Correlation between exhaled nitric oxide, sputum eosinophils, and methacholine responsiveness in patients with mild asthma

Exhaled nitric oxide levels after specific inahalatory challenge test in subjects with diagnosed occupational asthma

OBJECTIVES

Measuring exhaled nitric oxide (eNO) is a useful method for the assessment of bronchial inflammation in asthmatic subjects. The aim of the study was to evaluate the changes in eNO level in the subjects with suspected occupational asthma (OA) after a specific inhalation test (SIT) with occupational agents.

MATERIALS AND METHODS

Forty two patients, including 17 farmers, 15 bakers and 10 health care workers had a physical examination, skin prick tests with common and occupational allergens, total serum IgE level, specific anti-allergen IgE determinations, spirometry and SIT. Also, morphological changes in induced sputum (ISP) and nasal lavage fluid (NLF) were analysed and eNO measurements were performed.

RESULTS

SIT revealed a significant increase in the proportion of eosinophils in NLF and in ISP in the cases with diagnosed OA. Moreover, these cases showed significantly increased eNO levels only 24 h after SIT, compared to the measurements before SIT. We also found a significant correlation between eNO level at 24 h after SIT and the percentage of eosinophils in NLF before, and 4 and 24 h after SIT, as well as in ISP before and 24 h after SIT in all subjects with diagnosed OA.

CONCLUSION

The findings may confirm the usefulness of exhaled nitric oxide measurements for diagnosing OA.

Less air pollution leads to rapid reduction of airway inflammation and improved airway function in asthmatic children

OBJECTIVE

Air pollution can promote airway inflammation, posing significant health risks for children with chronic respiratory problems. However, it is unknown whether this process is reversible, so that limiting pollution will benefit these children. We measured the short-term response of allergic asthmatic children exposed to a real-life reduction in outdoor air pollution by using noninvasive biomarkers of airway inflammation and function.

PATIENTS AND METHODS

Thirty-seven untreated allergic children with mild persistent asthma were recruited from a highly polluted urban environment and relocated to a less polluted rural environment. Air pollution, pollen counts, and meteorological conditions were carefully monitored at both sites. Nasal eosinophils, fractional exhaled nitric oxide, peak expiratory flow, and urinary leukotriene E(4) were measured first in the urban environment and then again 7 days after relocation to the rural environment.

RESULTS

One week after relocation to the rural environment, we measured, on average, a fourfold decrease in nasal eosinophils and significant decrease in fractional exhaled nitric oxide. We also noted an improvement in lower airway function, reflected by highly significant increase in peak expiratory flow. In contrast, mean urinary leukotriene E(4) concentration remained unchanged after 1 week of exposure to the rural environment.

CONCLUSIONS

Better air quality is associated with a rapid reduction of airway inflammation in allergic asthmatic children. Nasal eosinophils and fractional exhaled nitric oxide are sensitive indicators of this effect, and their rapid decline is paralleled by improved airway function measured by peak expiratory flow. Leukotriene synthesis has a more variable response to environmental modifications.

Maximal response plateau to adenosine 5'-monophosphate in asthma. Relationship with the response to methacholine, exhaled nitric oxide, and exhaled breath condensate pH

BACKGROUND

No information is available on the plateau in response to adenosine 5'-monophosphate(AMP). The aims of the present study were (1) to determine whether plateau can be detected with AMP and the relation with the plateau in response to methacholine, and (2) to identify the relation between the plateau and indirect markers of airway inflammation, such as exhaled nitric oxide (ENO) and exhaled breath condensate (EBC) pH.

METHODS

Airway responsiveness to high concentrations of methacholine and AMP, ENO levels, and EBC pH values were obtained in 31 subjects with well-controlled asthma. Concentration-response curves were characterized by their concentration of agonist that produces a decrease in FEV(1) of 20% and, if possible, by the level of plateau.

RESULTS

Although the prevalence of plateau with methacholine (48%) and AMP (58%) was similar, the two challenges did not identify plateau in exactly the same individuals. In 14 subjects who showed plateau with both bronchoconstrictor agents, the mean plateau level for methacholine was 26.0% (95% confidence interval [CI], 21.3 to 30.8), compared with 16.5% (95% CI, 12.2 to 20.8; p < 0.0001) for AMP. Both ENO and EBC pH values were similar in subjects with plateau and in those without plateau.

CONCLUSIONS

In well-controlled asthmatics, the plateau in response to AMP can be identified at a milder degree of obstruction than the plateau in response to methacholine, but the two agonists are not identifying the same airway abnormalities. Furthermore, if ENO and EBC pH are markers of inflammation, the determination of the presence or level of plateau is not a reliable method to identify airway inflammation in asthma.

Exhaled nitric oxide, systemic inflammation, and the spirometric response to inhaled fluticasone propionate in severe chronic obstructive pulmonary disease: a prospective study

BACKGROUND

A subset of patients with chronic obstructive pulmonary disease (COPD) may respond more favorably to inhaled corticosteroids (ICS), but no simple method is currently utilized to predict the presence or absence of ICS responses in patients with COPD.We evaluated the ability of exhaled nitric oxide (FENO) and serum inflammatory markers (C-reactive protein [CRP], interleukin-6 [IL-6], and interleukin-8 [IL-8]) to independently predict spirometric responses to ICS in patients with COPD.

METHODS

Among 60 ex-smokers with severe COPD (mean FEV1 1.07 L, 36% of predicted), we conducted a single-arm, open-label study. Participants spent four weeks free of any ICS, followed by four weeks of ICS use (fluticasone propionate 500 mcg twice daily). FENO, CRP, IL-6, IL-8, and pre-bronchodilator spirometry were measured immediately before and after the four weeks of ICS use.

RESULTS

Baseline FENO, CRP, IL-6, and IL-8 showed no correlations to FEV1 responses to ICS. ICS responders (increase in FEV1 > or = 200 mL after four weeks of ICS) did have significantly higher baseline FENO levels compared with non-responders (46.5 parts per billion [ppb] vs. 25 ppb, p = 0.028). The receiver operating characteristic curve for FENO to discriminate responders from non-responders had an area under curve of 0.72. Baseline serum inflammatory markers did not differ between responders and non-responders.

CONCLUSION

In ex-smokers with severe COPD, a measure of local pulmonary inflammation, FENO, may be more closely associated with FEV1 responses to four weeks of ICS than are standard markers of systemic inflammation, serum CRP, IL-6, and IL-8.

Measurement of exhaled nitric oxide in the emergency department in patients with asthma

A great deal of research has been conducted on the utility and usefulness of exhaled nitric oxide (NO) as a biomarker of airway inflammation and its role in the diagnosis of acute asthma exacerbations. This article reviews the pathophysiology of NO in asthma, evidence for the use of exhaled NO in acute asthma exacerbations, and the potential utility of devices available to emergency physicians for measuring exhaled NO.

Infections

This chapter reviews the epidemiological evidence implicating infectious pathogens as triggers and will discuss the mechanisms of interaction between the host–pathogen response and preexisting airway pathology that result in an exacerbation. Asthma is a multifaceted syndrome involving atopy, bronchial hyperreactivity, and IgE and non-IgE-mediated acute and chronic immune responses. The asthmatic airway is characterized by an infiltrate of eosinophils and of T-lymphocytes expressing the type 2 cytokines IL-4, IL-5, and IL-13. Trigger factors associated with acute exacerbations of asthma include exposure to environmental allergens, especially animals, molds, pollens and mites, cold, exercise, and drugs. The frequency of exacerbations is a major factor in the quality of life of patients with COPD. The typical clinical features of an exacerbation include increased dyspnea, wheezing, cough, sputum production, and worsened gas exchange. Although noninfectious causes of exacerbations such as allergy, air pollution, or inhaled irritants including cigarette smoke may be important, acute airway infections are the major precipitants. The infection and consequent host inflammatory response result in increased airway obstruction. The success of vaccination to prevent respiratory virus infections has been limited by significant variation within the major virus types causing disease. Currently much of the treatment of infective exacerbations of asthma and COPD is symptomatic, consisting of increased bronchodilators, either short-acting β 2—agonists in inhaled or intravenous form or anticholinergics or theophyllines, or supportive in the form of oxygen and in severe cases noninvasive or invasive ventilatory measures.

Non-asthmatic patients show increased exhaled nitric oxide concentrations

OBJECTIVE

Evaluate whether exhaled nitric oxide may serve as a marker of intraoperative bronchospasm.

INTRODUCTION

Intraoperative bronchospasm remains a challenging event during anesthesia. Previous studies in asthmatic patients suggest that exhaled nitric oxide may represent a noninvasive measure of airway inflammation.

METHODS

A total of 146,358 anesthesia information forms, which were received during the period from 1999 to 2004, were reviewed. Bronchospasm was registered on 863 forms. From those, three groups were identified: 9 non-asthmatic patients (Bronchospasm group), 12 asthmatics (Asthma group) and 10 subjects with no previous airway disease or symptoms (Control group). All subjects were submitted to exhaled nitric oxide measurements (parts/billion), spirometry and the induced sputum test. The data was compared by ANOVA followed by the Tukey test and Kruskal-Wallis followed by Dunn's test.

RESULTS

The normal lung function test results for the Bronchospasm group were different from those of the asthma group (p <0.05). The median percentage of eosinophils in induced sputum was higher for the Asthma [2.46 (0.45-6.83)] compared with either the Bronchospasm [0.55 (0-1.26)] or the Control group [0.0 (0)] (p <0.05); exhaled nitric oxide followed a similar pattern for the Asthma [81.55 (57.6-86.85)], Bronchospasm [46.2 (42.0 -62.6] and Control group [18.7 (16.0-24.7)] (p< 0.05).

CONCLUSIONS

Non-asthmatic patients with intraoperative bronchospasm detected during anesthesia and endotracheal intubation showed increased expired nitric oxide.

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.

Mechanisms of airway hyperresponsiveness in asthma

Airway hyperresponsiveness (AHR) is a fundamental abnormality in asthma. There are many potential factors contributing to the excessive airway response demonstrable on airway challenge. These range from abnormalities of airway smooth muscle, airway remodelling and airway inflammation to abnormalities in the neural control of airway calibre. None of these by themselves fully explains the abnormalities seen on the dose response curves of the asthmatic. In this review, the main mechanisms are described, together with recent evidence providing a pathway by which a number of these mechanisms may interact to cause AHR through abnormality in ventilation distribution and airway closure. There is now evidence for a close relationship between ventilation heterogeneity and AHR which could be exploited clinically.

Usefulness of exhaled nitric oxide and sputum eosinophils in the long-term control of eosinophilic asthma

BACKGROUND

The aim of the present study was to treat unstable asthma according to exhaled nitric oxide (eNO) and induced-sputum eosinophils (sEos) levels to assess if this strategy is better than the conventional approach based on symptoms and function to achieve asthma control.

METHODS

Fourteen patients with mild-to-moderate persistent asthma (6 men, 8 women) were recruited. During the recruitment visit, the patients, previously treated for asthma following Global Initiative for Asthma recommendations, underwent clinical evaluation and pulmonary function tests (PFTs). Then, after 4 weeks of washout from inhaled antiinflammatory treatment, the patients underwent a basal visit performing PFTs, challenge test to methacholine, and determination of eNO and sEos counts. These procedures were repeated after 3, 6, and 12 months while the patients were treated with inhaled steroids in a stepwise fashion according to eNO and sEos values.

RESULTS

At the end of the study, a significant decrease in eNO and sEos was observed (57.2 +/- 32.8 parts per billion [ppb] vs 22.1 +/- 10.8 ppb, p < 0.01; and 27.1 +/- 27.1% vs 3.7 +/- 3.5%, p < 0.01, respectively). A close correlation (r2 = 0.41, p < 0.01) between the percentage change of eNO and sEos was observed only after 6 months. Patients treated according to the levels of these inflammatory markers had fewer symptoms and fewer exacerbations compared to those the year before when they were conventionally treated.

CONCLUSIONS

Our results show the usefulness of eNO and sEos for titrating treatment in asthmatic patients in order to achieve better long-term control of the disease. The eNO decrease reflects adequately the reduction of sEos only after 6 months.

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.

Symptoms, spirometry, exhaled nitric oxide, and asthma exacerbations in clinical practice

BACKGROUND

Patient symptoms, spirometry measurements, exacerbation rates, and exhaled nitric oxide (FE(NO)) levels have all been used to quantify asthma severity.

OBJECTIVE

To determine the relationships among these disease surrogates in clinical practice.

METHODS

Data were collected from 5 primary care asthma clinics on patient symptoms, reliever use, spirometry measurements, maintenance pharmacotherapy, disease severity (British Thoracic Society treatment step), and FE(NO) level. Exacerbation data (asthma-related unscheduled health care contact or rescue oral corticosteroid therapy) for the 12 months before and 3 months after the clinic visit were then obtained.

RESULTS

A total of 267 adult asthmatic patients (mean [SEM] age, 51.6 [1.1] years; forced expiratory volume in 1 second, 86.3% [1.2%] of predicted) participated, and 157 exacerbations were captured. For the 12 months before the clinic visit, exacerbation rate was positively correlated with dose of inhaled corticosteroid (P < .001), treatment step (P < .001), reliever use (P = .002), and symptom score (P < .001) but was negatively correlated with FE(NO) level (P = .04); only symptom scores correlated with exacerbation rate in the 3 months after the visit. Levels of FE(NO) were significantly lower in frequently exacerbating patients receiving higher doses of maintenance inhaled corticosteroids compared with patients with mild disease who were corticosteroid naive (19.7 vs 40.4 ppb, P < .001). Measurement of FE(NO) was an insensitive method (sensitivity, 66.7%; specificity, 51.9% at a cutoff value of 20 ppb) for identifying patients who subsequently exacerbated.

CONCLUSION

Levels of FE(NO) are paradoxically decreased in patients with more severe asthma and frequent exacerbations and may, therefore, be of limited utility in primary care.

The use of exhaled nitric oxide in the management of asthma

It has recently become clear that airways disease associated with eosinophilic airway inflammation, but not other patterns of inflammation, is closely associated with favourable short-and long-term responses to corticosteroid therapy, irrespective of the clinical context in which it occurs. Moreover, a raised exhaled nitric oxide (FE(NO)) is a reasonable marker of eosinophilic airway inflammation, which has a number of advantages as a diagnostic and monitoring tool. In this review we outline essential background information on the use of FE(NO) in clinical practice and discuss some recent work evaluating the clinical value of this technique.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

History, technical and regulatory aspects of exhaled nitric oxide

The history of nitric oxide (NO) in exhaled breath as a marker of inflammation is summarized, followed by measurement aspects of exhaled NO including NO excretion models of NO in the airway, the estimation of flow-independent NO exchange parameters and issues with the standardization of these methods. Regulatory considerations in the US are also presented. A brief summary of the state of the art for clinical application of exhaled NO is also included.

Exhaled nitric oxide decreases in association with attendance at an asthma summer cAMP

Attendance at a summer asthma camp has been associated with improved outcomes in children with asthma. We hypothesized that one mechanism involved in improved asthma outcomes is reduction in airway inflammation. To investigate this, we measured the fractional concentration of exhaled nitric oxide (FeNO), lung function (forced expiratory volume in 1 sec, FEV(1)) and asthma control (Juniper Asthma Control Questionnaire, ACQ) from children at the beginning and end of a 1-week asthma summer camp. We also obtained a symptoms-only ACQ at 1 and 6 months after the end of camp. We enrolled 10 girls, 17 boys, mean (+/- SD) age = 9.6 +/- 1.3 years. At baseline, FeNO (ppb), median (25-75 IQR) = 11.4 (7.2-21.3); ACQ = 0.86 (0.43-1.21); FEV(1) (%pred, mean +/- SD) = 87 +/- 10. At the end of camp, FeNO = 6.2 (4.4-8.4), a change of -45%, p < 0.0001; ACQ = 0.71 (0.43-1.14), a fall of 14%, p = 0.72; and mean FEV(1)% predicted remained unchanged. There were no significant changes in the follow-up symptoms-only ACQ at 1 and 6 months. We conclude that airway inflammation, as measured by FeNO, improved during 1 week of asthma camp, but there were no significant changes in lung function or asthma control. Since no child had a change in anti-inflammatory therapy during camp, these findings suggest that airway inflammation was reduced because of improved adherence to therapy and/or reduced exposure to pro-inflammatory stimuli in the home environment. The finding of reduced inflammation following attendance at an asthma summer camp should motivate the child, the parents and the clinician to focus their efforts on improving adherence to therapy and reducing exposures at home.

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.

Urinary eosinophil protein X in children with atopic asthma

The aim of this study was to investigate the relationship between urinary eosinophil protein X (uEPX) and asthma symptoms, lung function, and other markers of eosinophilic airway inflammation in asthmatic school children.

METHODS

A cross-sectional study was performed in 180 steroid dependent atopic children with stable moderately severe asthma, who were stable on 200 or 500 microg of fluticasone per day. uEPX was measured in a single sample of urine and was normalized for creatinine concentration (uEPX/c). Symptom scores were kept on a diary card. FEV1 and PD20 methacholine were measured. Sputum induction was performed in 49 and FE(NO) levels measured in 24 children.

RESULTS

We found an inverse correlation between uEPX/c and FEV1 (r = -.20, P = .01) and a borderline significant correlation between uEPX/c and PD20 methacholine (r = -.15, P = .06). Symptom score, %eosinophils and ECP in induced sputum and FE(NO) levels did not correlate with uEPX/c.

CONCLUSION

uEPX/c levels did not correlate with established markers of asthma severity and eosinophilic airway inflammation in atopic asthmatic children.

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.

The value of exhaled nitric oxide in predicting bronchial hyperresponsiveness in children

Reduced attention span and motor skills in children limit the practicability of bronchial provocation tests. To assess exhaled nitric oxide (FeNO) as a surrogate for bronchial hyperresponsiveness (BHR) in children with possible reactive airway disease, FeNO was measured using the single-breath method in 169 successive outpatients 11 +/- 5 years of age before lung function testing and subsequent bronchial provocation by exercise (n = 165) and methacholine (n = 134). Baseline forced expiratory volume in 1 second (FEV(1)) less than 80% of predicted and/or BHR were seen in 59%. FeNO correlated weakly with PD(20) to methacholine (r = -0.24, p < 0.05), but not with the change in FEV(1) due to exercise-induced bronchoconstriction (EIB) (r = 0.1, p > 0.05). The negative predictive value of FeNO less than 10 ppb for EIB was 94%, but overall accuracy for predicting BHR was low. Measurement of FeNO is not a substitute for bronchial provocation in children.

Effect of nasal steroid treatment on airway inflammation determined by exhaled nitric oxide in allergic schoolchildren with perennial rhinitis and asthma

Rhinitis is common in asthmatic schoolchildren who are allergic to animal dander and constantly and indirectly exposed to these allergens in their everyday environment. As a patho-physiological linkage between nasal and bronchial inflammation has been proposed to exist, the primary objective of this study was to determine whether nasal administration of mometasone furoate (MSNF) can reduce bronchial inflammation, as reflected in the level of exhaled nitric oxide (F(E)NO) in asthmatic schoolchildren with dander allergy and mild-to-moderate rhinitis. Forty such children were assigned randomly to be treated for 4 wk with MSNF or placebo, employing a double-blind procedure. F(E)NO was the primary end-point measured and secondary end-points were nasal levels of NO, the concentration of eosinophilic cationic protein (ECP) in nasal lavage, the relative numbers of eosinophils in blood, forced expiratory volume in 1 s (FEV(1)), peak expiratory flow (PEF) and scoring of symptoms. There was no significant difference in the F(E)NO values of the treated and control groups at any time-point, whereas the nasal level of ECP was lower in the treated group compared with placebo (p = 0.05) on both days 7 and 28, and compared with baseline for the treated group (p = 0.06 on day 7, p = 0.02 on day 28). Furthermore, the mean blood eosinophil count decreased in the treated group, which also demonstrated lower scores for nasal symptoms compared with placebo, but neither of these differences were statistically significant. FEV(1), PEF and nasal levels of NO remained unchanged in both groups. Four weeks of nasal treatment with MSNF had no effect on bronchial inflammation, as reflected by exhaled NO, whereas signs of nasal and systemic eosinophil activation were reduced. Thus, nasal administration of a steroid as a strategy to reduce asthmatic inflammation remains questionable in mild-to-moderately severe cases of perennial rhinitis and asthma.

Tailored interventions based on exhaled nitric oxide versus clinical symptoms for asthma in children and adults

BACKGROUND

The measurement of severity and control of asthma in both children and adults can be based on subjective or objective measures. It has been advocated that fractional exhaled nitric oxide (FeNO) can be used to monitor airway inflammation as it correlates with some markers of asthma. Interventions for asthma therapies have been traditionally based on symptoms and/or spirometry.

OBJECTIVES

To evaluate the efficacy of tailoring asthma interventions based on exhaled nitric oxide in comparison to clinical symptoms (with or without spirometry/peak flow) for asthma related outcomes in children and adults.

SEARCH STRATEGY

We searched the Cochrane Airways Group Specialised Register of Trials, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and reference lists of articles. The last search was completed in December 2006.

SELECTION CRITERIA

All randomised controlled comparisons of adjustment of asthma therapy based on exhaled nitric oxide compared to traditional methods (primarily clinical symptoms and spirometry/peak flow).

DATA COLLECTION AND ANALYSIS

Results of searches were reviewed against pre-determined criteria for inclusion. Relevant studies were independently selected in duplicate. Two authors independently assessed trial quality and extracted data. Authors were contacted for further information but none were received. Data was analysed as "intervention received" and sensitivity analyses performed.

MAIN RESULTS

Four (2 adult and 2 paediatric) studies were included; these studies differed in a variety of ways including definition of asthma exacerbations, FeNO cut off levels and duration of study. Of 356 participants randomised, 324 completed the trials. In the meta-analysis, there was no difference between groups for the primary outcome of asthma exacerbations or for other outcomes (clinical symptoms, FeNO level and spirometry). In post-hoc analysis, a significant reduction in mean final daily dose inhaled corticosteroid per adult was found in the group where treatment was based on FeNO in comparison to clinical symptoms; WMD -282.46 (95% CI -422.08 to -142.84). There was no difference in ICS dose between the groups in the overall daily dose in the adult studies or in the paediatric studies.

AUTHORS' CONCLUSIONS

Tailoring the dose of inhaled corticosteroids based on exhaled nitric oxide in comparison to clinical symptoms was carried out in different ways in the four studies that were found, and the results show only modest differences. The role of utilising exhaled nitric oxide to tailor the dose of inhaled corticosteroids is currently uncertain.

Once-daily inhaled glucocorticosteroid administration in controlled asthma patients

BACKGROUND

Inhaled glucocorticosteroids are usually administered in two equal daily doses. To simplify the method of treatment, once-daily administration has been used. However, little information regarding whether once-daily treatment can sufficiently control airway inflammation is available. We aimed to investigate whether once-daily administration of inhaled glucocorticosteroids can control airway inflammation.

METHODS

Twenty-four well-controlled asthma patients were enrolled in a randomized crossover trial to compare the efficacies of once-daily and twice-daily administration of inhaled glucocorticosteroids. Initially, the patients were randomly assigned to receive either once-daily or twice-daily administration for 16 weeks. After an 8-week washout period, patients who originally received twice-daily administration were assigned to once-daily administration for 16 weeks and vice versa. We assessed the changes in the forced expiratory volume in 1s, morning and evening peak expiratory flows, asthma symptoms, health-related quality of life and fractional exhaled nitric oxide levels.

RESULTS

Patients with once-daily administration showed the same level of clinical control and lung functions as patients receiving twice-daily administration. There was no difference in the fractional exhaled nitric oxide levels between the beginning and end of the twice-daily treatment (35.69 and 33.23ppb, respectively). In contrast, the fractional exhaled nitric oxide level was significantly higher at the end of the once-daily treatment (33.87 and 39.38ppb, respectively, p< 0.001).

CONCLUSION

Although once-daily administration is sufficient for clinical control of asthma, it might not control airway inflammation sufficiently.

Arginine homeostasis in allergic asthma

Allergic asthma is a chronic disease characterized by early and late asthmatic reactions, airway hyperresponsiveness, airway inflammation and airway remodelling. Changes in l-arginine homeostasis may contribute to all these features of asthma by decreased nitric oxide (NO) production and increased formation of peroxynitrite, polyamines and l-proline. Intracellular l-arginine levels are regulated by at least three distinct mechanisms: (i) cellular uptake by cationic amino acid (CAT) transporters, (ii) metabolism by NO-synthase (NOS) and arginase, and (iii) recycling from l-citrulline. Ex vivo studies using animal models of allergic asthma have indicated that attenuated l-arginine bioavailability to NOS causes deficiency of bronchodilating NO and increased production of procontractile peroxynitrite, which importantly contribute to allergen-induced airway hyperresponsiveness after the early and late asthmatic reaction, respectively. Decreased cellular uptake of l-arginine, due to (eosinophil-derived) polycations inhibiting CATs, as well as increased consumption by increased arginase activity are major causes of substrate limitation to NOS. Increasing substrate availability to NOS by administration of l-arginine, l-citrulline, the polycation scavenger heparin, or an arginase inhibitor alleviates allergen-induced airway hyperresponsiveness by restoring the production of bronchodilating NO. In addition, reduced l-arginine levels may contribute to the airway inflammation associated with the development of airway hyperresponsiveness, which similarly may involve decreased NO synthesis and increased peroxynitrite formation. Increased arginase activity could also contribute to airway remodelling and persistent airway hyperresponsiveness in chronic asthma via increased synthesis of l-ornithine, the precursor of polyamines and l-proline. Drugs that increase the bioavailability of l-arginine in the airways - particularly arginase inhibitors - may have therapeutic potential in allergic asthma.

Assessing airway inflammation in clinical practice - experience with spontaneous sputum analysis

Background

The assessment of airway inflammation for the diagnosis of asthma or COPD is still uncommon in pneumology-specialized general practices. In this respect, the measurement of exhaled nitric oxide (NO), as a fast and simple methodology, is increasingly used. The indirect assessment of airway inflammation, however, does have its limits and therefore there will always be a need for methods enabling a direct evaluation of airway inflammatory cell composition. Sampling of spontaneous sputum is a well-known, simple, economic and non-invasive method to derive a qualitative cytology of airway cells and here we aimed to assess today's value of spontaneous sputum cytology in clinical practice.

Methods

Three pneumologists provided final diagnoses in 481 patients having sputum cytology and we retrospectively determined posterior versus prior probabilities of inflammatory airway disorders. Moreover, in a prospective part comprising 108 patients, pneumologists rated their confidence in a given diagnosis before and after knowing sputum cytology and rated its impact on the diagnostic process on an analogue scale.

Results

Among the 481 patients, 45% were diagnosed as having asthma and/or airway hyperresponsiveness. If patients showed sputum eosinophilia, the prevalence of this diagnosis was elevated to 73% (n = 109, p < 0.001). The diagnosis of COPD increased from 40 to 66% in patients with neutrophilia (n = 29, p < 0.01).

Thirty-three of the 108 patients were excluded from the prospective part (26 insufficient samples, 7 incomplete questionnaires). In 48/75 cases the confidence into a diagnosis was raised after knowing sputum cytology, and in 15/75 cases the diagnosis was changed as cytology provided new clues.

Conclusion

Our data suggest that spontaneous sputum cytology is capable of assisting in the diagnosis of inflammatory airway diseases in the outpatient setting. Despite the limitations by the semiquantitative assessment and lower sputum quality, the supportive power and the low economic effort needed can justify the use of this method, particularly if the diagnosis in question is thought to have an allergic background.

Association between exhaled nitric oxide and systemic inflammatory markers

BACKGROUND

Asthma is an inflammatory condition of the airways, and there is some evidence to suggest that it is associated with a systemic inflammatory response, as measured by C-reactive protein (CRP) and fibrinogen. Exhaled nitric oxide is a noninvasive measure of asthmatic airway inflammation.

OBJECTIVE

To determine if there is an association between exhaled nitric oxide and these systemic inflammatory markers.

METHODS

The Dunedin Multidisciplinary Health and Development Study is a birth cohort of approximately 1,000 individuals born between April 1, 1972, and March 31, 1973. At the age of 32 years, study members were assessed for diagnosis of asthma, atopy by skin prick testing, smoking, body mass index, exhaled nitric oxide, high-sensitivity serum CRP, and plasma fibrinogen level.

RESULTS

There was no significant association between exhaled nitric oxide and CRP (P = .99). There was a trend to an inverse association between exhaled nitric oxide and fibrinogen (P = .049), but this was not significant after adjusting for smoking and use of corticosteroids or after further adjustment for body mass index and atopy (P = .71).

CONCLUSION

In this population-based sample of young adults, there was no association between airway inflammation, as measured by exhaled nitric oxide, and systemic inflammation, as measured by either CRP or fibrinogen.

Exhaled nitric oxide

Exhaled nitric oxide (FENO) is a noninvasive easily measurable biomarker that is proving to be an excellent surrogate for eosinophilic inflammation in the lungs of patients who have asthma. Although large-scale normative data are still awaited, preliminary studies have shown FENO to be helpful in diagnosing and assessing severity and control for asthma. FENO levels have also proven helpful in diagnosing and managing several other inflammatory lung diseases.

Bronchoprovocation testing in asthma

Bronchial hyperresponsiveness (BHR) is an important feature of asthma and is useful in diagnosis, monitoring, and prognostication. It probably represents inherent elements of the disease process such as genetic predisposition, airway inflammation, and airway remodeling. Airway inflammation likely accounts for the variable component of BHR, whereas the persistent component of BHR correlates significantly with structural changes in the airway, such as basement membrane thickness and epithelial damage. It might be this component that is resistant or refractory to the effects of available interventions. A few trials of immunomodulatory therapy have shown considerable improvements in markers of airway inflammation, without significantly modifying airway reactivity. Interventions to impact the more permanent feature of BHR are needed.

Off-line fractional exhaled nitric oxide measurement is useful to screen allergic airway inflammation in an adult population

To determine whether off-line fractional exhaled nitric oxide (FeNO) measurement is applicable to screen allergic airway inflammation for epidemiologic studies, we examined 280 adults, measuring off-line FeNO samplings, pulmonary function, and serum immunoglobulin E (IgE). Subjects with recurrent wheeze (recurrent wheezers) had significantly higher FeNO and IgE levels and significantly lower forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) than non-wheezers. Statistical analysis showed that FeNO and FEV1/FVC were significant predictors for recurrent wheezers, independent of smoking. The cut-off FeNO level for screening allergic airway inflammation was 38 ppb in non-smokers and 32.9 ppb in smokers. Thus, off-line FeNO can be used as a good marker to screen allergic airway inflammation, regardless of smoking.

Exhaled nitric oxide: a test for diagnosis and control of asthma?

The fractional concentration of nitric oxide (FE(NO)) in exhaled breath is a noninvasive marker of airway inflammation in asthma. The precise role of FE(NO) in the asthma management algorithm has not been defined. However, there are compelling data for use of FE(NO) for diagnosing asthma, assessing control and severity, titrating inhaled corticosteroids, and detecting ongoing airway inflammation. This article reviews the biology of nitric oxide in airway pathology and its role in asthma.

A mechanism of benefit of soy genistein in asthma: inhibition of eosinophil p38-dependent leukotriene synthesis

BACKGROUND

Dietary intake of the soy isoflavone genistein is associated with reduced severity of asthma, but the mechanisms responsible for this effect are unknown.

OBJECTIVE

To determine whether genistein blocks eosinophil leukotriene C(4) (LTC(4)) synthesis and to evaluate the mechanism of this effect, and to assess the impact of a 4-week period of soy isoflavone dietary supplementation on indices of eosinophilic inflammation in asthma patients.

METHODS

Human peripheral blood eosinophils were stimulated in the absence and presence of genistein, and LTC(4) synthesis was measured. 5-lipoxygenase (5-LO) nuclear membrane translocation was assessed by confocal immunofluorescence microscopy. Mitogen-activated protein (MAP) kinase activation was determined by immunoblot. Human subjects with mild-to-moderate persistent asthma and minimal or no soy intake were given a soy isoflavone supplement (100 mg/day) for 4 weeks. The fraction of exhaled nitric oxide (FE(NO)) and ex vivo eosinophil LTC(4) production were assessed before and after the soy isoflavone treatment period.

RESULTS

Genistein inhibited eosinophil LTC(4) synthesis (IC(50) 80 nm), blocked phosphorylation of p38 MAP kinase and its downstream target MAPKAP-2, and reduced translocation of 5-LO to the nuclear membrane. In patients with asthma, following 4 weeks of dietary soy isoflavone supplementation, ex vivo eosinophil LTC(4) synthesis decreased by 33% (N=11, P=0.02) and FE(NO) decreased by 18% (N=13, P=0.03).

CONCLUSION

At physiologically relevant concentrations, genistein inhibits eosinophil LTC(4) synthesis in vitro, probably by blocking p38- and MAPKAP-2-dependent activation of 5-LO. In asthma patients, dietary soy isoflavone supplementation reduces eosinophil LTC(4) synthesis and eosinophilic airway inflammation. These results support a potential role for soy isoflavones in the treatment of asthma.

Rate of response of individual asthma control measures varies and may overestimate asthma control: an analysis of the goal study

BACKGROUND

Using a composite measure based on clinical outcomes, the GOAL study showed that achievement of Total Control of asthma was time dependent with the proportion of controlled patients continuing to rise through the year-long study. Taking data from this study, we compared time taken to achieve Total Control with time taken to achieve total control of each individual clinical criterion on treatment with salmeterol/fluticasone propionate (SFC) or fluticasone propionate (FP) alone.

METHODS

Time to achieving total control of individual outcomes (day-time symptoms, night-time awakenings, rescue medication use, PEF > or =80% predicted every day) were analyzed by Kaplan Meier plots and compared with achievement of composite Total Control.

RESULTS

Night-time awakenings responded most rapidly and daytime symptoms took longest to respond. After 12 weeks, the proportion of patients who achieved control of any individual clinical criterion was higher than the proportion who achieved control when using the composite outcome (no night-time awakenings achieved by 73% with SFC and 65% with FP; PEF > or =80% predicted every day, 55% and 45% respectively; no rescue usage 46% and 35% respectively; and no daytime symptoms, 35% and 24% respectively, compared with Total Control, 23% and 14% respectively). In every measure except night-time awakenings, more rapid responses were seen for SFC compared with FP alone.

CONCLUSIONS

Speed of response of individual asthma measures varies and evaluation of control using any single measure overestimates total asthma control. Treatment should be continued until composite control is reached, rather than control of individual outcomes.

Plasma resistin levels in asthmatics as a marker of disease state

BACKGROUND

Resistin is a protein produced by adipocytes and circulating macrophages that has been found to be associated with inflammatory states.

OBJECTIVE

To determine the levels of resistin in relation to asthma disease state and severity, we investigated a cohort of adult patients with asthma.

METHODS

A cohort of moderate to severe persistent asthma patients and control patients were recruited and underwent fasting labs to evaluate levels of serum glucose, C-reactive protein (CRP), and resistin.

RESULTS

No significant differences were found between the control and asthma group with respect to serum CRP at 0.78 +/- 0.60 mg/dL and 0.48 +/- 0.60 mg/dL, (p < 0.36) or glucose at 92.2 +/- 11.9 mg/dL and 89.5 +/- 7.2 mg/dL, (p < 0.084), respectively (mean +/- SD). However, plasma resistin levels were found to be significantly elevated in asthma patients, 186 ng/mL (95%CI 169-202) compared with control patients 121 ng/mL (95%CI 90.4-151), (p < 0.005).

CONCLUSIONS

Patients with asthma were found to have higher levels of resistin, and resistin levels were increased with disease severity in the asthma cohort.

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.

Exhaled nitric oxide and carbon monoxide in respiratory diseases

Breath tests have gained increasing interest in recent years mainly driven by the unmet clinical need to monitor airway diseases and to obtain information on unravelled aspects of respiratory disorders. A prototype of such measurement reaching clinical significance besides its use as a research tool is the measurement of exhaled nitric oxide (NO). It took hardly more than a decade after the discovery that exhaled breath contains NO for this measurement to be approved for clinical practice to monitor anti-inflammatory treatment in asthma. Recent studies demonstrate that using exhaled NO measurement to guide anti-inflammatory treatment in asthma may help clinical decision making. A similarly small molecule present in exhaled breath is carbon monoxide, which is not only a biomarker of cigarette smoking but has also been suggested to reflect ongoing oxidative stress/antioxidant defense. The scope of this review is the exciting field of exhaled monoxides. Since several other biomarkers have also been studied in the exhaled breath this review will provide a brief introduction to them.

Association between exhaled nitric oxide and systemic inflammatory markers

BACKGROUND

Asthma is an inflammatory condition of the airways, and there is some evidence to suggest that it is associated with a systemic inflammatory response, as measured by C-reactive protein (CRP) and fibrinogen. Exhaled nitric oxide is a noninvasive measure of asthmatic airway inflammation.

OBJECTIVE

To determine if there is an association between exhaled nitric oxide and these systemic inflammatory markers.

METHODS

The Dunedin Multidisciplinary Health and Development Study is a birth cohort of approximately 1,000 individuals born between April 1, 1972, and March 31, 1973. At the age of 32 years, study members were assessed for diagnosis of asthma, atopy by skin prick testing, smoking, body mass index, exhaled nitric oxide, high-sensitivity serum CRP, and plasma fibrinogen level.

RESULTS

There was no significant association between exhaled nitric oxide and CRP (P = .99). There was a trend to an inverse association between exhaled nitric oxide and fibrinogen (P = .049), but this was not significant after adjusting for smoking and use of corticosteroids or after further adjustment for body mass index and atopy (P = .71).

CONCLUSION

In this population-based sample of young adults, there was no association between airway inflammation, as measured by exhaled nitric oxide, and systemic inflammation, as measured by either CRP or fibrinogen.

[Analysis of induced sputum in refractory asthma]

Induction of sputum by inhalation of hypertonic or isotonic fluid makes possible the safe and noninvasive harvesting of airway cells from patients with asthma, regardless of disease severity. Analysis of sputum cells has helped to identify different phenotypes of refractory asthma and shown that such asthma can be eosinophilic, neutrophilic, or both. Elevated eosinophil levels in sputum indicate a risk of exacerbation if the corticosteroid dose is reduced in stabilized patients. Surveillance of eosinophilia levels as an indicator for corticosteroid adjustment in refractory asthma makes it possible to reduce the frequency of severe exacerbations.

Suppression of plasma matrix metalloproteinase-9 following montelukast treatment in childhood asthma

BACKGROUND

Montelukast and ketotifen are commonly prescribed anti-inflammatory medications used in the treatment of childhood asthma.

METHODS

To investigate the modulation effect of montelukast and ketotifen, the levels of exhaled nitric oxide (eNO) and plasma matrix metalloproteinase-9 (MMP-9) were analyzed in a group of 30 children with mild persistent asthma.

RESULTS

Patients on montelukast therapy for 8 weeks had significantly decreased levels of eNO and plasma MMP-9, which were associated with improved symptoms and enhanced peak expiratory flow but not significantly associated with increased level of tissue inhibitor metalloproteinase-1 (TIMP-1). In contrast, treatment with ketotifen produced no significant changes in these parameters until 4-6 weeks into the therapy and no effect on plasma MMP-9.

CONCLUSION

Leukotriene antagonists, such as montelukast, may be better non-steroidal anti-inflammatory drugs for preventing airway inflammation in mild childhood asthma.

Parent-reported symptoms may not be adequate to define asthma control in children

INTRODUCTION

Asthma guidelines have suggested that treatment decisions should be guided by indices of asthma control and not only by disease severity. In adults, symptom-based asthma control parameters have been shown to predict exacerbations and health care services use (HSU). We hypothesize that defining asthma control using parent-reported symptoms alone is not adequate in children.

MATERIALS AND METHODS

Cross-sectional data from the population-based asthma in Canada study were reanalyzed. Random-digit dialing was used to produce the final sample, consisting of 1,001 asthmatics: 801 adults (aged 16+) and 200 children (aged 4-15) participating by parental proxy. Weighted frequencies of Canadian guideline defined asthma control parameters, perceived asthma control, HSU and medication use were calculated separately for adults and children. Stratified analyses compared HSU in controlled versus uncontrolled asthmatics.

RESULTS

Over 90% of parents of asthmatic children believed their child's asthma to be controlled. Only 45% were actually controlled as defined by guideline parameters. Among controlled asthmatics, children reported higher HSU (32% reported 2+ health care encounters versus 17% of adults, P < 0.001). Irrespective of control and despite similar use of controller therapy, children reported a higher number of health care encounters than adults (any emergency department visits 37% vs. 24%, P = 0.00003; unscheduled doctor visits 59% vs. 36%, P < 0.00001). While reporting higher HSU, asthmatic children had less frequent episodes of excessive daytime symptoms than adults (29% vs. 49%, respectively, P < 0.0001).

DISCUSSION

Current symptom-based asthma control parameters reported by parental proxy are likely poor predictors of asthma HSU and may not provide adequate asthma control estimates in children.

Factors affecting exhaled nitric oxide measurements: the effect of sex

Background

Exhaled nitric oxide (F_ENO) measurements are used as a surrogate marker for eosinophilic airway inflammation. However, many constitutional and environmental factors affect F_ENO, making it difficult to devise reference values. Our aim was to evaluate the relative importance of factors affecting F_ENO in a well characterised adult population.

Methods

Data were obtained from 895 members of the Dunedin Multidisciplinary Health and Development Study at age 32. The effects of sex, height, weight, lung function indices, smoking, atopy, asthma and rhinitis on F_ENO were explored by unadjusted and adjusted linear regression analyses.

Results

The effect of sex on F_ENO was both statistically and clinically significant, with F_ENO levels approximately 25% less in females. Overall, current smoking reduced F_ENO up to 50%, but this effect occurred predominantly in those who smoked on the day of the F_ENO measurement. Atopy increased F_ENO by 60%. The sex-related differences in F_ENO remained significant (p < 0.001) after controlling for all other significant factors affecting F_ENO.

Conclusion

Even after adjustment, F_ENO values are significantly different in males and females. The derivation of reference values and the interpretation of F_ENO in the clinical setting should be stratified by sex. Other common factors such as current smoking and atopy also require to be taken into account.

Use of exhaled nitric oxide in predicting response to inhaled corticosteroids for chronic cough

OBJECTIVE

To evaluate our experience with patients who presented with chronic cough and how exhaled nitric oxide predicted response to inhaled corticosteroid (ICS) therapy.

PATIENTS AND METHODS

This retrospective observational study of 114 patients evaluated for chronic cough with measured exhaled nitric oxide and methacholine challenge testing was conducted from December 1, 2004, through November 30, 2005. Clinical records were extracted. Patients with no documented follow-up were contacted by telephone and administered a questionnaire.

RESULTS

In 64 patients, ICS therapy was started or the current ICS dose increased. Forty-one patients had elevated exhaled nitric oxide levels (defined as >or=35 ppb), 36 (88%) of whom had significant improvement in their chronic cough (likelihood ratio of a positive response, 4.9; 95% confidence interval, 2.2-10.9). Twenty-three patients with exhaled nitric oxide levels in the reference range were also prescribed ICS, and only 2 had cough improvement (likelihood ratio of a negative response, 0.07; 95% confidence interval, 0.02-0.25). Patients had documented follow-up that ranged from 4 weeks to 16 months. A cutoff of 38 ppb was found to best differentiate ICS responders and nonresponders.

CONCLUSIONS

Measurement of exhaled nitric oxide accurately predicted response to ICS therapy for chronic cough. Patients with a positive exhaled nitric oxide test result had a strong likelihood of response to ICS, whereas a negative exhaled nitric oxide test result indicated an unlikely response to ICS. This finding may potentially have an impact on how patients with chronic cough are evaluated and treated.

Economic evaluation of FE(NO) measurement in diagnosis and 1-year management of asthma in Germany

OBJECTIVE

Fractional exhaled nitric oxide (FE(NO)) is a marker for airway inflammation in asthma. The objective of this study was to assess the cost-effectiveness of FE(NO) measurement at a reimbursement price of euro34 using NIOX MINO, a portable non-invasive FE(NO) monitor, in asthma diagnosis and management.

METHODS

Two decision trees were constructed to capture the different alternatives and consequences in asthma diagnosis and management, comparing FE(NO) measurement against standard diagnostics and treatment guidelines. The impact of asthma management with FE(NO) measurement on resource use and health outcomes was evaluated over a 1-year timeframe. A German payer perspective was chosen. Effectiveness was measured in quality-adjusted life-years.

RESULTS

Asthma diagnosis based on FE(NO) measurement results in a cost of euro38 per patient compared with euro26 for standard diagnostics. In mild to severe patients, asthma management with FE(NO) measurement instead of standard guidelines results in cost-savings of euro30 per patient and year. In a more severe population, management with FE(NO) measurement would save costs of euro160 per patient.

CONCLUSION

Asthma diagnosis based on FE(NO) measurement alone (exemplified with NIOX MINO) costs euro12 more per patient than standard diagnostic methods, while offering improved accuracy. The use of FE(NO) measurement in treatment decisions is less costly than asthma management based on standard guidelines and provides similar health benefits.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

[Exhaled nitric oxide in the diagnosis and monitoring of lung diseases]

In recent 10 years there has been an explosion of interest in the analysis of breath constituents as a way of monitoring airway inflammation in lung diseases. Monitoring of inflammation may assist in differential diagnosis of lung diseases, assessment of their severity and response to appropriate treatment. Among these novel non-invasive methods, exhaled nitric oxide has been the most extensively studied. Its measurement has recently been standardized, and there are now commercially available nitric oxide analyzers. Concentration of exhaled nitric oxide is markedly elevated in asthma, and its elevation is positively related to the degree of eosinophilic airway inflammation, airway hyperresponsiveness and symptoms. Furthermore, evidence suggests that exhaled nitric oxide-driven asthma treatment provides more precise asthma control compared to conventional treatment protocols. With regard to other lung diseases, in chronic obstructive pulmonary disease exhaled nitric oxide may be useful in predicting steroid responsiveness, while in lung transplant recipients its measurement could contribute to the detection of asymptomatic infections and rejection processes.

Diagnostic utility of inflammatory biomarkers in asthma: exhaled nitric oxide and induced sputum eosinophil count

BACKGROUND

Even though an inflammatory process is known to be the underlying cause of asthma, diagnosis is based on clinical history, reversible airway obstruction and bronchial hyperresponsiveness according to international guidelines. The fraction of exhaled nitric oxide (FE(NO)) and induced sputum eosinophil count (Eos%) have been used as non-invasive inflammatory biomarkers.

OBJECTIVES

The aim of this study was to compare the sensitivity and specificity of FE(NO), Eos% and spirometry and to assess whether their combined use in clinical practice would improve diagnostic yield.

METHODS

In 50 patients with asthma symptoms we performed spirometry, a methacholine challenge test, FE(NO) measurement and assessment of Eos% in induced sputum. The standard diagnosis of asthma followed the guidelines of the Global Initiative for Asthma.

RESULTS

Twenty-two of the 50 patients were diagnosed with asthma. The sensitivity and diagnostic accuracy were higher for FE(NO) measurement (77%; area under the receiver operating curve [AUC], 0.8) than for spirometry (22%; AUC, 0.63). The sensitivity and specificity of Eos% in induced sputum were 40% and 82%, respectively, and the diagnostic accuracy of Eos% was lower (AUC, 0.58). When both inflammatory biomarkers were used together specificity increased to 76%.

CONCLUSIONS

The diagnostic accuracy of FE(NO) measurement was superior to that of the standard diagnostic spirometry in patients with symptoms suggestive of asthma. The use of FE(NO) measurement and induced sputum Eos% together to diagnose asthma in clinical practice is more accurate than spirometry or FE(NO) assessment alone and easier to perform.