Atopy influences exhaled nitric oxide levels in adult asthmatics

Airway Nitric Oxide in Children with HDM-Induced Allergic Rhinitis

BACKGROUND

Rhinitis is a common problem in children. Airway nitric oxide (NO) was proposed to represent eosinophilic inflammation.

OBJECTIVES

To evaluate airway NO level in children with house dust mite (HDM)-induced allergic rhinitis.

METHODS

Children aged 5 to 18 years old with moderate-severe persistent rhinitis and positive result for the HDM nasal provocation test (NPT) was enrolled. The nasal symptoms evaluated by total nasal symptom score (TNSS) and visual analog scale (VAS) were recorded. Skin prick test (SPT) to common aeroallergens, fractional exhaled nitric oxide (FeNO), nasal nitric oxide (nNO), and blood test for specific IgE (sIgE) to HDM was measured. Rhinitis severity was categorized as severe if the VAS score > 7.

RESULTS

Forty-eight children with HDM-induced allergic rhinitis with the mean age of 9.3 ± 2.4 years were enrolled. nNO levels and VAS score were significantly correlated (R = 0.398, P = .005). Children with severe rhinitis had significantly higher nNO levels than moderate rhinitis (1652.05 vs 941.30 parts per billion [ppb], P = .002), while there was no difference in FeNO level. ROC curve analysis demonstrated the cut-off value of nNO at 1350 ppb (AUC 0.764, 95% CI: 0.616-0.911, P = .002) for detecting severe HDM-induced allergic rhinitis with the sensitivity of 78% and the specificity of 71%. The level of FeNO in children who had HDM mean wheal diameter (MWD) > 8 mm was significantly higher than those with HDM MWD of 3 to 8 mm and those with a negative test (39.7 vs 14.3 vs 14.4 ppb; P = .006, respectively). Children who had sIgE to HDM < 0.35 KUA/L had significantly lower FeNO than those with sIgE to HDM 0.35 to 50 KUA/L and >50 KUA/L (9.5 vs 19.7 vs 40.4 ppb; P = .029, respectively).

CONCLUSIONS

Cut-off value for the diagnosis of severe HDM-induced chronic rhinitis was proposed. Rhinitis children who had a higher degree of HDM sensitization had a higher level of FeNO.

Fractional Exhaled Nitric Oxide and Nanomaterial Exposure in Workplaces

Background:

The widespread application of engineered nanomaterials (ENMs) and the increasing likelihood of general and occupational exposure raised concerns on their possible human health impact. ENMs, in fact, may induce alterations in different organ systems, and particularly in the respiratory tract. This makes it important to identify possible biomarkers of early lung effect in exposed workers. In this regard, the possibility to use the fractional exhaled levels of nitric oxide (FENO) in biological monitoring has attracted considerable interest.

Objective:

To comprehensively assess the role of FENO as a possible biomarker of lung effect in ENM exposed workers.

Methods:

A systematic search was performed on Pubmed, Scopus, and ISI Web of Knowledge databases according to the PRISMA guidelines.

Results:

Seven studies investigated FENO in workers exposed to different kinds of metal-(i.e. silver and gold), metal oxide- (titanium and silica dioxide), and carbon-based ENMs (carbon nanotubes). In general, no significant alterations were detected between exposed workers and controls.

Conclusions:

Definite conclusion on the function of FENO in occupational biological monitoring cannot be extrapolated due to the limited number of available studies and the small size of investigated populations. Additionally, the lack of environmental monitoring data and the fragmented knowledge on ENM modes of action prevent to establish dose-response relationships. Future research appears necessary to deeply define the possibility to employ FENO as an early biomarker of lung effects taking in consideration possible occupational exposure issues, i.e. differently characterized ENMs and work tasks, as well as individual influencing factors, i.e. smoking and atopy.

Discrimination Between Atopic, Allergic, and Asthmatic Volunteers for Human Exposure Studies on Sensory Irritation

Atopic, allergic, and especially asthmatic subjects might be particularly susceptible to sensory irritation induced by airborne chemicals compared to healthy individuals. Therefore, a good characterization of subjects is essential in inhalation exposure studies on sensory irritants. A total of 105 volunteers, 87% of whom reported to be non-allergic, participated in a medical examination that included skin prick test (SPT), measurements of total IgE, specific IgE (sIgE) to an ubiquitous allergen mix (sx1), and fractionated exhaled nitric oxide (FeNO), as well as pulmonary function and methacholine test. The median value of sIgE to sx1 was 0.20 kU/L (0.07-91.3 kU/L) and correlated significantly with total IgE (28.8 kU/L (2-756 kU/L)) and FeNO (14 ppb (5-100 ppb)). Forty-three subjects (41%) had sIgE to sx1 ≥ 0.35 kU/L and were classified as atopic. Thirty-five subjects, all also sx1-positive, were positive in SPT. Obstruction, small airway disease, and/or bronchial hyperreactivity were diagnosed in 18 subjects. Receiver operating characteristics (ROC) were performed to check whether signs of sensitization are useful to discriminate subjects with and without airway diseases. However, sx1, total IgE, FeNO, and SPT reached only low areas under the curve (AUC: 0.57-0.66). Although predominantly young and, according to their own statements, mostly non-allergic subjects participated in the study, almost half of them were atopic, and 10% had airway disease or bronchial hyperreactivity. This indicates that the validity of self-reported data might be inaccurate. In summary, diversified investigations of the allergy-related health status appear necessary for a thorough characterization of subjects for exposure studies on sensory irritants.

The Pattern of Sensitization Influences Exhaled and Nasal Nitric Oxide Levels in Young Adults

Nitric oxide (NO) from upper (nasal NO, nNO) or lower airways (fractional exhaled NO, FeNO) is considered a surrogate marker for Th2-type inflammation, which is influenced by atopy. The aim of this study was to analyze nNO and FeNO in regard to qualitative and quantitative aspects of sensitization. We evaluated 244 non-smoking young adults. All of them were first-year students recruited for a longitudinal study. An inhalation allergy screening tool was used for atopy definition (specific immunoglobulin E (sIgE) to sx1 ≥ 0.35 kU/L), and also sIgE response to three inhalant perennial allergens, house dust mite (HDM, d1), cat (e1), and dog (e5), was determined in the non-pollen season. With respect to sx1, 100 subjects could be classified as atopic. Sensitization to one, two, or three perennial allergens could be demonstrated in 46, 10, and 16 students, respectively. The subjects with positive IgE response to sx1, but not sensitized to HDM, cat, and/or dog, had FeNO levels comparable to those of non-atopic subjects (13.5 vs. 13.0 ppb, respectively; p = 0.485). These levels were significantly lower compared to atopic subjects being sensitized to any perennial allergen (19.0 ppb; p = 0.0003). After grouping the atopic subjects for perennial sensitization patterns, significantly higher FeNO could be detected in subjects with poly-sensitization (n = 26; 26.0 ppb) compared to the mono-sensitized ones (n = 46; 18.0 ppb; p = 0.023). Regarding nNO, no differences could be observed. Applying a two-way ANOVA, we could reveal a significant correlation of specific HDM-IgE CAP-class with FeNO (p < 0.0001) and nNO levels (p = 0.007). Finally, a significant relationship was found between nNO and FeNO for the whole cohort (p < 0.0001). In summary, our findings support the argument that atopy and perennial sensitization should be considered for the interpretation of NO.

The clinical usefulness of a new hand-held device for fractional exhaled nitric oxide measurement, NIOX VERO®, for diagnosing the etiology of cough

Cough is one of the most common symptoms seen in clinical practice, however the differential diagnosis is often difficult. The utility of fractional exhaled nitric oxide (FeNO) measurement in the differential diagnosis of the etiology of cough has been reported. NIOX VERO® (NOV) is a new hand-held device that will replace NIOX MINO®, but its diagnostic utility has not been fully elucidated in clinical practice. In this study, the performance of NOV for FeNO measurements was determined. We retrospectively analyzed 243 consecutive patients complaining cough. Among 243 patients, final diagnosis was cough variant asthma (CVA) in 74 (30.5%), bronchial asthma (BA) in 48 (19.8%), post-infectious cough (PIC) in 52 (21.4%), atopic chough (AC) in 24 (9.9%), gastroesophageal reflux disease (GERD) in 10 (4.1%), and Others in 35 (14.4%). FeNO values were significantly higher in CVA and BA as compared to PIC, AC, GERD, and Others. In the multivariate analysis, only FeNO value was identified as independent factors to discriminate CVA and non-CVA other than BA. These findings indicated that FeNO measured by using NOV could be used as a diagnostic marker of intractable cough, especially for the differential diagnosis of CVA from non-CVA. J. Med. Invest. 67 : 265-270, August, 2020.

Diagnostic utility of fractional exhaled nitric oxide in prolonged and chronic cough according to atopic status

BACKGROUND

Cough-variant asthma (CVA) and cough-predominant asthma (CPA) are the major causes of persistent cough in Japan. The utility of fractional exhaled nitric oxide (FeNO) measurement in the differential diagnosis of persistent cough has been reported, but the influence of atopic status, which is associated with higher FeNO levels, on the diagnostic utility of FeNO has been unknown.

METHODS

We retrospectively analyzed 105 non-smoking patients with prolonged and chronic cough that were not treated with corticosteroids and anti-leukotrienes.

RESULTS

CPA was diagnosed in 37 patients, CVA in 40, and non-asthmatic cough (NAC) in 28. FeNO levels were significantly higher in the CPA [35.8 (7.0-317.9) ppb] and CVA [24.9 (3.1-156.0) ppb] groups than in the NAC group [18.2 (6.9-49.0) ppb] (p < 0.01 by Kruskal-Wallis test). The optimal cut-off for distinguishing asthmatic cough (AC; CPA and CVA) from NAC was 29.2 ppb [area under the curve (AUC) 0.74, p < 0.01]. Ninety-one percent of subjects with FeNO levels ≥29.2 ppb had AC. Meanwhile, 40% of AC patients had FeNO levels <29.2 ppb. Stratified cut-off levels were 31.1 ppb (AUC 0.83) in atopic subjects vs. 19.9 ppb (AUC 0.65) in non-atopic subjects (p = 0.03 for AUC).

CONCLUSIONS

Although high FeNO levels suggested the existence of AC, lower FeNO levels had limited diagnostic significance. Atopic status affects the utility of FeNO levels in the differential diagnosis of prolonged and chronic cough.

Systemic and bronchial inflammation following LPS inhalation in asthmatic and healthy subjects

Background: Inhaled endotoxin is known to induce airway inflammation, causing bronchial hyper-reactivity.

Objective: We characterized the response to lipopolysaccharide-inhalation by measuring exhaled nitric oxide (eNO) and inflammatory mediators.

Patients and Methods : A total of 43 adult volunteers (13 asthmatics, 30 healthy controls) inhaled stepwise LPS every 30 min up to a cumulative dose of 100 µg (2.5, 10.5, 42, 45 µg). After each provocation and up to 24 h later, FEV1 was determined; the procedure was stopped when FEV1 declined more than 12.5%. We measured eNO, leucocytes, eosinophils, polymorphonuclear neutrophils (PMNs), C-reactive protein (CrP), lipopolysaccharide binding protein (LBP), eosinophilic cationic protein (ECP), leucotriene B4 (LTB4), thromboxane B2 (TXB2), and body temperature.

Results: Initial eNO values were higher in asthmatics ( P < 0.01), but only increased in an asthmatic subgroup. Marked differences were observed in the systemic response to LPS inhalation. Significant increases were found for CrP, LBP, and PMNs. There was no correlation between FEV1 decrease and basal eNO levels.

Conclusions: Inhalation of endotoxin was followed by clinical and laboratory signs of systemic inflammation, with asthmatics responding to the challenge similar as healthy subjects. Bronchial eNO increased only temporarily in asthmatics.

Evolution of exhaled nitric oxide levels throughout development and aging of healthy humans

It is not fully understood how the fraction of exhaled nitric oxide (FeNO) varies with age and gender in healthy individuals. We aim to describe the evolution of FeNO with age, giving special regard to the effect of gender, and to relate this evolution to natural changes in the respiratory tract.We studied 3081 subjects from NHANES 2007-08 and 2009-10, aged 6-80 years, with no self-reported diagnosis of asthma, chronic bronchitis or emphysema, and with normal values of blood eosinophils and C-reactive protein. The relationship of the mean values of FeNO to age, in all participants and divided by gender, was computed, and compared with changes in anatomic dead space volume and forced vital capacity. A change-point analysis technique and subsequent piecewise regression was used to detect breakpoints in the evolution of FeNO with age.Three distinct phases in the evolution of FeNO throughout the age range 6-80 years can be seen. FeNO values increase linearly between 6-14 years of age in girls and between 6-16 years of age in boys, in parallel with somatic growth. After that, FeNO levels plateau in both genders until age 45 years in females and age 59 years in males, when they start to increase linearly again. This increase continues until age 80.Our data clearly show a triphasic evolution of FeNO throughout the human age range in healthy individuals. This should be accounted for in development of reference equations for normal FeNO values.

Correlation of exhaled nitric oxide, nasal nitric oxide and atopic status: A cross-sectional study in bronchial asthma and allergic rhinitis

Objective:

Exhaled nitric oxide (FE_NO) and nasal nitric oxide (n NO) measurement is an area of ongoing research in the study of airway inflammation. The atopic status is known to influence the levels of FE_NO and n NO. This study was undertaken to study the relationship between nitric oxide measurements in bronchial asthma and allergic rhinitis along with their correlation with atopic profile of Indian population.

Materials and Methods:

Ninety subjects were recruited for the study comprising of 25 each of bronchial asthma (BA), allergic rhinitis (AR), bronchial asthma with allergic rhinitis (BA-AR) and 15 healthy controls. These were assessed for atopy and exhaled breath analysis of nitric oxide. The measurements of FE_NO and n NO levels were done using NIOX chemiluminescence analyzer. Atopy was assessed by skin prick testing (SPT) against 58 common aero-allergens and subjects with ≥1 positive SPT were labeled as atopic.

Results:

The BA-AR and BA groups had higher FE_NO levels in comparison to the control (P < 0.05) and AR group (P < 0.05). The AR and BA-AR groups had higher n NO levels compared to the control group (P < 0.05) and BA group (P < 0.05). The increasing FE_NO levels significantly correlated with the increase in the number of allergen sensitization in patients suffering from BA-AR (P < 0.05). However, the BA group showed a weaker positive correlation (P = 0.07).

Conclusion:

FE_NO is a non-invasive marker of airway inflammation. Also, FE_NO levels correlate with presence and degree of atopy in BA and AR. Simultaneously, n NO could be a surrogate marker of rhinitis.

Biomarker discovery in asthma and COPD by proteomic approaches

Asthma and chronic obstructive pulmonary disease (COPD) are multifactorial respiratory diseases, characterized by reversible and irreversible airway obstruction, respectively. Even if the primary causes of these diseases remain unknown, inflammation is a central feature that leads to progressive and permanent pulmonary tissue damage (airway remodeling) up to the total loss of lung function. Therefore, the elucidation of the inflammation mechanisms and the characterization of the biological pathways, involved in asthma and COPD pathogenesis, are relevant in finding new possible diagnostic/prognostic biomarkers and for the validation of new drug targets. In this context, current advances in proteomic approaches, especially those based on MS, provide new tools to facilitate the discovery-driven studies of new biomarkers in respiratory diseases and improve the clinical reliability of the next generation of biomarkers for these diseases consisting of multiple phenotypes. This review will report an overview of the current proteomic methods applied to the discovery of candidate biomarkers for asthma and COPD, giving a special emphasis to emerging MS-based techniques.

Exhaled nitric oxide as screening tool in subjects with suspected asthma without reversibility

BACKGROUND

As fractional exhaled nitric oxide (FeNO) has been evaluated only in certain settings for asthma diagnosis, we investigated whether FeNO values could predict positive methacholine challenge testing (expressed as PD20) in subjects with suspected asthma but without spirometric reversibility.

METHODS

Subjects with asthma-like symptoms and negative bronchodilation test were initially evaluated to undergo FeNO measurement and methacholine bronchial challenge. Diagnostic performance of FeNO to predict PD20 to methacholine <800 μg was examined by constructing receiver-operating characteristic curves.

RESULTS

A total of 112 subjects met the inclusion criteria. In all subjects, FeNO >32 ppb was associated with a sensitivity of 0.47 and a specificity of 0.85 for the identification of the PD20 <800 μg (AUC = 0.691, 95% CI = 0.6-0.775, p = 0.00002). In smokers, FeNO >11 ppb was associated with a sensitivity of 0.85 and a specificity of 0.5 for the identification of PD20 <800 μg (AUC = 0.625, 95% CI = 0.45-0.772, p = 0.18), while in atopics a FeNO level >26 ppb was associated with a sensitivity of 0.55 and a specificity of 0.85 (AUC = 0.677, 95% CI = 0.53-0.8, p = 0.02).

CONCLUSIONS

In subjects with symptoms compatible with asthma but without spirometric reversibility, specific cutoff levels for FeNO levels significantly predict the positive methacholine challenge, with significant confounding factors being atopy and current smoking.

[Interest for evaluation of bronchial inflammation in asthma]

Asthma is a heterogeneous chronic inflammatory disease. The respiratory functional tests are sometimes insufficient to confirm the diagnosis. Other tools are developed to estimate the bronchial inflammation such as tests of bronchial provocation, measure of exhaled nitric oxide, induced sputum and exhaled breath condensate. This review presents these non-invasive methods, approaches their interests on the identification of the disease and the treatment.

Fractional exhaled nitric oxide in healthy non-asthmatic 7-year olds and prenatal exposure to polycyclic aromatic hydrocarbons: nested regression analysis

The main goal of the study was to assess possible association between transplacental exposure to genotoxic PAH compounds assessed by the cord blood PAH-DNA adducts and fractional exhaled nitric oxide (FeNO) measured in healthy non-asthmatic children at the age of 7 years. The subjects included the subsample of 89 children who took part in the ongoing population based birth cohort study in Krakow and attended FeNO testing. The effect of transplacental PAH exposure was adjusted for potential confounders, such as maternal allergy and children's specific atopy to common domestic allergens.

RESULTS

FeNO values were significantly elevated in children with higher prenatal PAH exposure (gmean = 7.7 ppb; 95% CI: 5.8-10.2 ppb) compared with those at low exposure level (gmean = 3.8 ppb; 95% CI: 2.3-6.3) (P = 0.011). Children with maternal allergy had also significantly higher mean FeNO values (gmean = 13.7 ppb, 95% CI: 8.8-21.4 ppb) compared with the subjects whose mothers denied allergy (gmean = 5.6 ppb, 95% CI: 4.3-7.3 ppb) (P = 0.012). Similarly, FeNO values in atopic children were higher (gmean = 11.2 ppb; 95% CI: 3.8-32.8 ppb) than in non-atopic individuals (gmean = 6.0 ppb; 95% CI: 4.7-7.7 ppb, P = 0.079). The results of the nested multivariable linear regression analysis showed that both maternal allergy and sensitization of children to domestic aeroallergens jointly explained 10.4% of FeNO variance, however, the additional 10.9% was determined by prenatal PAH exposure.

CONCLUSION

FeNO is more than a marker useful for screening atopy or symptomatic bronchial inflammation and may also be a proxy for cytokine deregulation and "allergic response" phenotype possibly established in fetal period due to transplacental PAH exposure. Preliminary results of our study should encourage more studies on intrauterine PAH exposure and later respiratory symptoms.

Asthma outcomes: biomarkers

BACKGROUND

Measurement of biomarkers has been incorporated within clinical research studies of asthma to characterize the population and associate the disease with environmental and therapeutic effects.

OBJECTIVE

National Institutes of Health institutes and federal agencies convened an expert group to propose which biomarkers should be assessed as standardized asthma outcomes in future clinical research studies.

METHODS

We conducted a comprehensive search of the literature to identify studies that developed and/or tested asthma biomarkers. We identified biomarkers relevant to the underlying disease process progression and response to treatment. We classified the biomarkers as either core (required in future studies), supplemental (used according to study aims and standardized), or emerging (requiring validation and standardization). This work was discussed at an National Institutes of Health-organized workshop convened in March 2010 and finalized in September 2011.

RESULTS

Ten measures were identified; only 1, multiallergen screening to define atopy, is recommended as a core asthma outcome. Complete blood counts to measure total eosinophils, fractional exhaled nitric oxide (Feno), sputum eosinophils, urinary leukotrienes, and total and allergen-specific IgE are recommended as supplemental measures. Measurement of sputum polymorphonuclear leukocytes and other analytes, cortisol measures, airway imaging, breath markers, and system-wide studies (eg, genomics, proteomics) are considered as emerging outcome measures.

CONCLUSION

The working group participants propose the use of multiallergen screening in all asthma clinical trials to characterize study populations with respect to atopic status. Blood, sputum, and urine specimens should be stored in biobanks, and standard procedures should be developed to harmonize sample collection for clinical trial biorepositories.

Exhaled nitric oxide and spirometry in respiratory health surveillance

BACKGROUND

Exposure to pollutants in bakeries and hairdressing salons can cause airway syndromes varying from bronchial irritation to asthma. Workplace respiratory health surveillance aims to identify possible cases requiring further investigation.

AIMS

To compare the performance of fractional exhaled nitric oxide (FE(NO)) and spirometry for health surveillance of apprentice bakers (ABs) and apprentice hairdressers (AHDs). Determinants of FE(NO) were also identified.

METHODS

Symptoms and physician-diagnosed asthma were evaluated by questionnaire. FE(NO) was measured and spirometry was carried out. Subjects with elevated FE(NO) (FE(NO) > upper limit normal), airway obstruction [forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) < 95th percentile] and atopy (history of allergies) were identified.

RESULTS

A total of 126 apprentices (59 ABs and 67 AHDs) participated. Twenty-nine (23%) apprentices had abnormal tests: 4 had associated high FE(NO) and airway obstruction, while 25 had either high FE(NO) (n = 15) or airway obstruction (n = 10) alone. Compared with ABs (n = 16), AHDs (n = 13) had more asthma (38 versus 0%; P < 0.05) and atopy (62 versus 6%; P < 0.05). There was no difference in symptoms, smoking FE(NO) or airways obstruction. Among 97 subjects with normal tests, no differences existed between ABs (n = 53) and AHDs (n = 44). Average FE(NO) was increased in atopic non-smokers compared with atopic smokers and non-atopic subjects (P < 0.05). Smoking, a history of allergies, FEV(1)/FVC % observed and respiratory symptoms were the main determinants of FE(NO).

CONCLUSIONS

FE(NO) and spirometry were not overlapping dimensions in ABs and hairdressers, each test contributing unique information on the physiological status of the respiratory system. FE(NO) may provide added information on airway inflammation not provided by spirometry.

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.

Nitric oxide in both bronchoalveolar lavage fluid and serum is associated with pathogenesis and severity of antigen-induced pulmonary inflammation in rats

BACKGROUND

Nitric oxide (NO) is considered as a hallmark for allergic airway inflammation in asthmatics and animal models. But the correlation between NO and antigen-induced pulmonary inflammation (AIPI), a rat model for asthma, in varying genetic background population has not been completely understood.

OBJECTIVE

The objective in this study is to observe the different responsiveness to AIPI in two commonly used inbred rat strains and verify the correlation between NO from different sources and pathological parameters of AIPI by using Dark Agouti (DA), E3, F1 (E3 x DA), and F2 rat populations.

METHODS

AIPI was induced by systemically immunizing and intranasally challenging E3, DA, F1 (DA x E3), and F2 rats with ovalbumin (OVA). Pathological changes and mucus secretion in lungs were observed after hematoxylin and eosin (HE) and periodic acid Schiff (PAS) staining, whereas eosinophils in bronchoalveolar lavage fluid (BALF) were counted after Giemsa staining. Delayed-type hyperresponsiveness was determined by subcutaneous injection of OVA in ear. Total immunoglobulin E (IgE) and OVA-specific IgG1 were detected with enzyme-linked immunosorbent assay (ELISA). NO concentration was measured by the Griess method.

RESULTS

DA rats were unresponsive to OVA treatment, whereas E3 rats were susceptible to AIPI. F1 rats manifested the same responsiveness to OVA treatment as DA rats, and individual F2 rats showed the variable severity of AIPI. NO concentration in BALF and serum was significantly elevated in E3 rats but not in DA and F1 rats after OVA treatment. In F2 rats, NO concentration in serum was positively correlated with eosinophils in BALF, total IgE, and pathological scores, whereas NO concentration in BALF correlated only with eosinophils in BALF and total IgE.

CONCLUSION

DA and F1 rats are resistant, whereas E3 rats are sensitive, to AIPI. NO in serum can represent the severity of allergic inflammation and pathological changes in lungs in F2 population.

Utility of exhaled nitric oxide in the diagnosis and management of asthma

PURPOSE OF REVIEW

The fraction of nitric oxide in exhaled air (FeNO) is elevated in the presence of airway inflammation, and it may be a useful biomarker in asthma. The purpose of the present review is to highlight the current literature investigating the use of exhaled nitric oxide in the diagnosis and management of asthma.

RECENT FINDINGS

The measurement of exhaled nitric oxide has been studied in normal populations and in asthmatics. FeNO appears to be a useful screening tool for asthma, although nondisease factors may confound the interpretation of an elevated FeNO level. Clinical trials investigating the use of FeNO measurements in predicting asthma exacerbation and tailoring maintenance therapy have had varying success. Further studies incorporating individualized FeNO profiles into treatment algorithms are needed.

SUMMARY

FeNO shows promise as a tool in the diagnosis and treatment of asthma. However, further studies are needed to address outstanding questions about its exact role in guiding asthma management.

Two variants of occupational asthma separable by exhaled breath nitric oxide level

Exhaled nitric oxide (FE(NO)) has been used as a marker of asthmatic inflammation in non-occupational asthma, but some asthmatics have a normal FE(NO). In this study we investigated whether, normal FE(NO) variants have less reactivity in methacholine challenge and smaller peak expiratory flow (PEF) responses than high FE(NO) variants in a group of occupational asthmatics.

METHODS

We measured FE(NO) and PD(20) in methacholine challenge in 60 workers currently exposed to occupational agents, who were referred consecutively to a specialist occupational lung disease clinic and whose serial PEF records confirmed occupational asthma. Bronchial responsiveness (PD(20) in methacholine challenge) and the degree of PEF change to occupational exposures, (measured by calculating diurnal variation and the area between curves score of the serial PEF record in Oasys), were compared between those with normal and raised FE(NO). Potential confounding factors such as smoking, atopy and inhaled corticosteroid use were adjusted for.

RESULTS

There was a significant correlation between FE(NO) and bronchial hyper-responsiveness in methacholine challenge (p = 0.011), after controlling for confounders. Reactivity to methacholine was significantly lower in the normal FE(NO) group compared to the raised FE(NO) group (p = 0.035). The two FE(NO) variants did not differ significantly according to the causal agent, the magnitude of the response in PEF to the asthmagen at work, or diurnal variation.

CONCLUSIONS

Occupational asthma patients present as two different variants based on FE(NO). The group with normal FE(NO) have less reactivity in methacholine challenge, while the PEF changes in relation to work are similar.

An elevated bronchodilator response predicts large airway inflammation in mild asthma

Exhaled nitric oxide (eNO) is elevated in asthmatics and is a purported marker of airway inflammation. The bronchodilator response (BDR) has also been shown to correlate with markers of airway inflammation, including eNO at 50 ml/sec (FE(NO,50)) which is comprised of NO from both the proximal and distal airways. Using eNO at multiple flows and a two-compartment model of NO exchange, the eNO signal can be partitioned into its proximal [J'aw(NO) (nl/sec)] and distal contributions [CA(NO) (ppb)]. We hypothesized that the BDR reflects the inflammatory status of the larger airways with smooth muscle, and thus would correlate with J'aw(NO). In 179 predominantly (95%) Hispanic children with mild asthma (69 steroid naïve), and 21 non-asthmatic non-atopic controls, spirometry and eNO at multiple flows were measured prior and 10 min following inhalation of albuterol. A trumpet-shaped axial diffusion model of NO exchange was used to characterize J'aw(NO) and CA(NO). The BDR correlated moderately (r = 0.44) with proximal airway NO (J'aw(NO)), but weakly (r = 0.26) with distal airway/alveolar NO (CA(NO)), and only in inhaled corticosteroid naïve asthmatics. A BDR cut point as low as >or=8% had a positive predictive value of 83% for predicting an elevated J'aw(NO) or FE(NO,50). We conclude that the BDR reflects inflammation in the large airways, and may be an effective clinical tool to predict elevated large airway inflammation.

Exhaled nitric oxide in evaluation of young adults with chronic cough

BACKGROUND

Bronchial asthma (A) is frequently diagnosed in patients with chronic cough. The study was conducted to determine whether an evaluation of fractional exhaled nitric oxide (FeNO) concentration can be used as a screening test for asthma in young adults with chronic cough (CCP).

METHODS

The study was performed on 540 (mean age 26.5; range 18-45 years), nonsmoking young CCP. All patients had resting spirometry within normal limits and no abnormalities on chest radiographs. Skin prick tests with common aeroallergens, bronchial provocation challenge with histamine, and evaluation of FeNO concentration were performed in all patients. One hundred healthy, nonsmoking, nonatopic subjects were used as control subjects (HC).

RESULTS

Asthma (A) was diagnosed in 178 CCP (32.96%). Other frequent diagnoses included rhinitis/sinusitis (R) and gastroesophageal reflux (GERD). The median FeNO concentration in A (86 ppb; 95% CI 72 to 94,5 ppb) was significantly greater than in R (37 ppb; 95% CI 35,6 to 42,9 ppb; p < 0.0001), GERD (14,8 ppb; 95%CI 13.3 to 16.2 ppb; p < 0.0001), or in HC (13 ppb; 95%CI 11 to 15 ppb; p < 0.0001). Significant correlation was found between log(FeNO) and bronchial reactivity expressed as log(PC20) (r = -0.529; 95%CI -0.616 to -0.429; p < 0.0001), but even stronger correlation was demonstrated between log(FeNO) and peripheral blood eosinophilia (r = 0.757; 95%CI 0.717 to 0.792). Receiver Operator Characteristic (ROC) curve analysis revealed that CCP can be screened for A by measuring FeNO concentration. Using 40 ppb as a cut-off value for the FeNO concentration, the specificity 82.6% and sensitivity 88.3% can be achieved.

CONCLUSION

In clinical practice, assessment of FeNO concentration can be used as a screening test for asthma in young adults who have chronic cough.

Fractional exhaled nitric oxide in asthma: an update

In asthma, clinical symptoms and lung function are insensitive in reflecting the underlying airway inflammation, and monitoring of this process has only recently become available. Fractional exhaled nitric oxide (Fe(NO)) is now recognized as a reliable surrogate marker of eosinophilic airway inflammation and offers the advantage of being completely non-invasive and very easy to obtain. This review summarizes the clinical use of Fe(NO) in asthma. It covers the relationship between Fe(NO) and the underlying eosinophilic inflammation, the pathophysiology and production of Fe(NO), technical aspects of Fe(NO) measurement and potential confounding factors in interpreting levels. Fe(NO) reference values and the role of Fe(NO) in asthma assessment, diagnosis and management are also discussed.

Correlation between airway inflammation and loss of deep-inhalation bronchoprotection in asthma

BACKGROUND

One of the characteristic features of the hyperresponsive airway smooth muscle in asthma is the loss of deep-inhalation bronchoprotection and bronchodilation. The airway of individuals with asthma is also characterized by inflammation.

OBJECTIVE

To evaluate whether the loss of deep-inhalation bronchoprotection is correlated with the degree of inflammation in the asthmatic airway.

METHODS

Eighteen study participants performed 2 methacholine challenges (identical doses), 1 with deep inhalations and 1 without, separated by at least 24 hours. Airway inflammation was evaluated by measurement of fraction of exhaled nitric oxide (FE(NO)) and induced sputum eosinophils.

RESULTS

A significant negative correlation was found between the degree of deep-inhalation bronchoprotection and airway inflammation when measured by FE(NO) (P = .02, r = .54, n = 18) and by percentage of eosinophils (P = .002, r = .76, n = 12). A significant positive correlation was also found between the FE(NO) and percentage of eosinophils (P = .009, r = .68, n = 12).

CONCLUSIONS

Deep-inhalation bronchoprotection was significantly impaired in individuals with greater airway inflammation. This finding suggests that therapy directed at decreasing airway inflammation may promote the recovery of normal deep-inhalation bronchoprotection.

Atopic sensitization to common allergens without symptoms or signs of airway disorders does not increase exhaled nitric oxide

BACKGROUND

Elevated fractional exhaled nitric oxide (FENO) associates positively with symptomatic atopy among asthmatics and in the general population. It is, however, unclear whether sensitization to common allergens per se- as verified with positive skin prick tests--affects FENO in healthy individuals.

OBJECTIVE

The aim of this study was to examine the association between FENO and sensitization to common allergens in healthy nonsmoking adults with no signs or symptoms of airway disorders.

METHODS

FENO measurements (flow rate: 50 mL/s), skin prick tests to common inhalant allergens, structured interviews, spirometry, bronchodilatation tests and bronchial histamine challenges were performed on a randomly selected population of 248 subjects. Seventy-three of them (29%) were nonsmoking asymptomatic adults with no history of asthma, persistent or recurrent upper or lower airway symptoms and no signs of airway disorders in the tests listed above.

RESULTS

FENO concentrations were similar in skin prick test positive (n = 32) and negative (n = 41) healthy subjects, with median values of 13.2 and 15.5 ppb, respectively (P = 0.304). No correlation appeared between FENO and the number of positive reactions (r = -0.138; P = 0.244), or the total sum of wheal diameters (r = -0.135; P = 0.254). The nonparametric one-tailed 95% upper limits of FENO among skin prick positive and negative healthy nonsmoking subjects were 29 and 31 ppb, respectively.

CONCLUSIONS

Atopic constitution defined as positive skin prick test results does not increase FENO in healthy nonsmoking adults with no signs or symptoms of airway disorders. This suggests that same reference ranges for FENO can be applied to both skin prick test positive and negative subjects.

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.

Sputum proteomics in inflammatory and suppurative respiratory diseases

RATIONALE

Markers of inflammatory activity are important for assessment and management of many respiratory diseases. Markers that are currently unrecognized may be more valuable than those presently believed to be useful.

OBJECTIVES

To identify potential biomarkers of suppurative and inflammatory lung disease in induced sputum samples.

METHODS

Induced sputum was collected from 20 healthy control subjects, 24 patients with asthma, 24 with chronic obstructive pulmonary disease, 28 with cystic fibrosis (CF), and 19 with bronchiectasis. Twelve patients with CF had sputum sampled before and after antibiotic therapy for an infective exacerbation. The fluid phase of induced sputum was analyzed by surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectroscopy on three protein array surfaces. Some protein markers were selected for identification, and relevant ELISA assays sought. For 12 patients with CF, both SELDI-TOF and ELISA monitored changes in inflammatory responses during infective exacerbations.

MEASUREMENTS AND MAIN RESULTS

SELDI-TOF identified potential biomarkers that differentiated each of the disease groups from healthy control subjects: at a significance of P < 0.01, there were 105 for asthma, 113 for chronic obstructive pulmonary disease, 381 for CF, and 377 for bronchiectasis. Peaks selected for protein identification yielded calgranulin A, calgranulin B, calgranulin C, Clara cell secretory protein, lysosyme c, proline rich salivary peptide, cystatin s, and hemoglobin alpha. On treatment of an infective CF exacerbation, SELDI-TOF determined falls in levels of calgranulin A and calgranulin B that were mirrored by ELISA-measured falls in calprotectin (heterodimer of calgranulins A and B).

CONCLUSIONS

Proteomic screening of sputum yields potential biomarkers of inflammation. The early development of a clinically relevant assay from such data is demonstrated.

Exhaled nitric oxide in the diagnosis and management of asthma

PURPOSE OF REVIEW

Gaseous nitric oxide is present in our exhaled breath and may be a biomarker for asthma. The purpose of the present paper is to review recent studies that have explored the potential of exhaled nitric oxide as a biomarker for asthma diagnosis and treatment.

RECENT FINDINGS

The upper limit of exhaled nitric oxide has been described in several populations, using a standard methodology. Measurements of exhaled nitric oxide have good specificity but relatively poor sensitivity for diagnosing asthma. The inter- and intra-subject variability of exhaled nitric oxide values in asthmatics remains uncertain. Clinical trials have used exhaled nitric oxide to guide steroid treatment in asthmatics with varied success. The greatest success is in studies where inhaled corticosteroids are reduced and/or withdrawn in stable asthmatics. These pioneering clinical trials have given insight into how exhaled nitric oxide might be a useful index of control of eosinophilic airway inflammation.

SUMMARY

Measurements of exhaled nitric oxide have the potential to be useful in the management of allergic asthma and the answers to a number of important questions are awaited.

Reproducibility of exhaled nitric oxide in smokers and non-smokers: relevance for longitudinal studies

Background

Currently, there is much interest in measuring fractional exhaled nitric oxide (FE_NO) in populations. We evaluated the reproducibility of FE_NO in healthy subjects and determined the number of subjects necessary to carry out a longitudinal survey of FE_NO in a population containing smokers and non-smokers, based on the assessed reproducibility.

Methods

The reproducibility of FE_NO was examined in 18 healthy smokers and 21 non-smokers. FE_NO was assessed once at 9 AM on five consecutive days; in the last day this measurement was repeated at 2 PM. Respiratory symptoms and medical history were assessed by questionnaire. The within- and between-session repeatability of FE_NO and log-transformed FE_NO was described. The power of a longitudinal study based on a relative increase in FE_NO was estimated using a bilateral t-test of the log-transformed FE_NO using the between-session variance of the assay.

Results

FE_NO measurements were highly reproducible throughout the study. FE_NO was significantly higher in males than females regardless of smoking status. FE_NO was positively associated with height (p < 0.001), gender (p < 0.034), smoking (p < 0.0001) and percent FEV₁/FVC (p < 0.001) but not with age (p = 0.987). The between-session standard deviation was roughly constant on the log scale. Assuming the between-session standard deviation is equal to its longitudinal equivalent, either 111 or 29 subjects would be necessary to achieve an 80% power in detecting a 3% or a 10% increase in FE_NO respectively.

Conclusion

The good reproducibility of FE_NO is not influenced by gender or smoking habits. In a well controlled, longitudinal study it should allow detecting even small increases in FE_NO with a reasonable population size.

Airway biomarkers of the oxidant burden in asthma and chronic obstructive pulmonary disease: current and future perspectives

The pathogenesis of asthma and chronic obstructive pulmonary disease (COPD) has been claimed to be attributable to increased systemic and local oxidative stress. Detection of the oxidant burden and evaluation of their progression and phenotypes by oxidant biomarkers have proved challenging and difficult. A large number of asthmatics are cigarette smokers and smoke itself contains oxidants complicating further the use of oxidant biomarkers. One of the most widely used oxidant markers in asthma is exhaled nitric oxide (NO), which plays an important role in the pathogenesis of asthma and disease monitoring. Another oxidant marker that has been widely investigated in COPD is 8-isoprostane, but it is probably not capable of differentiating asthma from COPD, or even sensitive in the early assessment of these diseases. None of the current biomarkers have been shown to be better than exhaled NO in asthma. There is a need to identify new biomarkers for obstructive airway diseases, especially their differential diagnosis. A comprehensive evaluation of oxidant markers and their combinations will be presented in this review. In brief, it seems that additional analyses utilizing powerful tools such as genomics, metabolomics, lipidomics, and proteomics will be required to improve the specificity and sensitivity of the next generation of biomarkers.

Determinants of exhaled nitric oxide levels in healthy, nonsmoking African American adults

BACKGROUND

Asthma is a significant cause of morbidity and mortality for African Americans. Fraction of exhaled nitric oxide (FeNO) levels are increased in patients with asthma, and airway levels of nitric oxide metabolites regulate airway inflammation and airway diameter. More needs to be known about the factors that regulate FeNO. There is a need for FeNO reference values for African Americans.

OBJECTIVE

We sought to establish reference values and identify factors associated with FeNO levels in healthy African American adults.

METHODS

FeNO levels were measured in 895 healthy, nonsmoking African Americans between the ages of 18 and 40 years. FeNO measurements were repeated in 84 subjects. Factors potentially associated with FeNO were measured, including blood pressure, height, weight, and serum total IgE, eosinophil cationic protein, C-reactive protein, and nitrate levels. Data on respiratory symptoms, including upper respiratory tract infection (URI) symptoms, were collected. Univariate and multivariate analyses of the relationship between these variables and FeNO levels were performed.

RESULTS

In healthy, nonsmoking African Americans FeNO levels were stable during repeated measurements (intraclass correlation coefficient, 0.81). Sex (P < .0001), serum total IgE levels (P < .0001), and current URI symptoms (P = .0002) contributed significantly to FeNO variability but together accounted for less than 50% of the variation in FeNO levels.

CONCLUSION

The high correlation between repeated measurements of FeNO and the low correlation coefficients of known factors associated with FeNO suggest that other factors might contribute substantially to variability of FeNO levels in African Americans.

Portable exhaled nitric oxide as a screening tool for asthma in young adults during pollen season

BACKGROUND

The fraction of exhaled NO (FeNO) is valuable for the follow-up of asthmatic patients. However, its usefulness as a screening tool for asthma is not established.

METHODS

We screened a population of 961 university students with a modified European Community Respiratory Health Survey questionnaire that has been previously used for the screening of respiratory symptoms related to asthma. All subjects with a positive answer to at least one question (n = 149) were submitted to FeNO measurement with a portable nitric oxide analyzer. Subsequently, they were submitted to spirometry and evaluated by a physician blinded to FeNO measurements. Seventy students with no respiratory symptoms served as control subjects.

RESULTS

Asthma was diagnosed in 63 subjects, and allergic rhinitis was diagnosed in 57 subjects. Asthmatics presented higher FeNO values than control subjects (median, 20 parts per billion [ppb]; interquartile range, 14 to 31 ppb; vs median, 11 ppb; interquartile range, 7 to 13 ppb, respectively; p < 0.0001), whereas they did not differ from patients with allergic rhinitis (median, 17 ppb; interquartile range, 12 to 23 ppb; p = 0.28). FeNO values > 19 ppb presented 85.2% specificity and 52.4% sensitivity for the diagnosis of asthma (area under the curve [AUC], 0.723). The diagnostic performance of FeNO was better in nonsmokers (AUC, 0.805), yet FeNO values > 25 ppb were characterized by specificity > 90% for the diagnosis of asthma both in smokers and in nonsmokers. However, FeNO was not a good marker for the differentiation between asthma and allergic rhinitis.

CONCLUSIONS

FeNO measurement with a portable analyzer is useful for the screening for asthma in young adults. Significant confounding factors are allergic rhinitis and current smoking.

Associations between antioxidant status, markers of oxidative stress and immune responses in allergic adults

BACKGROUND

There has been growing interest in the role of antioxidant function in controlling inflammatory disease states, such as allergy. This study investigated the relationship between antioxidant status, markers of airways inflammation [exhaled nitric oxide (eNO)], oxidative stress (F(2) isoprostanes) and immune responses in allergic adults.

METHODS

Antioxidants (vitamins C, E, beta-carotene and selenium) and total antioxidant capacity (tAC) in serum were examined in relation to eNO, plasma F(2) isoprostanes and peripheral blood mononuclear cell (PBMC) cytokine and lymphoproliferative response to house dust mite (HDM) allergen, Staphylococcus enterotoxin B (SEB), phytohaemaglutinin (PHA) and lipopolysaccharide (LPS) in 54 allergic adults.

RESULTS

Firstly, levels of specific vitamins did not correlate with tAC. Secondly, we did not see any evidence that specific vitamin levels (or tAC) were associated with either polarization or attenuation of in vitro immune responses. If anything, there were positive correlations between antioxidant (vitamin C and selenium) levels and HDM allergen responses [lymphoproliferation (selenium; r=0.35, P=0.013) and both Th2 IL13 (vitamin C; tau=0.254, P=0.028) and Th1 IFN-gamma (vitamin C; tau=0.302, P=0.009) responses]. There were also significant positive relationships between antioxidant levels and IL-10 responses to polyclonal stimulation by SEB (r=0.292, P=0.036) and LPS (r=0.34, P=0.015) (beta-carotene) and PHA (r=0.34, P=0.021) (tAC). Thirdly, although airways inflammation (eNO) was associated with both in vitro and in vivo (skin test reactivity) to HDM, we did not see any correlation between eNO and oxidative stress (F(2)-isoprostanes). Finally, there were no consistent relationships between oxidative stress and immune responses.

CONCLUSION

There was no evidence that higher antioxidant levels were associated with reduced allergen responsiveness in allergic adults. If anything, antioxidant status was associated with increased immune responsiveness. The significance of this needs to be addressed in future intervention studies.

Diagnostic tests for asthma in firefighters

BACKGROUND

Subjects with asthma do not meet medical requirements for professions such as firefighting.

OBJECTIVE

To prospectively determine the diagnostic value of respiratory symptoms and various tests used in the assessment of asthma in a cohort of firefighters.

METHODS

A questionnaire, spirometry, direct and indirect airway challenge tests, exhaled nitric oxide, and skin-prick tests were administered prospectively to 101 of 107 firefighters employed in Basel, Switzerland. Asthma was defined as the combination of respiratory symptoms with airway hyperresponsiveness.

RESULTS

Six of 101 firefighters (6%) had physician-diagnosed asthma, which could be confirmed in 4 firefighters. In contrast, asthma was diagnosed in 14% (14 of 101 firefighters). Wheezing was the most sensitive symptom for the diagnosis of asthma (sensitivity, 78%; specificity, 93%). Other respiratory symptoms showed a higher specificity than wheezing but a markedly lower sensitivity. Bronchial airway challenge with mannitol was the most sensitive (92%) and specific (97%) diagnostic test for asthma. Using a cutoff point of 47 parts per billion, nitric oxide had a similar specificity (96%) but lower sensitivity (42%) compared to the direct (methacholine) and indirect (mannitol) airway challenge tests.

CONCLUSION

Asthma was considerably underdiagnosed in firefighters. The combination of a structured symptom questionnaire with a bronchial challenge test allows to identify patients with asthma and should routinely be used in the assessment of active firefighters and may be of help when evaluating candidates for this profession.

Effect of inhaled steroid therapy on exhaled nitric oxide and bronchial responsiveness in children with asthma

Inhaled steroid therapy is reported to reduce the level of exhaled nitric oxide (eNO), but the effects of inhaled corticosteroids (ICS) on bronchial hyperresponsiveness (BHR) have been controversial. The aim of this study was to determine the effects of ICS on the relationship between eNO and BHR. Twenty-six children with asthma were recruited, including 14 children who were receiving ICS (ICS group) and 12 who were not (ICS-naive group). The fractional exhaled nitric oxide concentration (FE(NO)) was examined by the recommended online method. To evaluate BHR, an acetylcholine challenge test was performed. In the ICS-naive group, FE(NO) was significantly correlated with PC20 (p < 0.05, r = -0.70), but not in the ICS group. In conclusion, FE(NO) was significantly correlated with BHR in the ICS-naive group, but this relationship was not present in the ICS group. Our results suggest that the use of ICS should be taken into consideration when evaluating the relation between BHR and airway inflammation.

Height, age, and atopy are associated with fraction of exhaled nitric oxide in a large adult general population sample

STUDY OBJECTIVES

The fraction of exhaled nitric oxide (Feno) is elevated in subjects with asthma and atopy, and it has been proposed to be a noninvasive marker of airway inflammation. In addition to asthma and atopy, there is limited information about the determinants of Feno in a general population.

DESIGN

Cross-sectional.

SETTING

A random adult general population sample.

PARTICIPANTS

A total of 2,200 subjects, 1,111 women and 1,089 men, aged 25 to 75 years.

INTERVENTIONS

The subjects were examined with regard to Feno, pulmonary function, anthropometric variables, and blood samples for Ig E, and completed a respiratory questionnaire. The associations between different determinants and Feno were analyzed with multiple linear regression models.

RESULTS

The median value of Feno was 16.0 parts per billion (ppb), ranging from 2.4 to 199 ppb. Height, age, atopy, reporting of asthma symptoms in the last month, and reported use of inhaled steroids were positively associated with Feno. Current smokers had lower values of Feno. Gender was not associated with Feno.

CONCLUSIONS

In this random adult population sample, height, but not gender, was associated with Feno. Furthermore, asthma symptoms in the last month, reported use of inhaled steroids, and atopy were positively and independently associated with Feno, while there was a negative association with smoking.

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.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

The use of exhaled nitric oxide concentration to identify eosinophilic airway inflammation: an observational study in adults with asthma

BACKGROUND

Assessment of eosinophilic airway inflammation may be helpful in the management of asthma. Nitric oxide (NO) has potential advantages as a tool to monitor airway inflammation although little is known about the relationship between NO and eosinophilic airway inflammation and the factors which influence it.

METHODS

We set out to define the relationship between exhaled NO and the sputum eosinophil count, identify the exhaled NO concentration that best identified a sputum eosinophil count >3% and investigate the impact of several potential confounding factors in 566 consecutive patients with varying severity of asthma. Finally we examined the ability of exhaled NO concentrations measured at differing exhalation flows to identify the presence of a sputum eosinophilia.

RESULTS

We found a significant positive relationship between exhaled NO and sputum eosinophil count (R(2)=0.26, P<0.001) which was best described using a non-linear model. There were no clinically important confounding factors to this model. In non-smokers an exhaled NO concentration of >8.3 p.p.b. at 250 mL/s gave 71% sensitivity and 72% specificity for identifying a sputum eosinophil count of >3%.

CONCLUSIONS

This value of exhaled NO would seem to be the best for identifying significant eosinophilic airway inflammation. It is applicable to a wide range of non-smoking patients with asthma; exhalation flow does not alter the ability of exhaled NO concentration to detect a sputum eosinophilia.

Exhaled nitric oxide predicts airway hyper-responsiveness to hypertonic saline in children that wheeze

BACKGROUND

Exhaled nitric oxide (eNO) has shown good validity for the assessment of airway inflammation in asthmatic children. In large-scale epidemiological studies, this method would be preferred above airway challenge tests, because it is a quick and easy applicable tool.

OBJECTIVE

In this study, we aimed to assess the discriminatory capacity of eNO, and prechallenge FEV1 for airway hyper-responsiveness (AHR) in 8-13-year old schoolchildren.

MATERIALS AND METHODS

Parents completed the ISAAC questionnaire, and children were tested for atopy, AHR to hypertonic (4.5%) saline (HS), and eNO. Diagnostic value was assessed by the area under the receiver operating curves (ROC), and calculation of positive and negative predicted values at different cut-off points for eNO and prechallenge FEV1.

RESULTS

Areas under the ROC-curves of AHR were 0.65 for eNO and 0.62 for FEV1. Values increased to 0.71 and respectively 0.75 for a combined occurrence of AHR and current wheeze. Highest sensitivity and specificity were obtained at a cut-off value of 43 ppb for eNO and 103% predicted for FEV1. At these cut-off values, the positive predictive values for the presence of AHR in symptomatic children were respectively 83% (eNO) and 33% (FEV1), and negative predictive values in asymptomatic children were, respectively, 90 (eNO) and 80% (FEV1).

CONCLUSION

Exhaled nitric oxide is a valid screening tool for AHR to HS in children that present with current wheeze, and it outperforms FEV1 as a predictor of AHR.

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.

Measuring exhaled nitric oxide levels in adults: the importance of atopy and airway responsiveness

BACKGROUND

Raised exhaled nitric oxide (Feno) levels have been associated with asthma. However, we have found that in children, Feno was increased in atopic children with increased airway responsiveness (AR), and this was independent of a diagnosis of asthma.

STUDY OBJECTIVES

The current study was designed to test the hypothesis that in adults there is no association between Feno and asthma after controlling for atopy and AR.

MEASUREMENTS

One hundred fifteen adults (77 women; mean age, 41 years) underwent an assessment that included Feno measurements, spirometry, skin-prick testing, blood eosinophil count, and inhaled histamine challenge (results are expressed as a dose-response slope [DRS]).

RESULTS

When only atopic individuals were considered (n = 73), Feno was positively associated with the DRS (p = 0.003), male gender (0.02), and negatively associated with current smoking (p = 0.09). Only male gender (p = 0.03) was associated with Feno among nonatopic individuals (n = 36). In multivariate analysis, there was no association between Feno and current asthma, current wheeze, or asthma ever.

CONCLUSIONS

We conclude that in adult subjects, elevated Feno measurements are associated with a phenotype characterized by atopy and increased AR regardless of the presence of asthma or asthma-like symptoms.

Exhaled nitric oxide is reduced in infants with rhinorrhea

In infants, the effect of colds and other respiratory tract infections (RTI) on exhaled nitric oxide (FE(NO)) is not clear. In this study, we measured FE(NO) in 24 infants (14 boys) who presented with rhinorrhea, with or without cough but not wheeze. Twelve of these infants had a history of recurrent wheeze. Levels were compared with a group of 23 healthy infants (13 boys). Further, 8 infants (5 with a history of recurrent wheeze) with rhinorrhea were tested after symptoms had resolved. Infants with rhinorrhea had significantly lower FE(NO) than the healthy infants (11.9 vs. 23.8 ppb, respectively, P < 0.0007). Levels increased from 7.5 ppb to 34.1 ppb in the 8 infants tested with and without symptoms (P = 0.0002). Infants with rhinorrhea have reduced FE(NO), irrespective of their respiratory history.

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.

Exhaled nitric oxide: relation to sensitization and respiratory symptoms

BACKGROUND

Conflicting data have been presented as to whether nitric oxide (NO) in exhaled air is merely reflecting atopy rather than airway inflammation.

OBJECTIVE

To investigate the relationship between exhaled NO (eNO) and nasal NO (nNO), respiratory symptoms, and atopy, in the context of a cross-sectional study of the respiratory health of bleachery workers.

METHODS

Two hundred and forty-six non-smoking bleachery and paper-mill workers answered a questionnaire and were examined by measurements of eNO and nNO and spirometry, outside the pollen season. Blood samples were collected and analysed for specific IgE against common aeroallergens (birch, timothy, cat and house dust mite). Atopy was defined as a positive Phadiatop trade mark test.

RESULTS

The atopic and the non-atopic subjects without asthma or rhinitis had similar levels of eNO. Subjects reporting asthma or rhinitis who were also sensitized to perennial allergens had higher levels of eNO, whereas those sensitized to only seasonal allergens had similar eNO levels as non-atopic subjects with asthma or rhinitis. In multiple linear regression models adjusted for nNO, eNO was associated with asthma and sensitization to perennial allergens.

CONCLUSION

The results indicate that only atopic subjects who have recently been exposed to the relevant allergen have elevated levels of eNO. Atopic subjects who are not being exposed to a relevant allergen or have never experienced symptoms of asthma or rhinitis show normal eNO. These data indicate that eNO relates to airway inflammation in atopic subjects.

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.

The prevalence of allergic sensitisation in immigrant children in The Netherlands

BACKGROUND

Differences in the prevalence of allergic sensitisation have been reported in immigrant children living in the same urban environment. The purpose of this study is to investigate the prevalence of allergic sensitisation in school children of Dutch, Turkish and Moroccan origin.

METHODS

The prevalence of sensitisation to aero-allergens was assessed using the skin prick test in a non-selected sample of 512 children (response rate 54%) living in the same inner city district of Utrecht. In addition, exhaled nitric oxide (FeNO) was determined.

RESULTS

The prevalence of allergic sensitisation was dependent on the ethnic origin. As compared with Dutch children (19.1%), a higher prevalence of allergic sensitisation was observed in immigrant children for whom both parents were born in Turkey (23.6%, not significant) or Morocco (30.6%, p<0.05). The prevalence of allergic sensitisation in Dutch children was nearly 2 times lower than the reported prevalence in German children. In all sensitised children, the mean FeNO value was significantly (p<0.05) higher than in non-sensitised children, and the mean FeNO level was highest in Moroccan children sensitised to indoor allergens.

CONCLUSION

In The Netherlands, immigrant children show a higher prevalence of allergic sensitisation as compared to Dutch children.