Application of exhaled nitric oxide (FeNO) in pediatric asthma

Exhaled Nitric Oxide fraction in asthma and obstructive sleep apnea among children at high altitudes. A cross-sectional study

INTRODUCTION

Exhaled nitric oxide fraction (FeNO) is employed for the diagnosis and phenotyping of asthma as an inflammatory biomarker of the airway. Limited evidence exists regarding its behavior in the presence of asthma and obstructive sleep apnea (OSA). Our objective was to determine whether FeNO levels are associated with the severity of OSA or the coexistence of asthma and OSA in residents at high altitudes.

MATERIALS AND METHODS

Observational, analytical, cross-sectional study in children aged 5-16 years residing at 2600 m above sea level treated at a Sleep Study Center between 2019 and 2021. We conducted a medical history, polysomnogram, and measurement of FeNO levels. The children were categorized into four groups: OSA, asthma, asthma with OSA, and controls (without asthma or OSA). FeNO levels among the groups were compared using the Kruskal-Wallis test, and correlations were explored using the Spearman correlation coefficient. Analyses considered statistical significance at a two-tailed p-value <0.05.

RESULTS

Among the 261 included children, 68 (26.1 %) had OSA, 42 (16.1 %) were diagnosed with asthma, 109 (41.8 %) had both asthma and OSA, and 42 (16.1 %) were controls. Their FeNO medians were 10 ppb, 18.5 ppb, 15 ppb, and 14 ppb, respectively, with no significant differences between the evaluated groups (p = 0.263). We found no correlation between FeNO and apnea-hypopnea index and obstructive apnea index even for the groups of patients with FeNO >20 ppb and FeNO >35 ppb (>75th percentile). In the adjusted model, a significant association was observed between asthma and FeNO levels.

CONCLUSIONS

Our findings suggest that FeNO measurements in children would not allow establishing this biomarker as part of the diagnosis of OSA. However, these findings may be related to high altitude.

Precision care in the treatment of pediatric asthma

PURPOSE OF REVIEW

Precision medicine in pediatric asthma involves identification of asthma phenotypes, genetic markers, biomarkers, and biologics that target specific pathways. This review includes a discussion of the efficacy of currently approved biologics for pediatric asthma and most recent advances in biomarker/phenotype identification and genetic associations that affect asthma care.

RECENT FINDINGS

Biologics targeting type-2 mediated pathways have shown success in the treatment of moderate to severe asthma in pediatric and adult patients. In comparative studies, dupilumab, an interleukin-4 (IL-4) alpha receptor inhibitor, and mepolizumab, an IL-5 inhibitor, have shown more improvement in asthma exacerbation rates and lung function compared to other biologics such as tezepelumab, omalizumab and benralizumab. Other methods used to categorize asthma treatment response have been investigated and include use of biomarkers such as fractional exhaled nitric oxide (FeNO). Genomic studies are also emerging in precision care for pediatric asthma.

SUMMARY

An understanding of underlying immunologic and genetic mechanisms affecting the development of asthma in pediatric patients has resulted in the production of numerous targeted therapies that have led to improvement in lung function and reduced exacerbation burden.

Serum interleukin-33 combined with FEF75% z-score and FeNO improves the diagnostic accuracy of asthma in children

OBJECTIVE

To investigate the diagnostic efficacy of serum IL-33 single indicator and combined indicators for asthma in children.

METHODS

132 children were initially diagnosed with asthma during acute exacerbation and 100 healthy children were included. Serum IL-33 concentration differences were compared between asthmatic and normal children. Correlations between IL-33 with pulmonary function parameters, FeNO, peripheral blood EOS counts and serum total IgE were analyzed in asthmatic children. ROC curves were used to assess IL-33 diagnostic efficacy and its combined indicators. To prevent overfitting of the predictive model, the hold-out cross-validation method was used.

RESULTS

(1) Serum IL-33 concentrations were significantly higher in children with asthma than in normal children (p < 0.001). (2) IL-33 concentration was negatively correlated with FVC z-score, FEV1 z-score and FEF75% z-score in asthmatic children (p < 0.05). (3) The area under the ROC curve of IL-33 was 0.821, which was higher than those of FeNO, FVC z-score, and FEV1 z-score. (4) Cross-validation of the combined indicators showed that IL-33 significantly improved asthma diagnostic efficacy. The combination of IL-33, FEF75% z-score, and FeNO showed the highest diagnostic efficacy, with the AUC, sensitivity, and specificity of the combined indicator being 0.954, 90.1%, and 89. 0%, respectively, and good extrapolation of the predictive model.

CONCLUSION

Serum IL-33 is higher in children with asthma and increases with the severity of pulmonary ventilation obstruction. A single indicator of serum IL-33 demonstrates moderate diagnostic accuracy, and its combination with FEF75% z-score and FeNO significantly improves the diagnostic accuracy in childhood asthma.

Characteristics of Allergic, Eosinophilic, and Overlapping Asthma Phenotypes Among Pediatric Patients with Current Asthma: A Cross-Sectional Study from Saudi Arabia

Purpose

Asthma is one of the most common chronic diseases affecting 10%-30% of children in Saudi Arabia. Although data exist on adult asthma phenotyping and endotyping in Saudi Arabia, little is known about asthma phenotypes in Saudi children.

Patients and Methods

This cross-sectional study enrolled pediatric patients diagnosed with bronchial asthma and followed in the pediatric pulmonology clinic of the Abha Maternity and Children Hospital between August 2021 and May 2023.

Results

A total of 321 children (aged 5-14 years) were analyzed. The population was classified into allergic [169 (52.6%)], eosinophilic [144 (44.9%)], and overlapping allergic and eosinophilic asthma [97 (30.2%)] phenotypes. Regarding asthma severity, 35.5%, 50.2%, and 14.3% were classified as mild, moderate, and severe, respectively. Of the 321 patients in the study, 124 (38.6%) had at least one asthma exacerbation that required hospitalization. The number of reported missed school days in the previous year was 1571 days [190 (59.2%) patients reported at least one missed school day]. The factors associated with the likelihood of uncontrolled asthma for all study participants included: emergency room (ER) visit last year (OR = 3.7, 95% CI:0.6-15.9]), overlapping eosinophilic and allergic (OR = 3.2, 95% CI = 1.8-5.9), and allergic phenotype (OR = 2.7, 95% CI = 1.3-5.4). The level of asthma control differed significantly among the three asthma phenotypes (p = 0.037).

Conclusion

Allergic asthma is the most prevalent asthma phenotype in this study, followed by the eosinophilic phenotype. The research has also shown that several factors predict uncontrolled asthma, including a family history of asthma, previous admission to the PICU, and previous hospitalization ever. There is, therefore, a definite need for multicenter cohort studies to better understand the phenotypes and endotypes of childhood asthma, as it could offer therapeutic and prognostic relevance.

Exhaled nitric oxide is only an asthma-relevant biomarker among children with allergic sensitization

BACKGROUND

Fraction of exhaled nitric oxide (FeNO) is used for diagnosing and monitoring asthma in children, but the influence of allergic sensitization is still poorly understood. Here, we investigate how asthma and allergic sensitization influence FeNO levels during childhood.

METHODS

We investigated the associations between asthma, aeroallergen sensitization, and FeNO measured from age 5-18 years in the COPSAC2000 birth cohort of 411 children using repeated measurement mixed models adjusted for gestational age, sex, concurrent airway infection, inhaled corticosteroids, and tobacco exposure. Replication was sought in the similarly designed COPSAC2010 cohort of 700 children.

RESULTS

In the COPSAC2000 cohort, 133 had asthma between age 5 and 18 years, and in the COPSAC2010 cohort, 112 had asthma between age 5 and 10 years. In the COPSAC2000 cohort, asthma and aeroallergen sensitization were both associated with higher FeNO from age 5 to 18 years: adjusted geometric mean ratio (aGMR), 1.22 (1.08-1.35), p < .01, and 1.41 (1.21-1.65), p < 0.001, respectively. However, asthma was associated with increased FeNO among children with aeroallergen sensitization: 1.44 (1.23-1.69), p < .0001, whereas asthma was associated with decreased FeNO among nonsensitized children: 0.80 (0.65-0.99), p = .05 (p-interaction<.0001 for asthma x sensitization). Replication in the COPSAC2010 cohort showed similar results (p-interaction <.01). Further, blood eosinophil count, total-IgE, bronchodilator response, and bronchial hyperreactivity were all associated with increased FeNO among children sensitized to aeroallergens, but not among nonsensitized children.

CONCLUSION

Fraction of exhaled nitric oxide is elevated through childhood in children with asthma and is correlated with asthma-associated traits depending on the presence of aeroallergen sensitization. These findings indicate that FeNO is only a valid asthma biomarker in children with concurrent aeroallergen sensitization, which is important for guideline recommendations on the clinical use of FeNO.

Can the Chinese study on the normal range of FeNO in children evaluate standardized asthma treatment efficacy in 6- to 12-year-old children?

Objective

By examining fractional exhaled nitric oxide (FeNO) levels and performing pulmonary function testing, this study explored whether the multicenter study on the normal range of FeNO in children in China can be used to evaluate standardized treatment efficacy in 6- to 12-year-old children with asthma.

Methods

A total of 115 children aged 6-12 years old who were first diagnosed with asthma and received standardized asthma treatment from April 2018 to July 2022 were selected. According to the FeNO level at the first visit, the subjects were divided into different high- and low-FeNO groups according to the American Thoracic Society (ATS) guidelines and the Chinese multicenter study recommendations. The consistency of the two grouping methods and the differences between the high- and low-FeNO groups were compared after standardized treatment. The grouping method that was the most suitable for children in the cross group was discussed.

Results

(i) There was fair consistency between the Chinese multicenter study recommendations and the ATS guidelines regarding the classification of high- and low-FeNO groups (Kappa = 0.338). (ii) Repeated-measures ANOVA showed that the level of improvement in FVC%, FEV1%, FEF25%, FEF50%, and FeNO in the American high- and low-FeNO groups differed with the duration of therapy (P < 0.05), however, there was no significant difference between the Chinese groups. (iii) FEV1% and FeNO improved more after treatment in the fixed high-FeNO group than in the cross group (P < 0.05).

Conclusion

The Chinese multicenter study on the normal range of FeNO in children in China has a limited role in evaluating standardized asthma treatment efficacy in 6- to 12-year-old children. The ATS guidelines are currently recommended for clinical assessment of asthma treatment efficacy.

Assessment of Fraction of Exhaled Nitric Oxide and Soluble Receptor for Advanced Glycation End Products Biomarkers for Jordanian Asthmatic Children

PURPOSE

Fraction of exhaled nitric oxide (FeNO) and soluble advanced glycation end-product receptor (sRAGE) are proposed as biomarkers of asthma, therefore we sought to assess their use in asthmatic children of Jordan.

PATIENTS AND METHODS

We conducted a case-control study at The University of Jordan Hospital. A total of 141 asthmatic children followed by respiratory pediatricians and 118 healthy children aged 4-18 years were recruited. FeNO was measured by NObreath device and serum sRAGE by ELISA that detect endogenously soluble isoform (esRAGE) and total soluble RAGE (sRAGE).

RESULTS

sRAGE in asthmatic was half of the control (p <0.001). In addition, ratio of esRAGE/sRAGE was two-fold higher in asthmatic (p = <0.001). Neither FeNO nor esRAGE levels were significantly different between groups. FeNO and asthma control test (ACT) score were negatively correlated corrected for age and body mass index (BMI), (r = -0.180, p= 0.034). For the uncontrolled asthma group, esRAGE/sRAGE negatively correlated with ACT score (r = -.329, p = 0.038). Receiver operating curve (ROC) analysis revealed significant predictive value (PV) for sRAGE and esRAGE/sRAGE in asthma detection with area under the curve (AUC) of (0.751 ± 0.031) and (0.711±.033), consequently. However, no biomarker had a significant PV for lack of control.

CONCLUSION

The current study supports utilizing sRAGE as a marker for asthma and present a potential therapeutic target. However, our results indicate that both FeNO and sRAGE have a limited role in the management of asthmatic children or assessment of asthma control.

Neutrophil-lymphocyte ratios in blood to distinguish children with asthma exacerbation from healthy subjects

OBJECTIVE

Airway inflammation is a prominent feature of asthma and may play an important role in disease pathophysiology. Despite the increasing incidence of asthma worldwide, reliable diagnostic biomarkers are lacking and widely lead to asthma misdiagnosis. Neutrophil-lymphocyte ratio (NLR) is a biomarker of systemic inflammation, in addition to NLR-alanine aminotransferase ratio (NAR) and NLR-albumin ratio (NBR). The aim of this study was to evaluate associations of NLR, NAR, and NBR with diagnosis of childhood asthma to determine if they can aid clinical childhood asthma diagnosis.

METHODS

This retrospective case-control study included 89 children with asthma and 53 healthy children from the Wuxi Children's Hospital affiliated with Nanjing Medical University. We applied various statistical tests to the dataset: Mann-Whitney U test to compare characteristics of the case and control groups; chi-squared test to compare categorical variables; Kruskal-Wallis test to compare statistical differences of asthma indicators among groups; receiver operating characteristic (ROC) curves to assess the diagnostic value of indices; and Spearman correlation analysis to evaluate relationships between NLR and lactate dehydrogenase, albumin, aspartate transaminase, and alanine transaminase levels.

RESULTS

Compared with controls, the asthma case group had significantly higher white blood cell (p < 0.01), neutrophil, lactate dehydrogenase, C-reactive protein, and NLR levels (p < 0.01) and significantly lower lymphocyte (p = 0.001), platelet (p = 0.039), and albumin levels (p = 0.04). We determined optimal cutoff levels for several metrics: 1.723 for NLR, with sensitivity of 0.73 and specificity of 0.906; 0.135 for NAR, with sensitivity of 0.685 and specificity of 0.887; and 0.045 for NBR, with sensitivity of 0.674 and specificity of 0.906. The areas under the curve (AUCs) were 0.824 for NLR, 0.788 for NAR, 0.818 for NBR, and 0.83 for the combination of NLR + NAR + NBR.

CONCLUSION

The combination of NLR, NAR, and NBR biomarkers distinguished asthmatic ones suffering from exacerbation of the condition from healthy children. Thus, our results indicate NLR + NAR + NBR could be used as a clinical biomarker for asthma in children.

Utility of biomarkers in the diagnosis and monitoring of asthmatic children

Asthma imposes a heavy morbidity burden during childhood; it affects over 10% of children in Europe and North America and it is estimated to exceed 400 million people worldwide by the year 2025. In clinical practice, diagnosis of asthma in children is mostly based on clinical criteria; nevertheless, assessment of both physiological and pathological processes through biomarkers, support asthma diagnosis, aid monitoring, and further lead to better treatment outcomes and reduced morbidity. Recently, identification and validation of biomarkers in pediatric asthma has emerged as a top priority across leading experts, researchers, and clinicians. Moreover, the implementation of non-invasive biomarkers for the assessment and monitoring of paediatric patients with asthma, has been prioritized; however, only a proportion of them are currently included in the clinical practise. Although, the use of non-invasive biomarkers is highly supported in recent asthma guidelines for documenting diagnosis and supporting monitoring of asthmatic patients, data on the Pediatric population are limited. In the present report, the Pediatric Asthma Committee of the World Allergy Organization (WAO), aims to summarize and discuss available data for the implementation of non-invasive biomarkers in the diagnosis and monitoring in children with asthma. Information on the most studied biomarkers, including spirometry, oscillometry, markers of allergic sensitization, fractional exhaled nitric oxide, and the most recent exhaled breath markers and "omic" approaches, will be reviewed. Practical limitations and considerations based on both experts' opinion and critical review of the literature, on the utility of all "well-known" and newly introduced non-invasive biomarkers will be presented. A critical commentary on biomarkers' use in diagnosing and monitoring asthma during the COVID-19 pandemic, cost and availability of biomarkers in different settings and in developing countries, the differences on the biomarkers use between Primary Practitioners, Pediatricians, and Specialists and their role on the longitudinal aspect of asthma is provided.

Exhaled Breath Analysis for Investigating the Use of Inhaled Corticosteroids and Corticosteroid Responsiveness in Wheezing Preschool Children

Exhaled breath analysis has great potential in diagnosing various respiratory and non-respiratory diseases. In this study, we investigated the influence of inhaled corticosteroids (ICS) on exhaled volatile organic compounds (VOCs) of wheezing preschool children. Furthermore, we assessed whether exhaled VOCs could predict a clinical steroid response in wheezing preschool children. We performed a crossover 8-week ICS trial, in which 147 children were included. Complete data were available for 89 children, of which 46 children were defined as steroid-responsive. Exhaled VOCs were measured by GC-tof-MS. Statistical analysis by means of Random Forest was used to investigate the effect of ICS on exhaled VOCs. A set of 20 VOCs could best discriminate between measurements before and after ICS treatment, with a sensitivity of 73% and specificity of 67% (area under ROC curve = 0.72). Most discriminative VOCs were branched C11H24, butanal, octanal, acetic acid and methylated pentane. Other VOCs predominantly included alkanes. Regularised multivariate analysis of variance (rMANOVA) was used to determine treatment response, which showed a significant effect between responders and non-responders (p < 0.01). These results show that ICS significantly altered the exhaled breath profiles of wheezing preschool children, irrespective of clinical treatment response. Furthermore, exhaled VOCs were capable of determining corticosteroid responsiveness in wheezing preschool children.

Understanding the Cellular Sources of the Fractional Exhaled Nitric Oxide (FeNO) and Its Role as a Biomarker of Type 2 Inflammation in Asthma

Fractional exhaled nitric oxide (FeNO) has gained great clinical importance as a biomarker of type 2 inflammation in chronic airway diseases such as asthma. FeNO originates primarily in the bronchial epithelium and is produced in large quantities by the enzyme inducible nitric oxide synthase (iNOS). It should be noted that nitric oxide (NO) produced at femtomolar to picomolar levels is fundamental for respiratory physiology. This basal production is induced in the bronchial epithelium by interferon gamma (IFNγ) via Janus kinases (JAK)/STAT-1 signaling. However, when there is an increase in the expression of type 2 inflammatory cytokines such as IL-4 and IL-13, the STAT-6 pathway is activated, leading to overexpression of iNOS and consequently to an overproduction of airway NO. Increased NO levels contributes to bronchial hyperreactivity and mucus hypersecretion, increases vascular permeability, reduces ciliary heartbeat, and promotes free radical production, airway inflammation, and tissue damage. In asthmatic patients, FeNO levels usually rise above 25 parts per billion (ppb) and its follow-up helps to define asthma phenotype and to monitor the effectiveness of corticosteroid treatment and adherence to treatment. FeNO is also very useful to identify those severe asthma patients that might benefit of personalized therapies with monoclonal antibodies. In this review, we revised the cellular and molecular mechanisms of NO production in the airway and its relevance as a biomarker of type 2 inflammation in asthma.

Clinical utility of preoperative pulmonary function testing in pediatrics

Perioperative respiratory adverse events pose a significant risk in pediatric anesthesia, and identifying these risks is vital. Traditionally, this is assessed using history and examination. However, the perioperative risk is multifactorial, and children with complex medical backgrounds such as chronic lung disease or obesity may benefit from additional objective preoperative pulmonary function tests. This article summarizes the utility of available pulmonary function assessment tools as preoperative tests in improving post-anesthetic outcomes. Currently, there is no evidence to support or discourage any pulmonary function assessment as a routine preoperative test for children undergoing anesthesia. In addition, there is uncertainty about which patients with the known or suspected respiratory disease require preoperative pulmonary function tests, what time period prior to surgery these are required, and whether spirometry or more sophisticated tests are indicated. Therefore, the need for any test should be based on information obtained from the history and examination, the child's age, and the complexity of the surgery.

Prevalence of allergic rhinitis with lower airways inflammation: A new endotype with high risk of asthma development?

AIM

Asthma and allergic rhinitis share common pathophysiological mechanisms. However, while asthma phenotypes and endotypes are defined basing on both clinical and immunological features, rhinitis classification is still based on severity and frequency of symptoms. Recently, fractional exhaled nitric oxide (FeNO) has been suggested as a possible biomarker of rhinitis to asthma development. The aim of our study was to define the prevalence of a high FeNO allergic rhinitis endotype in a paediatric population of children with allergic rhinitis in order to quantify the impact of such patients in general practice.

METHODS

A total of 159 children (aged 7-16 years) with allergic rhinitis and no asthmatic symptoms were enrolled in our study. Severity assessment of rhinitis and asthma was evaluated in accordance with ARIA and GINA guidelines. All patients performed the following assessments: skin prick test (SPT), spirometry and FeNO measurement.

RESULTS

FeNO was increased in 54 (33.9%) of 159 patients. No significant correlation with age, severity and frequency of rhinitis was evidenced. Positive SPT for house dust mites was related with a higher prevalence of high FeNO (P = 0.04), with no significant correlation with other sensitisations. All patients showed normal spirometric values.

CONCLUSION

A possible new endotype of allergic rhinitis and lower airways inflammation showed to be significantly present in our population. The lack of correlation with allergic rhinitis severity assessment suggests that FeNO could be considered as an independent variable, possibly linked to a higher risk of asthma development in children with no lower airways symptoms and normal spirometry.

Childhood asthma- pathogenesis and phenotypes

In the pathogenesis of asthma in children there is a pivotal role for a type 2 inflammatory response to early life exposures or events. Interactions between infections, atopy, genetic susceptibility, and environmental exposures (such as farmyard environment, air pollution, tobacco smoke exposure) influence the development of wheezing illness and the risk for progression to asthma. The immune system, lung function and the microbiome in gut and airways develop in parallel and dysbiosis of the microbiome may be a critical factor in asthma development. Increased infant weight gain and preterm birth are other risk factors for development of asthma and reduced lung function. The complex interplay between these factors explains the heterogeneity of asthma in children. Subgroups of patients can be identified as phenotypes based on clinical parameters, or endotypes, based on a specific pathophysiological mechanism. Paediatric asthma phenotypes and endotypes may ultimately help to improve diagnosis of asthma, prediction of asthma development and treatment of individual children, based on clinical, temporal, developmental or inflammatory characteristics. Unbiased, data-driven clustering, using a multidimensional or systems biology approach may be needed to better define phenotypes. The present knowledge on inflammatory phenotypes of childhood asthma has now been successfully applied in the treatment with biologicals of children with severe therapy resistant asthma, and it is to be expected that more personalized treatment options may become available.

The Value of Fractional Exhaled Nitric Oxide and Impulse Oscillometric and Spirometric Parameters for Predicting Bronchial Hyperresponsiveness in Adults with Chronic Cough

Purpose

To evaluate the contribution of fractional exhaled nitric oxide (FeNO) and impulse oscillometry (IOS) and spirometric parameters in predicting bronchial hyperresponsiveness (BHR) in adults with chronic cough.

Patients and Methods

In total, 112 patients with chronic cough were enrolled in this prospective diagnostic study. Receiver operating characteristic (ROC) curves were generated to assess the diagnostic efficiency and optimal cut-off values of FeNO and IOS and spirometric parameters in predicting BHR. Optimal combinations of FeNO and IOS and spirometric parameters for BHR prediction were investigated using univariate and multivariate logistic regression models. Bootstrapping was employed for internal validation. Model discrimination and calibration were assessed using indices and calibration plots.

Results

Rhinitis and values of FeNO, IOS parameters (resonant frequency (Fres), reactance at 5 Hz (X5), and integrated area of low-frequency X (AX)) and spirometric parameters (FEV1, PEF, MEF₇₅, MEF₅₀, MEF₂₅, MMEF) were significantly different between patients with BHR and those without BHR (P < 0.05). After adjusting for rhinitis, logistic analyses showed that FeNO combined with Fres, FeNO combined with MMEF, or the combination of FeNO, Fres and MMEF had high predictive value in diagnosing BHR; the areas under the ROC curves (AUCs) of the corresponding three models were 0.914, 0.919 and 0.927, respectively. In addition, the three models displayed good discrimination, with high C-index values and good calibration.

Conclusion

FeNO combined with Fres or MMEF or a combination of these three parameters may be conveniently used as indicators in BHR prediction.