Exhaled nitric oxide correlates with airway eosinophils in childhood asthma

Clinical applications of lung function tests: a revisit

The development and clinical application of lung function tests have a long history, and the various components of lung function tests provide very important tools for the clinical evaluation of respiratory health and disease. Spirometry, measurement of the diffusion factor, bronchial provocation tests and forced oscillation techniques have found diverse clinical applications in the diagnosis and monitoring of respiratory diseases, such as chronic obstructive pulmonary disease, interstitial lung diseases and asthma. However, there are some practical issues to be resolved, including the establishment of reference values for individual test parameters and the roles of these tests in preoperative risk assessment and pulmonary rehabilitation. Novel measurements, including negative expiratory pressure, the fraction of exhaled nitric oxide and analysis of exhaled breath condensate, may provide new insights into physiological abnormalities or airway inflammation in respiratory diseases, but their clinical applications need to be further evaluated. The clinical application of lung function tests continues to face challenges, which may be overcome by further improvement of conventional techniques for lung function testing and further specification of new testing techniques.

Exhaled nitric oxide

Nitric oxide (NO) is now considered an important biomarker for respiratory disease. Studies have confirmed that the fractional concentration of exhaled nitric oxide (FENO) is elevated in the airways of patients who have asthma in comparison with controls. The level of FENO correlates well with the presence and level of inflammation, and decreases with glucocorticoid treatment. NO has potential to be used not only as a diagnostic aid but also as a management tool for assessing severity, monitoring response to therapy, and gaining control of asthma symptoms. This article reviews the biology of NO and its role in respiratory disease.

Comparative repeatability of two handheld fractional exhaled nitric oxide monitors

BACKGROUND

The use of portable fractional exhaled nitric oxide (FENO) devices is increasingly common in the diagnosis and management of allergic airways inflammation.

METHODS

We tested two handheld FENO devices, to determine (a) if there was adequate intradevice repeatability to allow the use of single breath testing, and (b) if the devices could be used interchangeably. In a mixed pediatric population, including normal, asthmatic, and children with peanut allergies, 858 paired values were collected from the NIOX-MINO® and/or the NObreath® devices.

RESULTS

The NIOX-MINO® showed excellent repeatability (mean difference of 0.1 with 95% limits of agreement between -7.93 to 7.72 ppb), while the NObreath® showed good repeatability (mean difference of -1.61 with 95% limits of agreement between -14.1 and 10.8 ppb). Intradevice repeatability was good but not adequate and the NIOX-MINO® systematically produced higher results than the NObreath® [mean difference of 7.8 ppb with 95% limits of agreement from -11.55 to 27.52 ppb (-33% to 290%)].

CONCLUSIONS

Our results support the manufacturer's advice that single breath testing is appropriate for the NIOX-MINO®. NObreath® results indicate that the mean of more than one breath should be utilized. The devices cannot be used interchangeably.

Exhaled nitric oxide is related to bronchial eosinophilia and airway hyperresponsiveness to bradykinin in allergen-induced asthma exacerbation

Exhaled nitric oxide (FeNO) has been associated with bronchial eosinophilia and with airway hyperresponsiveness (AHR) in mild stable asthma. We previously demonstrated in a large project that allergen exposure is able to raise FeNO and to worsen AHR to bradykinin. We postulated that allergen-induced increase in FeNO could be related to heightened mucosal eosinophils and AHR to bradykinin in atopic asthma. We performed a new immunohistochemical analysis on bronchial biopsy specimens, previously obtained from the same large project, in order to assess the number of mucosal eosinophils (EG-2+ cell) and other inflammatory cells at 48 hours after diluent and allergen exposures. Inflammatory cell counts were related to FeNO and AHR to BK (expressed as logPD20 bradykinin). In 10 atopic mild asthmatics, we found that the numbers of EG-2+ and CD4+ cells in bronchial submucosa were significantly increased after allergen compared to the respective counts after diluent (p < 0.01). EG-2+ cells in the bronchial submucosa were negatively correlated with logPD20 bradykinin only after allergen challenge (rho = -0.709, p = 0.027). We also found a positive strong correlation between EG-2+ cells and FeNO values in atopic asthmatics at 48 hours after both diluent (rho = 0.746, p = 0.017) and allergen (rho = 0.644, p = 0.049) challenge. FeNO values negatively correlated with responsiveness to bradykinin only after allergen challenge (rho = -0.675, p = 0.039). This study indicates that after allergen exposure heightened level of exhaled NO may reflect augmented airway eosinophilic inflammation and airway responsiveness to bradykinin indicating loss of asthma control.

IgE antibodies to animal-derived lipocalin, kallikrein and secretoglobin are markers of bronchial inflammation in severe childhood asthma

BACKGROUND

Component-resolved allergy diagnostics enables the detection of crossreactive or species-specific allergen components. This study analysed Immunoglobulin E (IgE) profiles to single allergen components in relation to bronchial inflammation in severe childhood asthma.

METHODS

Ninety-five schoolchildren were assessed, 39 with controlled mild-to-moderate asthma and 56 uncontrolled severe asthmatics. Allergen components (n = 111) of food allergens, pollen and perennial aeroallergens were analysed using an immunosolid-phase allergen chip. Blood eosinophils (10(9) × l(-1)), bronchial inflammation (FeNO, ppb), lung function (FEV(1)%) and bronchial hyper-responsiveness (BHR) (dose-response slope of methacholine challenge) were measured.

RESULTS

A specific IgE response to more than three animal-derived components--lipocalin (nMus m 1, rEqu c 1, Fel d 4, rCan f 1, 2), kallikrein (rCan f 5) and secretoglobin (rFel d 1)--was more common among severe asthmatics compared to children with controlled asthma (n = 14 vs n = 3, P = 0.030). These subjects also displayed higher blood eosinophils (0.65 vs 0.39, P = 0.021), higher Fractional exhaled nitric oxide (38 ppb vs 25 ppb, P = 0.021) and increased BHR (112 vs 28, P = 0.002) compared to other severe asthmatics positive to fewer lipocalin/kallikrein/secretoglobin components. Among all sensitized subjects, there were correlations between specific IgE levels for rFel d 4 and nMus m 1 (r = 0.751, P ≤ 0.001) and for rFel d 4 and rEqu c 1 (r = 0.850, P ≤ 0.001).

CONCLUSION

Multi-sensitization towards lipocalin, kallikrein and secretoglobin components is associated with increased bronchial inflammation in severe asthmatics. In addition, crossreactive patterns were observed between different lipocalin components.

Asthma outcomes: biomarkers

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Bronchial responsiveness is related to increased exhaled NO (FE(NO)) in non-smokers and decreased FE(NO) in smokers

RATIONALE

Both atopy and smoking are known to be associated with increased bronchial responsiveness. Fraction of nitric oxide (NO) in the exhaled air (FE(NO)), a marker of airways inflammation, is decreased by smoking and increased by atopy. NO has also a physiological bronchodilating and bronchoprotective role.

OBJECTIVES

To investigate how the relation between FE(NO) and bronchial responsiveness is modulated by atopy and smoking habits.

METHODS

Exhaled NO measurements and methacholine challenge were performed in 468 subjects from the random sample of three European Community Respiratory Health Survey II centers: Turin (Italy), Gothenburg and Uppsala (both Sweden). Atopy status was defined by using specific IgE measurements while smoking status was questionnaire-assessed.

MAIN RESULTS

Increased bronchial responsiveness was associated with increased FE(NO) levels in non-smokers (p = 0.02) and decreased FE(NO) levels in current smokers (p = 0.03). The negative association between bronchial responsiveness and FE(NO) was seen only in the group smoking less <10 cigarettes/day (p = 0.008). Increased bronchial responsiveness was associated with increased FE(NO) in atopic subjects (p = 0.04) while no significant association was found in non-atopic participants. The reported interaction between FE(NO) and smoking and atopy, respectively were maintained after adjusting for possible confounders (p-values<0.05).

CONCLUSIONS

The present study highlights the interactions of the relationship between FE(NO) and bronchial responsiveness with smoking and atopy, suggesting different mechanisms behind atopy- and smoking-related increases of bronchial responsiveness.

Utility of fractional exhaled nitric oxide (F(E)NO) measurements in diagnosing asthma

BACKGROUND

To facilitate the use of fractional exhaled nitric oxide (F(E)NO) as a clinical test, F(E)NO measurements need more clarification.

AIM

We sought to evaluate the yield of F(E)NO measurement for the diagnosis of asthma and identify the determinants of F(E)NO in children.

METHODS

Two hundred forty five consecutive steroid-naïve patients aged 8-16 years with symptoms suggestive of asthma were included. Children were evaluated using F(E)NO measurements, questionnaires, skin prick tests, spirometries, and methacholine challenge tests.

RESULTS

Asthma was diagnosed in 167 children. The sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of F(E)NO measurements for the diagnosis of asthma at the best cutoff value of 22 ppb were 56.9%, 87.2%, 90.5%, and 48.6%, respectively. At a cutoff value of 42 ppb, specificity and PPV were all 100% but at the cost of very low sensitivity (23.4%) and NPV (37.9%). Both atopy and asthma were identified as independent risk factors associated with high F(E)NO. The association of asthma with high F(E)NO was found only in atopic children because F(E)NO was low in non-atopic children regardless of asthma status. Although highest F(E)NO was observed in atopic asthmatic patients, 28% of these patients had F(E)NO values lower than 22 ppb.

CONCLUSION

Atopic asthmatic patients with low F(E)NO values and non-atopic asthmatic patients were responsible for false-negative cases that might contribute to low sensitivity of F(E)NO measurements in diagnosing asthma. High specificity of F(E)NO measurements may help identify patients with atopic asthma among subjects with respiratory symptoms.

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

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

Canadian Thoracic Society 2012 guideline update: diagnosis and management of asthma in preschoolers, children and adults

BACKGROUND

In 2010, the Canadian Thoracic Society (CTS) published a Consensus Summary for the diagnosis and management of asthma in children six years of age and older, and adults, including an updated Asthma Management Continuum. The CTS Asthma Clinical Assembly subsequently began a formal clinical practice guideline update process, focusing, in this first iteration, on topics of controversy and⁄or gaps in the previous guidelines.

METHODS

Four clinical questions were identified as a focus for the updated guideline: the role of noninvasive measurements of airway inflammation for the adjustment of anti-inflammatory therapy; the initiation of adjunct therapy to inhaled corticosteroids (ICS) for uncontrolled asthma; the role of a single inhaler of an ICS⁄long-acting beta(2)-agonist combination as a reliever, and as a reliever and a controller; and the escalation of controller medication for acute loss of asthma control as part of a self-management action plan. The expert panel followed an adaptation process to identify and appraise existing guidelines on the specified topics. In addition, literature searches were performed to identify relevant systematic reviews and randomized controlled trials. The panel formally assessed and graded the evidence, and made 34 recommendations.

RESULTS

The updated guideline recommendations outline a role for inclusion of assessment of sputum eosinophils, in addition to standard measures of asthma control, to guide adjustment of controller therapy in adults with moderate to severe asthma. Appraisal of the evidence regarding which adjunct controller therapy to add to ICS and at what ICS dose to begin adjunct therapy in children and adults with poor asthma control supported the 2010 CTS Consensus Summary recommendations. New recommendations for the adjustment of controller medication within written action plans are provided. Finally, priority areas for future research were identified.

CONCLUSIONS

The present clinical practice guideline is the first update of the CTS Asthma Guidelines following the Canadian Respiratory Guidelines Committee's new guideline development process. Tools and strategies to support guideline implementation will be developed and the CTS will continue to regularly provide updates reflecting new evidence.

Assessing asthma control: symptom scores, GINA levels of asthma control, lung function, and exhaled nitric oxide

BACKGROUND

The childhood asthma control test (C-ACT) is a validated symptom score for assessing asthma control in children. We used a slightly modified version (C-ACT(M) ) of the German C-ACT and compared our results with the literature, correlated the children's part of C-ACT (C-ACT(children) ) with a visual analogue scale (VAS(children) ), explored the agreement between C-ACT(M) and GINA levels of asthma control, as well as the relationship between C-ACT(M) and lung function and exhaled nitric oxide (FeNO).

METHODS

We investigated 107 children with a diagnosis of asthma. The study protocol consisted of a clinical examination, assessment of asthma control according to GINA guidelines, administration of C-ACT(M) , VAS(children) , lung function, and FeNO.

RESULTS

Of our patients 66% had, according to GINA, partly controlled-/uncontrolled asthma, 18% were uncontrolled according to C-ACT(M) . Children with partly controlled-/uncontrolled asthma according to GINA had lower C-ACT(M) scores than did children with controlled asthma (16.1 ± 3.6 SD vs. 25.4 ± 1.8 SD; P < 0.000), and children with a C-ACT(M) score ≤ 19 had poorer lung function (mean FEV1% predicted 81.5 ± 13.5 SD vs. 94.2 ± 12.1 SD; P = 0.002). Spearman's rank correlation coefficients revealed significant correlations between all symptom scores. Multiple linear regression adjusted for age, gender, FEV1 and FeNO demonstrated a significant relationship between C-ACT(M) , VAS(children) , and FEV1 (P = 0.003, resp. <0.000), but no significant correlation between C-ACT(M) , VAS(children) , and FeNO.

CONCLUSIONS

The German version of C-ACT(M) is valid and useful for monitoring children with asthma along with tests aimed to follow up lung function and airway inflammation. Concordance between C-ACT(M) and GINA is moderate, because asthma control assessed by C-ACT(M) allows more symptoms and lung function is not included in the scoring.

Asthma, atopy and exhaled nitric oxide in a cohort of 6-yr-old New Zealand children

BACKGROUND

Exhaled nitric oxide has been promoted as a non-invasive measure of airway inflammation, with clinical utility for the diagnosis and management of asthma.

AIM

We studied associations between exhaled nitric oxide, asthma and atopy in a variety of clinically relevant phenotypes in a cohort of 6-yr-old children.

METHOD

Asthma was defined using standard questionnaire criteria, atopy was measured using skin prick tests (SPT) and specific IgE to common allergens, and exhaled nitric oxide was measured using a chemiluminescence analyser according to American and European Thoracic Society criteria.

RESULTS

Exhaled nitric oxide was strongly related to atopy and in particular to sensitization to house dust mites. Children with non-allergic asthma had no increase in exhaled nitric oxide compared with non-asthmatic children. Compared with children who never wheezed both late onset and persistent, wheezing was associated with increased FE(NO), while early transient wheezing was not. Elevated levels of exhaled nitric oxide amongst children with allergic asthma were almost entirely explained by their levels of specific IgE to aeroallergens, predominantly D pteronyssinus.

CONCLUSION

Airway inflammation as measured by exhaled nitric oxide in young New Zealand children is related to their level of specific IgE to aeroallergens. This has implications for the utility of nitric oxide as a diagnostic and management tool in childhood asthma and for the importance of specific IgE as a marker of asthma severity.

[Asthma exacerbations: pharmacological prevention]

Asthma exacerbations are responsible for many emergency medical interventions and account for a significant proportion of the health costs of the disease. Increased airway inflammation is a key feature of exacerbations in asthma and therefore inhaled corticosteroids (ICS) are considered as first-line therapy for long-term asthma control. ICS have been demonstrated to reduce the risk of asthma exacerbations, as well as improving lung function. Oral leukotriene receptor antagonists also reduce the incidence of asthma exacerbations but are less effective than ICS. In patients with inadequately controlled persistent asthma despite low-dose ICS, the addition of a long-acting inhaled beta-agonist (LABA) should be considered. LABA should not be given alone and should always be associated with ICS in asthma. The anti-immunoglobulin E antibody, omalizumab, reduces severe exacerbations and emergency visits in patients with severe allergic asthma. In clinical trials measurement of the inflammatory response in induced sputum could provide information concerning appropriate drug therapy. Asthma-associated comorbidities should be investigated and treated, particularly in severe asthma. Despite a high prevalence of both gastro-oesophageal reflux and allergic rhinitis among patients with asthma, treatment with proton-pump inhibitors or nasal corticosteroids does not reduce the rate of asthma exacerbations.

Measures of asthma control

PURPOSE OF REVIEW

Over the past decade, the concept of asthma control as distinct from asthma severity has been clearly defined. Well controlled asthma is the goal of therapy in all asthma patients. This review is a comprehensive description of the tools currently available for a methodical assessment of different aspects of asthma control in clinical practice and research.

RECENT FINDINGS

Several questionnaires for assessing asthma control have been extensively validated in adults. In children, validation data are less extensive. Considerable overlap exists between asthma control measures and measures of asthma-specific quality of life. Asthma-specific quality-of-life questionnaires have been used as primary outcome measures in major clinical trials evaluating asthma therapy. Biomarkers that reflect eosinophilic inflammation of the airways are used as intermediate outcome measures to reflect the biological basis of asthma control. There is some controversy, however, over which biomarkers are best incorporated into therapeutic algorithms that attempt to achieve maximal asthma control while minimizing treatment intensity.

SUMMARY

In designing clinical studies to evaluate different asthma therapies, researchers will find this review to be a useful resource in terms of choosing the appropriate tool for assessing asthma control. This is also a valuable resource for a methodical assessment of response to asthma therapy in routine clinical care.

Fractional exhaled nitric oxide measurements in rhinitis and asthma in children

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

An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications

BACKGROUND

Measurement of fractional nitric oxide (NO) concentration in exhaled breath (Fe(NO)) is a quantitative, noninvasive, simple, and safe method of measuring airway inflammation that provides a complementary tool to other ways of assessing airways disease, including asthma. While Fe(NO) measurement has been standardized, there is currently no reference guideline for practicing health care providers to guide them in the appropriate use and interpretation of Fe(NO) in clinical practice.

PURPOSE

To develop evidence-based guidelines for the interpretation of Fe(NO) measurements that incorporate evidence that has accumulated over the past decade.

METHODS

We created a multidisciplinary committee with expertise in the clinical care, clinical science, or basic science of airway disease and/or NO. The committee identified important clinical questions, synthesized the evidence, and formulated recommendations. Recommendations were developed using pragmatic systematic reviews of the literature and the GRADE approach.

RESULTS

The evidence related to the use of Fe(NO) measurements is reviewed and clinical practice recommendations are provided.

CONCLUSIONS

In the setting of chronic inflammatory airway disease including asthma, conventional tests such as FEV(1) reversibility or provocation tests are only indirectly associated with airway inflammation. Fe(NO) offers added advantages for patient care including, but not limited to (1) detecting of eosinophilic airway inflammation, (2) determining the likelihood of corticosteroid responsiveness, (3) monitoring of airway inflammation to determine the potential need for corticosteroid, and (4) unmasking of otherwise unsuspected nonadherence to corticosteroid therapy.

An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications

BACKGROUND

Measurement of fractional nitric oxide (NO) concentration in exhaled breath (Fe(NO)) is a quantitative, noninvasive, simple, and safe method of measuring airway inflammation that provides a complementary tool to other ways of assessing airways disease, including asthma. While Fe(NO) measurement has been standardized, there is currently no reference guideline for practicing health care providers to guide them in the appropriate use and interpretation of Fe(NO) in clinical practice.

PURPOSE

To develop evidence-based guidelines for the interpretation of Fe(NO) measurements that incorporate evidence that has accumulated over the past decade.

METHODS

We created a multidisciplinary committee with expertise in the clinical care, clinical science, or basic science of airway disease and/or NO. The committee identified important clinical questions, synthesized the evidence, and formulated recommendations. Recommendations were developed using pragmatic systematic reviews of the literature and the GRADE approach.

RESULTS

The evidence related to the use of Fe(NO) measurements is reviewed and clinical practice recommendations are provided.

CONCLUSIONS

In the setting of chronic inflammatory airway disease including asthma, conventional tests such as FEV(1) reversibility or provocation tests are only indirectly associated with airway inflammation. Fe(NO) offers added advantages for patient care including, but not limited to (1) detecting of eosinophilic airway inflammation, (2) determining the likelihood of corticosteroid responsiveness, (3) monitoring of airway inflammation to determine the potential need for corticosteroid, and (4) unmasking of otherwise unsuspected nonadherence to corticosteroid therapy.

The effect of airway remodelling on airway hyper-responsiveness in asthma

RATIONALE

The mechanisms of airway hyper-responsiveness are only partially understood and the contribution of airway remodelling is unknown. Airway remodelling can be assessed by measuring airway distensibility, which is reduced in asthma, even when lung function is normal. We hypothesised that airway remodelling contributes to airway hyper-responsiveness in asthma, independent of steroid-responsive airway inflammation.

OBJECTIVES

To determine the relationship between airway distensibility and airway responsiveness at baseline and after 12 weeks of inhaled corticosteroid therapy in a group of asthmatics with airway hyper-responsiveness.

METHODS

Nineteen doctor-diagnosed asthmatics had airway distensibility measured as the slope of the relationship between conductance and lung volume by the forced oscillation technique. Lung function, exhaled nitric oxide and methacholine challenge were also measured. Subjects had inhaled corticosteroid therapy for 12 weeks after which all measurements were repeated.

RESULTS

At baseline, airway distensibility (mean, 95%CI) was 0.19(0.14-0.23) cm H(2)O(-1)s(-1), exhaled nitric oxide was 13.1(10.3-16.6)ppb and airway distensibility correlated with eNO (p=0.04) and disease duration (p=0.02) but not with airway responsiveness (p=0.46), FEV(1) (p=0.09) or age (p=0.23). After treatment, exhaled nitric oxide decreased (p=0.0002), FEV(1) improved (p=0.0001), airway responsiveness improved (p=0.0002), and there was a small improvement in airway distensibility but it did not normalise (p=0.05). Airway distensibility was not correlated with either exhaled nitric oxide (p=0.49) or airway responsiveness (p=0.20).

CONCLUSIONS

Uncontrolled airway inflammation causes a small decrease in the distensibility of the airways of asthmatics with airway hyper-responsiveness. The lack of association between airway responsiveness and airway distensibility, both before and after 12 weeks ICS treatment, suggests that airway remodelling does not contribute to airway hyper-responsiveness in asthma.

Does a parent-reported history of pneumonia increase the likelihood of respiratory symptoms needing therapy in asthmatic children and adolescents?

BACKGROUND

Asthmatic children and adolescents attending outpatient clinics often have a history of pneumonia. Whether respiratory symptoms, lung function, and airway inflammation differ in asthmatic patients with and without a history of pneumonia remains controversial.

AIMS

To compare clinical, lung functional, and inflammatory variables in asthmatic outpatients with and without a history of pneumonia. Methods. In 190 asthmatic outpatients, aged 6-18 years, we assessed respiratory symptoms, lung function (flows, volumes, and pulmonary diffusion capacity, DLCO/VA), and atopic-airway inflammation as measured by the fractional concentration of exhaled nitric oxide (FE(NO)). A previous medical and radiological diagnosis of pneumonia was defined as "recurrent pneumonia" if subjects had at least three pneumonia episodes or two episodes within a year.

RESULTS

Of the 190 outpatients studied, 38 (20%) had a history of pneumonia. These patients had more frequent upper-respiratory symptoms, nighttime awakenings in the past 4 weeks, daily use of inhaled corticosteroids, and lower FE(NO) than the 152 asthmatic children without previous pneumonia (FE(NO): 20.6 ppb, 95% CI: 15.2-28.0 vs. 31.1 ppb, 95% CI: 27.0-35.8; p < .05). Of the 38 patients with previous pneumonia, 14 had recurrent pneumonia. Despite comparable lung volumes and flows, they also had lower DLCO/VA than asthmatic children with no recurrent pneumonia and asthmatic children without previous pneumonia (DLCO/VA%: 91.2 ± 11.3 vs. 108.5 ± 14.7 vs. 97.9 ± 18.6, p < .05).

CONCLUSION

Respiratory assessment in asthmatic children and adolescents with a history of pneumonia, especially recurrent pneumonia, often discloses symptoms needing corticosteroid therapy, and despite normal lung volumes and flows, mild reductions in the variables reflecting gas diffusion and atopic-airway inflammation (DLCO/VA and FE(NO)). Whether these respiratory abnormalities persist in adulthood remains an open question.

The role of measuring airway hyperresponsiveness and inflammatory biomarkers in asthma

Asthma is characterized by inflammation and airway hyperresponsiveness, which results in episodic airflow obstruction. It is diagnosed once a compatible clinical history plus objective evidence of diurnal variability in peak expiratory flow or significant reversibility to inhaled bronchodilator is documented. In accordance with current guidelines, measures of airway calibre and symptoms allow patients and clinicians to assess the degree of asthma control and titrate pharmacotherapy. However, these parameters fail to reflect the extent of underlying endobronchial inflammation and airway hyperresponsiveness, which in turn suggests that additional measures of asthma control may be of benefit. This evidence-based review highlights ways by which inflammation and airway hyperresponsiveness can be assessed and how they may provide additional useful information in the diagnosis and management of asthmatic patients.

Exhaled nitric oxide levels during treatment of pediatric acute asthma exacerbations and association with the need for hospitalization

OBJECTIVES

To examine how exhaled nitric oxide (eNO) levels measured before and after treatment of asthma exacerbations relate to emergency department (ED) disposition.

METHODS

We enrolled children 6 to 17 years old treated for asthma exacerbations in a pediatric ED. Using an offline single-breath eNO sampling technique, we collected replicate initial samples before treatment and replicate final samples when disposition was decided. We determined correlations and coefficients of variability of eNO values (parts per billion, ppb) of samples and compared by disposition (hospitalization or discharge) mean initial and final eNO levels and initial-to-final change.

RESULTS

Eighty-one subjects had initial and final eNO values; 24 subjects with more severe presentations had final values only. Replicate eNO samples were correlated (initial r = 0.98, final r = 0.99) and had low coefficients of variability (initial, 0.059 ± 0.057; final, 0.061 ± 0.070). For subjects with initial and final values, initial eNO levels were similar by disposition (mean difference, -8.0 ppb; 95% confidence interval [CI], -24.8 to 8.9 ppb), as were final levels (mean difference, -2.8 ppb; 95% CI, -23.8 to 18.2 ppb). Overall, final eNO was higher than initial (36.3 ± 29.7 vs 31.5 ± 23.9 ppb), but only 63% of subjects had any increase. Change in eNO was similar by disposition (mean difference, 4.6 ppb; 95% CI, -3.4 to 12.6). For more severe subjects with final eNO only, eNO was similar by disposition (P = 0.47).

CONCLUSIONS

For children aged 6 to 17 years with asthma exacerbations, eNO levels can be reliably measured. However, eNO levels measured before treatment or when disposition was determined did not distinguish children needing hospitalization.

Subjects in a Population Study with High Levels of FENO Have Associated Eosinophil Airway Inflammation

Background. Measurement of fraction of exhaled nitric oxide (FENO) is a promising tool to increase validity in epidemiological studies of asthma. The association between airway inflammation and FENO has, however, only been examined in clinical settings and may be biased by selection of patients with asthma. Methods. In a population study with FENO registrations on 370 individuals, we identified nine subjects out of thirty subjects with high levels of FENO (>85th percentile, 30.3 ppb), irrespective of presence of respiratory symptoms, and 21 control subjects with FENO at median levels (11.1–16.4 ppb) willing to undergo bronchoscopy and bronchoalveolar lavage (BAL), all nonsmokers. FENO was measured in accordance with ATS criteria, and the examination also included spirometry, methacholine challenge test, and sampling of exhaled breath condensate (EBC). Results. Subjects with high FENO levels had significantly higher median the percentage of eosinophils in BAL than controls (2.1 versus 0.6, P < .006), and there was a significant association between FENO and the percentage of eosinophils in BAL (ρ=0.6, P < .002) and ECP in BAL (ρ=0.65, P < .05) examining the whole group, but no association with gender, FEV1, or degree of metacholine sensitivity or any of the biomarkers in EBC. All subjects with high FENO had respiratory symptoms, but only three had diagnosed asthma. There were a significant association between hydrogen peroxide in EBC and the percentage of neutrophils in bronchial wash. Conclusion. High FENO levels signal asthmatic or allergic respiratory disease in a population-based study. FENO levels are associated with degree of eosinophil airway inflammation as measured by the percentage of eosinophils and ECP in BAL.

Associations of Fraction of Exhaled Nitric Oxide with Beta Agonist Use in Children with Asthma

The fraction of exhaled nitric oxide (FeNO), a measure of airway inflammation, is a potential noninvasive tool to guide asthma management in children. It remains unclear, however, if FeNO adds any information beyond clinical assessment of asthma control. We evaluated the associations of FeNO level with short acting beta agonist use and compared it with other clinical asthma assessments. We examined a prospective cohort study of 225 tobacco-smoke-exposed children aged 6-12 years with doctor-diagnosed asthma, including measures of FeNO, reported days of short acting beta agonist use, and unscheduled asthma visits. FeNO was analyzed in relation to current and future (3 months later) short acting beta agonist use. Mean FeNO at baseline, 6, and 12 months was 15.5, 15.7, and 16.8 ppb. In multivariable analyses, higher FeNO level was associated with increased short acting beta agonist use but only among children who were not on inhaled corticosteroids. Among those not on an inhaled steroid, there was a 12% increase in current and 15% increase in future days of short acting beta agonist use for every 10 ppb increase in FeNO level. FeNO levels remained associated with current short acting beta agonist use even after adjusting for unscheduled asthma visits. FeNO levels remained associated with future short acting beta agonist use even after adjusting for current short acting beta agonist use or unscheduled asthma visits. We conclude that FeNO levels are associated with short acting beta agonist use but only among children who are not on an inhaled corticosteroid.

Inflammatory markers in childhood asthma

The major characteristic of asthma is persistent airway inflammation that fails to resolve spontaneously. Dysregulation of pro- and anti-inflammatory mechanisms is responsible for the development of chronic inflammation. The inflammatory reaction is mediated by numerous cells and their mediators. Detection and quantification of airway inflammation in children are subject to many requirements, e.g., use of biologic samples obtained in a non-invasive way; use of standardized analytical methods to determine biomarkers that can identify inflammation processes (inflammation itself, oxidative stress, apoptosis and remodelling); determining the role of systemic inflammation; assessment of correlation of various biomarkers of inflammation with clinical parameters and their diagnostic efficacy; providing a tool(s) to monitor diseases, and to evaluate adequacy of therapy; and predicting the clinical course of inflammation and prognosis of asthma. Using standardized analyses, it is now possible to determine direct markers of local inflammation, i.e., fractional nitric oxide (marker of oxidative stress) in exhaled breath, pH (marker of acid stress) in breath condensate, and indirect markers in blood/serum, i.e., eosinophil granulocytes (indicating migration), eosinophil cationic protein (marker of activated eosinophil granulocytes) and C-reactive protein (marker of systemic inflammation). However, none of these biomarkers are specific for asthma. Further standardization of the known pulmonary biomarkers of local inflammation and identification of new ones will allow for longitudinal follow-up of inflammation in children with asthma.

Peanut allergy and allergic airways inflammation

Asthma is a major risk cofactor for anaphylactic deaths in children with peanut allergy. Peanut allergy is generally thought to be a lifelong condition, but some children outgrow their coexistent asthma. It has recently been shown that children who have 'outgrown' their asthma symptoms may have ongoing eosinophilic airways inflammation. The need for regular inhaled corticosteroid treatment in peanut allergic children and adolescents who have outgrown their asthma is however unclear. The aims of our study were to look at fractional exhaled nitric oxide levels (FeNO), as a non-invasive marker of eosinophilic airways inflammation, in peanut allergic children and assess whether children with outgrown asthma had elevated levels. Children with peanut allergy were recruited at two pediatric allergy clinics in Belfast, UK. Exhaled nitric oxide levels (FeNO) were measured using the Niox Mino in all children. Of the 101 peanut allergic children who consented for enrollment in the study, 94 were successfully able to use the NIOX Mino. Age range was 4-15 yr (median 10 yr); 61% were boys. Thirty (32%) had never wheezed, 37 (39%) had current treated asthma, 20 (21%) had at least 1 wheezing episode within the last year but were not taking any regular asthma medication (wheeze no treatment), and 7 (7%) had outgrown asthma. All children with outgrown asthma had elevated levels of FeNO (> 35 ppb), and 75% of children defined as 'wheeze no treatment' had elevated FeNO levels (> 35 ppb). Outgrown asthma and children defined as 'wheeze no treatment' had higher levels of FeNO than those with no history of wheeze or current treated asthma (p = 0.003). In children with peanut allergy, we found that those who had outgrown asthma had elevated FeNO levels in keeping with ongoing eosinophilic airways inflammation.

[Comparison of the Asthma Control Test (ACT) with lung function, levels of exhaled nitric oxide and control according to the Global Initiative for Asthma (GINA)]

INTRODUCTION

The current goal of asthma treatment is to achieve and maintain control. This study aimed to explore the relationship between the ACT (Asthma Control Test) questionnaire and the levels of control according to GINA (Global Initiative for Asthma) to establish the cut-off points for the ACT and evaluate its relationship with lung function and fractionated exhaled nitric oxide level (FeNO).

PATIENTS AND METHODS

A multi-centre prospective study including 441 patients followed up in an outpatient Chest Clinic. A clinical protocol was followed, and FeNO, spirometry and ACT performed. Disease was classified according to levels of control using GINA. The study analysed sensitivity, specificity and area under the curve (ROC), and the ACT cut-off points. We studied the differences between the functional parameters and FeNO between levels of control.

RESULTS

For controlled asthma the cut-off obtained was ACT> or =21 (area under the curve 0.791) and for uncontrolled < or =18 (AUC 0.774). We found significant differences in FeNO levels and pulmonary function among ACT> or =21 and ACT< or =18, although only 26.3% of patients with ACT< or =18 had a FEV1 <80% and 40% higher FeNO (> or =35 ppb). We found a correlation between baseline FEV1 and ACT (r=0.19, P<0.01) and between ACT and FeNO (r=-0.16, P<0.01).

CONCLUSIONS

The cut-off points would be, for controlled asthma ACT> or =21, partly controlled asthma ACT=19-20 and uncontrolled asthma ACT< or =18. A more complete assessment would require including monitoring operating parameters and FeNO.

Comparison of exhalation time methods (6 sec vs. 10 sec) of a hand-held exhaled nitric oxide analyzer

Standard exhalation time for measuring fractional exhaled nitric oxide (FeNO) is 10 sec, but this is not easy for younger children. We aimed to investigate the agreement between FeNO values during 10-sec (FeNO-10) and 6-sec (FeNO-6) exhalation and the feasibility of measuring FeNO-6, using a hand-held analyzer, NIOX-MINO®. FeNO values measured during 10- and 6-sec (random order) were compared. Success rates of the two different time modes were also evaluated. In 119 asthmatic children (median age 8 years [range 4-15]) who had been already accustomed to NIOX-MINO®, median FeNO-10 (29 ppb [IQR 15.2-42.0]) and FeNO-6 (27 ppb [IQR 16.0-43.5]) did not differ significantly (P = 0.90), and there was a good correlation between both values (r = 0.984, P < 0.001). Mean difference (FeNO-10-FeNO-6) was -0.151 ppb (95% CI: -0.95 to 0.65, limits of agreement: -8.8 to 8.5). In 46 asthmatic children (median age 7 years [range 4-15]) who had never used any FeNO analyzers, all the children aged 8 years and more (n = 21) succeeded in measuring FeNO on both time modes, whereas for children aged younger than 8 years (n = 25) success rates of the 10- and 6-sec mode were 60.0% and 92.0%, respectively. In conclusion, we showed good agreement between FeNO-10 and FeNO-6, and the 6-sec mode of NIOX-MINO® is more feasible than 10-sec mode for measuring FeNO in younger children.

Management of severe asthma in children

Children who are referred to specialist care with asthma that does not respond to treatment (problematic severe asthma) are a heterogeneous group, with substantial morbidity. The evidence base for management is sparse, and is mostly based on data from studies in children with mild and moderate asthma and on extrapolation of data from studies in adults with severe asthma. In many children with severe asthma, the diagnosis is wrong or adherence to treatment is poor. The first step is a detailed diagnostic assessment to exclude an alternative diagnosis ("not asthma at all"), followed by a multidisciplinary approach to exclude comorbidities ("asthma plus") and to assess whether the child has difficult asthma (improves when the basic management needs, such as adherence and inhaler technique, are corrected) or true, therapy-resistant asthma (still symptomatic even when the basic management needs are resolved). In particular, environmental causes of secondary steroid resistance should be identified. An individualised treatment plan should be devised depending on the clinical and pathophysiological characterisation. Licensed therapeutic approaches include high-dose inhaled steroids, the Symbicort maintenance and reliever (SMART) regimen (with budesonide and formoterol fumarate), and anti-IgE therapy. Unlicensed treatments include methotrexate, azathioprine, ciclosporin, and subcutaneous terbutaline infusions. Paediatric data are needed on cytokine-specific monoclonal antibody therapies and bronchial thermoplasty. However, despite the interest in innovative approaches, getting the basics right in children with apparently severe asthma will remain the foundation of management for the foreseeable future.

Exhaled nitric oxide, lung function, and exacerbations in wheezy infants and toddlers

BACKGROUND

There are limited data assessing the relationship between fraction of exhaled nitric oxide and lung function or exacerbations in infants with recurrent wheezing.

OBJECTIVES

In a longitudinal pilot study of children less than 2 years old, we assessed whether baseline fraction of exhaled nitric oxide was associated with lung function, bronchodilator responsiveness, changes in lung function, or subsequent exacerbations of wheezing.

METHODS

Forced expiratory flows and volumes using the raised-volume rapid thoracic compression method were measured in 44 infants and toddlers (mean age, 15.7 months) with recurrent wheezing. Single-breath exhaled nitric oxide (SB-eNO) was measured at 50 mL/s. Lung function was again measured 6 months after enrollment.

RESULTS

At enrollment, forced expiratory volume in 0.5 seconds (FEV(0.5)), forced expiratory flow at 25% to 75% of expiration (FEF(25-75)), and forced expiratory flow at 75% of expiration (FEF(75)) z scores for the cohort were significantly less than zero. There was no correlation between enrollment SB-eNO levels and enrollment lung function measures. SB-eNO levels were higher in infants with bronchodilator responsiveness (46.1 vs 23.6 ppb, P < .001) and was associated with a decrease in FEV(0.5) (r = -0.54, P = .001), FEF(25-75) (r = -0.6, P < .001), and FEF(75) (r = -0.55, P = .001) over 6 months. A 10-ppb increase in SB-eNO level was associated with a 0.4-point z score decrease in FEV(0.5), a 0.4-point z score decrease in FEF(25-75), and a 0.42-point z score decrease in FEF(75). SB-eNO level was superior to lung function and bronchodilator responsiveness in predicting subsequent wheezing treated with systemic steroids.

CONCLUSIONS

SB-eNO level might predict changes in lung function and risk of future wheezing and holds promise as a biomarker to predict asthma in wheezy infants and toddlers.

Adenosine triphosphate concentration of exhaled breath condensate in asthma

BACKGROUND

Purinergic signaling is involved in asthma pathogenesis. Not only adenosine but also adenosine triphosphate (ATP) might play a role, but human evidence is scarce. ATP can be measured in exhaled breath condensate (EBC), a noninvasive airway sample suggested as being suitable for patient monitoring. We determined EBC ATP concentration in asthma, investigated its relation to disease parameters, and calculated airway ATP level.

METHODS

EBC was collected from 45 patients with persistent asthma (age 34.7 +/- 13.2 years; FEV(1), 87.0 +/- 15.5% predicted; mean +/- SD) and 32 healthy control subjects (age 36.9 +/- 12.6 years; FEV(1), 98.9 +/- 9.9% predicted). Exhaled nitric oxide concentration (FeNO) and lung function were measured, and Asthma Control Test (ACT) score was obtained. EBC ATP was measured in luciferin-luciferase assay. Airway ATP concentration was calculated using dilution estimated from conductivity of vacuum-treated EBC samples. Parametric tests were applied in the analyses. ATP concentrations and nitric oxide levels were logarithmically transformed.

RESULTS

EBC ATP and calculated airway ATP concentrations were not elevated in asthma, and none of them was related to FeNO or ACT score. EBC ATP concentration was influenced by airway droplet dilution (r = -0.32, P < .05), and there was a relation between calculated airway ATP level and FEV(1) (r = -0.35, P < .05).

CONCLUSIONS

EBC ATP concentration does not seem to be useful for asthma monitoring. The relation between EBC mediator concentration and EBC conductivity highlights the importance of further standardization of EBC methodology and the need for more studies to understand airway droplet formation.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

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

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Feasibility of exhaled nitric oxide measurements at various flow rates in children with asthma

Measurement of bronchial and alveolar exhaled nitric oxide (NO) levels could be of clinical importance for the treatment of asthma. To discriminate between alveolar and bronchial NO, measurements need to be assessed at various flow rates. To study the feasibility, linearity, and long-term repeatability of NO measurements at four different exhalation flow rates in children with asthma. Twenty-one children with moderate persistent asthma, aged 6-12 yrs, were included in the study. NO was measured according to the ATS/ERS guidelines, using the NIOX analyzer with flow restrictors of 30, 50, 100, and 200 ml/s. Duration of the measurements ranged from 6-10 s, depending on the flow rate. The tests were repeated 3 and 6 months after the first NO measurement. Feasibility of NO measurements at these four flow rates increased from 67% to 91% and 95% at the first, second and third visit, respectively. A significant learning effect was present. Age and lung function indices did not influence success or failure of the tests. At the first measurements occasions, no problems occurred during the NO analysis at a 100 ml/s flow rate. There was a 75-90% success rate when performing the test using flow rates of 30, 50, and 200 ml/s. However, repeating the tests resulted in a 100% success rate. Measurements were not successful if: (i) children ran out of air; (ii) NO concentration exceeded 200 ppb; (iii) the measured NO flow was unstable; and (iv) the NO plateau was not formed. This study showed good feasibility and linearity of NO measurements in asthmatic children of 6 yrs and over at flow rates between 50-200 ml/s. A significant learning effect was present. The long-term reproducibility of alveolar and bronchial NO values during 6 months was moderate.

A single dose of Sildenafil does not enhance FeNO: a randomised, cross-over and placebo-controlled study

Monitoring of asthma control can be performed with different means including measurement of the concentration of nitric oxide (NO) in exhaled air. Due to its action on the NO-metabolism; we hypothesized that the intake of Sildenafil might augment and falsify the NO-values in exhaled air of subjects taking the drug to treat erectile dysfunction. This randomised, placebo-controlled cross-over study including 10 male non-asthmatic volunteers taking a single dose of 50 mg Sildenafil did not confirm this assumption in non-asthmatic subjects. We cannot think of any reason why asthmatics should behave differently. On the basis of these results, it does not seem necessary to ask asthma patients with elevated NO-values if they had taken any selective inhibitor of the cGMP-specific phosphodiesterase Type 5 as Sildenafil prior to the test.

Childhood Asthma Control Test and airway inflammation evaluation in asthmatic children

BACKGROUND

The Childhood Asthma Control Test (C-ACT) has been proposed as a tool in assessing the level of disease control in asthmatic children. To evaluate the position of C-ACT in the clinical management of asthmatic children, in relationship to the level of airway inflammation as assessed by fractional exhaled nitric oxide (FeNO) and with lung function.

METHODS

A total of 200 asthmatic children were included in the study: 47 children with newly diagnosed asthma ('New') and without any regular controller therapy; and 153 children with previously diagnosed asthma, treated according to GINA guidelines, and evaluated during a scheduled follow-up visit ('Follow-up'). Childhood Asthma Control Test, FeNO and lung function [forced expiratory volume 1 (FEV1) and forced vital capacity (FVC)] were evaluated.

RESULTS

In New vs Follow-up participants, C-ACT score (P < 0.001), FVC (P < 0.005) and FEV1 (P < 0.05) were significantly lower, and FeNO (P = 0.011) were significantly higher. In New, but not in Follow-up participants, significant correlations were observed between C-ACT score and FeNO (r = -0.51; P < 0.001), FEV1 (r = 0.34; P = 0.022) and FEV1/FVC (r = 0.32; P = 0.03). This lack of correlation in Follow-up visits seemed attributable to dissociation between inadequately controlled asthma by C-ACT ratings with normalization of other measures such as FeNO levels.

CONCLUSIONS

This study confirms and expands the concept that C-ACT is complementary to, but not a substitute for, other markers of disease control in asthmatic children, especially in the context of follow-up visits.

Nitric oxide measurement in chronic cough

Chronic cough is a common symptom-based diagnostic challenge for primary care physicians and respiratory specialists. Measurement of exhaled nitric oxide is a convenient, reproducible, and inexpensive point-of-service test. It can simplify the evaluation process of chronic cough by providing information regarding the state of airway inflammation. If exhaled nitric oxide is elevated, this is predictive of a favorable response to inhaled corticosteroids. This has the effect of reducing empirical trials for cough-variant asthma or eosinophilic bronchitis. The inclusion of exhaled nitric oxide in the diagnostic approach to chronic cough should be considered.

Fractional exhaled nitric oxide in asthma: an update

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

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The use of exhaled nitric oxide in the diagnosis of asthma in school children

OBJECTIVES

To evaluate the yield of the fractional exhaled nitric oxide (FeNO) in the diagnosis of asthma compared with spirometry and induced sputum cytologic study in school-age children.

STUDY DESIGN

Consecutive children referred for evaluation of possible asthma were included. At referral, all children completed FeNO measurement, sputum induction for eosinophil count (eos%) and spirometry. The diagnosis of asthma was performed after 18 months with conventional criteria. Receiver operating curves were used to determine cutoff points for disease status, and accuracy was calculated.

RESULTS

A total of 150 children were included: 69 with steroid-naïve asthma, 44 without asthma, and 37 with asthma treated with controllers. FeNO and eos% levels were significantly higher in those with steroid-naïve asthma (P < .0001). The area under the receiver operating curve for FeNO and eos% were very high compared with forced expiratory volume in 1 second (0.906, 0.921, 0.606, respectively). The sensitivity, specificity, and positive and negative predictive values for best cutoff points of FeNO (19 parts per billion) were 80%, 92%, 89%, and 86%, respectively, and were similar to eos% (best cutoff = 2.7%): 81%, 92%, 89%, 85%, respectively.

CONCLUSIONS

FeNO measurement is useful in early diagnosis of pediatric asthma. We suggest considering FeNO measurement in the evaluation of children suspected of having asthma, especially in cases where the diagnosis is not clear.

[Exhaled nitric oxide in children under 4 years of age with recurrent bronchitis]

BACKGROUND

The objective of the study was to assess bronchial inflammation in preschool children with recurrent bronchitis by measuring exhaled nitric oxide.

PATIENTS AND METHODS

The study included patients under 4 years of age with at least 3 episodes of wheezing in the past year (n=63) and a control group (n=30). Exhaled nitric oxide was measured in samples collected offline during spontaneous tidal breathing with a face mask and stored in Mylar balloons.

RESULTS

The fractional exhaled nitric oxide concentration (FE(NO)) was higher in the group with bronchitis (mean [SD], 5.3 [1.3] parts per billion [ppb]) than in the control group (4.6 [1.1]ppb) (P=.02). There was a significant difference between the control group and children in the bronchitis group not treated with inhaled corticosteroids (P<.05), but not between controls and corticosteroid-treated patients. A relationship with eosinophil count was observed in that those with higher counts (>400 microL) had higher FE(NO) levels (P<.01). No relationship was observed between FE(NO) and a positive methacholine challenge test. Follow-up lasted at least 20 months. The initial FE(NO) level did not differ significantly according to whether patients were subsequently transient, infrequent, or frequent wheezers (5.2 [0.98]ppb, 5.6 [1.5]ppb, and 4.8 [1.34]ppb, respectively; P=.36).

CONCLUSIONS

In children under 4 years of age with recurrent wheezing bronchitis who were asymptomatic at study entry, a small increase in FE(NO) was observed although there was a good deal of overlap with the control group.

Biomarkers in asthma

PURPOSE OF REVIEW

The purpose of this review is to highlight seminal and current literature that informs our understanding of the clinical and investigative utility of biomarkers in asthma. Biomarkers derive from a variety of sources [bronchiolar lavage (BAL), sputum, exhaled breath, and blood], and have widely variant performance characteristics, and applicability.

RECENT FINDINGS

Increasing attention is given to biomarkers in exhaled breath, both gaseous (exhaled nitric oxide) and higher molecular weight moieties [in exhaled breath condensate (EBC)]. Current research in EBC analysis has focused on validation, standardization, and technical considerations, whereas research on exhaled nitric oxide (ENO) has moved to testing its predictive value in clinical situations. The use of advanced biostatistical techniques, and combinatorial analyses has led to additional advances in the utility of biomarkers.

SUMMARY

To date, the best validated, and best performing biomarkers for clinical asthma appear to be measures of inflammation in induced sputum, and measures of ENO. Some trials using ENO appear particularly promising for early clinical use. EBC metrics are at present too inchoate for clinical purposes. However, not all important clinical and research questions can be addressed with sputum, EBC, or ENO metrics, leaving an important place for BAL, bronchial biopsy, and perhaps EBC measurements in the research arena.

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.