Effect of natural grass pollen exposure on exhaled nitric oxide in asthmatic children

Association of early life and acute pollen exposure with lung function and exhaled nitric oxide (FeNO). A prospective study up to adolescence in the GINIplus and LISA cohort

BACKGROUND

Pollen exposure has both acute and chronic detrimental effects on allergic asthma, but little is known about its wider effects on respiratory health. This is increasingly important knowledge as ambient pollen levels are changing with the changing global climate.

OBJECTIVE

To assess associations of pollen exposure with lung function and fractional exhaled nitric oxide (FeNO) at age 15 in two prospective German birth cohorts, GINIplus and LISA.

METHODS

Background city-specific pollen exposure was measured in infancy (during the first three months of life), and contemporary (on the day of and 7 days prior to lung function measurement). Greenness levels within circular buffers (100-3000 m) around the birth and 15-year home addresses were calculated using the satellite-derived Normalized Difference Vegetation Index. Regression models were used to assess the associations of grass and birch pollen with lung function and FeNO, and the modifying effects of residential greenness were explored.

RESULTS

Cumulative early life exposure to grass pollen was associated with reduced lung function in adolescence (FEV₁: -4.9 mL 95%CI: -9.2, -0.6 and FVC: -5.2 mL 95%CI: -9.8, -0.5 per doubling of pollen count). Acute grass pollen exposure was associated with increased airway inflammation in all children, with higher FeNO increases in children living in green areas. In contrast acute birch pollen exposure was associated with reduced lung function only in children sensitised to birch allergens.

CONCLUSION

This study provides suggestive evidence that early pollen exposure has a negative effect on later lung function, which is in turn influenced by acute pollen exposures.

Outdoor pollen-related changes in lung function and markers of airway inflammation: A systematic review and meta-analysis

BACKGROUND

Experimental challenge studies have shown that pollen can have early and delayed effects on the lungs and airways. Here, we qualitatively and quantitatively synthesize the evidence of outdoor pollen exposure on various lung function and airway inflammation markers in community-based studies.

METHODS

Four online databases were searched: Medline, Web of Science, CINAHL and Google Scholar. The search strategy included terms relating to both exposure and outcomes. Inclusion criteria were human-based studies published in English that were representative of the community. Additionally, we only considered cross-sectional or short-term longitudinal studies which investigated pollen exposure by levels or season. Study quality assessment was performed using the Newcastle-Ottawa scale. Meta-analysis was conducted using random-effects models.

RESULTS

We included 27 of 6551 studies identified from the search. Qualitative synthesis indicated associations between pollen exposure and predominantly type-2 inflammation in both the upper and lower airways, but little evidence for lung function changes. People with ever asthma and/or seasonal allergic rhinitis (SAR) were at higher risk of such airway inflammation. Meta-analysis confirmed a positive relationship between pollen season, eosinophilia and eosinophil cationic protein (ECP) in people with ever SAR but the results between studies were highly variable. Heterogeneity was reduced after further subgrouping by age, and the forest plots indicated that eosinophilic airway inflammation to outdoor pollen exposure increased with age.

CONCLUSION

Among people with ever asthma and ever SAR, exposure to increased ambient pollen triggers type-2 upper and lower airway inflammation rather than a non-specific or innate inflammation. These findings can lead to the formulation of specific pollen immunotherapy for susceptible individuals. Future research should be directed towards investigating lagged associations and effect modifications using larger and more generalized populations.

SYSTEMATIC REVIEW REGISTRATION

CRD42020146981 (PROSPERO).

Association between lung function of school age children and short-term exposure to air pollution and pollen: the PARIS cohort

BACKGROUND

Daily levels of ambient air pollution and pollen may affect lung function but have rarely been studied together. We investigated short-term exposure to pollen and air pollution in relation to lung function in school-age children from a French population-based birth cohort.

METHODS

This study included 1063 children from the PARIS (Pollution and Asthma Risk: an Infant Study) cohort whose lung function and FeNO measurements were performed at age 8 years old. Exposure data were collected up to 4 days before testing. We estimated daily total pollen concentration, daily allergenic risk indices for nine pollen taxa, as well as daily concentrations of three air pollutants (particulate matter less than 10 µm (PM₁₀), nitrogen dioxide (NO₂), ozone (O₃)). Children with similar pollen and air pollution exposure were grouped using multidimensional longitudinal cluster analysis. Associations between clusters of pollen and air pollution exposure and respiratory indices (FEV₁, FVC, FeNO) were studied using multivariable linear and logistic regression models adjusted for potential confounders.

RESULTS

Four clusters of exposure were identified: no pollen and low air pollution (Cluster 1), grass pollen (Cluster 2), PM₁₀ (Cluster 3) and birch/plane-tree pollen with high total pollen count (Cluster 4). Compared with children in Cluster 1, children in Cluster 2 had significantly lower FEV₁ and FVC levels, and children from Cluster 3 had higher FeNO levels. For FEV₁ and FVC, the associations appeared stronger in children with current asthma. Additional analysis suggested a joint effect of grass pollen and air pollution on lung function.

CONCLUSION

Daily ambient chemical and biological air quality could adversely influence lung function in children.

What is a clinically meaningful change in exhaled nitric oxide for children with asthma?

INTRODUCTION

Fractional exhaled nitric oxide (F_E NO) may be a useful objective measurement to guide asthma treatment. What remains uncertain is what change in F_E NO is clinically significant.

METHODS

An individual patient data analysis was performed using data from seven randomized clinical trials which used F_E NO to guide asthma treatment. The absolute and percentage intra-subject change in F_E NO measurements over "stable" and also "unstable" 3-month periods were described.

RESULTS

Data were available in 1112 randomized controlled trial participants and ≥1 stable period was present for 665 individuals. The interquartile range (IQR) and limits of agreement (LoA) for change in absolute F_E NO among individuals whose initial F_E NO was <50 parts per billion (ppb) were -7 to +9 ppb and -43 to +50 ppb, and for those with initial F_E NO ≥50 ppb IQR was -29 to +17 ppb and LoA was -80 to +76 ppb. For percentage change in F_E NO, the IQR and LoA for individuals whose initial F_E NO was <50 ppb were -33% to +51% and -157% to +215%, and for those with initial F_E NO ≥50 ppb were -33% to +35% and -159% to +192%. The variation in F_E NO values for a stable period was similar irrespective of whether it was followed by a stable or unstable period.

CONCLUSIONS

Over a 3-month period where F_E NO is initially <50 ppb, a rise of <10 ppb or of <50% (based on IQR) is unlikely to be related to asthma. When F_E NO is initially ≥50 ppb an percentage change of <50% (based on IQR) is unlikely to be asthma-related.

Short-term exposure to pollen and the risk of allergic and asthmatic manifestations: a systematic review and meta-analysis

BACKGROUND

Several studies have assessed effects of short-term exposure to pollen on allergic and asthmatic manifestations. The evidence is inconclusive, and no meta-analysis has been published.

OBJECTIVE

To synthesise the evidence on the relations between short-term pollen exposure and the risk of allergic and asthmatic manifestations.

METHODS

We performed a systematic literature search of PubMed and Scopus databases up to the end of August 2018. In addition, we reviewed the reference lists of relevant articles. Two authors independently evaluated the eligible articles and extracted relevant information in a structured form. We calculated summary effect estimates (EE) based on the study-specific ORs and regression coefficients (β) by applying both fixed-effects and random-effects models.

RESULTS

26 studies met the a priori eligibility criteria, and 12 of them provided sufficient information for the meta-analysis. The summary EE related to 10 grains per m³ increase in pollen exposure showed an 1% increase (EE 1.01, 95% CI 1.00 to 1.02) in the risk of lower respiratory symptoms and a 2% increase (EE 1.02, 95% CI 1.01 to 1.03) in the risk of any allergic or asthmatic symptom. Correspondingly, the risk of upper respiratory symptoms and ocular symptoms increased 7% (EE 1.07, 95% CI 1.04 to 1.09) and 11% (EE 1.11, 95% CI 1.05 to 1.17), respectively, in relation to such pollen exposure. Short-term exposure to pollen did not show any significant effect on daily lung function levels.

CONCLUSION

Our results provide new evidence that short-term pollen exposure significantly increases the risks of allergic and asthmatic symptoms.

Pollen exposure at birth and adolescent lung function, and modification by residential greenness

BACKGROUND

Exposure to high levels of pollen in infancy is a risk factor for allergic respiratory diseases in later childhood, but effects on lung function are not fully understood. We aim to examine associations between grass pollen exposure in the first months of life and lung function at 12 and 18 years, and explore potential modification.

METHODS

Using the Melbourne Atopy Cohort Study, a birth cohort of children with a family history of allergic diseases, we modeled the association between cumulative grass pollen exposure up to 3 months after birth, on FEV₁ , FVC, and FEV₁ /FVC ratio at 12 and 18 years. We also assessed modifying effects of residential greenness levels (derived from satellite imagery), asthma, and early life sensitization to ryegrass.

RESULTS

Grass pollen exposure in the first 7 days was associated with a reduction in FEV₁ (-15.5 mL; 95% CI: -27.6, -3.3 per doubling of pollen count) and FVC (-20.8 mL; -35.4, -6.1) at 12 years, but not at 18 years. Increase in cumulative grass pollen exposure up to 3 months was negatively associated with FVC at 12 and 18. Exposure to high residential greenness modified the association at 18 years.

CONCLUSION

Early exposure to grass pollen was associated with decreased lung function in children and adolescents. Targeted interventions for pollen avoidance strategies that take into account local topography could be implemented alongside other clinical interventions such as immunotherapy.

Setting reference values for exhaled nitric oxide: a systematic review

BACKGROUND

The values obtained when the fraction of exhaled nitric oxide (FeNO) is measured are affected by several factors that are specific to the individual patient, making interpretation difficult, especially in the initial assessment of patients with respiratory symptoms.

METHODS

Systematic review of studies on FeNO reference values and individual-specific factors that influence them.

RESULTS

From 3739 references, 15 studies were included. Four studies included children and adolescents. In nine studies, samples were selected from the general population. Most studies reported objective measures for atopy (nine studies), but not for smoking status (one). Significant determinants of FeNO values reported were age and height (seven studies), atopy (six), smoking (four), weight (four), sex (three) and race (three). Additional factors were included in eight studies. R2 was reported in only five studies. The logarithmic transformation of FeNO was inadequately described in seven studies.

CONCLUSION

There are several equations for FeNO reference values that may be used in clinical practice, although the factors they include and the statistical methods they use vary considerably. We recommend the development of standard methods for the evaluation of normal FeNO data and that reference equations should be formulated based on a predetermined physiological model.

Exhaled nitric oxide monitoring does not reduce exacerbation frequency or inhaled corticosteroid dose in paediatric asthma: a randomised controlled trial

INTRODUCTION

Inhaled corticosteroid therapy (ICS) for asthma is currently modified according to symptoms and lung function. Fractional exhaled nitric oxide (FENO) has been demonstrated to be a non-invasive marker of eosinophilic inflammation. Studies of FENO-driven asthma management show variable success. Objectives: This study aimed to evaluate whether monitoring FENO can improve outpatient management of children with moderate to severe asthma using a pragmatic design.

METHODS

Children aged 6–17 years with moderate to severe asthma were recruited. Their asthma was stabilised before randomisation to FENO-driven therapy or to a standard management group where therapy was driven by conventional markers of asthma control. ICS or long-acting bronchodilator therapies were altered according to FENO levels in combination with reported symptoms in the FENO group. Participants were assessed 2 monthly for 12 months. ICS dose and exacerbation frequency change were compared between groups in an intention to treat analysis.

RESULTS

Ninety children were randomised. No difference was found between the two groups in either change in corticosteroid dose or exacerbation frequency. Results were similar in a planned secondary analysis of atopic asthmatics.

CONCLUSION

FENO-guided ICS titration does not appear to reduce corticosteroid usage or exacerbation frequency in paediatric outpatients with moderate to severe asthma. This may reflect limitations in FENO-driven management algorithms, as there are now concerns that FENO levels relate to atopy as much as they relate to asthma control.

A pathophysiological approach for FeNO: A biomarker for asthma

The present review is focused on literature concerning the relevance of fractional exhaled nitric oxide (FeNO) in clinical practice from a pathophysiological point of view. There is increasing evidence that asthma is a heterogeneous pathological condition characterised by different phenotypes/endotypes related to specific biomarkers, including FeNO, helpful to predict therapeutic response in selected asthmatic populations. Nowadays FeNO, a non-invasive biomarker, appears to be useful to foresee asthma developing, to recognise specific asthma phenotypes, like the eosinophilic, to ameliorate asthma diagnosis and management in selected populations and to predict standard corticosteroid and biologic therapy efficacy. In addition, FeNO assessment may also be useful in patients with allergic rhinitis in order to detect the potential involvement of eosinophilic bronchial inflammation in "case finding" subjects at risk of asthma diagnosis. Therefore, it is possible to hypothesise a future with an appropriate use of FeNO by physicians dealing with worrisome clinical issues in specific asthma phenotypes.

Effects of pollen season on central and peripheral nitric oxide production in subjects with pollen asthma

BACKGROUND

Pollen exposure of allergic subjects with asthma causes increased nitric oxide (NO) in exhaled air (FENO) suggestive of increased airway inflammation. It is, however, unclear to what extent NO production in peripheral airways and alveoli are involved.

OBJECTIVES

The aim of the present investigation was to analyze the relationship between central and peripheral components of FENO to clarify the distribution of pollen induced inflammation in asthma.

SUBJECTS AND METHODS

13 pollen allergic non-smoking subjects with mild-intermittent asthma and 12 healthy non-smoking control subjects were examined with spirometry and FENO at flows between 50 and 270 mL/s during and out of pollen season.

RESULTS

Spirometry was normal and unaffected by season in subjects with asthma as well as controls. Out of season subjects with asthma had significantly higher FENO, elevated airway production (JáwNO) and preacinar/acinar production (CANO) than controls. Pollen exposure resulted in significantly increased FENO and JáwNO but not CANO. FENO among controls were not affected by season. Individual results showed, however, that CANO increased substantially in a few subjects with asthma. The increased CANO in subjects with asthma may be explained by increased NO production in preacinar/acinar airways and back diffusion towards the alveoli.

CONCLUSIONS

The findings may indicate that subjects with allergic asthma have airway inflammation without alveolar involvement outside the pollen season and pollen exposure causes a further increase of airway inflammation and in a few subjects obstruction of intra acinar airways causing impeded back diffusion. Increased NO production in central airways, unassociated with airway obstruction could be an alternative explanation. These effects were not disclosed by spirometry.

Advances in the diagnosis and management of asthma in older adults

Global estimates on aging predict an increased burden of asthma in the older population. Consequently, its recognition, diagnosis, and management in clinical practice require optimization. This review aims to provide an update for clinicians, highlighting advances in the understanding of the aging process and immunosenescence together with their applicability to asthma from a diagnostic and therapeutic perspective. Aging impacts airway responses and immune function, and influences efficacy of emerging phenotype-specific therapies when applied to the elderly patient. Differentiating eosinophilic and neutrophilic disease accounts for atopic illness and distinguishes long-standing from late-onset asthma. Therapeutic challenges in drug delivery, treatment adherence, and side-effect profiles persist in the older patient, while novel recording devices developed to aid detection of an adequate inhalation evaluate treatment effectiveness and compliance more accurately than previously attainable. Anticytokine therapies improve control of brittle asthma, while bronchial thermoplasty is an option in refractory cases. Multidimensional intervention strategies prove best in the management of asthma in the older adult, which remains a condition that is not rare but rarely diagnosed in this patient population.

Lack of heritability of exhaled volatile compound pattern: an electronic nose twin study

Electronic noses can distinguish various disorders by analyzing exhaled volatile organic compound (VOC) pattern; however it is unclear how hereditary and environmental backgrounds affect the exhaled VOC pattern. A twin study enrolling monozygotic (MZ) and dizygotic (DZ) twins is an ideal tool to separate the influence of these factors on the exhaled breath pattern. Exhaled breath samples were collected in duplicates from 28 never smoking twin pairs (in total 112 samples) without lung diseases and processed with an electronic nose (Cyranose 320). Univariate quantitative hereditary modeling (ACE analysis) adjusted for age and gender was performed to decompose the phenotypic variance of the exhaled volatile compound pattern (assessing principal components (PCs) derived from electronic nose data) into hereditary (A), shared (C), and unshared (E) environmental effects. Exhaled VOC pattern showed good intra-subject reproducibility as assessed with the Bland-Altman plot. Significant correlations were found between exhaled VOC patterns of both MZ and DZ twins. The hereditary background did not influence the VOC pattern. The shared environmental effect on PC 1, 2 and 3 was estimated to be 93%, 94% and 54%, respectively. The unshared (unique) environmental influence explained a smaller variance (7%, 6% and 46%). For the first time using the twin design, we have shown that the environmental background largely affects the exhaled volatile compound pattern in never smoking volunteers without respiratory disorders. Further studies should identify these environmental factors and also assess their influence on exhaled breath patterns in patients with lung diseases.

Daytime physical activity levels in school-age children with and without asthma

BACKGROUND

Physical activity (PA) is a significant predictor of health outcomes in children with and without chronic conditions. Few researchers have used actigraphy as an objective measure of PA during the child's normal daily routines, and the findings have been inconsistent. It is unclear if asthma can contribute to low PA levels.

OBJECTIVES

The aim of this study was to compare daytime PA levels in children with and without asthma and examine the relationships among asthma, PA, body mass index (BMI), and child reports of symptoms.

METHODS

Physical activity as measured by actigraphy and self-report symptoms of coughing, wheezing, chest tightness, perceived tiredness, sleepiness, and alertness were obtained in 54 children aged 9-11 years with and without asthma for 7 consecutive days. Activity variables derived from actigraphy included (a) mean daytime activity level; (b) peak daytime activity level; and (c) time duration spent in sedentary, light, moderate, vigorous, and total moderate plus vigorous PA (MVPA).

RESULTS

Children with and without asthma did not differ on BMI or activity levels. Children with asthma reported more activity limitations due to breathing problems than children without asthma (p < .01). In multivariate analyses, asthma predicted reduced mean, peak, and total time spent in MVPA level after controlling for gender, BMI, and self-report of symptoms. A significant interaction was found between asthma and BMI on mean, peak, and total time spent in MVPA.

DISCUSSION

The association between asthma and PA is complex when the child's BMI is considered. Results suggest that reduced PAs with respect to respiratory symptom severity, childhood obesity, and functional impairment are important areas for future studies.

Breath biomarkers in diagnosis of pulmonary diseases

Breath analysis provides a convenient and simple alternative to traditional specimen testing in clinical laboratory diagnosis. As such, substantial research has been devoted to the analysis and identification of breath biomarkers. Development of new analytes enhances the desirability of breath analysis especially for patients who monitor daily biochemical parameters. Elucidating the physiologic significance of volatile substances in breath is essential for clinical use. This review describes the use of breath biomarkers in diagnosis of asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), lung cancer, as well as other pulmonary diseases. A number of breath biomarkers in lung pathophysiology will be described including nitric oxide (NO), carbon monoxide (CO), hydrogen peroxide (H₂O₂) and other hydrocarbons.

Domestic airborne black carbon and exhaled nitric oxide in children in NYC

Differential exposure to combustion by-products and allergens may partially explain the marked disparity in asthma prevalence (3-18%) among New York City neighborhoods. Subclinical changes in airway inflammation can be measured by fractional exhaled nitric oxide (FeNO). FeNO could be used to test independent effects of these environmental exposures on airway inflammation. Seven- and eight-year-old children from neighborhoods with lower (range 3-9%, n=119) and higher (range 11-18%, n=121) asthma prevalence participated in an asthma case-control study. During home visits, FeNO was measured, and samples of bed dust (allergens) and air (black carbon; BC) were collected. Neighborhood built-environment characteristics were assessed for the 500 m surrounding participants' homes. Airborne BC concentrations in homes correlated with neighborhood asthma prevalence (P<0.001) and neighborhood densities of truck routes (P<0.001) and buildings burning residual oil (P<0.001). FeNO concentrations were higher among asthmatics with than in those without frequent wheeze (≥4 times/year) (P=0.002). FeNO concentrations correlated with domestic BC among children without seroatopy (P=0.012) and with dust mite allergen among children with seroatopy (P=0.020). The association between airborne BC in homes and both neighborhood asthma prevalence and FeNO suggest that further public health interventions on truck emissions standards and residual oil use are warranted.

Exhaled nitric oxide in pediatrics: what is new for practice purposes and clinical research in children?

Fractional exhaled NO (FeNO) is universally considered an indirect marker of eosinophilic airways inflammation, playing an important role in the physiopathology of childhood asthma. Advances in technology and standardization have allowed a wider use of FeNO in clinical practice in children from the age of four years. FeNO measurements add a new dimension to the traditional clinical tools (symptoms scores, lung function tests) in the assessment of asthma. To date a number of studies have suggested a possible use of FeNO in early identification of exacerbation risk and in inhaled corticosteroids titration. The aim of this paper is to address practical issues of interest to paediatric clinicians who are attempting to use FeNO measurements as an adjunctive tool in the diagnosis and management of childhood airway diseases.

Asthma in the elderly: Current understanding and future research needs--a report of a National Institute on Aging (NIA) workshop

Asthma in the elderly is underdiagnosed and undertreated, and there is a paucity of knowledge on the subject. The National Institute on Aging convened this workshop to identify what is known and what gaps in knowledge remain and suggest research directions needed to improve the understanding and care of asthma in the elderly. Asthma presenting at an advanced age often has similar clinical and physiologic consequences as seen with younger patients, but comorbid illnesses and the psychosocial effects of aging might affect the diagnosis, clinical presentation, and care of asthma in this population. At least 2 phenotypes exist among elderly patients with asthma; those with longstanding asthma have more severe airflow limitation and less complete reversibility than those with late-onset asthma. Many challenges exist in the recognition and treatment of asthma in the elderly. Furthermore, the pathophysiologic mechanisms of asthma in the elderly are likely to be different from those seen in young asthmatic patients, and these differences might influence the clinical course and outcomes of asthma in this population.

Forced expiratory flow between 25% and 75% of vital capacity and FEV1/forced vital capacity ratio in relation to clinical and physiological parameters in asthmatic children with normal FEV1 values

BACKGROUND

The assumption that the assessment of forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) does not provide additional information in asthmatic children with normal FEV(1) percent predicted has not been adequately tested.

OBJECTIVE

We sought to determine whether the measurement of FEF(25-75) percent predicted offers advantages over FEV(1) percent predicted and FEV(1)/forced vital capacity (FVC) percent predicted for the evaluation of childhood asthma.

METHODS

This is a secondary analysis of data from the Pediatric Asthma Controller Trial and the Characterizing the Response to a Leukotriene Receptor Antagonist and Inhaled Corticosteroid trials. Pearson correlation coefficients, Pearson partial correlation coefficients, canonical correlations, and receiver operating characteristic (ROC) curves were constructed.

RESULTS

Among 437 children with normal FEV(1) percent predicted, FEF(25-75) percent predicted, and FEV(1)/FVC percent predicted were (1) positively correlated with log(2) methacholine PC(20), (2) positively correlated with morning and evening peak expiratory flow percent predicted, and (3) negatively correlated with log(10) fraction of exhaled nitric oxide and bronchodilator responsiveness. Pearson partial correlations and canonical correlations indicated that FEF(25-75) percent predicted was better correlated with bronchodilator responsiveness and log(2) methacholine PC(20) than were FEV(1) percent predicted or FEV(1)/FVC percent predicted. In the ROC curve analysis, FEF(25-75) at 65% of predicted value had a 90% sensitivity and a 67% specificity for detecting a 20% increase in FEV(1) after albuterol inhalation.

CONCLUSION

FEF(25-75) percent predicted was well correlated with bronchodilator responsiveness in asthmatic children with normal FEV(1). FEF(25-75) percent predicted should be evaluated in clinical studies of asthma in children and might be of use in predicting the presence of clinically relevant reversible airflow obstruction.

Relationship between exhaled nitric oxide and IgE sensitisation in patients with asthma: influence of steroid treatment

INTRODUCTION

The influence of the degree of immunoglobulin E (IgE) sensitisation on the fraction of expired nitric oxide (FE(NO)) in asthma patients being treated with inhaled corticosteroids (ICS) is not well known.

OBJECTIVES

To investigate the relationship between IgE sensitisation and FE(NO), and the effect of a step-up in ICS treatment on this relationship, in patients with allergic asthma.

METHODS

A primary health care centre recruited 20 non-smoking patients with perennial allergic asthma (18 years-50 years, six male) outside the pollen season. At every visit (0, 2, 4, 8 weeks), FE(NO) was measured and an exposure questionnaire was completed. ICS dose was adjusted according to FE(NO) (>or=22 ppb prescribed increase in ICS). Quantitative analyses of serum IgE (eight common aeroallergens) confirmed allergy.

RESULTS

At baseline, FE(NO) and the sum of IgE antibody titres for perennial allergens correlated significantly (r = 0.47, P = 0.04). After a step-up in ICS treatment, this correlation had disappeared. Nine patients had persistently elevated FE(NO) at last visit (mean 35 ppb vs 16 ppb). This group was more frequently exposed to relevant allergens or colds (89% vs 27% of patients, P < 0.05) and had higher IgE antibody titres (perennial allergens) compared with the normalised group (mean 28.9 kU/L vs 10.7 kU/L, P < 0.05).

CONCLUSION

Serum IgE against perennial allergens and FE(NO) correlate in patients with allergic asthma. However, this relationship disappears after a high-dose ICS regimen, suggesting that FE(NO) relates to bronchial inflammation and not IgE levels per se. High degree of IgE sensitisation together with allergen exposure may lead to ICS-resistant airways inflammation.

Exhaled nitric oxide levels in childhood asthma: a more reliable indicator of asthma severity than lung function measurement?

The level of exhaled nitric oxide (NO) has been demonstrated to reflect the degree of airway inflammation in patients with asthma and to be related to the severity of asthma, as well as to the efficacy of treatment. In contrast, lung function tests provide information about airway volumes and flows reflecting the level of airway obstruction, but do not allow any direct information about the degree of airway inflammation. Several studies have evaluated the relationships between the level of airway inflammation assessed by exhaled NO and the levels of airway obstruction and/or bronchial hyperresponsiveness in asthmatic adults and children. These studies highlight the complex pathophysiology of asthma and suggest that exhaled NO may have a promising role in addition to lung function measurement in the evaluation of asthma severity in children.

Exhaled nitric oxide in the diagnosis and management of asthma: clinical implications

Exhaled nitric oxide (eNO) used as an aid to the diagnosis and management of lung disease is receiving attention from pulmonary researchers and clinicians alike because it offers a noninvasive means to directly monitor airway inflammation. Research evidence suggests that eNO levels significantly increase in individuals with asthma before diagnosis, decrease with inhaled corticosteroid administration, and correlate with the number of eosinophils in induced sputum. These observations have been used to support an association between eNO levels and airway inflammation. This review presents an update on current opportunities regarding use of eNO in patient care, and more specifically on its potential usage for asthma diagnosis and monitoring. The review will also discuss factors that may complicate use of eNO as a diagnostic tool, including changes in disease severity, symptom response, and technical measurement issues. Regardless of the rapid, convenient, and noninvasive nature of this test, additional well-designed, long-term longitudinal studies are necessary to fully evaluate the clinical utility of eNO in asthma management.

Discrepancy between clinical asthma control assessment tools and fractional exhaled nitric oxide

BACKGROUND

Asthma is an inflammatory disease, yet clinical tools that evaluate asthma control do not include measures of inflammation.

OBJECTIVE

To determine the correlation between fractional exhaled nitric oxide (FeNO) and each of 5 asthma control evaluation tools, namely, the Asthma Control Questionnaire (ACQ), the Asthma Control Test (ACT), the National Asthma Education and Prevention Program (NAEPP) goals of therapy, the Joint Task Force Practice Parameter (JTFPP) on attaining optimal asthma control, and the Global Initiative for Asthma (GINA) guidelines.

METHODS

Patients 6 years or older who had asthma were clinically evaluated by an asthma specialist. Patients completed the ACT and ACQ and underwent spirometry and FeNO measurement. The physician was blinded to FeNO results until asthma control assessments were concluded. Correlations between FeNO level and each clinical evaluation tool were calculated.

RESULTS

One hundred patients 6 to 86 years old were enrolled. No significant association was found between FeNO level and asthma control based on ACQ (P > .99), ACT (P = .53), NAEPP (P = .53), JTFPP (P = .30), or GINA (P = .86) criteria. Agreement was high among the NAEPP, the JTFPP, and GINA; moderate between the ACQ and the ACT; and poor to fair between the ACT or the ACQ and the other 3 tools.

CONCLUSIONS

In addition to clinical evaluation, the incorporation of FeNO measurement in evaluating asthma is likely to lead to a more optimal pharmacotherapy, guidance in adjusting the dosage of anti-inflammatory agents, and positive long-term disease outcome.

Effects of montelukast treatment and withdrawal on fractional exhaled nitric oxide and lung function in children with asthma

BACKGROUND

Leukotriene receptor antagonists (LTRAs) reduce fractional exhaled nitric oxide (Feno) concentrations in children with asthma, but the effect of LTRA withdrawal on Feno and lung function is unknown. We aimed to study the effect of treatment and withdrawal of montelukast, a LTRA, on airway inflammation as reflected by Feno and lung function in children with asthma.

METHODS

A double-blind, randomized, placebo controlled, parallel group study was undertaken in 14 atopic children with mild persistent asthma who were treated with oral montelukast (5 mg/d for 4 weeks) and 12 atopic children with mild persistent asthma who received matching placebo. A follow-up visit was performed 2 weeks after montelukast or placebo withdrawal.

RESULTS

Montelukast reduced Feno concentrations by 17% (p = 0.067), an effect that was more pronounced (35%) [p = 0.0029] when children with seasonal atopy who were exposed to relevant allergens during the treatment phase were excluded from analysis (n = 3). Compared to those at the end of treatment, Feno concentrations were increased 2 weeks after montelukast withdrawal (p = 0.023) concomitant with a reduction in absolute FEV(1) values (p = 0.011), FEV(1) percentage of predicted values (p = 0.006), FEV(1)/FVC ratio (p = 0.002), and forced expiratory flow at 25% to 75% of FVC values (p = 0.021). These changes were not observed in the placebo group.

CONCLUSIONS

LTRAs reduce Feno concentrations in children with asthma, and withdrawal can result in increased Feno values and worsening of lung function in children with asthma.

Exhaled nitric oxide in childhood asthma: a review

As an 'inflammometer', the fraction of nitric oxide in exhaled air (Fe(NO)) is increasingly used in the management of paediatric asthma. Fe(NO) provides us with valuable, additional information regarding the nature of underlying airway inflammation, and complements lung function testing and measurement of airway hyper-reactivity. This review focuses on clinical applications of Fe(NO) in paediatric asthma. First, Fe(NO) provides us with a practical tool to aid in the diagnosis of asthma and distinguish patients who will benefit from inhaled corticosteroids from those who will not. Second, Fe(NO) is helpful in predicting exacerbations, and predicting successful steroid reduction or withdrawal. In atopic asthmatic children Fe(NO) is beneficial in adjusting steroid doses, discerning those patients who require additional therapy from those whose medication dose could feasibly be reduced. In pre-school children Fe(NO) may be of help in the differential diagnosis of respiratory symptoms, and may potentially allow for better targeting and monitoring of anti-inflammatory treatment.

Reliability of a new hand-held device for the measurement of exhaled nitric oxide

BACKGROUND

Given the importance of airway inflammation in asthma, there has been an effort to incorporate inflammatory markers into its management. Measurement of fractional exhaled nitric oxide (FeNO) is a noninvasive marker of airway inflammation; however, the use of the available FeNO analyzer is limited by several factors including its cost and lack of transportability. The aim of this study was to compare the performance of a new hand-held FeNO measuring device (NIOX MINO) to the current clinical standard - the chemiluminescence FeNO analyzer (NIOX).

METHODS

Subjects 6 years and older presenting to an allergy and asthma clinic underwent FeNO evaluation by NIOX and each of three NIOX MINOs. The mean of two acceptable measurements from the NIOX and the first approved measurement from each NIOX MINO were used for analysis.

RESULTS

One hundred ten patients aged 6-86 years completed the study. Intrasubject FeNO levels obtained by each of the three NIOX MINOs revealed no significant difference between the measurements (P = 0.59). There was a very strong correlation between FeNO measurements by NIOX and by NIOX MINO (r = 0.98, P < 0.0001). The mean intrasubject FeNO difference between NIOX and NIOX MINO was -0.5 p.p.b. which was not statistically significantly different from zero (P = 0.21).

CONCLUSIONS

Fractional exhaled nitric oxide measurements by the NIOX MINO showed a strong correlation and a high degree of agreement with the current standard stationary device. The NIOX MINO may be reliably used in clinical practice.

Exhaled nitric oxide daily evaluation is effective in monitoring exposure to relevant allergens in asthmatic children

BACKGROUND

Though asthma is an airway inflammatory disease, the assessment of treatment efficacy is mainly based on symptom monitoring and the evaluation of lung function parameters. This study was aimed to evaluate the feasibility of exhaled nitric oxide monitoring in allergic asthmatic children who were exposed to relevant allergens in their homes.

METHODS

Twenty-two children allergic to mites underwent twice-daily fractional exhaled nitric oxide (FeNO) therapy using a portable device (NIOX MINO; Aerocrine AB; Stockholm, Sweden) and peak expiratory flow (PEF) measurements before, during, and after periods of natural exposure to mite allergens. The children were admitted to the study if they had lived in a mite-free environment for 3 months. They were observed in this environment for 10 days and then were moved to a site with natural mite exposure at sea level for 19 days. Finally, they were relocated to the mite-free environment for a period of 6 days for follow-up measurements.

RESULTS

Significant differences were seen between the mite-free baseline FeNO level (26.4 parts per billion [ppb]; range, 19.3 to 36.2 ppb) and FeNO levels measured during natural mite exposure (37.3 ppb; 27.3 to 51 ppb) and after natural mite exposure (34.9 natural mite exposure; 25.2 to 48.2 ppb). Six children reported asthma symptoms during the mite exposure, and an increase in FeNO was observed in each case (p<0.031); PEF values showed no significant differences, whether between the different environments or between different periods.

CONCLUSIONS

These data give further evidence for a possible role of frequent determinations of FeNO in order to promptly assess changes in the level of airway inflammation in asthmatic children.

Exhaled nitric oxide: interactions between asthma, hayfever, and atopic dermatitis in school children

BACKGROUND

Clinicians frequently rely on reported symptoms and basic pulmonary function testing to assess asthma prevalence in the community. However, given that spirometry results are often normal for asthmatic children and the fact that there is no equivalent word for 'wheeze' in languages other than English, the assessment of asthma prevalence can be troublesome.

OBJECTIVE

To evaluate in a population based setting, whether FeNO as a non-invasive marker, contributes to the detection of asthma.

METHODS

This cross-sectional study was carried out on primary school children from Northern and Southern Tyrol. FeNO measurements were made using the online single breath technique prior to spirometry. Symptom status including asthma, hayfever and atopic dermatitis was determined by the ISAAC questionnaire.

RESULTS

Six hundred and forty-four Tyrolean children aged 8-10 years participated. In terms of FEV1 % predicted, the asthma and hayfever group had significantly lower values compared to the asymptomatic group, the hayfever only, and the atopic dermatitis only groups. For FeNO, participants with asthma and hayfever, asthma and atopic dermatitis, and hayfever only recorded significantly greater FeNO values when compared to the asymptomatic group. Moreover, the asthma and atopic dermatitis group recorded significantly greater FeNO when compared to the asthma only group. Multivariate regression revealed that asthma had a small significant inverse association with FEV1 % predicted for the individual model and when combined with hayfever. For FeNO, each of the individual and combined model analyses achieved significance.

CONCLUSION

Although FeNO appears to be influenced by asthma, the presence of other atopic conditions confounds the relationship. Elevated levels of FeNO do not distinguish between asthma and other atopic conditions. Therefore, FeNO does not contribute to the detection of asthma in the community.

CLINICAL IMPLICATION

FeNO is not a valuable tool for the detection of asthma in the community as it is confounded by other atopic conditions.

Nasal levels of nitric oxide as an outcome variable in allergic upper respiratory tract disease: Influence of atopy and hayfever on nNO

BACKGROUND

The role of nasal levels of nitric oxide (nNO) as noninvasive marker of inflammation and as an outcome variable in allergic upper respiratory tract disease has not been defined. Our aim is to determine in patients with perennial allergic rhinitis (i) whether nNO is elevated, (ii) whether increased nNO is correlated with upper respiratory tract symptoms (discrimination), and (iii) whether changes in symptom scores are associated with changes in nNO levels (responsiveness).

METHODS

Subjects (n = 38) with perennial rhinitis were studied weekly for 3 weeks. At each visit they completed a validated symptom questionnaire and had expired NO and nNO measured.

RESULTS

Nasal NO levels were higher in those allergic to house-dust mite and cat. Nasal NO levels in subjects with perennial rhinitis were not elevated compared with non-atopic asymptomatic subjects. The intra-week reproducibility of nNO measurements was poor. There was no relationship between the symptom scores and nasal NO levels (discrimination). When analysis was confined to nasal symptoms, a weak but negative correlation was identified. Changes in symptom scores from week to week were not correlated with changes in nNO levels (responsiveness).

CONCLUSIONS

Nasal NO levels were not elevated in subjects with perennial rhinitis, and nNO levels were neither discriminatory nor responsive. The measurement of nNO therefore appears not to be a useful marker of disease activity in subjects with allergic rhinitis.

Intranasal air sampling in homes: relationships among reservoir allergen concentrations and asthma severity

BACKGROUND

The relationship among inhaled allergen exposure, sensitization, and asthma severity is unknown.

OBJECTIVES

To investigate the relationship among personal allergen exposure, reservoir dust allergen concentrations, and physiological measures of asthma severity; to examine the numbers of particles inspired that react with autologous IgE and IgG4.

METHODS

A total of 117 patients with asthma wore 5 nasal air samplers (NASs) at home: 1 each for exposure to mite, cat and dog allergens, NAS-IgE, and NAS-IgG4. NASs were processed by HALOgen assay for allergen measurement and incubated with autologous serum for detection of NAS-IgE and NAS-IgG4. Reservoir allergen concentrations were measured by ELISA. Subjects' asthma severity was ascertained by measurement of lung function, exhaled nitric oxide, and nonspecific bronchial reactivity to histamine.

RESULTS

Nasal air sampler counts correlated with reservoir concentrations for cat (r=0.31; P=.001) and dog (r=0.20; P=.03) but not mite allergen (r=0.001; P=1.0). There was no significant relationship between sensitization with exposure measured by NAS to any allergen and PD20FEV1 (F[3,60]=1.60; P=.20); however, sensitization with exposure in dust reservoirs had significant effects on PD20FEV1 for any allergen (F[3,59]=3.12; P=.03), cat (F[3,59]=3.77; P=.01), and mite (F[3,59]=2.78; P=.05), but not dog (F[3,59]=1.06; P=.37). We repeated the analysis with separate variables for sensitization and exposure, controlling for the confounders; sensitization but not exposure conferred lower PD20FEV1 values. However, increasing cat allergen exposure was associated with improving bronchial reactivity in not cat-sensitized patients. NAS-IgE and NAS-IgG4 counts bore no relationship to any measure of asthma severity.

CONCLUSION

Nasal air samplers confer no advantage over reservoir dust analysis for studies of asthma severity.

CLINICAL IMPLICATIONS

In common with other measures of exposure, single nasal air samples do not provide a useful measure of home allergen exposure for the individual patient with allergic asthma.

Local nitric oxide levels reflect the degree of allergic airway inflammation after segmental allergen challenge in asthmatics

Nitric oxide (NO) levels are increased in the exhaled air of asthmatics. As NO levels correlate with allergic airway inflammation, NO measurement has been suggested for disease monitoring. In patients with asthma, we previously demonstrated that intrabronchial treatment with a natural porcine surfactant enhanced airway inflammation after segmental allergen provocation. We studied whether local levels of NO reflect the degree of allergic airway inflammation following segmental allergen challenge with or without surfactant pretreatment. Segmental NO, as well as nitrite and nitrate in bronchoalveolar lavage (BAL) fluid, was measured before and after segmental challenge with either saline, saline plus allergen, or surfactant plus allergen in 16 patients with asthma and five healthy subjects. The data were compared with inflammatory BAL cells. Segmental NO levels were increased after instillation of saline (p < 0.05), or surfactant plus allergen in asthmatics (p < 0.05), and values were higher after surfactant plus allergen compared to saline challenge. Nitrate BAL levels were not altered after saline challenge but increased after allergen challenge (p < 0.05) and further raised by surfactant (p < 0.05), whereas nitrite levels were not altered by any treatment. Segmental NO and nitrate levels correlated with the degree of eosinophilic airway inflammation, and nitrate levels also correlated with neutrophil and lymphocyte numbers in BAL. In healthy subjects, NO, nitrite, and nitrate were unaffected. Thus, segmental NO and nitrate levels reflect the degree of allergic airway inflammation in patients with asthma. Measurement of both markers can be useful in studies using segmental allergen provocation, to assess local effects of potential immunomodulators.

Exhaled nitric oxide in a population-based study of asthma and allergy in schoolchildren

Exhaled nitric oxide (NO) reflects inflammation in the lower airways and is well adapted for use in children. The aims of this study were to investigate the distribution of the fraction of expired NO (FENO) in school children and to compare FENO and spirometry in relation to the International Study of Asthma and Allergies in Childhood questionnaire. The study was performed in 959 randomly selected 13-14-year-old school children in Uppsala, Sweden. Exhaled NO was measured at an inhalation rate of 0.1 l/s (FENO0.1) and a spirometric test was performed and data from these measurements were related to questionnaire data. Exhaled NO was measured according to American Thoracic Society recommendations, except the use of a mouth wash and an exhalation flow rate of 0.1 l/s. The distribution of the mean FENO0.1 values was skewed, with a preponderance of very low levels and a widespread tail of values ranging up to 102 parts per billion (ppb). Boys exhibited significantly higher mean FENO0.1 values than girls, 5.2 (4.7-5.7) vs 4.4 (4.0-4.8) ppb (geometric mean and 95% CI), P <0.01). Children who reported wheezing in the last year had higher FENO0.1 values than children that had not, 8.5 (7.1-10.2) vs 4.3 (4.0-4.6) ppb, P <0.001). The same association was found to most symptoms indicating hay fever and eczema. In contrast to this, only weak or inconsistent associations were found between asthma and spirometric indices. Exhaled NO levels were found to be independently related to male gender, wheeze and rhinoconjuctivitis but not to current eczema. In conclusion, exhaled NO was closely associated with reported asthma and allergy symptoms whereas spirometric indices such as percent predicted forced expiratory volume in 1 s were not. As most asthma cases in a population are mild, the findings suggest that exhaled NO is a sensitive marker of asthma and allergy.

Nitric oxide levels and ciliary beat frequency in indigenous New Zealand children

New Zealand children's morbidity from respiratory disease is high. This study examines whether subclinical ciliary abnormalities underlie the increased prevalence of respiratory disease in indigenous New Zealand children. A prospective study enrolled a group of healthy children who were screened for respiratory disease by questionnaire and lung function. Skin-prick tests were performed to control for atopy. Exhaled and nasal NO was measured online by a single-breath technique using chemiluminescence. Ciliary specimens were obtained by nasal brushings for assessment of structure and function. The ciliary beat frequency (CBF) (median CBF, 12.5 Hz; range, 10.4-16.8 Hz) and NO values (median exhaled NO, 5.6 ppb; range, 2.3-87.7 ppb; median nasal NO, 403 ppb; range, 34-1,120 ppb) for healthy New Zealand European (n=58), Pacific Island (n=61), and Maori (n=16) children were comparable with levels reported internationally. No ethnic differences in NO, atopy, or CBF were demonstrated. Despite an apparently normal ciliary beat, the percentage of ciliary structural defects was 3 times higher than reported controls (9%; range, 3.6-31.3%), with no difference across ethnic groups. In conclusion, it is unlikely that subclinical ciliary abnormalities underlie the increased prevalence of respiratory disease in indigenous New Zealand children. The high percentage of secondary ciliary defects suggests ongoing environmental or infective damage.

Additive effect of eosinophilia and atopy on exhaled nitric oxide levels in children with or without a history of respiratory symptoms

Although atopy and blood eosinophilia both influence exhaled nitric oxide (eNO) measurements, no study has quantified their single or combined effect. We assessed the combined effect of atopy and blood eosinophilia on eNO in unselected schoolchildren. In 356 schoolchildren (boys/girls: 168/188) aged 9.0-11.5 yr, we determined eNO, total serum IgE, blood eosinophil counts and did skin prick tests (SPT) and spirometry. Parents completed a questionnaire on their children's current or past respiratory symptoms. Atopy was defined by a SPT >3 mm and eosinophilia by a blood cell count above the 80th percentile (>310 cells/ml). eNO levels were about twofold higher in atopic-eosinophilic subjects than in atopic subjects with low blood eosinophils [24.3 p.p.b. (parts per billion) vs. 14.1 p.p.b.] and than non-atopic subjects with high or low blood eosinophils (24.3 p.p.b. vs. 12.2 p.p.b. and 10.9 p.p.b.) (p <0.001 for both comparisons). The additive effect of atopy and high eosinophil count on eNO levels remained unchanged when subjects were analyzed separately by sex or by a positive history of wheeze (n=60), respiratory symptoms other than wheeze (n=107) or without respiratory symptoms (n=189). The frequency of sensitization to Dermatophagoides (Dpt or Dpf) was similar in atopic children with and without eosinophilia (66.2% and 67.4%, respectively); eosinophilia significantly increased eNO levels in Dp-sensitized children as well in children sensitized to other allergens. In a multiple linear regression analysis, eNO levels were mainly explained by the sum of positive SPT wheals and a high blood eosinophil count (t=4.8 and 4.3, p=0.000), but also by the presence of respiratory symptoms (especially wheeze) and male sex (t=2.6 and 2.0, p=0.009 and 0.045, respectively). Measuring eNO could be a simple, non-invasive method for identifying subjects at risk of asthma in unselected school populations.

[The measurement of exhaled nitric oxide, a new tool in the management of asthma?]

A GOOD DIAGNOSTIC TEST FOR ASTHMA: Chronic airway inflammation, main feature of asthma, can be assessed by measuring the exhaled nitric oxide (NO) level. Measurement of NO is standardized, non-invasive and easy to use in both children and adults. Studies have shown that it is a good diagnostic test for asthma when NO is high. However, other conditions or pathologies must be searched for because they may influence the results. ITS PLACE IN TREATMENT: Although exhaled NO helps to characterise the patients with asthma, other studies are required to show that it can help to improve the follow-up of such patients. Nevertheless, this tool has not yet been validated in the daily treatment of asthma and further research is still ongoing.

Exhaled nitric oxide in the clinical management of asthma

Management of asthma has gradually evolved from the concept of controlling bronchial hyperresponsiveness to focusing on control of inflammation. The awareness of airway remodeling, and the emergence of data suggesting irreversibility of some of these changes, despite standard-of-care pharmacotherapies such as inhaled steroids, has highlighted the need for early detection; effective diagnosis and treatment; monitoring responses and adhering to treatment; and predicting exacerbations. Pre-clinical intervention strategies targeted toward picking up early suggestions of asthma before irreversible airway changes occur may open the door to primary prevention approaches. Although invasive methods, such as bronchial biopsy, remain the gold standard to understanding and treating asthma, there is a preference for noninvasive techniques for reasons of convenience, ease of use, and patient comfort. In this article, recent data that support the use of exhaled nitric oxide as a noninvasive biomarker of inflammation in clinical practice are reviewed.

Longitudinal study of grass pollen exposure, symptoms, and exhaled nitric oxide in childhood seasonal allergic asthma

BACKGROUND

Exhaled nitric oxide (NO) has been proposed as a marker of airway eosinophilic inflammation in asthma. There is currently a paucity of longitudinal data relating it to allergen exposure and asthma symptoms.

METHODS

Forty four children (6-16 years) with seasonal allergic asthma were sequentially followed before and during the grass pollen season. Asthma symptoms, lung function, NO levels, and pollen counts were recorded. The relationship between exhaled NO and both the pollen levels and asthma control were assessed longitudinally, comparing a subject's measurements with their previous ones.

RESULTS

The median exhaled NO concentration was significantly increased during the pollen season (6.2 v 9.2 parts per billion (ppb), p<0.002; median change 2.9 ppb, 95% confidence interval 1.5 to 5.4). Exhaled NO was best associated with the mean pollen count in the week before measurement. It was also significantly associated with asthma control.

CONCLUSIONS

The results suggest that, within a longitudinal model, the exhaled NO concentration is related to preceding allergen exposure and asthma control. It may be clinically more useful to compare exhaled NO values with a subject's previous values than to compare them with a population based normal range.

Biological markers in diagnosing, monitoring, and treating asthma: a focus on noninvasive measurements

Asthma is a major concern for society, healthcare professionals, and individuals and families directly affected by asthma due to rising morbidity rates and costs associated with the disease. The pathological hallmark of asthma is airway inflammation that is considered to be a major cause of exacerbations and persistent structural alterations of the airways. Assessing airway inflammation is important for investigating the underlying mechanisms of the disease and possibly for following the progression and resolution of the disease. The presence and type of airway inflammation can be difficult to detect clinically, and may result in delays in initiating appropriate therapy. The purpose of this article is to review noninvasive methods for assessing biological markers of airway inflammation and their potential role in the future for diagnosing, monitoring, and treating asthma. The article reviews the noninvasive measurements of induced sputum and exhaled nitric oxide as indicators of airway inflammation.

Maternal atopic disease modifies effects of prenatal risk factors on exhaled nitric oxide in infants

In a prospective healthy birth cohort, we determined whether levels of exhaled nitric oxide (eNO) in healthy unselected infants at the age of 1 month were associated with maternal atopic disease and prenatal and early postnatal environmental exposures. Tidal eNO was measured in 98 healthy, unsedated infants (35 from mothers with atopy) (mean age +/- SD, 36.0 +/- 6.2 days) and was compared with histories taken in standardized interviews. eNO was higher in males compared with females (17.7 vs. 14.6 ppb, p = 0.042) and infants exposed to postnatal maternal smoking (+4.4 ppb, p = 0.027), adjusting for weight and tidal breathing parameters. Prenatal tobacco exposure was associated with higher eNO (+12.0 ppb, p = 0.01) in infants of mothers with asthma and lower eNO (-5.7 ppb) in infants of mothers without asthma (p for interaction < 0.0001). Coffee consumption in pregnancy decreased eNO (-6.0 ppb, p = 0.008) only in children of mothers with atopy (p for interaction = 0.015). Paternal atopy had no influence. In the early phase of immunologic development, before the onset of infections and allergic disease, the effect of prenatal or early postnatal environmental factors on eNO was modified by the presence of maternal atopic disease. This underlines the complex interaction of maternal and environmental factors in the development of airway disease.

Heterogeneity of FeNO response to inhaled steroid in asthmatic children

BACKGROUND

Nitric oxide in exhaled air is regarded as an inflammation marker, and may be used to monitor the anti-inflammatory control from inhaled corticosteroids (ICSs). However, this response to ICSs exhibits a heterogeneous pattern.

OBJECTIVE

The study aimed to describe the independent variables associated with the heterogeneity in the response of exhaled nitric oxide to ICSs.

METHODS

Exhaled nitric oxide (FeNO), lung function, bronchial hyper-responsiveness (BHR), specific IgE to common inhalant allergens, blood eosinophils, other atopic manifestations and variants in nitric oxide synthethase 1 (NOS1) gene were studied in a double-blind, placebo-controlled crossover comparison of budesonide (BUD) Turbohaler 1600 mcg daily vs. placebo in asthmatic schoolchildren.

RESULTS

Forty children were included in the study from a screening of 184 asthmatic children with moderately persistent asthma, well controlled on regular BUD 400 mcg daily: 20 children with normal FeNO and 20 with raised FeNO. FeNO, BHR and forced expiratory volume in 1 s improved significantly after BUD 1600 mcg (BUD1600). However, FeNO after ICS treatment exhibited a Gaussian distribution and FeNO was significantly raised in 15 children. Allergy and BHR, but none of the other independent variables under study were significantly related to FeNO after BUD1600.

CONCLUSION

Exhaled nitric oxide exhibited a heterogeneous response to ICS in asthmatic schoolchildren. Allergy and BHR were driving FeNO level independently of high-dose steroid treatment. This should be considered when using FeNO for steroid dose titration and monitoring of ICS anti-inflammatory control in asthmatic children.

Clinical relevance of spore and pollen counts

Many people with allergies monitor daily pollen and spore counts with the belief that they can act on that information to improve their health. Because many factors can affect personal exposure, the value of community-wide counts for an individual is questionable. These factors include the presence of local pollen and spore sources, diurnal variations, weather effects, air pollution, and a particle-free bioaerosol. To take advantage of bioparticulate counts, the public needs to be informed about their meaning and factors that can influence personal exposure.

Relationship of exhaled nitric oxide to clinical and inflammatory markers of persistent asthma in children

BACKGROUND

Exhaled nitric oxide (eNO) is a noninvasive test that measures airway inflammation. Insufficient information is available concerning correlations between eNO and biologic, physiologic, and clinical characteristics of asthma in children currently not taking controller medications.

OBJECTIVE

The aim of this study was to find correlations between eNO and other characteristics of children with mild to moderate asthma currently not taking medications.

METHODS

Children aged 6 to 17 years with mild to moderate persistent asthma, taking only albuterol as needed, were characterized during 2 visits 1 week apart before being randomly assigned into a clinical trial. At the screening visit, online measurements of eNO, spirometry before and after bronchodilator, and biomarkers of peripheral blood eosinophils, serum eosinophil cationic protein, total serum IgE, and urinary leukotriene E4 were obtained. During a week characterization period before randomization, symptoms were recorded on a diary and peak expiratory flows were measured twice daily using an electronic device. At the randomization visit, eNO was repeated followed by a methacholine challenge and aeroallergen skin testing. Correlations and rank regression analyses between eNO and clinical characteristics, pulmonary function, and biomarkers were evaluated.

RESULTS

eNO was significantly correlated with peripheral blood eosinophils (r =.51, P <.0001), IgE (r =.48, P <.0001), and serum eosinophil cationic protein (r =.31, P =.0003) but not with urinary leukotriene E4 (r =.16, P =.08). A moderate correlation was found between eNO and the number of positive aeroallergen skin tests (r =.45, P <.0001). eNO did not correlate with FEV1% predicted but was weakly correlated with FEV1/forced vital capacity (r = -.19, P =.032), bronchodilator response (r =.20, P =.023), and FEV1 PC20 methacholine (r = -.31, P =.0005). No significant correlations were found between eNO and clinical characteristics or morning or evening peak expiratory flow measurements. The rank regression analysis demonstrated that 5 variables accounted for an R square of.52 (eosinophils [P <.0001], IgE [P =.0023], age [P <.0001], months of inhaled corticosteroid use in the year before study entry [P =.01], and FEV1 PC20 [P =.0061]).

CONCLUSIONS

These findings suggest that eNO provides information about the asthmatic state consistent with information from other markers of inflammation. It is a noninvasive technique that could be used in decisional management of children with asthma.

Relationship among pulmonary function, bronchial reactivity, and exhaled nitric oxide in a large group of asthmatic patients

BACKGROUND

Bronchial reactivity and exhaled nitric oxide (eNO) are not often used to monitor control and severity of asthma in clinical practice.

OBJECTIVE

To evaluate the relationship among different physiologic measures (pulmonary function, nonspecific bronchial reactivity, and eNO) in asthmatic patients.

METHODS

Cross-sectional, hospital-based study conducted in patients with varied asthma severity.

RESULTS

A total of 392 patients participated in the study. There was no difference in eNO levels between patients taking inhaled corticosteroids (ICS group) and patients not receiving inhaled corticosteroids (NICS group). However, the percentage of predicted forced expiratory volume in 1 second (FEV1) and the provocative dose of methacholine causing a 20% decrease in FEV1 were significantly lower in the ICS group compared with the NICS group (mean, 83.2%; 95% confidence interval [CI], 80.4%-86.0%; vs mean, 94.1%; 95% CI, 91.1%-97.1%; P = .001; and geometric mean, 0.32 mg; 95% CI, 0.23-0.45 mg; vs geometric mean, 0.58 mg; 95% CI, 0.42-0.81 mg; P = .01; respectively). Patients with more severe bronchial hyperresponsiveness had a lower percentage of predicted FEV1 values (P < .001) and levels of eNO were significantly increased with increasing bronchial hyperresponsiveness (P < .001). There was no relationship between the percentage of predicted FEV1 and eNO. Atopic patients had significantly higher eNO levels than nonatopic patients (geometric mean, 11.21 ppb; 95% CI, 10.07-12.49 ppb; vs geometric mean, 7.76 ppb; 95% CI, 6.11-9.85 ppb; P = .006; respectively).

CONCLUSIONS

eNO values are not related to the degree of airway obstruction but are related to airway reactivity and atopic status independent of inhaled corticosteroid use. Higher values of eNO are seen with increased airway reactivity.

Exhaled nitric oxide is age-dependent in asthma

We determined whether the exhaled nitric oxide (eNO) level in asthmatics is age-dependent. Eighty-seven asthmatic patients aged 2-41 years were studied. Hyperreactivity to adenosine 5'-monophosphate (AMP) was used to confirm asthma (</= 200 mg/ml). In the younger group of children (2-5 years), AMP challenge was performed by the provocation concentration causing wheeze (PCW) method, while in the older groups of patients (6-41 years), regular spirometry was used. Exhaled NO was measured in the younger group by the tidal breathing method (TBm) and in the older subjects by the slow vital capacity method (SVCm). TBm and SVCm were compared in 21 other subjects, and there was a significant correlation between the two values (r = 0.96, P < 0.0001). The equation of correlation between the two methods was eNOTBm = 0.78eNOSVCm - 0.51. Within asthmatic patients, we found a significant increase in eNO with age (P < 0.0001), while there was no significant difference in AMP reactivity (P = 0.35). We conclude that eNO in asthmatic patients is age-dependent, with lower values in young children.

Exhaled nitric oxide corresponds with office evaluation of asthma control

Exhaled NO (ENO) has been studied as a noninvasive marker of airway inflammation, and has been shown to be elevated in asthma patients. The aim of this study was to investigate whether ENO measurements differ significantly between groups of asthmatic children with different disease control and to compare ENO measurements with the clinical assessment of asthma control. Seventy-three children between 5-18 years old with a diagnosis of asthma were recruited. ENO was measured online during a slow vital capacity maneuver. The mean of three plateau NO levels was used for analysis. Baseline and postbronchodilator spirometry were performed. The assessment of disease control was based on the frequency of use of beta2-agonists, occurrence of day- and nighttime asthma symptoms, and spirometry results. Twenty-one children (group 1) had good asthma control. In 31 patients (group 2), asthma control was acceptable. In 21 patients (group 3), asthma was insufficiently controlled. ENO levels were (median (quartiles)): group 1, 11 ppb (9-21); group 2, 15 ppb (11-26); and group 3, 28 ppb (19-33). Measurements were significantly different between all three groups (P = 0.009, Kruskal-Wallis), between groups 1 and 3 (P = 0.01, Mann-Whitney U test), and between groups 2 and 3 (P = 0.01, Mann-Whitney-U test). The same was true for reversibility testing. We found significantly different ENO levels between a group of pediatric asthma patients with insufficient and good/sufficient control, as defined by clinical assessment. These results suggest that ENO measurements may be useful for monitoring asthma patients.