Clinical aspects of using exhaled NO in asthma diagnosis and management

GC-MS analysis of exhaled gas for fine detection of inflammatory diseases

Exhaled gas analysis is a non-invasive test ideal for continuous monitoring of biological metabolic information. We analyzed the exhaled gas of patients with inflammatory diseases for trace gas components that could serve as biomarkers that enable early detection of inflammatory diseases and assessment of treatment efficacy. Furthermore, we examined the clinical potential of this method. We enrolled 34 patients with inflammatory disease and 69 healthy participants. Volatile components from exhaled gas were collected and analyzed by a gas chromatography-mass spectrometry system, and the data were examined for gender, age, inflammatory markers, and changes in markers before and after treatment. The data were tested for statistical significance through discriminant analysis by Volcano plot, Analysis of variance test, principal component analysis, and cluster analysis comparing healthy and patient groups. There were no significant differences in the trace components of exhaled gas by gender or age. However, we found differences in some components of the exhaled gas between healthy and untreated patients. In addition, after treatment, gas patterns including the patient-specific components changed to a state closer to the inflammation-free status. We identified trace components in the exhaled gas of patients with inflammatory diseases and found that some of these regressed after treatment.

Feasibility of Discontinuing Biologics in Severe Asthma: An Algorithmic Approach

In severe asthma with type 2 (T2) inflammation, biologics targeting key mediators of T2 inflammation, including interleukin (IL)-5, IL-4/IL-13, and immunoglobulin (Ig)E, remarkably improve the management of severe asthma, providing new insights into the clinical course of asthma such as disease modification and broad modulation of T2 inflammation. Once severe asthma has become a “controllable” condition, the question of discontinuation of biologics arises due to cost and side effects. The studies on discontinuing biologics in asthma demonstrate that some of patients successfully discontinue biologics, indicating that it is a feasible option in a subset of patients. Incorporating the evidence of discontinuation, we propose the criteria for the discontinuation of biologics. Our proposed criteria for the discontinuation of biologics consist of an absence of asthma symptoms (asthma control questionnaire [ACQ] score < 1.5 or asthma control test [ACT] score > 19), no asthma exacerbations, no use of oral corticosteroids, normalized spirometry (forced exhaled volume in 1 second [FEV₁] ≥ 80%), suppressed T2 inflammation (blood eosinophil counts < 300 μL and fractional exhaled nitric oxide [FeNO] < 50 ppb), and control of asthma comorbidities. Real-world evidence verified a subset of patients achieving highly well-controlled conditions after use of biologics, namely super-responders, who are candidates for the discontinuation of biologics. If super-responders meet all of the criteria, they are allowed to discontinue biological therapies. Our proposed algorithm may support physicians’ treatment decisions for patients receiving biologics.

Intrabreath oscillometry is a sensitive test for assessing disease control in adults with severe asthma

BACKGROUND

Asthma control is not well reflected by spirometry, yet this is the most frequently used measure of lung function in asthma clinics. Oscillometry is an alternative technique suitable for those with severe asthma.

OBJECTIVE

To investigate usefulness of oscillometry in subjects with severe asthma to determine which outcome variables best reflected asthma control.

METHODS

Adults with severe asthma were recruited from a severe asthma clinic in Brazil. Oscillometry (conventional multifrequency measurements between 6 and 32 Hz; intrabreath tracking at 8 Hz) and spirometry were performed. Asthma control was determined by the asthma control test.

RESULTS

A total of 60 adults were evaluated; mean age was 56.7 years. There was predominance of women (82%), and most patients (63%) reported onset of asthma symptoms in childhood or adolescence. There were no differences between controlled and uncontrolled asthma in spirometry. Uncontrolled asthma was associated with higher resistance (at 8 and 10 Hz) and more negative reactance (for 6, 8, and 10 Hz) (P < .05) on conventional oscillometry. Intrabreath oscillometry revealed significant differences between controlled and uncontrolled patients with asthma (P < .01 for changes in resistance and reactance between end expiration and end inspiration). The accuracy of the lung function tests in discriminating between controlled and uncontrolled asthma was higher for intrabreath variables (area under the curve = 0.65-0.72).

CONCLUSION

Oscillometry, particularly the intrabreath technique, better reflected asthma control than spirometry measures. Our findings suggest that oscillometry may be a useful technique to aid management of severe asthma, with a potential to reflect loss of disease control.

Genetic effects of allergen-specific IgE levels on exhaled nitric oxide in schoolchildren with asthma: The STOPPA twin study

BACKGROUND

Exhaled nitric oxide and blood eosinophils are clinical asthma T-helper type 2 markers in use. Immunoglobulin E (IgE) is often involved in the inflammation associated with atopic asthma. The effect of both blood eosinophils and allergen-specific IgE on exhaled nitric oxide levels is not completely understood. Twin-design studies can improve understanding of the underlying contribution of genetically and/or environmentally driven inflammation markers in asthma. Our aim was to disentangle the covariance between asthma and exhaled nitric oxide into genetic and environmental contributions that can account for inflammation markers in a paediatric population.

METHODS

This population-based, cross-sectional twin study enrolled 612 monozygotic (MZ) and same-sex dizygotic (DZ) schoolchildren. Multivariate structural equation modelling was utilized to separate the covariance between asthma and exhaled nitric oxide into genetic and/or environmental effects, taking allergen-specific IgE level and blood eosinophil count into account while controlling for confounding factors.

RESULTS

The cross-twin/cross-trait correlations had a higher magnitude in the MZ twins than in the DZ twins, indicating that genes affect the association. The likelihood ratio test for model fitting resulted in the AE model (ie additive genetic effects, A, and non-shared environmental effects, E) as the most parsimonious. A majority, 73%, of the phenotypic correlation between asthma and exhaled nitric oxide, r = .19 (0.05-0.33), was attributable to genetic effects which mainly was due to the allergen-specific IgE level.

CONCLUSIONS

This study indicates that the association between asthma and exhaled nitric oxide in children is to a large extent explained by genetics via allergen-specific IgE level and not blood eosinophils. This might partly explain the clinical heterogeneity in this group. A next step could be to include allergen-specific IgE level in multivariate omic studies.

Toward clinically applicable biomarkers for asthma: An EAACI position paper

Inflammation, structural, and functional abnormalities within the airways are key features of asthma. Although these processes are well documented, their expression varies across the heterogeneous spectrum of asthma. Type 2 inflammatory responses are characterized by increased levels of eosinophils, FeNO, and type 2 cytokines in blood and/or airways. Presently, type 2 asthma is the best-defined endotype, typically found in patients with allergic asthma, but surprisingly also in nonallergic patients with (severe) asthma. The etiology of asthma with non-type 2 inflammation is less clear. During the past decade, targeted therapies, including biologicals and small molecules, have been increasingly integrated into treatment strategies of severe asthma. These treatments block specific inflammatory pathways or single mediators. Single or composite biomarkers help to identify patients who will benefit from these treatments. So far, only a few inflammatory biomarkers have been validated for clinical application. The European Academy of Allergy & Clinical Immunology Task Force on Biomarkers in Asthma was initiated to review different biomarker sampling methods and to investigate clinical applicability of new and existing inflammatory biomarkers (point-of-care) to support diagnosis, targeted treatment, and monitoring of severe asthma. Subsequently, we discuss existing and novel targeted therapies for asthma as well as applicable biomarkers.

Exhaled NO reference limits in a large population-based sample using the Lambda-Mu-Sigma method

Absolute values are used in the interpretation of the fraction of exhaled nitric oxide (FeNO), but it has been suggested that equations to calculate reference values may be a practical and clinically useful approach. We hypothesize that the application of the Lambda-Mu-Sigma (LMS) method may improve FeNO reference equations and their interpretation. Our aims were to develop FeNO reference equations with the LMS method and to describe the difference between this method and the absolute fixed cut-offs of the current recommendations. We utilized the United States National Health and Nutrition Examination Surveys 2007-2012 and included healthy individuals with no respiratory diseases and blood eosinophils <300/mm³ ( n = 8,340). Natural log-transformed FeNO was modeled using the LMS method, imbedded in the generalized additive models for location, scale, and shape models. A set of FeNO reference equations was developed. The explanatory variables were sex, age, height, smoking habits, and race/ethnicity. A significant proportion of individuals with normal FeNO given by the equations were classified as having intermediate levels by the current recommendations. Further lower predicted FeNO compared with previous linear models was seen. In conclusion, we suggest a novel model for the prediction of reference FeNO values that can contribute to the interpretation of FeNO in clinical practice. This approach should be further validated in large samples with an objective measurement of atopy and a medical diagnosis of asthma and rhinitis. NEW & NOTEWORTHY Novel reference equations and fraction of exhaled nitric oxide (FeNO)-predicted values to improve interpretation of FeNO in clinical practice are presented. These may increase the accuracy of ruling out airway inflammation in patients with asthma or suspected asthma.

The STOPPA Twin Study Explains the Exhaled Nitric Oxide and Asthma Link by Genetics and Sensitization

BACKGROUND

The link between asthma and exhaled nitric oxide (FENO) is not completely understood. The aim of this study was to estimate the association between FENO and asthma, taking genetics, sensitization, and inhaled corticosteroids (ICS) into account.

METHODS

A total of 681 twins (53% monozygotic [MZ] and 47% dizygotic [DZ]) from the population-based STOPPA study (mean age 12.6 years) were recruited and information on FENO (parts per billion), parental report of current asthma, sensitization to airborne allergens (Phadiatop; IgE ≥0.35 kUA/l), and ICS-treatment was collected. We estimated the association between FENO and asthma, sensitization, and ICS in all twins and within pairs (DZ and MZ) to address shared genetic and environmental factors. Linear regression of log-transformed FENO was used and results presented as exponentiated regression coefficients (exp[β]), with 95% confidence interval (CI).

RESULTS

We found an association between asthma and FENO in all twins, exp(β) 1.31 [1.11, 1.54]. In within-pairs analysis, the association was stronger within DZ pairs discordant for FENO, exp(β) 1.50 [1.19, 1.89], compared to MZ pairs, exp(β) 1.07 [0.84, 1.37], p = .049. There was no difference in FENO in non-sensitized children with asthma, compared to children with neither asthma nor sensitization, exp(β) 0.89 [0.77, 1.03]. However, increased FENO was associated with sensitization, exp(β) 1.48 [1.30, 1.69], and with sensitization together with asthma, exp(β) 1.98 [1.57, 2.51], in all twins and within DZ pairs discordant for FENO, but not in MZ pairs. The FENO asthma association remained in DZ pairs without regular ICS-treatment.

CONCLUSIONS

The association between FENO and asthma is explained by genetics and sensitization.

Measuring Airway Inflammation in Asthmatic Children

Asthma is the most common chronic respiratory disease in children characterized by airways inflammation, bronchial hyperresponsiveness, recurrent reversible airways obstruction, and respiratory symptoms. The diagnosis of the disease is based on clinical history, airways obstruction at spirometry, and bronchial reversibility. Asthma treatment is aimed to disease control, through the use of controller treatment and monitoring lung function. However, lung function and symptoms not always reflect the underlying airways inflammation and response to the therapy. Objective parameters of asthma inflammation could be important for the clinician in the management of patients with asthma. In the last years, some studies were focused on biomarkers to identify phenotype, inflammation, and pathobiological pathways to help the clinician in the diagnosis and in personalizing the management. Accordingly, clinically feasible tests are represented by the collection of exhaled breath condensate (EBC) and measurement of exhaled nitric oxide (FeNO). Other-methods such as the evaluation of volatile organic compound (VOCs), that reflect airways inflammation and treatment efficacy, are currently used for research purposes For some of these methods, The lack of standardization in pre-collection, collection, post-collection of samples, and interpretation of the results may a problem in clinical practice. Improved these limitations, several biomarkers will be useful to distinguish patients with a different disease condition to personalize the treatment.

The Value of Fractional Exhaled Nitric Oxide and Forced Mid-Expiratory Flow as Predictive Markers of Bronchial Hyperresponsiveness in Adults with Chronic Cough

BACKGROUND

Bronchial provocation tests are standard for diagnosing the etiology of chronic cough, but they are time consuming and can induce severe bronchospasm. A safer and faster clinical examination to predict bronchial hyperresponsiveness (BHR) is needed.

OBJECTIVE

The objective of this study was to investigate whether small-airway function tests can predict BHR in adult patients with chronic cough.

METHODS

A retrospective, cross-sectional study of diagnoses made using spirometry and bronchial provocation test results was performed in 290 patients with chronic nonproductive cough. BHR-predictive values were analyzed via the area under receiver operating characteristic curves (AUCs). Optimal cutoff values were determined by maximizing the sum of sensitivity and specificity.

RESULTS

Patients with chronic cough with BHR showed lower forced expiratory flow between 25% and 75% (FEF_25%-75%), higher fractional exhaled nitric oxide (FENO), and a higher percentage of eosinophils in blood than patients without BHR (P < .0001 for all). The AUCs of FENO and FEF_25%-75% for a BHR diagnosis were 0.788 (95% CI, 0.725-0.851) and 0.702 (95% CI, 0.641-0.763), respectively. Optimal cutoff values were 43 ppb for FENO and 78.5% for FEF_25%-75%, with negative predictive values of 85.38% and 81.34%, respectively. The combined use of FENO and FEF_25%-75% increased the AUC to 0.843 (95% CI, 0.794-0.892), significantly higher than either FENO (P = .012) or FEF_25%-75% (P < .0001) alone.

CONCLUSIONS

Small-airway dysfunction is present in patients with chronic cough and BHR. FEF_25%-75% has value as a negative predictive parameter for BHR, especially when combined with FENO. FENO > 43 ppb and FEF_25%-75% < 78.5% strongly predicted a positive bronchial provocation test.

Upper airway and skin symptoms in allergic and non-allergic asthma: Results from the Swedish GA2LEN study

BACKGROUND

Allergic and non-allergic asthma are viewed as separate entities, despite sharing similarities. The aims of this study were to determine differences in symptoms from the upper airways and the skin in allergic and non-allergic asthma. The secondary aims were to identify childhood risk factors and to compare quality of life in the two asthma groups.

METHODS

This cohort (age 17-76 years) consisted of 575 subjects with allergic or non-allergic asthma and 219 controls. The participants participated in an interview, spirometry, FeNO, skin prick test, and responded to the Mini Asthma Quality of Life Questionnaire.

RESULTS

Self-reported allergic rhinitis was significantly more common in both allergic and non-allergic asthma (82.3 and 40.7%) groups compared with the controls. The prevalence of chronic rhinosinusitis (CRS) was similar in both asthma groups. Eczema was significantly more common in both asthmatic groups (72.3 and 59.8%) than controls (47.0%) (p < 0.001 and p = 0.012). Severe respiratory infection in childhood and parental allergy were risk factors for both allergic and non-allergic asthma groups. Quality of life was significantly lower in non-allergic than allergic asthma groups (p = 0.01).

CONCLUSION

Concomitant symptoms from the upper airways and the skin were significantly more common in both allergic and non-allergic asthma. This indicates that non-allergic asthma has a systemic component with similarities to what is found in allergic asthma. There were similarities in the childhood risk factor pattern between the two types of asthma but asthma-related quality of life was lower in the non-allergic asthma group.

Does Ethnicity Influence Fractional Exhaled Nitric Oxide in Healthy Individuals?: A Systematic Review

BACKGROUND

Fractional exhaled nitric oxide (Feno) is used clinically as a biomarker of eosinophilic airway inflammation. Awareness of the factors influencing Feno values is important for valid clinical interpretation.

METHODS

We undertook a systematic review of PubMed, Cochrane Library, Scopus, and Web of Science databases and reference lists of included articles to evaluate whether ethnicity influences Feno values, and to determine if this influence affects clinical interpretation according to current guidelines. We included all studies that performed online Feno measurements on at least 25 healthy, non-Caucasian individuals, and examined the effect of ethnicity on Feno.

RESULTS

From 62 potential studies, 12 studies were included. One study recruited only children (< 12 years of age), six studies recruited children and/or adolescents, four studies recruited adults only, and a single study involved children, adolescents, and adults. In total, 16 different ethnic populations representing 11 ethnicities were studied. Ethnicity was considered a significant influencing factor in 10 of the included studies. We found the geometric mean Feno to be above the normal healthy range in two studies. We also identified five studies in which at least 5% of participants had Feno results above the age-specific inflammatory ranges.

CONCLUSIONS

Ethnicity influences Feno values, and for some ethnic groups this influence likely affects clinical interpretation according to current guidelines. There is a need to establish healthy Feno reference ranges for specific ethnic groups to improve clinical application.

Asthma phenotypes in childhood

INTRODUCTION

Asthma is no longer thought of as a single disease, but rather a collection of varying symptoms expressing different disease patterns. One of the ongoing challenges is understanding the underlying pathophysiological mechanisms that may be responsible for the varying responses to treatment. Areas Covered: This review provides an overview of our current understanding of the asthma phenotype concept in childhood and describes key findings from both conventional and data-driven methods. Expert Commentary: With the vast amounts of data generated from cohorts, there is hope that we can elucidate distinct pathophysiological mechanisms, or endotypes. In return, this would lead to better patient stratification and disease management, thereby providing true personalised medicine.

Exercise-Induced Changes in Exhaled NO Differentiates Asthma With or Without Fixed Airway Obstruction From COPD With Dynamic Hyperinflation

Asthmatic patients with fixed airway obstruction (FAO) and patients with chronic obstructive pulmonary disease (COPD) share similarities in terms of irreversible pulmonary function impairment. Exhaled nitric oxide (eNO) has been documented as a marker of airway inflammation in asthma, but not in COPD. To examine whether the basal eNO level and the change after exercise may differentiate asthmatics with FAO from COPD, 27 normal subjects, 60 stable asthmatics, and 62 stable COPD patients were studied. Asthmatics with FAO (n = 29) were defined as showing a postbronchodilator FEV1/forced vital capacity (FVC) ≤70% and FEV1 less than 80% predicted after inhaled salbutamol (400 μg). COPD with dynamic hyperinflation (n = 31) was defined as a decrease in inspiratory capacity (ΔIC%) after a 6 minute walk test (6MWT). Basal levels of eNO were significantly higher in asthmatics and COPD patients compared to normal subjects. The changes in eNO after 6MWT were negatively correlated with the percent change in IC (r = -0.380, n = 29, P = 0.042) in asthmatics with FAO. Their levels of basal eNO correlated with the maximum mid-expiratory flow (MMEF % predicted) before and after 6MWT. In COPD patients with air-trapping, the percent change of eNO was positively correlated to ΔIC% (rs = 0.404, n = 31, P = 0.024). We conclude that asthma with FAO may represent residual inflammation in the airways, while dynamic hyperinflation in COPD may retain NO in the distal airspace. eNO changes after 6MWT may differentiate the subgroups of asthma or COPD patients and will help toward delivery of individualized therapy for airflow obstruction.

A pathophysiological approach for FeNO: A biomarker for asthma

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

Fluticasone propionate in clinically suspected asthma patients with negative methacholine challenge test

INTRODUCTION

Despite reports of response to steroid inhaler in some clinically suspected asthma patients with negative methacholine challenge test (CSA/MCT-), treatment in these patients has not been prospectively studied.

OBJECTIVE

We studied the role of a 12 week high dose inhaled fluticasone trial in CSA/MCT- patients.

METHODS

After a 2 week run-in period, CSA/MCT-patients were treated with 12 weeks of Fluticasone propionate 1000 µg/day. The Asthma Control Test (ACT), numeric cough score (NCS) and bronchodilator use were compared with their pretreatment values.

RESULTS

Thirty-four of 42 CSA/MCT-patients completed the study. Mean pretreatment ACT score (pACT) was significantly increased after treatment (14.7 ± 3.37 to 20.9 ± 3.1, P < 0.001). Posttreatment values of daytime (1.0 ± 1.0) and night-time (0.6 ± 0.9) NCS decreased compared to their pretreatment values (2.8 ± 1.1 and 1.9 ± 1.3, respectively; P < 0.001). ACT score change (ΔACT) were significantly greater in those with pACT < 15 than in those ≥15 (P < 0.001) . Fifteen of 21 patients with ΔACT > 5 did not need to use bronchodilator for their symptom relief. Wheeze disappeared in all six patients with ΔACT > 5 after the trial. Six months after the study, steroid inhaler continued to be used by 72.2% of patients.

CONCLUSION

A significant portion of CSA/MCT- (especially those with pretreatment ACT score <15) respond to high dose fluticasone inhaler in terms of symptoms relief, disappearance of wheeze and need to bronchodilator use. ΔACT could not be predicted with any individual symptoms or signs before MCT, % FEV1 decline or symptoms during MCT and exhaled nitric oxide.

Childhood asthma biomarkers: present knowledge and future steps

Asthma represents the most common chronic respiratory disease of childhood. Its current standard diagnosis relies on patient history of symptoms and confirmed expiratory airflow limitation. Nevertheless, the spectrum of asthma in clinical presentation is broad, and both symptoms and lung function may not always reflect the underlying airway inflammation, which can be determined by different pathogenetic mechanisms. For these reasons, the identification of objective biomarkers of asthma, which may guide diagnosis, phenotyping, management and treatment is of great clinical utility and might have a role in the development of personalized therapy. The availability of non-invasive methods to study and monitor disease inflammation is of relevance especially in childhood asthma. In this sense, a promising role might be played by the measurement of exhaled biomarkers, such as exhaled nitric oxide (FE(NO)) and molecules in exhaled breath condensate (EBC). Furthermore, recent studies have shown encouraging results with the application of the novel metabolomic approach to the study of exhaled biomarkers. In this paper the existing knowledge in the field of asthma biomarkers, with a special focus on exhaled biomarkers, will be highlighted.

RespDoc: a new clinical decision support system for childhood asthma management based on Fraction of Exhaled Nitric Oxide (FeNO) measurements

The use of Fraction of Exhaled Nitric Oxide (FeNO) for measurement of inflammation in the respiratory system is a good way to assess the level of asthma in children. In this paper we present a new Clinical Decision Support System (CDSS) for Childhood Asthma Management based on FeNO, which is named RespDoc. The core of RespDoc is a decision making algorithm and a patient's monitoring process that are extensively analyzed in the paper. The performance of RespDoc is tested through the process and assessment of archived patients' data.

Albuterol inhalation increases FeNO level in steroid-naive asthmatics but not COPD patients with reversibility

INTRODUCTION

Fractional exhaled nitric oxide (FeNO) has been used as a marker of airway inflammation. Airway caliber is related to the level of FeNO in asthmatics.

OBJECTIVES

This study aimed to investigate whether airway obstruction could interfere with real FENO levels and if different FeNO changes after albuterol inhalation could assist in distinguishing asthma from chronic obstructive pulmonary disease (COPD).

METHODS

FeNO and spirometry measurements were performed before and after albuterol inhalation in the following three patient groups: 30 steroid-naive asthmatics, 25 asthmatics inhaling corticosteroids/long-acting β(2)-adrenergic agonists for at least 1 month and 20 COPD patients. Bronchodilator test (BDT) results were positive in all patients enrolled. The correlations among FeNO levels, pulmonary function and sputum eosinophil counts were analyzed.

RESULTS

FeNO increased significantly after albuterol inhalation in steroid-naive asthmatics but not in ICS-treated asthmatics or COPD patients. The FeNO levels demonstrated no significant correlation with spirometry results or sputum eosinophil counts before or after inhaling bronchodilator in all three groups. Both the levels of FeNO and changes in FENO after albuterol inhalation in steroid-naive asthma patients were higher than those in ICS-treated asthmatics and COPD patients (P < 0.001). The differences remained after proper adjustment for confounding factors (gender, age, smoking pack-years, ICS-treated and pulmonary function index).

CONCLUSIONS

Our results support the role of FeNO in differentiating asthmatics from COPD patients with positive BDT. FeNO detection after albuterol inhalation should be encouraged in steroid-naive asthma patients with airway obstruction.

Exhaled Nitric Oxide and Airway Hyperresponsiveness to Adenosine 5'-monophosphate and Methacholine in Children with Asthma

BACKGROUND

There is increasing interest in the role of indirect bronchial challenges because clinical studies have shown that indirect airway hyperresponsiveness (AHR) reflects underlying airway inflammation better than direct AHR. Fractional exhaled nitric oxide (FeNO) appears to be a useful clinical tool for assessing airway inflammation noninvasively. We examined whether FeNO is more closely related to AHR to indirect stimuli than AHR to direct stimuli in children with mild to moderate asthma.

METHODS

Fifty-nine asthmatic children aged 6-16 years without rhinitis, underwent spirometry, FeNO measurement and blood tests for serum total IgE, blood eosinophil count and serum eosinophil cationic protein (ECP). All subjects underwent methacholine and adenosine 5-monophosphate (AMP) challenge tests at intervals of 3 days.

RESULTS

In a univariate linear regression analysis, FeNO was significantly associated with both PC20 AMP (R(2) = 0.341, p < 0.001) and PC20 methacholine (R(2) = 0.188, p = 0.001). After adjustment for age, sex, serum total IgE and blood eosinophil count, the association between FeNO and PC20 AMP (β = -1.98, p = 0.001) was more robust than that between FeNO and PC20 methacholine (β = -0.87, p = 0.081). The significant correlation between FeNO and PC20 AMP was observed in the steroid-naïve group (β = -2.48, p = 0.001), but not in the steroid-treated group (β = 0.88, p = 0.463).

CONCLUSIONS

FeNO levels were more closely associated with PC20 AMP than with PC20 methacholine. This relationship could only be seen in the steroid-naïve subjects. These results suggest that FeNO levels in children with asthma may be more closely related to indirect AHR than to direct AHR.

Exhaled nitric oxide and the management of childhood asthma--yet another promising biomarker "has been" or a misunderstood gem

Childhood asthma is a common chronic condition. Approximately five percent of all children in western countries are prescribed treatment with inhaled corticosteroids (ICS) to prevent asthma symptoms. Current guidelines advocate titrating ICS dose to symptoms but this approach is not without problem, e.g. how to discern asthmatic from non-asthmatic symptoms? And when to reduce ICS dose? This review describes the strengths and weaknesses of fractional exhaled nitric oxide (FENO) as an objective index for individualising asthma control in children. Epidemiological and mechanistic evidence suggest that FENO should be a promising biomarker for eosinophilic airway inflammation (a hall mark for asthma) but somewhat surprisingly, clinical trials in children have not consistently found benefit from adding FENO to a symptom-based approach to ICS treatment in children. There are a number of reasons why FENO has apparently failed to translate from promising biomarker to clinically useful tool, and one reason may be a lack of understanding of what merits a significant intrasubject change in FENO. This review describes the rise and apparent fall of FENO as biomarker for asthma and then focuses on more recent evidence which suggest that FENO may prove to have a role in the management of childhood asthma, and in particular preventing exacerbations.

Breath analysis as a potential and non-invasive frontier in disease diagnosis: an overview

Currently, a small number of diseases, particularly cardiovascular (CVDs), oncologic (ODs), neurodegenerative (NDDs), chronic respiratory diseases, as well as diabetes, form a severe burden to most of the countries worldwide. Hence, there is an urgent need for development of efficient diagnostic tools, particularly those enabling reliable detection of diseases, at their early stages, preferably using non-invasive approaches. Breath analysis is a non-invasive approach relying only on the characterisation of volatile composition of the exhaled breath (EB) that in turn reflects the volatile composition of the bloodstream and airways and therefore the status and condition of the whole organism metabolism. Advanced sampling procedures (solid-phase and needle traps microextraction) coupled with modern analytical technologies (proton transfer reaction mass spectrometry, selected ion flow tube mass spectrometry, ion mobility spectrometry, e-noses, etc.) allow the characterisation of EB composition to an unprecedented level. However, a key challenge in EB analysis is the proper statistical analysis and interpretation of the large and heterogeneous datasets obtained from EB research. There is no standard statistical framework/protocol yet available in literature that can be used for EB data analysis towards discovery of biomarkers for use in a typical clinical setup. Nevertheless, EB analysis has immense potential towards development of biomarkers for the early disease diagnosis of diseases.

Investigation of C3-C10 aldehydes in the exhaled breath of healthy subjects using selected ion flow tube-mass spectrometry (SIFT-MS)

Aldehydes have attracted great scientific and clinical interest as potential disease biomarkers. We have investigated selected ion flow tube-mass spectrometry (SIFT-MS) in detecting and quantifying C3 to C10 saturated aldehydes (propanal, butanal, pentanal, hexanal, heptanal, octanal, nonanal and decanal) from the exhaled breath of 26 healthy human volunteers. To assess the reliability of the Nalophan® bag sampling method employed, the water level in the breath sample was measured up to 4 h after collection and showed no significant degradation. Propanal was found to be the most abundant aldehyde in the exhaled breath of healthy volunteers. For the C4-C10 aldehydes, their median concentrations were all less than 3 ppbv, demonstrating only trace quantities are present in the exhaled breath of the 26 healthy volunteers.

Revisiting the role of exhaled nitric oxide in asthma

PURPOSE OF REVIEW

This review focuses on the most recent studies investigating fractional nitric oxide concentration in exhaled breath (FeNO) as a useful biomarker for identifying specific phenotypes in asthma and as a tool for asthma diagnosis, monitoring and clinical decision-making.

RECENT FINDINGS

On the basis of the current literature, it has been highlighted that FeNO is a clinically relevant marker in various clinical aspects of asthma: FeNO is a predictor for developing asthma in persistent rhinitis or in infants with respiratory symptoms; FeNO contributes to identification of asthma phenotypes in both children and adults, also in relation to severity; FeNO is useful in monitoring the effectiveness of inhaled corticosteroids (including compliance) and biologic treatments like omalizumab; FeNO, in conjunction with symptom registration and lung function measurements, contributes to asthma diagnosis and optimizes asthma management.

SUMMARY

FeNO provides further information in distinguishing different phenotypes in asthma, allowing a much more appropriate control of the disease, especially in patients with difficult/severe asthma. In the future, it would be interesting to shed light on the hidden biological mechanisms responsible for low or normal FeNO values in symptomatic asthmatic patients.

Rapid point-of-care breath test for biomarkers of breast cancer and abnormal mammograms

Background

Previous studies have reported volatile organic compounds (VOCs) in breath as biomarkers of breast cancer and abnormal mammograms, apparently resulting from increased oxidative stress and cytochrome p450 induction. We evaluated a six-minute point-of-care breath test for VOC biomarkers in women screened for breast cancer at centers in the USA and the Netherlands.

Methods

244 women had a screening mammogram (93/37 normal/abnormal) or a breast biopsy (cancer/no cancer 35/79). A mobile point-of-care system collected and concentrated breath and air VOCs for analysis with gas chromatography and surface acoustic wave detection. Chromatograms were segmented into a time series of alveolar gradients (breath minus room air). Segmental alveolar gradients were ranked as candidate biomarkers by C-statistic value (area under curve [AUC] of receiver operating characteristic [ROC] curve). Multivariate predictive algorithms were constructed employing significant biomarkers identified with multiple Monte Carlo simulations and cross validated with a leave-one-out (LOO) procedure.

Results

Performance of breath biomarker algorithms was determined in three groups: breast cancer on biopsy versus normal screening mammograms (81.8% sensitivity, 70.0% specificity, accuracy 79% (73% on LOO) [C-statistic value], negative predictive value 99.9%); normal versus abnormal screening mammograms (86.5% sensitivity, 66.7% specificity, accuracy 83%, 62% on LOO); and cancer versus no cancer on breast biopsy (75.8% sensitivity, 74.0% specificity, accuracy 78%, 67% on LOO).

Conclusions

A pilot study of a six-minute point-of-care breath test for volatile biomarkers accurately identified women with breast cancer and with abnormal mammograms. Breath testing could potentially reduce the number of needless mammograms without loss of diagnostic sensitivity.

Current evidence and future research needs for FeNO measurement in respiratory diseases

Although not yet widely implemented, fraction of exhaled nitric oxide (FeNO) has emerged in recent years as a potentially useful biomarker for the assessment of airway inflammation both in undiagnosed patients with non-specific respiratory symptoms and in those with established airway disease. Research to date essentially suggests that FeNO measurement facilitates the identification of patients exhibiting T-helper cell type 2 (Th2)-mediated airway inflammation, and effectively those in whom anti-inflammatory therapy, particularly inhaled corticosteroids (ICS), is beneficial. In some studies, FeNO-guided management of patients with established airway disease is associated with lower exacerbation rates, improvements in adherence to anti-inflammatory therapy, and the ability to predict risk of future exacerbations or decline in lung function. Despite these data, concerns regarding the applicability and utility of FeNO in clinical practice still remain. This article reviews the current evidence, both supportive and critical of FeNO measurement, in the diagnosis and management of asthma and other inflammatory airway diseases. It additionally provides suggestions regarding the practical application of FeNO measurement: how it could be integrated into routine clinical practice, how its utility could be assessed and its true value to both clinicians and patients could be established. Although some unanswered questions remain, current evidence suggests that FeNO is potentially a valuable tool for improving the personalised management of inflammatory airway diseases.

Evaluation of exhaled nitric oxide in acute paraquat poisoning: a pilot study

BACKGROUND

Fractional exhaled nitric oxide (FENO) is nitric oxide (NO) in the lower airway measured by oral exhalation. FENO can be a useful non-invasive marker for asthma. Paraquat-mediated lung injury can be reflective of an ROS-induced lung injury. We aimed to verify if FENO is a clinical parameter of ROS formation and responsiveness to medical therapies in acute paraquat intoxication.

MATERIAL AND METHODS

We recruited 12 patients admitted with acute paraquat poisoning. A portable and noninvasive device called NIOX MINO™ (Aerocrine AB, Solna, Sweden) was used to measure FENO. Measurements were made at the time of hospital admission and at 24, 48, 72, 96, and 120 h after paraquat ingestion.

RESULTS

Six out of the total 12 recruited patients had general conditions (e.g. oral pain) that made it difficult for them to exhale with adequate force. Mean plasma paraquat level was 1.4 ± 2.5 g/mL. We found no direct correlation between the paraquat levels (both ingestion amount and plasma concentration) and FENO (initial, maximal, and minimal values). All the measured FENO values were no greater than 20 ppb for the 2 patients who died. FENO did not vary more than 20% from the baseline. Compared to the above findings, FENO measurements were found to be greater than 20 ppb for the patients who survived. FENO tends to reach its peak value at between 50 h and 80 h.

CONCLUSIONS

FENO did not predict mortality, and there was no increase of FENO in patients with severe paraquat intoxication.