Exhaled nitric oxide levels in non-allergic and allergic mono- or polysensitised children with asthma

Changes in FeNO, d-ROMs, and BH4 by Intravenous L-Arginine in Children and Its Putative Role in Asthma Treatment

Purpose

Pteridines are metabolites of tetrahydrobiopterin (BH4), being coenzymes for nitric oxide synthase (NOS). No study has clarified the relationship among pteridines and NOS, fractional exhaled nitric oxide (FeNO) generated by pteridines, and reactive oxygen species. In this study, we administered arginine, a precursor of NO, and confirmed changes in the levels of pteridines, FeNO, and reactive oxygen species and their relationship to clarify the pathogenesis of airway inflammation in which oxidative stress is involved, such as bronchial asthma.

Patients and Methods

This is a prospective, randomized open-label study. Children, aged 2 to 15 years, who were scheduled for growth hormone stimulation tests and were able to undergo a respiratory function test were recruited. They were randomly divided into two groups: arginine-administered and control groups. In the former, L-arginine hydrochloride was intravenously administered. After administration, the levels of diacron-reactive oxygen metabolites (d-ROMs), serum pteridines, serum amino acids, and fractional exhaled NO (FeNO) were measured.

Results

We analyzed 15 children aged 4 to 14 years. In the arginine-administered group, there was an increase in the FeNO level and a decrease in the d-ROMs level, reaching a peak 30 min after administration, compared with the control group. In addition, there was a decrease in the serum biopterin level and an increase in the d-ROMs level, reaching peak 60 min after administration.

Conclusion

The administration of L-arginine increased the NO level and decreased the d-ROMs level. Due to this, biopterin may be consumed and decreased, leading to an increase in the d-ROMs level. As a reduction in reactive oxygen species leads to the relief of inflammation, arginine and biopterin may be useful for inhibiting inflammation.

Use of exhaled nitric oxide in the diagnosis and monitoring of childhood asthma: myth or maxim?

Asthma is a common condition in children. This review describes the evidence from the literature and international asthma guidelines for using fractional exhaled nitric oxide (FENO) in the diagnosis and monitoring of childhood asthma. The accuracy of FENO measuring devices could be further improved, the difference in FENO results between devices are equivalent to what is considered a clinically important difference. For diagnosing asthma no guideline currently recommends FENO is used as the first test, but many recommend FENO as part of a series of tests. A cut-off of 35 ppb is widely recommended as being supportive of an asthma diagnosis, but evidence from children at risk of asthma suggests that a lower threshold of 25 ppb may be more appropriate. Nine randomised clinical trials including 1885 children have added FENO to usual asthma care and find that exacerbations are reduced when care is guided by FENO (OR for exacerbation compared to usual care 0.77, 95% CI 0.62-0.94). What is not clear is what cut-off(s) of FENO should be used to trigger a change in treatment. After 30 years of intensive research there is not sufficient evidence to recommend FENO for routine diagnosing and monitoring asthma in children.

Educational aims

To give the reader an overview of literature that supports and does not support the role of FENO in diagnosing asthma in children.To give the reader an overview of literature that supports and does not support the role of FENO in monitoring asthma in children.To give the reader an understanding of the role of FENO in international guidelines for diagnosing and monitoring asthma in children.

Fractional exhaled nitric oxide and eosinophil count in induced sputum to guide the management of children with asthma: a cost-utility analysis

Introduction

Previous evidence has shown that fractional exhaled nitric oxide (FeNO) and eosinophil count in induced sputum (EO) are cost-effective relative to standard of care in guiding the management of children with persistent asthma. There is some doubt as if there are differences between these two biomarkers in terms of costs and benefits. Clarifying this doubt would allow prioritization of the design of clinical practice guidelines. The study aimed to compare in terms of costs and benefits these biomarkers in patients with asthma between 4 and 18 years of age.

Methods

A Markov model was used to estimate the cost-utility of asthma management using FeNO and EO in patients between 4 and 18 years of age. Transition probabilities, cost and utilities were estimated from previously published local studies, while relative risks were obtained from the systematic review of published randomized clinical trials. The analysis was carried out from a societal perspective.

Results

The expected annual cost per patient with EO was US $1376 (CI 95% US $1376–US $1377) and for FeNO was US $1934 (CI 95% US $1333–US $1334), with a difference of US $42.3 between these strategies. The Quality-adjusted life years (QALYs) per person estimated with EO was 0.95 (CI 95% 0.951–0.952) and for FeNO was 0.94 (CI 95% 0.930–0.940), with a difference of 0.01 between these strategies. The NMB with EO was US $4902 (CI 95% 4900–4904) and for FeNO was US $4841 (CI 95% 4839–4843). The incremental cost-effectiveness ratio of EO was $3566 per QALY gained regarding FeNO.

Conclusion

Our study demonstrates that induced sputum-guided management is a strategy cost-effective over FeNO and standard asthma management in Colombia. This evidence should encourage the adoption of any of these techniques to objectively guide the management of children with asthma in routine clinical practice in low-resource settings.

Cost utility of fractional exhaled nitric oxide monitoring for the management of children asthma

Introduction

Fractional exhaled nitric oxide is a simple, non-invasive measurement of airway inflammation with minimal discomfort to the patient and with results available within a few minutes. This study aimed to evaluate the cost-effectiveness of asthma management using fractional exhaled nitric oxide monitoring in patients between 4 and 18 years of age.

Methods

A Markov model was used to estimate the cost-utility of asthma management using fractional exhaled nitric oxide monitoring versus asthma management without using fractional exhaled nitric oxide monitoring (standard therapy) in patients between 4 and 18 years of age. Cost data were obtained from a retrospective study on asthma from a tertiary center, in Medellin, Colombia, while probabilities of the Markov model and utilities were obtained from the systematic review of published randomized clinical trials. The analysis was carried out from a societal perspective.

Results

The model showed that fractional exhaled nitric oxide monitoring was associated with a lower total cost than standard therapy (US $1333 vs. US $1452 average cost per patient) and higher QALYs (0.93 vs. 0.92 average per patient). The probability that fractional exhaled nitric oxide monitoring provides a more cost-effective use of resources compared with standard therapy exceeds 99% for all willingness-to-pay thresholds.

Conclusion

Asthma management using fractional exhaled nitric oxide monitoring was cost-effective for treating patients between 4 and 18 years of age with mild to moderate allergic asthma. Our study suggests evidence that could be used by decision-makers to improve clinical practice guidelines, but this should be replicated in different clinical settings.

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

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

Determinants of fractional exhaled nitric oxide in healthy men and women from the European Community Respiratory Health Survey III

INTRODUCTION

The fractional exhaled nitric oxide (F_E NO) is a marker for type 2 inflammation used in diagnostics and management of asthma. In order to use F_E NO as a reliable biomarker, it is important to investigate factors that influence F_E NO in healthy individuals. Men have higher levels of F_E NO than women, but it is unclear whether determinants of F_E NO differ by sex.

OBJECTIVE

To identify determinants of F_E NO in men and women without lung diseases.

METHOD

Fractional exhaled nitric oxide was validly measured in 3881 healthy subjects that had answered the main questionnaire of the European Community Respiratory Health Survey III without airways or lung disease.

RESULTS

Exhaled NO levels were 21.3% higher in men compared with women P < 0.001. Being in the upper age quartile (60.3-67.6 years), men had 19.2 ppb (95% CI: 18.3, 20.2) higher F_E NO than subjects in the lowest age quartile (39.7-48.3 years) P = 0.02. Women in the two highest age quartiles (54.6-60.2 and 60.3-67.6 years) had 15.4 ppb (14.7, 16.2), P = 0.03 and 16.4 ppb (15.6, 17.1), P = <0.001 higher F_E NO, compared with the lowest age quartile. Height was related to 8% higher F_E NO level in men (P < 0.001) and 5% higher F_E NO levels in women (P = 0.008). Men who smoked had 37% lower F_E NO levels and women had 30% lower levels compared with never-smokers (P < 0.001 for both). Men and women sensitized to both grass and perennial allergens had higher F_E NO levels compared with non-sensitized subjects 26% and 29%, P < 0.001 for both.

CONCLUSION AND CLINICAL RELEVANCE

Fractional exhaled nitric oxide levels were higher in men than women. Similar effects of current smoking, height, and IgE sensitization were found in both sexes. F_E NO started increasing at lower age in women than in men, suggesting that interpretation of F_E NO levels in adults aged over 50 years should take into account age and sex.

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.

Pulmonary Function Test Abnormalities in Pediatric Inflammatory Bowel Disease

BACKGROUND

Pulmonary involvement in adult patients with inflammatory bowel disease (IBD) seems more common than previously appreciated. Its prevalence and development over time in pediatric IBD patients are largely unknown.

OBJECTIVES

The aim was to study lung function including fraction of exhaled nitric oxide (FeNO) and transfer capacity for carbon monoxide (TLCO) in pediatric IBD patients and to describe the longitudinal development in a subset of patients with lung function abnormalities.

METHODS

Sixty-six measurements were made in 48 IBD patients (30 patients with Crohn's disease and 18 with ulcerative colitis) and 108 matched controls. Patients with abnormal TLCO or elevated residual volume/total lung capacity (RV/TLC) ratios were invited for a follow-up. Statistical comparisons were made by nonparametric tests and ANOVA.

RESULTS

TLCO was decreased in IBD patients [median: 88% predicted (interquartile range, IQR, 22) vs. 99% predicted (IQR 19) in controls]. RV/TLC ratios were mildly elevated in patients with ulcerative colitis [32% (IQR 9) vs. 27% (IQR 8) in controls], and maximum expiratory flows at 50 and 25% of vital capacity were mildly reduced in patients with Crohn's disease. FeNO and disease activity did not correlate with lung function abnormalities. Abnormalities did not consistently persist over a median follow-up period of 34 months.

CONCLUSIONS

This study supports evidence that variable and fluctuating pulmonary involvement also occurs in pediatric IBD patients. Its clinical significance is unclear.

Airway gas exchange and exhaled biomarkers

During inspiration and expiration, gases traverse the conducting airways as they are transported between the environment and the alveolar region of the lungs. The term "conducting" airways is used broadly as the airway tree is thought largely to provide a conduit for the respiratory gases, oxygen and carbon dioxide. However, despite a significantly smaller surface area, and thicker barrier separating the gas phase from the blood when compared to the alveolar region, the airway tree can participate in gas exchange under special conditions such as high water solubility, high chemical reactivity, or production of the gas within the airway wall tissue. While these conditions do not apply to the respiratory gases, other gases demonstrate substantial exchange of the airways and are of particular importance to the inflammatory response of the lungs, the medical-legal field, occupational health, metabolic disorders, or protection of the delicate alveolar membrane. Given the significant structural differences between the airways and the alveolar region, the physical determinants that control airway gas exchange are unique and require different models (both experimental and mathematical) to explore. Our improved physiological understanding of airway gas exchange combined with improved analytical methods to detect trace compounds in the exhaled breath provides future opportunities to develop new exhaled biomarkers that are characteristic of pulmonary and systemic conditions.

Fractional exhaled nitric oxide in children with acute exacerbation of asthma

OBJECTIVE

To determine whether fractional exhaled nitric oxide (FENO) has a utility as a diagnostic or predictive maker in acute exacerbations of asthma in children.

DESIGN

Analysis of data collected in a pediatric asthma cohort.

SETTING

Pediatric Chest Clinic of a tertiary care hospital.

METHODS

A cohort of children with asthma was followed up every 3 months in addition to any acute exacerbation visits. Pulmonary function tests (PFT) and FENO were obtained at all visits. We compared the FENO values during acute exacerbations with those at baseline and those during the follow up.

RESULTS

243 asthmatic children were enrolled from August 2009 to December 2011 [mean (SD) follow up - 434 (227) days]. FENO during acute exacerbations was not different from FENO during follow up; however, FENO was significantly higher than personal best FENO during follow up (P < 0.0001). FENO during acute exacerbation did not correlate with the severity of acute exacerbation (P=0.29). The receiver operating characteristics curve for FENO as a marker for acute exacerbation had an area under the curve of 0.59. Cut-off of 20 ppb had a poor sensitivity (44%) and specificity (68.7%) for acute exacerbation.

CONCLUSIONS

FENO levels during acute exacerbation increase from their personal best levels. However, no particular cut off could be identified that could help in either diagnosing acute exacerbation or predicting its severity.

Relationships between exhaled nitric oxide and atopy profiles in children with asthma

Purpose

We examined whether fractional exhaled nitric oxide (FeNO) levels are associated with atopy profiles in terms of mono-sensitization and poly-sensitization in asthmatic children.

Methods

A total of 119 children underwent an assessment that included FeNO measurements, spirometry, methacholine challenge, and measurement of blood eosinophil count, serum total IgE, and serum eosinophil cationic protein (ECP). We also examined sensitization to five classes of aeroallergens (house dust mites, animal danders, pollens, molds, and cockroach) using skin prick testing. The children were divided into three groups according to their sensitization profiles to these aeroallergens (non-sensitized, mono-sensitized, and poly-sensitized).

Results

The geometric means (range of 1 SD) of FeNO were significantly different between the three groups (non-sensitized, 18.6 ppb [10.0-34.7 ppb]; mono-sensitized, 28.8 ppb [16.6-50.1 ppb]; and poly-sensitized, 44.7 ppb [24.5-81.3 ppb], P=0.001). FeNO levels were correlated with serum total IgE concentrations, peripheral blood eosinophilia, and serum ECP levels to different degrees.

Conclusions

FeNO levels vary according to the profile of atopy, as determined by positive skin prick test results to various classes of aeroallergens. FeNO is also moderately correlated with serum total IgE, blood eosinophilia, and serum ECP. These results suggest that poly-sensitized asthmatic children may have the highest risk of airway inflammation.

Clinical application of exhaled nitric oxide measurement in pediatric lung diseases

Fractional exhaled nitric oxide (FeNO) is a non invasive method for assessing the inflammatory status of children with airway disease. Different ways to measure FeNO levels are currently available. The possibility of measuring FeNO levels in an office setting even in young children, and the commercial availability of portable devices, support the routine use of FeNO determination in the daily pediatric practice. Although many confounding factors may affect its measurement, FeNO is now widely used in the management of children with asthma, and seems to provide significantly higher diagnostic accuracy than lung function or bronchial challenge tests. The role of FeNO in airway infection (e.g. viral bronchiolitis and common acquired pneumonia), in bronchiectasis, or in cases with diffuse lung disease is less clear. This review focuses on the most recent advances and the current clinical applications of FeNO measurement in pediatric lung disease.

Pulmonary function in adults with recent and former asthma and the role of sex and atopy

Background

Pulmonary function is not fully reversible in asthma in children and may continue into adult life. This study was to determine the association between asthma and reduced pulmonary function in adults and the modification by sex and atopic status.

Methods

A cross-sectional study of 1492 adults aged 18 years or over was conducted in a rural community. Atopy, height, weight, waist circumference (WC) and pulmonary function were measured. Participants with ever asthma were those who reported by questionnaire a history of asthma diagnosed by a physician during lifetime. Participants who had former (only) asthma were those who reported having physician-diagnosed asthma more than 12 months ago. Participants who had recent asthma were those who reported having asthma during the last 12 months.

Results

Men had higher values of forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁) compared with women, but FEV₁/FVC ratio showed no significant difference between sexes. Atopic status was not related to pulmonary function and the average values of the pulmonary function testing variables were almost the same for non-atopic and atopic individuals. Individuals with ever, recent or former asthma had significant lower values of FEV₁ and FEV₁/FVC ratio than those who reported having no asthma, and the associations tended to be stronger in men than in women. The interaction between atopy and asthma was not statistically significant.

Conclusions

Adults who reported having recent asthma or former asthma had reduced pulmonary function, which was significantly modified by sex but not by atopic status.

Fractional exhaled nitric oxide measurements in rhinitis and asthma in children

Exaled nitric oxide (FeNO) is considered a good noninvasive marker to assess airway inflammation in asthma and allergic rhinitis. In asthma, exhaled NO is very useful to verify adherence to therapy, and to predict upcoming asthma exacerbations. It has been also proposed that adjusting anti-inflammatory drugs guided by the monitoring of exhaled NO, could improve overall asthma control. Other studies showed increased FeNO levels in subjects with allergic rhinitis.

Determinants of exhaled nitric oxide levels (FeNO) in childhood atopic asthma: evidence for neonatal respiratory distress as a factor associated with low FeNO levels

BACKGROUND

In allergic asthmatic children exhaled nitric oxide (FeNO) levels are related to eosinophilic inflammation by correlation analysis. Whether FeNO can be modified by factors potentially influencing the natural history of asthma in early life is not known.

OBJECTIVE

To evaluate the frequency of anamnestic factors influencing the natural history of asthma and to identify potential determinants for elevated or low FeNO levels by multivariate analysis.

METHODS

One hundred seventy-one children with mild-moderate asthma were stratified according to their FeNO levels into three groups: low (<20 ppb), mid (20-40 ppb), and high (>40 ppb). The frequency of nine anamnestic factors together with indices of allergic sensitization (total and allergen-specific immunoglobulin E [IgE], blood eosinophil counts) and of airflow limitation (forced expiratory volume in one second [FEV(1)]% predicted) were evaluated. Results. Among factors related to the patient history, neonatal respiratory distress was reported only in children with low FeNO levels, whereas this factor was never reported in children with mid-to-high FeNO levels (p = .008). As compared with low FeNO group, mid and high FeNO groups showed higher eosinophil counts and a tendency to have lower FEV(1) values. By multivariate analysis, four factors (eosinophils >300 cells/mm(3), cat-specific IgE, house dust mites [HDM]-specific IgE, FEV(1) ≤ 86% predicted) turned out to be significantly associated with mid-high FeNO levels and two factors (eosinophils >600 cells/mm(3), total IgE >355 kU/L) with high FeNO levels.

CONCLUSIONS

Besides confirming the well-known tight association between blood eosinophilia and/or allergic sensitization and FeNO, these data provide new evidence for neonatal respiratory distress as potential factor associated with low FeNO levels in childhood atopic asthma.

Risk factors associated with allergic and non-allergic asthma in adolescents

INTRODUCTION

Risk factors for asthma have been investigated in a large number of studies in adults and children, with little progress in the primary and secondary prevention of asthma. The aim of this investigation was to investigate risk factors associated with allergic and non-allergic asthma in adolescents.

METHODS

In this study, 959 schoolchildren (13-14 years old) answered a questionnaire and performed exhaled nitric oxide (NO) measurements. All children (n = 238) with reported asthma, asthma-related symptoms and/or increased NO levels were invited to a clinical follow-up which included a physician evaluation and skin-prick testing.

RESULTS

Asthma was diagnosed in 96 adolescents, whereof half had allergic and half non-allergic asthma. Children with both allergic and non-allergic asthma had a significantly higher body mass index (BMI) (20.8 and 20.7 vs. 19.8 kg/m(2)) (p < 0.05) and a higher prevalence of parental asthma (30% and 32% vs. 16%) (p < 0.05). Early-life infection (otitis and croup) [adjusted odds ratio (OR) (95% confidence interval (CI)): 1.99 (1.02-3.88) and 2.80 (1.44-5.42), respectively], pets during the first year of life [2.17 (1.16-4.04)], window pane condensation [2.45 (1.11-5.40)] and unsatisfactory school cleaning [(2.50 (1.28-4.89)] was associated with non-allergic but not with allergic asthma.

CONCLUSION

This study indicates the importance of distinguishing between subtypes of asthma when assessing the effect of different risk factors. While the risk of both allergic and non-allergic asthma increased with increasing BMI, associations between early-life and current environmental exposure were primarily found in relation to non-allergic asthma.

Application of non-invasive biomarkers in a birth cohort follow-up in relation to respiratory health outcome

Asthma-related symptoms can manifest in children during the early years, but only some of the children will develop the disease. This feasibility study showed that it is possible to apply non-invasive markers (in urine, exhaled nitric oxide (FENO) and exhaled breath condensate (EBC)) in 3-year-old children, and evaluated the biomarkers in relation to health outcomes and potential modifiers. FENO was correlated with respiratory allergy, and was borderline significantly correlated with wheezing, but not with the asthma predictive index (mAPI). EBC pH and urinary 8-oxo-deoxyguanosine were not significantly correlated with these clinical outcomes. An EBC proteolytic peptide pattern was developed, which could distinguish between mAPI-positive and -negative children. Non-invasive biomarkers may become a promising tool for investigating respiratory health in children but further research is needed.

FeNO as a Marker of Airways Inflammation: The Possible Implications in Childhood Asthma Management

The aim of this study was to verify FeNO usefulness, as a marker of bronchial inflammation, in the assessment of therapeutic management of childhood asthma. We performed a prospective 1-year randomized clinical trial evaluating two groups of 32 children with allergic asthma: "GINA group", in which therapy was assessed only by GINA guidelines and "FeNO group", who followed a therapeutic program assessed also on FeNO measurements. Asthma Severity score (ASs), Asthma Exacerbation Frequency (AEf), and Asthma Therapy score (ATs) were evaluated at the start of the study (T1), 6 months (T2), and 1 year after (T3). ASs and AEf significantly decreased only in the FeNO group at times T2 and T3 (p[T1-T2] = 0.0001, and p[T1-T3] = 0.01; p[T1-T2] = 0.0001; and p[T1-T3] < 0.0001, resp.). After six months of follow-up, we found a significant increase of patients under inhaled corticosteroid and/or antileukotrienes in the GINA group compared to the FeNO group (P = .02). Our data show that FeNO measurements, might be a very useful additional parameter for management of asthma, which is able to avoid unnecessary inhaled corticosteroid and antileukotrienes therapies, however, mantaining a treatment sufficient to obtain a meaningful improvement of asthma.

Passive smoking is a major determinant of exhaled nitric oxide levels in allergic asthmatic children

BACKGROUND

Fraction of exhaled nitric oxide (FeNO) is considered, by some authors, to be a treatment follow-up parameter in allergic asthmatics. However, factors such as active smoking can influence NO production and must be taken into account in the interpretation of FeNO values. In children, the evidence in favour of an impact of passive smoking (PS) on FeNO values is controversial. The aim of this study was to evaluate the impact of chronic PS on FeNO in allergic asthmatic children.

METHODS

Seventy nontreated allergic asthmatic children over 5 years of age, exposed and unexposed to PS, underwent measurement of FeNO, spirometry, and allergic tests (skin prick tests, total and specific serum IgE, and blood eosinophilia). Children were considered to be exposed to PS when at least 1 cigarette per day was declared to be smoked at home.

RESULTS

Geometric mean FeNO value in 22 children exposed to PS was 26.3 +/- 1.5 ppb vs 56.3 +/- 1.7 ppb in 48 children unexposed (P < 0.001). After adjustment for age, blood eosinophilia, allergic sensitizations, total IgE, dust mite sensitization and asthma severity, multivariate analysis showed that PS exposure was negatively associated with FeNO values (P = 0.0001) and was the primary determinant of FeNO variations.

CONCLUSION

Passive smoking lowers FeNO, and might be a major determinant of FeNO levels in nontreated allergic asthmatic children.

Diagnostic value of exhaled nitric oxide in childhood asthma and allergy

Fractional exhaled nitric oxide (FE(NO) ) has been proposed as a diagnostic test of asthma. We aimed to investigate in a population based birth cohort of children the usefulness of FE(NO) as a diagnostic tool. The 10-yr follow up of the Environment and Childhood Asthma Study in Oslo included 616 children representative of the prospective birth cohort. Both FE(NO) (single breath technique) and skin prick test (SPT) were measured in 331, limited at the time by equipment availability. Structural parental interview, spirometry, methacholine challenge and exercise test were performed. FE(NO) was significantly elevated in children with current asthma (geometric mean 9.6 (95% confidence interval (CI) (6.9, 13.4) p.p.b.) compared with healthy children (5.8 (5.4, 6.3) p.p.b.; p < 0.001). FE(NO) was highest among children with current allergic asthma (asthma and positive SPT) (14.0 (8.9, 22.1) p.p.b.), whereas children with non-allergic asthma (6.1 (4.0, 9.2) p.p.b.) had comparable FE(NO) levels to healthy children (p = 0.99). Allergic sensitization was most closely associated with FE(NO) . A FE(NO) cut-off value of 20.4 p.p.b. had a high specificity (0.97), but a low sensitivity (0.41) and a Positive Likelihood Ratio of 16.1 for current allergic asthma. In the present childhood population-based study, high FE(NO) levels were closely associated with current allergic asthma and not with current asthma without allergic sensitization. Estimating the individual predictive probability of having asthma by use of FE(NO,) improves the diagnostic utility of the test.

Time-dependent effects of inhaled corticosteroids on lung function, bronchial hyperresponsiveness, and airway inflammation in asthma

BACKGROUND

Exhaled nitric oxide (F(ENO)) and exhaled breath condensate (EBC) are noninvasive markers that directly measure airway inflammation and may potentially be useful in assessing asthma control and response to therapy.

OBJECTIVE

To examine the time-dependent effects of inhaled corticosteroids on F(ENO) and EBC markers concomitantly with lung function and bronchial hyperresponsiveness.

METHODS

Eleven steroid-naive adults with mild-to-moderate persistent asthma were treated with mometasone furoate dry powder inhaler, 400 microg/d, for 8 weeks, followed by a 4-week washout. Forced expiratory volume in 1 second (FEV1), the concentration of methacholine calculated to cause a 20% decline in FEV1 (PC20), F(ENO), EBC pH, and EBC nitrite measurements before, during, and after treatment were analyzed and compared.

RESULTS

The mean (SEM) FEV1 increased from 3.01 (0.13) L (82% predicted) to 3.24 (0.18) L (87% predicted) by week 8 (P < .05). The PC20 level increased from 1.28 (0.31) mg/mL to 2.99 (0.51) mg/mL by treatment week 8 (P < .05) and remained relatively stable through washout week 4 (P < .05). The F(ENO) level decreased from 31.1 (4.1) ppb to 20.6 (4.5) ppb by treatment week 1 (P < .01), remained low through treatment week 8 (P < .01), then trended back to the baseline level by washout week 1 (P < .01). The median EBC pH increased from 7.81 (interquartile range, 7.49-8.09) to 8.02 (interquartile range, 7.87-8.12) by treatment week 4, but did not achieve statistical significance. The EBC nitrite level decreased from 17.6 (1.6) microM to 9.3 (0.9) microM by treatment week 8 (P < .01), and remained low throughout washout week 4 (P < .05). There was a negative correlation between F(ENO) and PC20 (Spearman rank correlation coefficient = -0.50, P < .001).

CONCLUSION

The F(ENO) level responded the earliest to treatment and withdrawal of inhaled corticosteroids, whereas changes in EBC markers were delayed but more sustained.

Both allergic and nonallergic asthma are associated with increased FE(NO) levels, but only in never-smokers

BACKGROUND

Allergic asthma is consistently associated with increased FE(NO) levels whereas divergence exists regarding the use of exhaled nitric oxide (NO) as marker of inflammation in nonallergic asthma and in asthmatic smokers. The aim of this study is to analyze the effect of having allergic or nonallergic asthma on exhaled nitric oxide levels, with special regard to smoking history.

METHODS

Exhaled NO measurements were performed in 695 subjects from Turin (Italy), Gothenburg and Uppsala (both Sweden). Current asthma was defined as self-reported physician-diagnosed asthma with at least one asthma symptom or attack recorded during the last year. Allergic status was defined by using measurements of specific immunoglobulin E (IgE). Smoking history was questionnaire-assessed.

RESULTS

Allergic asthma was associated with 91 (60, 128) % [mean (95% CI)] increase of FE(NO) while no significant association was found for nonallergic asthma [6 (-17, 35) %] in univariate analysis, when compared to nonatopic healthy subjects. In a multivariate analysis for never-smokers, subjects with allergic asthma had 77 (27, 145) % higher FE(NO) levels than atopic healthy subjects while subjects with nonallergic asthma had 97 (46, 166) % higher FE(NO) levels than nonatopic healthy subjects. No significant asthma-related FE(NO) increases were noted for ex- and current smokers in multivariate analysis.

CONCLUSIONS

Both allergic and nonallergic asthma are related to increased FE(NO) levels, but only in never-smoking subjects. The limited value of FE(NO) to detect subjects with asthma among ex- and current smokers suggests the predominance of a noneosinophilic inflammatory phenotype of asthma among ever-smokers.

Partitioned exhaled nitric oxide to non-invasively assess asthma

Asthma is a chronic inflammatory disease of the lungs, characterized by airway hyperresponsiveness. Chronic repetitive bouts of acute inflammation lead to airway wall remodeling and possibly the sequelae of fixed airflow obstruction. Nitric oxide (NO) is a reactive molecule synthesized by NO synthases (NOS). NOS are expressed by cells within the airway wall and functionally, two NOS isoforms exist: constitutive and inducible. In asthma, the inducible isoform is over expressed, leading to increased production of NO, which diffuses into the airway lumen, where it can be detected in the exhaled breath. The exhaled NO signal can be partitioned into airway and alveolar components by measuring exhaled NO at multiple flows and applying mathematical models of pulmonary NO dynamics. The airway NO flux and alveolar NO concentration can be elevated in adults and children with asthma and have been correlated with markers of airway inflammation and airflow obstruction in cross-sectional studies. Longitudinal studies which specifically address the clinical potential of partitioning exhaled NO for diagnosis, managing therapy, and predicting exacerbation are needed.

The use of fraction of exhaled nitric oxide in pulmonary practice

The measurement of the fractional concentration of exhaled nitric oxide (FeNO) is a convenient, noninvasive, point-of-service office test for airway inflammation. The first half of this practice management review presents the methodological, interpretative, and clinical applications of FeNO. The second half discusses practical management issues, including current and future technology, equipment specifications, US Food and Drug Administration regulations, cost, current procedural terminology coding, and reimbursement. The measurement of FeNO is helpful in the diagnosis of asthma. It is predictive of a response to inhaled corticosteroids (ICSs). Monitoring FeNO is useful in maintaining asthma control by allowing the assessment of adherence to medication and dose titration of ICSs. An elevated level of FeNO is predictive of asthma relapse following corticosteroid withdrawal especially in children. The advances in technology, ease of use, and clinical utility will lead to greater availability, acceptance, and routine application in the care of 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.

Relationship among pulmonary function, bronchial hyperresponsiveness, and atopy in children with clinically stable asthma

Pulmonary function testing plays a key role in the diagnosis and management of asthma in children. However, the literature does not clearly show whether children with clinically stable asthma have significantly reduced lung function when compared with normal children. We compared the lung function of 242 clinically stable asthmatic children who were initially diagnosed with mild intermittent or mild persistent asthma with the lung function of 100 nonasthmatic controls. The lung function was assessed using FEV1, FEV1/FVC, FEF25-75 and PEF. In addition, we measured bronchial hyperresponsiveness (BHR) using the provocation concentration of methacholine needed to produce a 20% fall in FEV1. All measures of pulmonary function were significantly decreased in the children with asthma. Pulmonary function was not influenced by atopy, serum IgE, or total eosinophil count (TEC). However, the likelihood ratio for trends revealed a significant association between our pulmonary parameters and the degree of BHR. Children with mild-to-severe BHR had greatly decreased lung function compared with those with normal BHR, the control group. In addition, a direct correlation was found between PC20 and our pulmonary parameters in asthmatic children. However, only atopic children with asthma had a significant correlation between PC20 and TEC. We found children with clinically stable asthma to have pulmonary obstruction, which associated strongly with their degree of BHR.

Exhaled nitric oxide in the management of childhood asthma: a prospective 6-months study

Fractional exhaled nitric oxide (FeNO) is elevated in asthma and reflects eosinophilic airway inflammation. The aim of this prospective, randomized, single-blind study was to examine whether the inclusion of repeated FeNO measurements into asthma monitoring leads to an improvement in asthma outcome. Forty-seven children with mild to moderate asthma were allocated to a FeNO group (n = 22) and to a control group (n = 25). In the FeNO group therapy was based on symptoms, beta-agonist use, lung function, and FeNO whereas in the control group therapy was based on symptoms, beta-agonist use and lung function only. Patients performed five visits in 6 weeks intervals. Frequency of respiratory symptoms, beta-agonist use, FEV(1)% predicted and the frequency of exacerbations were similar between groups. Patients in the FeNO group received higher doses of inhaled corticosteroids (ICS) (control group: median (interquartile range): 241 microg (26-607 microg); FeNo group: 316 microg (200-500 microg) and had significantly higher MEF(50)% predicted (control group: median (interquartile range): 68.5% (55.8-83.1%); FeNO group: 83.2% (62.9%-98.3%). At a cut-off point of 22.9 ppb FeNO the best predictive value for exacerbations with a sensitivity of 80% and specificity of 60% was found. Significant relationships were observed between FeNO and dose of ICS (beta = -8.77; P < 0.002), beta-agonist use 2 weeks prior to a visit (beta = 0.11; P < 0.05), asthma symptoms (beta = 0.02; P < 0.0001), and bronchial hyperresponsiveness (beta = 0.04; P = 0.02). In conclusion, FeNO was related to important markers of asthma control. A therapy regimen aimed at lowering FeNO in children with asthma improved parameters of small airway function, but was not able to improve clinical markers of asthma control.

Environmental exposures and exhaled nitric oxide in children with asthma

OBJECTIVE

To evaluate the relation of environmental factors with exhaled nitric oxide (FENO) concentrations among asthmatic children.

STUDY DESIGN

Cross-sectional analysis of 170 tobacco smoke-exposed children, ages 6 to 12 years, who have doctor-diagnosed asthma using measures of FENO, medication use, and exposures to settled indoor allergens and tobacco smoke.

RESULTS

In multivariable analysis, child's age, uncarpeted flooring, not owning a cat, higher income, dust mite exposure, and being sensitized to any allergens were associated with higher FENO concentrations. Children who were sensitized to indoor allergens had an adjusted geometric mean FENO of 15.4 ppb (95% CI, 13.1, 18.2) compared with 10 ppb (95% CI, 8.2, 12.2) for unsensitized children. There was no statistically significant association of serum cotinine, hair cotinine, or reported corticosteroid therapy with FENO.

CONCLUSIONS

FENO is higher among children who are sensitized to indoor allergens and exposed to dust mites. The results hold promise for the use of FENO as a tool to manage childhood asthma by using both pharmacologic and environmental treatments.

Exhaled nitric oxide as a screening tool for asthma in school children

It is now widely accepted that augmented levels of fractional exhaled nitric oxide (FeNO) reflect airway inflammation and the methodology has been optimised for potential clinical use. We were interested in investigating whether this measurement can be used as a tool to screen and identify school children with asthma. To do this, FeNO was measured using an on-line single exhalation analyser in 368 children aged 8-10 years in six Oxfordshire primary schools, by two investigators blinded to the disease status of the children. The children were then categorised into 'normal', 'atopic asthma', 'non-atopic asthma' and 'atopy only' groups, according to their responses to the ISAAC questionnaire and perusal of the children's medical records kept by their family practitioners. Increased levels of FeNO were found in 'atopic asthmatic', 'non-atopic asthmatics' and 'atopic only' groups (median values of 24.4, 7.8 and 15.3 ppb, respectively, compared to normal controls' of 6.9 ppb). Levels were increased in atopic children regardless of whether they had asthma and were significantly higher than non-atopic asthmatics. We conclude that FeNO measurement is not a useful tool for identifying children with asthma in the community, as increased levels did not discriminate between those with asthmatic and atopic symptoms.

Exhaled nitric oxide in children with asthma and short-term PM2.5 exposure in Seattle

The objective of this study was to evaluate associations between short-term (hourly) exposures to particulate matter with aerodynamic diameters < 2.5 microm (PM2.5) and the fractional concentration of nitric oxide in exhaled breath (FE(NO) in children with asthma participating in an intensive panel study in Seattle, Washington. The exposure data were collected with tapered element oscillation microbalance (TEOM) PM2.5 monitors operated by the local air agency at three sites in the Seattle area. FE(NO) is a marker of airway inflammation and is elevated in individuals with asthma. Previously, we reported that offline measurements of FE(NO) are associated with 24-hr average PM2.5 in a panel of 19 children with asthma in Seattle. In the present study using the same children, we used a polynomial distributed lag model to assess the association between hourly lags in PM2.5 exposure and FE(NO) levels. Our model controlled for age, ambient NO levels, temperature, relative humidity, and modification by use of inhaled corticosteroids. We found that FE(NO) was associated with hourly averages of PM2.5 up to 10-12 hr after exposure. The sum of the coefficients for the lag times associated with PM2.5 in the distributed lag model was 7.0 ppm FE(NO). The single-lag-model FE(NO) effect was 6.9 [95% confidence interval (CI), 3.4 to 10.6 ppb] for a 1-hr lag, 6.3 (95% CI, 2.6 to 9.9 ppb ) for a 4-hr lag, and 0.5 (95% CI, -1.1 to 2.1 ppb) for an 8-hr lag. These data provide new information concerning the lag structure between PM2.5 exposure and a respiratory health outcome in children with asthma.

Relationship between exhaled nitric oxide and atopy in Asian young adults

OBJECTIVES

The relationship between exhaled nitric oxide and atopy is controversial. The aim of this study was to determine the relationship between exhaled nitric oxide (FE(NO)) and atopy in Asian young adults.

METHODOLOGY

Subjects were assessed by: (i) the International Study of Asthma and Allergies in Childhood questionnaire to differentiate asthmatic from nonasthmatic and rhinitis from non-rhinitis subjects; (ii) skin prick testing to 10 allergens; and (iii) FE(NO) measurements performed online at a flow rate of 50 mL/s.

RESULTS

Complete results were available for 84 subjects. FE(NO) values were highest in atopic asthmatics (n = 34; median FE(NO), 59.8 p.p.b.; interquartile range, 30.4-85.5 p.p.b), followed by atopic nonasthmatics (n = 34; median, 38.4 p.p.b.; range, 16.7-49.3 p.p.b), nonatopic asthmatics (n = 5; median, 19.1 p.p.b.; range, 17.9-33.4 p.p.b), and lowest in nonatopic nonasthmatics (n = 11; median, 15.7 p.p.b.; range, 11.5-21.7 p.p.b). FE(NO) values were significantly higher in atopic (n = 68; median, 44.7 p.p.b.; range, 27.3-75.2 p.p.b) compared to nonatopic subjects (n = 16; median, 17.0 p.p.b.; range, 11.7-23.8 p.p.b.; P < 0.0001), regardless of asthma and rhinitis status. FE(NO) levels correlated with the severity of atopy (wheal size) for both asthmatic (r = 0.44, P = 0.005) and nonasthmatic subjects (r = 0.48, P = 0.001). There was no significant difference in FE(NO) levels between nonatopic asthmatics and nonatopic nonasthmatic subjects (P = 0.25).

CONCLUSIONS

Increased FE(NO) levels are more reflective of atopy rather than asthma, and increased nitric oxide production may be predominantly a feature of atopy in asthmatics.

Exhaled nitric oxide, total serum IgE and allergic sensitization in childhood asthma and allergic rhinitis

Exhaled nitric oxide (eNO) levels are correlated with several markers of atopy and inflammatory activity in the airways, but the relationship between eNO and total serum IgE has not been fully elucidated in the context of allergic sensitization. The aim of this study was to investigate the relationship between eNO, total serum IgE and allergic sensitization in childhood asthma and allergic rhinitis. eNO levels, lung function, skin prick tests and total serum IgE were determined in 109 children (mean age, 10.4 yr) with mild intermittent asthma and in 41 children (mean age, 10.1 yr) with allergic rhinitis; 25 healthy non-atopic children were recruited as controls. eNO levels (median) were significantly higher in patients with asthma (22.7 p.p.b.) and in those with allergic rhinitis (15.3 p.p.b.) than in healthy controls (5.9 p.p.b.). Children with allergic asthma had higher eNO levels than children with allergic rhinitis. A significant positive correlation was found between eNO and total serum IgE (asthma, r = 0.42, p < 0.0001; allergic rhinitis, r = 0.31, p < 0.01), and between eNO and the number of positive skin prick tests (asthma, r = 0.31, p < 0.0001; allergic rhinitis, r = 0.39, p < 0.01). eNO levels were better correlated with total IgE than with the number of positive skin prick tests. This correlation was independent of allergic sensitization. High total serum IgE represents a specific and predictive marker of eNO increase in children with asthma or allergic rhinitis. This finding adds further support to the hypothesis that increased serum IgE could be a marker itself of airway inflammation in patients with allergic disease.

Exhaled nitric oxide in relation to the clinical features of childhood asthma

BACKGROUND

Exhaled nitric oxide (ENO) has been shown to be a noninvasive marker of eosinophilic inflammation in asthmatic children. Few studies have evaluated the relationship between ENO levels and the clinical features of children with asthma. The aim of this study was to examine children attending a routine asthma clinic and evaluate the relationship between ENO levels and clinical parameters including decision making.

METHODS

Asthmatic children (n= 133, aged 5 to 14 years) attending a hospital asthma clinic were studied. ENO levels were measured and compared between subgroups of subjects according to recent symptoms, asthma control and treatment, and the clinician's decision (blinded to ENO levels) regarding further management.

RESULTS

ENO levels (median [IQR] ppb) were significantly elevated in children who had recent symptoms compared to those without recent symptoms (14.6 [6.5 to 45.3] vs. 6.0 [3.2 to 17.4], difference between medians 8.6, 95% confidence interval [CI] (1.8 to 13.9, p=0.004). ENO levels differed significantly between the controlled and uncontrolled subgroups (8.5 [4.2 to 26.4] vs. 26.4 [5.0 to 62.0], difference between medians 17.9, 95% CI 0.1 to 22.8, p=0.03) and between the three treatment decision subgroups (up, down, or unchanged; p < 0.001).

CONCLUSIONS

ENO levels are strongly related to the clinical features of childhood asthma and the clinical decision making process. To fully evaluate the role of ENO in the clinical management of asthma, this "proof of concept" study paves the way for prospective randomized trials of the inclusion of ENO levels in the decision making process in childhood asthma.

Fractional exhaled nitric oxide (FENO), lung function and airway hyperresponsiveness in naïve atopic asthmatic children

BACKGROUND

Measurement of fractional exhaled nitric oxide (FENO) is a noninvasive, simple, well-tolerated, and reproducible marker of airway inflammation. Asthmatic children with normal respiratory function could be affected by airway inflammation. The aim of this study was to assess the correlation between FENO and bronchial hyperesponsiveness (BHR) to methacholine, and between FENO and lung function in atopic children with intermittent asthma.

METHODS

Thirty-seven children (21 male), aged 7.2-14.4 years (median: 10.9 years), suffering from mild intermittent atopic asthma with a physician-diagnosed history of wheezing and/or chest tightness were studied. None had taken anti-asthmatic therapy for at least three months before the study. No child had symptoms of respiratory tract infection in the month before the study. All subjects underwent FENO measurement, pulmonary function testing and the methacholine provocation tests.

RESULTS

The mean percentages of FEV1 and FEF25-27 were 91.9+/-10.5 and 88.3+/-11.8, respectively. The mean FENO was 62.2+/-39.2 ppb and PC20 methacholine was 0.93 mg/ml+/-0.54. Significant correlations were identified between FENO and FEV1 (p<0.0059, r=0.468) and between FENO and FEF25-75 (p<0.0098, r=0.439). There was no correlation between FENO and logPC20 (p=0.14).

CONCLUSIONS

A single FENO measurement is probably of scarce prognostic and predictive value and it is not surprising to find discordance with BHR. We suggest that FENO measurement could represent a good marker of airway inflammation also in naïve atopic children with intermittent asthma. Repeated measurements over time are probably necessary to understand better the clinical implications of the data obtained in this study.

Correlations between exhaled nitric oxide levels and pH-metry data in asthmatics with gastro-oesophageal reflux

BACKGROUND

In gastro-oesophageal reflux (GER), micro-aspirations of gastric fluid may damage the epithelial surface of the airways, an important source of endogenous nitric oxide (NO).

OBJECTIVES

The aim of the study was to evaluate the possible influence of GER on fractional exhaled nitric oxide (FE(NO)) release.

METHODS

FE(NO) levels were compared in two age-matched groups of allergic children: (1) 20 with mild asthma, responding to standard anti-asthma pharmacologic therapy (asthmatic children) and (2) 12 with mild 'asthma-like symptoms' and GER.

RESULTS

No differences in pulmonary functions parameters (FEV(1), FVC and FEF(25-75%)) were found between the two groups of children (p > 0.1); FE(NO) levels were higher in asthmatic children compared with GER children (p = 0.0001). GER children underwent 24-hour oesophageal pH-metry, and possible correlations between pH-metry data, pulmonary functions and FE(NO) levels were evaluated. No correlations were found between pulmonary functions and pH-metry data (p > 0.05, each correlation). In contrast, correlations were observed between FE(NO) levels and pH-metry data, including (1) percentage of study time with pH < 4 (r = -0.80, p = 0.008), (2) number of episodes with pH < 4 (r = -0.76, p = 0.012), and (3) number of episodes >5 min with pH < 4 (r = -0.69, p = 0.02).

CONCLUSIONS

Thus, FE(NO) levels are lower in allergic children with 'asthma-like symptoms' and GER as compared to asthmatic children. The correlations between FE(NO) levels and pH-metry data suggest that inhalation of acid gastric content may interfere with NO production in the airways.

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.

Total and allergen-specific IgE levels in serum reflect blood eosinophilia and fractional exhaled nitric oxide concentrations but not pulmonary functions in allergic asthmatic children sensitized to house dust mites

Although elevated levels of serum immunoglobulin E (IgE) are considered the hallmark of atopic diseases, their clinical value in evaluating subjects with allergic disorders is under debate. To evaluate possible relationships between serum IgE levels and a variety of clinical parameters, 83 mild asthmatic children [10.98-year-old (2.95)], sensitized to house dust mites (HDM) Dermatophagoides pteronyssinus (Dp) or D. farinae (Df), were enrolled. As compared with normal control reference values detected in our laboratory, children with allergic asthma had higher blood eosinophil counts (expressed both as percentage and as absolute number) and higher fractional exhaled nitric oxide (FeNO) levels but similar values in pulmonary function parameters. In the allergic asthmatic population, serum levels of total, Dp-specific or Df-specific IgE correlated positively with eosinophil counts (Rho > or = 0.30, p < 0.01, each correlation) and FeNO levels (Rho > or = 0.33, p < 0.01, each correlation) but not with pulmonary function parameters (p > 0.1, each correlation). Finally, significant correlations, although moderate, were found in the allergic asthmatic population between eosinophil counts and FeNO levels (Rho > or = 0.42, p < 0.001, each correlation). Thus, in atopic children sensitized to HDM with mild intermittent asthma, IgE levels in blood appear to reflect systemic (blood eosinophils) and organ-specific (FeNO) markers of allergic inflammation but not pulmonary volumes or the degree of airflow limitation.

Measurement of offline exhaled nitric oxide in a study of community exposure to air pollution

As part of a large panel study in Seattle, Washington, we measured levels of exhaled nitric oxide (eNO) in children's homes and fixed-site particulate matter with aerodynamic diameters of 2.5 micro m or less (PM(2.5)) outside and inside the homes as well as personal PM(2.5) during winter and spring sessions of 2000-2001. Nineteen subjects 6-13 years of age participated; 9 of the 19 were on inhaled corticosteroid (ICS) therapy. Exhaled breath measurements were collected offline into a Mylar balloon for up to 10 consecutive days. Mean eNO values were 19.1 (SD +/- 11.4) ppb in winter sessions and 12.5 +/- 6.6 ppb in spring sessions. Fixed-site PM(2.5) mean concentrations were 10.1 +/- 5.7 microg/m(3) outside homes and 13.3 +/- 1.4 inside homes; the personal PM(2.5) mean was 13.4 +/- 3.2 microg/m(3). We used a linear mixed-effects model with random intercept and an interaction term for medications to test for within-subject-within-session associations between eNO and various PM(2.5) values. We found a 10 microg/m(3) increase in PM(2.5) from the outdoor, indoor, personal, and central-site measurements that was associated with increases in eNO in all subjects at lag day zero. The effect was 4.3 ppb [95% confidence interval (CI), 1.4-7.29] with the outdoor monitor, 4.2 ppb (95% CI, 1.02-7.4) for the indoor monitor, 4.5 ppb (95% CI, 1.02-7.9) with the personal monitor, and 3.8 ppb (95% CI, 1.2-6.4) for the central monitors. The interaction term for medication category (ICS users vs. nonusers) was significant in all analyses. These findings suggest that eNO can be used as an assessment tool in epidemiologic studies of health effects of air pollution.

Steroid-naive adolescents with mild intermittent allergic asthma have airway hyperresponsiveness and elevated exhaled nitric oxide levels

Although atopic asthma symptoms often seem to disappear around puberty, subjects in this age group may experience unexpected, often severe, asthma attacks. This may be related to persistence of untreated airway hyperresponsiveness/inflammation in a life period characterized by low perceptiveness of disease-related symptoms. This study was designed to evaluate the prevalence and the severity of bronchial hyperreactivity and the exhaled nitric oxide (FENO) levels in a group of steroid-naive asthmatic adolescents. Fifty-two patients with mild-intermittent asthma were studied, ages 12 to 16, sensitized to house dust mites; 22 age-matched controls, were also studied. Asthma patients showed FEV1, FEF25-75%, and FVC values not significantly different from controls, (p > 0.05, each comparison). By contrast, although none of the control subjects showed bronchial hyperreactivity, increased airway responsiveness to methacholine (MCh) was demonstrated in the majority of the patients and found to be severe in 36.5% (MCh PD20 > or = 400 microg or accumulative dose < or = 1220 microg) and moderate in 32.7% (MCh PD20 400-1400 microg or accumulative dose 1220-4620 microg). In addition, FENO concentrations were significantly higher in asthmatics, as compared with controls (20.4 +/- 5.3 ppb and 4.4 +/- 0.7 ppb, respectively; p < 0.01) and 83% of the patients had FENO levels higher than 8.9 ppb (i.e., > 2 standard deviations of the mean in control subjects). A positive, statistically significant correlation was found between FEF25-75% values and MCh PD20 (r = 0.358; p < 0.01) or MCh accumulative dose (r = 0.355; p < 0.05). No correlations were demonstrated between MCh responsiveness and FVC or FEV1 values or FENO levels and between FENO levels and pulmonary function parameters (p > 0.05). The high incidence of bronchial hyperresponsiveness to MCh and of airway inflammation (as demonstrated by the elevated FENO levels) in adolescents with mild asthma suggests the need for more accurate evaluation and, possibly, for early intervention with antiinflammatory drugs in a significant proportion of patients in this age group.

Nitric oxide in allergic airway inflammation

PURPOSE OF REVIEW

Exhaled nitric oxide has been proposed as a useful noninvasive marker of airway inflammation in asthma. Great efforts have been made to standardize the methodology for exhaled nitric oxide measurement in both children and adults. As a consequence there is now an opportunity to establish the precise relationship between exhaled nitric oxide, atopy and airway inflammation, and to investigate whether or not there is a role for the measurement of exhaled nitric oxide in the management of patients with asthma.

RECENT FINDINGS

A number of recent studies have investigated the relationship between exhaled nitric oxide and airway inflammation in asthma measured directly, using sputum induction, bronchoalveolar lavage and endobronchial biopsy. These measurements suggest that exhaled nitric oxide reflects eosinophilic airway inflammation in asthma, although there is no evidence for any relationship between exhaled nitric oxide and other airway inflammatory cells. Exhaled nitric oxide levels were found to be higher in atopic compared with nonatopic groups. These levels, however, are further elevated in atopic patients with asthma, suggesting that exhaled nitric oxide is not simply a marker of atopy. Although there is little evidence to support the routine use of measurement of exhaled nitric oxide in the management of patients with asthma, it may prove to be useful in assessing adherence to treatment with inhaled corticosteroids, or in the identification of patients in whom respiratory symptoms are associated with eosinophilic airway inflammation.

SUMMARY

There is good evidence that exhaled nitric oxide reflects eosinophilic airway inflammation in asthma. Well designed, long-term studies are needed to evaluate whether the addition of exhaled nitric oxide measurements to clinical and lung function assessment results in improved asthma control.

Nitric oxide in respiratory diseases

The formation and modulation of nitric oxide (NO) in the lungs is reviewed. Its beneficial and deleterious roles in airways diseases, including asthma, chronic obstructive pulmonary disease, and cystic fibrosis, and in animal models is discussed. The pharmacological effects of agents that modulate NO production or act as NO donors are described. The clinical pharmacology of these agents is described and the therapeutic potential for their use in airways disease is considered.

Concentrations of exhaled nitric oxide in asthmatics and subjects with allergic rhinitis sensitized to the same pollen allergen

BACKGROUND

Some studies have reported that the levels of exhaled nitric oxide (ENO) in asthmatics are similar to those in subjects with allergic rhinitis, and it has been postulated that atopic status might be the determinant of enhanced nitric oxide production in asthma.

OBJECTIVES

The aim of this study was to determine differences in ENO levels between asthmatics and subjects with allergic rhinitis sensitized to the same allergen, and to correlate these levels with airway responsiveness.

METHODS

Nineteen patients with asthma and 18 subjects with allergic rhinitis monosensitized to Parietaria pollen were enrolled in the study. ENO values and airway responsiveness to methacholine and adenosine 5'-monophosphate (AMP) were measured during the pollen season. The response to each bronchoconstrictor agent was measured by the provocative concentration required to produce a 20% fall in FEV1 (PC20). ENO was measured with the single-exhalation method.

RESULTS

The geometric mean (95% confidence interval) ENO values were significantly higher in asthmatics than in subjects with allergic rhinitis: 72.4p.p.b. (54.9-93.3p.p.b) vs. 44.7p.p.b. (30.9-64.6p.p.b., P = 0.03). In asthmatics, a significant correlation was found between ENO and PC20 AMP values (p = -0.57, P=0.02), whereas no correlation was detected between ENO and PC20 methacholine (p = -0.35, P = 0.14).

CONCLUSIONS

Our results suggest that atopy is not the only determinant of increased ENO levels detected in subjects with asthma, and that responsiveness to AMP may be a more sensitive marker for assessing airway inflammation in asthma compared to methacholine.

Plasma concentration of thymus and activation-regulated chemokine is elevated in childhood asthma

BACKGROUND

Thymus and activation-regulated chemokine (TARC) is responsible for the trafficking of T(H)2 lymphocytes into sites of allergic inflammation. Serum TARC levels correlate with the severity of atopic dermatitis. The relationship between this marker and the occurrence and severity of asthma has not been evaluated.

OBJECTIVE

We tested whether plasma TARC level is a useful marker for asthma and atopy in children.

METHODS

Plasma total IgE levels were measured by means of microparticle immunoassay, and specific IgE levels to common aeroallergens were measured by using a fluorescent enzyme immunoassay. We used a sandwich enzyme immunoassay to measure plasma TARC concentrations.

RESULTS

Sixty asthmatic children and 28 age- and sex-matched control subjects were recruited, with mean logarithmic plasma total IgE levels of 2.66 +/- 0.60 kIU/L and 1.74 +/- 0.58 kIU/L, respectively (P <.0001). The median plasma TARC concentration was higher in asthmatic patients without inhaled corticosteroid treatment (131.0 pg/mL) compared with those seen in steroid-treated patients (97.5 pg/mL) and control subjects (76.0 pg/mL; P =.01 and P <.0001, respectively). Plasma TARC concentration was found to correlate with total IgE level in plasma (r = 0.219, P =.04). This marker was also increased in subjects who were sensitized to cat allergen (P =.001) but not in subjects sensitized to other aeroallergens. Disease severity score, FEV(1) value, and atopy were not associated with increased plasma TARC levels.

CONCLUSION

Our results suggest that plasma TARC concentrations are elevated in childhood asthma. This marker is also linked to plasma total IgE levels and cat allergen sensitization.