Longitudinal assessment of high versus low levels of fractional exhaled nitric oxide among children with asthma and atopy

Allergic rhinitis co-morbidity on asthma outcomes in city school children

BACKGROUND

School based asthma programs have demonstrated that preventive asthma therapy administered in school reduces asthma morbidity. The burden of co-morbid allergic disease on asthma outcomes in a large school based asthma cohort has been unexplored.

OBJECTIVE

Evaluate the prevalence of allergic rhinitis (AR) in historically minoritized school children with persistent asthma, and determine if AR is an independent risk factor for asthma morbidity.

METHODS

We evaluated the prevalence of AR in children enrolled in 3 NIH funded school based asthma programs in Rochester, NY. We used linear regression and multivariate analyses to compare asthma outcomes for children whose caregivers did and did not report AR.

RESULTS

We used data from 1,029 children with asthma (mean age 7.4, 60.4% Black, 29.5% Hispanic, 72.8% insured with Medicaid). 63% of children reported AR. Children with AR had significantly fewer symptom free days over 2 weeks compared to children without AR (7.2 vs. 8.3, p < 0.001). Children with AR also had more daytime symptoms, (4.7 vs. 3.7, p < 0.001), more rescue medication use (4.5 vs. 3.4, p < 0.01), and more activity limitation due to asthma (3.6 vs. 2.5, p < 0.001). Only 44% of children with AR reported allergy medication use.

CONCLUSIONS

Among a large school-based cohort of minoritized children with asthma, we found that the majority of children have comorbid allergic rhinitis, which was associated with increased asthma morbidity. Inadequate recognition and treatment for allergic rhinitis likely represents substantial preventable morbidity for this group.

Oral cavity response to air pollutant exposure and association with pulmonary inflammation and symptoms in asthmatic children

Exposure to fine particulate matter (PM_2.5) and ozone (O₃) may lead to inflammation and oxidative damage in the oral cavity, which is hypothesized to contribute to the worsening of airway inflammation and asthma symptoms. In this panel study of 43 asthmatic children aged 5-13 years old, each child had 4 clinic visits with a 2-week interval between two consecutive visits. At each visit, saliva samples were collected and subsequently analyzed for interleukin 6 (IL-6) and eosinophil cationic protein (ECP) as biomarkers of inflammation and malondialdehyde (MDA) as a biomarker of oxidative stress in the oral cavity. At each visit, children were measured for fractional exhaled nitric oxide (FeNO) as a marker of pulmonary inflammation. Asthma symptoms of these children were measured using the Childhood Asthma Control Test (C-ACT). We found that an interquartile range (IQR) increase in 24-h average personal exposure to PM_2.5 measured 1 and 2 days prior was associated with increased salivary IL-6 concentration by 3.0% (95%CI: 0.2%-6.0%) and 4.2% (0.7%-8.0%), respectively. However, we did not find a clear association between personal O₃ exposure and any of the salivary biomarkers, except for a negative association between salivary MDA and O₃ exposure measured 1 day prior. An IQR increase in salivary IL-6 concentration was associated with significantly increased FeNO by 28.8% (4.3%-53.4%). In addition, we found that increasing salivary IL-6 concentrations were associated with decreased individual and total C-ACT scores, indicating the worsening of asthma symptoms. We estimated that 13.2%-22.2% of the associations of PM_2.5 exposure measured 1 day prior with FeNO and C-ACT scores were mediated by salivary IL-6. These findings suggest that the induction of inflammation in the oral cavity may have played a role in linking air pollution exposure with the worsening of airway inflammation and asthma symptoms.

Relationship between longitudinal changes in type-2 inflammation, immunoglobulin E sensitization, and clinical outcomes in young asthmatics

BACKGROUND

Asthma is a heterogeneous condition where biomarkers may be of considerable advantage in diagnosis and therapy monitoring. However, the changes in asthma biomarkers and immunoglobulin E (IgE) over the course of life has not been extensively investigated.

OBJECTIVE

To study longitudinal changes in type-2 inflammatory biomarkers, IgE, and clinical outcomes, and the association between these changes, in young asthmatics.

METHODS

Asthmatics (age 10-35 years, n = 253) were examined at baseline and at a follow-up visit, 43 [23-65] (median [range]) months later. Subjects were analyzed using the multi-allergen tests Phadiatop and fx5 (ImmunoCAP) and grouped based on the baseline allergen-specific IgE antibody (sIgE) concentration: <0.10, 0.10-0.34, and ≥0.35 kU_A /L. The relationship between changes (Δ values) in type-2 biomarkers (individualized fraction of exhaled nitric oxide [FeNO%], blood eosinophil [B-Eos] count, total IgE [tIgE] and sIgE, lung function [% predicted forced expiratory volume in 1 second (FEV₁ ) and FEV₁ /forced vital capacity (FVC)], and Asthma Control Test [ACT]) score were determined.

RESULTS

At follow up, FEV₁ and FEV₁ /FVC had decreased (93.6% vs. 95.8%, and 93.4% vs. 94.7% of predicted, respectively [p < 0.001 both]), whereas ACT score had increased (21.6 vs. 20.6, p = 0.001). A significant decline in lung function was seen in subjects with sIgE ≥ 0.10 kUA/L, but not in those with undetectable sIgE (<0.10 kU_A /L). Furthermore, tIgE and sIgE declined over time (p < 0.001 all) whereas FeNO% and B-Eos count were not significantly changed. In univariate analysis, significant negative correlations between ∆B-Eos count and ∆FeNO%, on one hand, and changes in lung function, on the other hand, were seen, and multivariate analysis showed an independent relationship between ΔFeNO%, and ΔFEV₁ (p < 0.05) and ΔFEV₁ /FVC% (p < 0.01). Sex-specific analysis showed that the independent association between ΔFeNO%, and ΔFEV₁ remained only in females (p = 0.005), and there was a significant interaction with sex (p = 0.02).

CONCLUSION

In young asthmatics, IgE levels declined over 43 months, whereas FeNO and B-Eos remained unchanged. In spite of improved asthma control, an accelerated lung function decline was seen in patients with detectable sIgE at baseline, and the decline correlated with changes in type-2 biomarkers. Particularly, the increase in individualized FeNO associated independently with decline in FEV₁ in females.

High fractional exhaled nitric oxide levels in asthma patients: Does size matter?

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is a biomarker for eosinophilic inflammation used for diagnosis and monitoring of asthma. High FeNO indicates significant airway eosinophilia and steroid-responsive airway inflammation. Some children with asthma have extremely high FeNO levels, but whether these levels represent a different asthma phenotype compared with those with mildly elevated FeNO is unclear. The objective of this study is to investigate whether the extent of high FeNO levels correlates with clinical phenotype, asthma control, comorbidity, and pulmonary function test (PFT) findings in children with asthma.

METHODS

Anthropometric data, daytime and nighttime symptoms, controller treatment, comorbidity, and PFT findings were retrieved from the Pediatric Pulmonology Unit database (2014-2020) and correlated with FeNO levels in pediatric asthma patients with high FeNO levels.

RESULTS

Two-hundred children and adolescents with high FeNO levels (range 36-227 ppb) were included. Within this range, higher FeNO levels positively correlated with increased daytime and nighttime symptoms (p = .013 and p = .01, respectively) and poorly controlled asthma (p = .034). A FeNO level of ≥80 ppb was the cutoff for significantly more severe daytime and nighttime symptoms and very poorly controlled asthma compared with levels <80 ppb (p = .004, p = .005, and p = .036, respectively). No correlation was found between FeNO and controller treatment, comorbidity, and PFT performance.

CONCLUSION

In pediatric asthma patients, high FeNO levels correlate with increased symptom severity and poor asthma control. A FeNO level of ≥80 ppb may serve as an objective indicator for severe asthma.

Recent Diagnosis Techniques in Pediatric Asthma: Impulse Oscillometry in Preschool Asthma and Use of Exhaled Nitric Oxide

Objective measures of lung function are important in the diagnosis and management of asthma. Spirometry, the pulmonary function test most widely used in asthma, requires respiratory maneuvers that may be difficult for preschoolers. Impulse oscillometry (IOS) is a noninvasive method of measuring lung function during tidal breathing; hence, IOS is an ideal test for use in preschool asthma. Fractional exhaled nitric oxide (FeNO) levels correspond to eosinophilic inflammation and predict responsiveness to corticosteroids. Basic concepts of IOS, methodology, and interpretation, including available normative values, and recent findings regarding FeNO are reviewed in this article.

Fractional Exhaled Nitric Oxide for the Diagnosis of Childhood Asthma: a Systematic Review and Meta-analysis

The gold standard for diagnosing asthma in children is based on clinical history of respiratory symptoms, physical examination, and respiratory function testing. Recent advances indicate that a non-invasive measure of airway inflammation, fractional exhaled nitric oxide (FeNO), provides objective data for use in asthma diagnosis. However, the diagnostic performance of FeNO in children with asthma has not been clearly defined. This systematic review and meta-analysis aimed to evaluate the diagnostic accuracy of FeNO in the clinical determination of asthma in children. Databases of PubMed, the Cochrane Library, EMBASE, MEDION, and Web of Science were searched for relevant articles through March 31, 2016. A bivariate model was used for pooling estimates of sensitivity, specificity, diagnostic odds ratio (DOR), and area under the summary receiver operating curves (SROC) as the main diagnostic measures. In total, eight studies met the inclusion criteria, which included 2933 subjects. The pooled estimates of sensitivity, specificity, and DOR for the detection of asthma in children were 0.79 [95 % confidence interval (CI), 0.64-0.89], 0.81 (95 % CI, 0.66-0.90), and 16.52 (95 % CI, 7.64-35.71). The SROC was 0.87 (95 % CI, 0.84-0.90). In brief, FeNO achieves a moderate diagnostic performance in the detection of asthma in children.

High prevalence of house dust mite sensitization in children with severe asthma living at high altitude in a tropical country

BACKGROUND

Some studies, mainly in Europe, have shown a low level of sensitization to house dust mite (HDM) allergens at high altitude (HA). Differently, some others in tropical countries have shown a higher level. The aim of this study was to evaluate allergens sensitization, including HDM, in children with severe asthma (SA), residents at HA in a tropical middle-income developing country.

METHODS

Observational, analytical, cross-sectional study in children aged 6-15 years old with SA at HA (2640 m). Skin prick tests (SPT), serum IgE, exhaled fraction of nitric oxide (FE_NO ), spirometry, and asthma questionnaire (ACT) were performed. Associations were explored by Pearson or Spearman coefficients.

RESULTS

We included 61 children. Most patients were male (61.3%), median age: 10 years (Interquartile range [IQR]: 8-12), median BMI: 17 kg/m² (IQR: 16-20); Median of positive SPT: 2 (IQR: 2-3). At least one SPT was positive in 88.7% of patients and 87.9% were positive for at least one HDM. Serum IgE: 348 UI/mL (IQR: 154-760) and FE_NO : 22 ppb (IQR: 9-41). Prebronchodilator values were (% predicted): FVC: 109.7% (±15.5%), FEV₁ : 98.4% (±16.3); FEV₁ /FVC: 82% (±8%). SPT were inversely correlated with the FEV₁ /FVC (Rho: -0.34; 95% CI: -0.55 a -0.09; P = 0.008).

CONCLUSIONS

These children with SA living at HA in a tropical middle-income developing country have a high prevalence of HDM sensitization. One explanation for this might be that tropical conditions, such as temperature and humidity, could modify the effect of the altitude on asthma.

Exhaled Nitric Oxide is Not a Biomarker for Pulmonary Tuberculosis

To reduce transmission of tuberculosis (TB) in resource-limited countries where TB remains a major cause of mortality, novel diagnostic tools are urgently needed. We evaluated the fractional concentration of exhaled nitric oxide (FeNO) as an easily measured, noninvasive potential biomarker for diagnosis and monitoring of treatment response in participants with pulmonary TB including multidrug resistant–TB in Lima, Peru. In a longitudinal study however, we found no differences in baseline median FeNO levels between 38 TB participants and 93 age-matched controls (13 parts per billion [ppb] [interquartile range (IQR) = 8–26] versus 15 ppb [IQR = 12–24]), and there was no change over 60 days of treatment (15 ppb [IQR = 10–19] at day 60). Taking this and previous evidence together, we conclude FeNO is not of value in either the diagnosis of pulmonary TB or as a marker of treatment response.

Identifying biomarkers for asthma diagnosis using targeted metabolomics approaches

BACKGROUND

The diagnosis of asthma in children is challenging and relies on a combination of clinical factors and biomarkers including methacholine challenge, lung function, bronchodilator responsiveness, and presence of airway inflammation. No single test is diagnostic. We sought to identify a pattern of inflammatory biomarkers that was unique to asthma using a targeted metabolomics approach combined with data science methods.

METHODS

We conducted a nested case-control study of 100 children living in a peri-urban community in Lima, Peru. We defined cases as children with current asthma, and controls as children with no prior history of asthma and normal lung function. We further categorized enrollment following a factorial design to enroll equal numbers of children as either overweight or not. We obtained a fasting venous blood sample to characterize a comprehensive panel of targeted markers using a metabolomics approach based on high performance liquid chromatography-mass spectrometry.

RESULTS

A statistical comparison of targeted metabolites between children with asthma (n = 50) and healthy controls (n = 49) revealed distinct patterns in relative concentrations of several metabolites: children with asthma had approximately 40-50% lower relative concentrations of ascorbic acid, 2-isopropylmalic acid, shikimate-3-phosphate, and 6-phospho-d-gluconate when compared to children without asthma, and 70% lower relative concentrations of reduced glutathione (all p < 0.001 after Bonferroni correction). Moreover, a combination of 2-isopropylmalic acid and betaine strongly discriminated between children with asthma (2-isopropylmalic acid ≤ 13 077 normalized counts/second) and controls (2-isopropylmalic acid > 13 077 normalized counts/second and betaine ≤ 16 47 121 normalized counts/second).

CONCLUSIONS

By using a metabolomics approach applied to serum, we were able to discriminate between children with and without asthma by revealing different metabolic patterns. These results suggest that serum metabolomics may represent a diagnostic tool for asthma and may be helpful for distinguishing asthma phenotypes.

[Research progress in relationship between fractional exhaled nitric oxide and asthma in children]

Bronchial asthma is a heterogeneous disease that is characterized by airway hyperresponsiveness and chronic inflammation. It is often accompanied by reversible airflow obstruction. Current laboratory testing methods for the diagnosis of asthma in children mainly include lung ventilation function test. Due to the non-cooperation of children, it is very challenging to conduct lung ventilation function test for preschoolers. Lung function testing is an instantaneous indicator, which is influenced by the children's understanding ability and mental factors. In addition, it could not assess the severity of airway inflammation. Fractional exhaled nitric oxide (FeNO) is a noninvasive, simple, and objective indicator of airway inflammation and has gradually gained increased use in children in recent years. This review article introduces the source of FeNO, the reference value of FeNO in laboratory testing, and the progress in the application of FeNO in the diagnosis, prediction, and treatment of asthma in children of various ages.

[Research progress in relationship between fractional exhaled nitric oxide and asthma in children]

Bronchial asthma is a heterogeneous disease that is characterized by airway hyperresponsiveness and chronic inflammation. It is often accompanied by reversible airflow obstruction. Current laboratory testing methods for the diagnosis of asthma in children mainly include lung ventilation function test. Due to the non-cooperation of children, it is very challenging to conduct lung ventilation function test for preschoolers. Lung function testing is an instantaneous indicator, which is influenced by the children's understanding ability and mental factors. In addition, it could not assess the severity of airway inflammation. Fractional exhaled nitric oxide (FeNO) is a noninvasive, simple, and objective indicator of airway inflammation and has gradually gained increased use in children in recent years. This review article introduces the source of FeNO, the reference value of FeNO in laboratory testing, and the progress in the application of FeNO in the diagnosis, prediction, and treatment of asthma in children of various ages.

Relationship between serum arginase I and l-arginine or exhaled nitric oxide in asthma

The relationship between serum arginase I and serum l-arginine or fractional exhaled nitric oxide (FENO) was evaluated cross-sectionally in asthmatic patients. No sex difference was observed in the serum mean levels of arginase I and l-arginine or FENO. Arginase I and FENO were higher in patients 60 or younger years than in those over 60 years. Asthmatic patients were divided into three groups: no steroid therapy, inhalation steroid therapy, and oral steroid therapy. Arginase I, FENO and high-sensitivity-C-reactive protein (hs-CRP) were significantly lower in the inhalation steroid therapy group than in the no steroid therapy group. Correlations were observed between arginase I and FENO, l-arginine, hs-CRP, WBC, and age, and also between FENO and IgE, WBC, and age. A logistic regression analysis revealed the positive association of arginase I with FENO, and the negative association of l-arginine. FENO was positively associated with arginase I and IgE. These results indicated that serum arginase I might influence serum levels of l-arginine and FENO, and that IgE might influence FENO in asthmatic patients.

An Overview of Fractional Exhaled Nitric Oxide and Children with Asthma

Asthma is the most common pediatric chronic disease and is characterized by lung inflammation. Fractional exhaled nitric oxide (FeNO) is thought to reflect the presence of eosinophilic airway inflammation, and is an easy, non-invasive test that has held promise in providing additional objective data. However, not all studies have shown a clinical benefit in the use of FeNO to guide management of asthma in children. This review will describe the results of the most recent studies examining the use of FeNO in the diagnosis and treatment of asthma in infants, preschool-aged children and in school-aged children. It will aid the clinician in providing a clinical context in which FeNO may be most useful in treating pediatric asthma.

Asthma severity, not asthma control, is worse in atopic compared with nonatopic adolescents with asthma

BACKGROUND

The effects of atopic and nonatopic asthma phenotypes on asthma morbidity are unclear. Moreover, asthma morbidity in patients without atopy might be mediated by immunoglobulin E (IgE).

OBJECTIVE

To determine differences in morbidity in patients with asthma with and without atopy in a population of inner-city adolescents with asthma and to assess the impact of total IgE (tIgE) in this population.

METHODS

Data were obtained from 546 inner-city adolescents in the Asthma Control Evaluation study. A positive skin prick test reaction to 14 aeroallergens and specific IgE to 5 aeroallergens determined atopic status. High (≥75th percentile) and low (≤25th percentile) tIgE levels were categorized. Asthma control (Asthma Control Test) and asthma severity (Composite Asthma Severity Index [CASI]) were measured at multiple time points over 1 year. Fractional exhaled nitric oxide (FeNO) and measurements of morbidity also were collected. Multivariable and repeated measures analyses modeled the relation between atopic status and morbidity.

RESULTS

Baseline CASI scores increased 0.90 point (P < .05) and FeNO increased 0.85 natural logarithmic unit (P < .001) in participants with vs without atopy. Repeated measures analyses showed consistent results. Participants without atopy and increased tIgE had FeNO 0.73 natural log unit higher (P < .01) than low tIgE and a nonsignificant increase in CASI. The CASI score and FeNO levels were higher for high than for low tIgE in participants with atopy.

CONCLUSION

In this population, participants with atopic asthma had worse asthma severity and higher FeNO compared with those with nonatopic asthma, but no difference in control. In all participants, higher tIgE indicated worse severity and higher FeNO. In this population, asthma severity and FeNO might be mediated by IgE in the 2 asthma phenotypes.

The importance of atopy on exhaled nitric oxide levels in African American children

BACKGROUND

For physicians to be maximally effective in managing asthma in minority populations, a better understanding of the factors that affect fractional exhaled nitric oxide (FeNO) measurements in African Americans is needed.

OBJECTIVE

To examine demographic, environmental, and physiologic factors that influence FeNO measurements in African American children with and without asthma.

METHODS

A cross-sectional study of 128 African American children aged 7 to 18 years (44% with asthma) was conducted. FeNO measurements, skin prick tests (as a measure of atopy), spirometry, and questionnaire data were obtained from all participants. Regression models were constructed after identifying factors significantly associated on univariate analysis.

RESULTS

Among all study participants, the mean FeNO measurement at baseline was 24.4 ppb. Children with asthma had a higher level than those without (30.9 vs 19.3 ppb, P = .002). When examining all children through logistic regression analysis, an elevated FeNO level was significantly associated with atopy, lower spirometric values, and current asthma (P < .05 for all). Among asthmatic children, univariate analysis revealed that an elevated FeNO level was associated with inhaled corticosteroid use, recent respiratory infection, and atopy (P < .05 for all). However, only atopy remained significant after regression analysis. For asthmatic and nonasthmatic children, FeNO levels were directly correlated with the number of positive skin test results.

CONCLUSION

In African American children with and without asthma, FeNO levels are strongly influenced by atopy. Guidelines for FeNO measurements that incorporate atopic status are needed.

Quantitative detection of nitric oxide in exhaled human breath by extractive electrospray ionization mass spectrometry

Exhaled nitric oxide (eNO) is a useful biomarker of various physiological conditions, including asthma and other pulmonary diseases. Herein a fast and sensitive analytical method has been developed for the quantitative detection of eNO based on extractive electrospray ionization mass spectrometry (EESI-MS). Exhaled NO molecules selectively reacted with 2-phenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) reagent, and eNO concentration was derived based on the EESI-MS response of 1-oxyl-2-phenyl-4, 4, 5, 5-tetramethylimidazoline (PTI) product. The method allowed quantification of eNO below ppb level (~0.02 ppbv) with a relative standard deviation (RSD) of 11.6%. In addition, eNO levels of 20 volunteers were monitored by EESI-MS over the time period of 10 hrs. Long-term eNO response to smoking a cigarette was recorded, and the observed time-dependent profile was discussed. This work extends the application of EESI-MS to small molecules (<30 Da) with low proton affinity and collision-induced dissociation efficiency, which are usually poorly visible by conventional ion trap mass spectrometers. Long-term quantitative profiling of eNO by EESI-MS opens new possibilities for the research of human metabolism and clinical diagnosis.