe asthma. In the future, it would be interesting to shed light on the hidden biological mechanisms responsible for low or normal FeNO values in symptomatic asthmatic patients.

Association of wheezing phenotypes with fractional exhaled nitric oxide in children

Asthma comprises a heterogeneous group of disorders characterized by airway inflammation, airway obstruction, and airway hyperresponsiveness (AHR). Airway inflammation, which induces AHR and recurrence of asthma, is the main pathophysiology of asthma. The fractional exhaled nitric oxide (FeNO) level is a noninvasive, reproducible measurement of eosinophilic airway inflammation that is easy to perform in young children. As airway inflammation precedes asthma attacks and airway obstruction, elevated FeNO levels may be useful as predictive markers for risk of recurrence of asthma. This review discusses FeNO measurements among early-childhood wheezing phenotypes that have been identified in large-scale longitudinal studies. These wheezing phenotypes are classified into three to six categories based on the onset and persistence of wheezing from birth to later childhood. Each phenotype has characteristic findings for atopic sensitization, lung function, AHR, or FeNO. For example, in one birth cohort study, children with asthma and persistent wheezing at 7 years had higher FeNO levels at 4 years compared to children without wheezing, which suggested that FeNO could be a predictive marker for later development of asthma. Preschool-aged children with recurrent wheezing and stringent asthma predictive indices also had higher FeNO levels in the first 4 years of life compared to children with wheezing and loose indices or children with no wheeze, suggesting that FeNO measurements may provide an additional parameter for predicting persistent wheezing in preschool children. Additional large-scale longitudinal studies are required to establish cutoff levels for FeNO as a risk factor for persistent asthma.

Advances in pediatric asthma in 2013: coordinating asthma care

Last year's "Advances in pediatric asthma: moving toward asthma prevention" concluded that "We are well on our way to creating a pathway around wellness in asthma care and also to utilize new tools to predict the risk for asthma and take steps to not only prevent asthma exacerbations but also to prevent the early manifestations of the disease and thus prevent its evolution to severe asthma." This year's summary will focus on recent advances in pediatric asthma on prenatal and postnatal factors altering the natural history of asthma, assessment of asthma control, and new insights regarding potential therapeutic targets for altering the course of asthma in children, as indicated in Journal of Allergy and Clinical Immunology publications in 2013 and early 2014. Recent reports continue to shed light on methods to understand factors that influence the course of asthma, methods to assess and communicate levels of control, and new targets for intervention, as well as new immunomodulators. It will now be important to carefully assess risk factors for the development of asthma, as well as the risk for asthma exacerbations, and to improve the way we communicate this information in the health care system. This will allow parents, primary care physicians, specialists, and provider systems to more effectively intervene in altering the course of asthma and to further reduce asthma morbidity and mortality.

Challenges and limitations of testing efficacy of aerosol device delivery in young children

An increasing number of medical conditions are chronically or acutely managed with some form of aerosolized therapy. Due to the benefit of directly administering medications to the intended site of action, there is great interest in evaluating treatments for aerosol use. One of the major challenges in selecting and testing new drug-device combinations in children is the uncertainty regarding the appropriate outcome measure to choose. In studies involving adult patients, typically exacerbations of disease or airflow obstruction are assessed as endpoints in drug trials or device assessment. However, in young children, choosing endpoints to assess efficacy is difficult due to the potential lack of sensitive, noninvasive endpoints that are easily performed across sites. In this review, we discuss the challenges and limitations of selecting clinical endpoints for drug-device trials in the youngest population, with a focus on novel emerging technologies. This article provides an overview of preschool and infant pulmonary function testing, multiple-breath washout, imaging techniques including computed tomography and magnetic resonance imaging, flexible bronchoscopy in children, mucociliary clearance scans, and exhaled breath condensate.