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

Relationship between fraction of exhaled nitric oxide and peripheral eosinophilia in asthma

BACKGROUND

Achieving disease control is the goal of asthma management. Serum or sputum eosinophil counts have been known traditional means of assessing eosinophilic airway inflammation in asthma, which is vital in predicting response to corticosteroid therapy which ultimately promotes control of the disease. Evidence suggests that fraction of exhaled nitric oxide (FeNO) may be a more useful non-invasive surrogate biomarker for the assessment of eosinophilic airway inflammation and could help with the timely adjustment of inhaled corticosteroid therapy in the uncontrolled asthma patient. The relationship between FeNO and other markers of airway inflammation has been variable in literature, with limited data in sub-Saharan Africa where FeNO testing is very sparse. We sought to define the relationship between FeNO levels, serum eosinophil counts, spirometry measures and symptom control among asthma patients.

MATERIALS AND METHODS

The study was conducted at the Asthma Clinic of a large tertiary hospital. This study included 82 patients with physician-diagnosed asthma being regularly managed at the clinic. All participants were taken through the asthma control test (ACT), had FeNO and spirometry measurements taken according to the American Thoracic Society (ATS) guidelines. Blood samples were obtained from all participants for serum eosinophil counts. Correlation coefficient was used to ascertain the relationship between FeNO levels and serum eosinophil counts, ACT scores, and spirometry measurements. Logistic regression was used to examine the association between high FeNO and abnormal FEV1 percentage predicted (<80%) with adjustments for age, sex, and BMI.

RESULTS

A total of 82 patients with asthma were included in the study, with higher prevalence of females (72%). Majority (40.2%) of the patients were found in the 60 and above age category. The median FeNO level and ACT score was 42.00 (26.00-52.50) parts per billion (ppb) and 20.0 (18-23) respectively. The median serum eosinophil counts was 0.25(0.90-0.38) × 109/L. The median FeNO levels were significantly higher in patients with partly and very poorly controlled asthma than in the well-controlled group (p < 0.001). A total of 47(57%) of the patients were classified as having well controlled asthma and 35 (42%) uncontrolled. FeNO correlated with serum eosinophil counts (r = 0.450, p < 0.001), ACT (r = -0.648, p < 0.001), and FEV1 percentage predicted (r = -0.353, p = 0.001). High FeNO (>50 ppb) was associated with an over fivefold increased risk of having an abnormal FEV1 percentage predicted.

CONCLUSION

FeNO levels significantly correlated with the ACT scores, serum eosinophil counts and FEV1% predicted among the asthma patients who were on inhaled corticosteroid therapy. High FeNO was significantly associated with abnormal FEV1 percentage predicted. We suggest that the point of care assessment of FeNO is a reliable marker of eosinophilic inflammation in our cohort of patients and together with 'ACT scores' in our asthma clinics could increase asthma control rates.

ERS technical standard on bronchial challenge testing: pathophysiology and methodology of indirect airway challenge testing

Recently, this international task force reported the general considerations for bronchial challenge testing and the performance of the methacholine challenge test, a "direct" airway challenge test. Here, the task force provides an updated description of the pathophysiology and the methods to conduct indirect challenge tests. Because indirect challenge tests trigger airway narrowing through the activation of endogenous pathways that are involved in asthma, indirect challenge tests tend to be specific for asthma and reveal much about the biology of asthma, but may be less sensitive than direct tests for the detection of airway hyperresponsiveness. We provide recommendations for the conduct and interpretation of hyperpnoea challenge tests such as dry air exercise challenge and eucapnic voluntary hyperpnoea that provide a single strong stimulus for airway narrowing. This technical standard expands the recommendations to additional indirect tests such as hypertonic saline, mannitol and adenosine challenge that are incremental tests, but still retain characteristics of other indirect challenges. Assessment of airway hyperresponsiveness, with direct and indirect tests, are valuable tools to understand and to monitor airway function and to characterise the underlying asthma phenotype to guide therapy. The tests should be interpreted within the context of the clinical features of asthma.

Biomarkers in inflammometry pediatric asthma: utility in daily clinical practice

Asthma is a common disease in both high and lower income countries that starts early and persists often for life. A correct and accurate diagnosis, treatment and follow-up during childhood are essential for a better understanding of adult asthma and avoiding over- or under-treatment. Th2 inflammation in children with asthma symptoms is usually assessed by measuring with serum total IgE, blood eosinophilia and FeNO levels that may help to predict asthma, particularly in those infants and young children in whom lung function tests are difficult to perform. FeNO measurement, compared to intra-individual levels, may be useful also for ascertaining treatment adherence. Nevertheless, an isolated measurement may be insufficient and only the combination of these markers improves the diagnosis, phenotyping and follow-up of an asthmatic child.

Fractional Exhaled Nitric Oxide: A Potential Biomarker in Allergic Rhinitis?

BACKGROUND

The fractional concentration of exhaled nitric oxide (FeNO) is a surrogate biomarker for Th2-dependent bronchial inflammation. The present study investigated whether FeNO may characterize allergic rhinitis (AR) patients.

METHODS

A total of 553 AR patients (497 males, mean age 28.8 years) were evaluated. Those patients with a high FeNO underwent a 2-year follow-up.

RESULTS

Increased FeNO was associated with a significantly longer AR duration, impaired lung function, more severe symptoms, and more frequent bronchial hyperresponsiveness (BHR). At follow-up, 22 out of 82 patients (26.8%) with high FeNO levels (>50 ppb) developed asthma.

CONCLUSIONS

AR patients may frequently have high FeNO values, exceeding 50 ppb. This might be associated with an initial impaired lung function, BHR, a perceived worsening of respiratory symptoms, and potential progression to asthma.

Airway hyperresponsiveness to mannitol and methacholine and exhaled nitric oxide in children with asthma

OBJECTIVE

Asthma is characterized by airway hyperresponsiveness (AHR), inflammation, and obstruction. AHR to stimuli that indirectly cause bronchial smooth muscle (BSM) contractions via release of endogenous mediators is thought to better reflect airway inflammation than AHR to stimuli that act directly on BSM. Fractional exhaled nitric oxide (FeNO) is a useful parameter for noninvasive clinical airway inflammation assessments. Accordingly, this study aimed to examine the relationships of mannitol and methacholine challenge test outcomes with FeNO and the influence of inhaled corticosteroid treatment in children with asthma.

METHODS

One hundred thirty-four asthmatic children (89 males; ages: 5-17 years, median: 9 years) underwent spirometry, FeNO measurement, serum total/specific IgE testing, and blood eosinophil count. All subjects were challenged with mannitol dry powder (MDP; AridolH, Pharmaxis, Australia) and methacholine at 7-day intervals. Data of steroid-treated and steroid-naïve children were compared.

RESULTS

Positive responses to MDP and methacholine challenge tests were observed in 74.6% and 67.2% of total subject group, respectively, and 72 children had positive response to both challenge tests. The median FeNO level, response-dose ratio (RDR) of PC₂₀ methacholine, and RDR of PD₁₅ MDP were significantly higher in the steroid-treated group than in the steroid-naïve group (p < 0.001, 0.226, and 0.004, respectively). FeNO levels associated significantly with PD₁₅ MDP and RDR PD₁₅ MDP in total subject populations (p = 0.016 and 0.003, respectively); however, a significant correlation between FeNO and RDR PD₁₅ MDP was observed only in the steroid-naïve group.

CONCLUSIONS

Compared with AHR to methacholine, AHR to MDP more closely reflected the level of FeNO in steroid-naïve asthmatic children.

Concordance between bronchial hyperresponsiveness, fractional exhaled nitric oxide, and asthma control in children

BACKGROUND

Previous studies on association between level of asthma control, markers of airway inflammation and the degree of bronchial hyperresponsiveness (BHR) have yielded conflicting results. Our aim was to determine the presence and severity of BHR and the concordance between BHR, asthma control, and fractional exhaled nitric oxide (FeNO) in children with asthma on therapy.

METHODS

In this cross-sectional observational study, children (aged 6-18 years) with asthma on British Thoracic Society (BTS) treatment steps 2 or 3, underwent comprehensive assessment of their asthma control (clinical assessment, spirometry, asthma control test [ACT], Pediatric Asthma Quality of Life Questionnaire [PAQLQ]), measurement of FeNO and BHR (using mannitol dry powder bronchial challenge test [MCT], Aridol™, Pharmaxis, Australia).

RESULTS

Fifty-seven children (63% male) were studied. Twenty-seven children were on BTS treatment step 2 and 30 were on step 3. Overall, 25 out of 57 (43.8%) children had positive MCT. Of note, 9 out of 27 (33.3%) children with clinically controlled asthma had positive MCT. Analyses of pair-wise agreement between MCT (positive or negative), FeNO (>25 or ≤25 ppb) and clinical assessment of asthma control (controlled or partially controlled/uncontrolled) showed poor agreement between these measures.

CONCLUSIONS

A substantial proportion of children with asthma have persistent BHR despite good clinical control. The concordance between clinical assessment of asthma control, BHR and FeNO was observed to be poor. Our findings raise concerns in the context of emerging evidence for the role of bronchoconstriction in inducing epithelial stress that may drive airway remodeling in asthma. Pediatr Pulmonol. 2016;51:1004-1009. © 2016 Wiley Periodicals, Inc.

Association of FEF25-75% Impairment with Bronchial Hyperresponsiveness and Airway Inflammation in Subjects with Asthma-Like Symptoms

BACKGROUND

Forced expiratory flow at 25 and 75% of the pulmonary volume (FEF25-75%) might be considered as a marker of early airway obstruction. FEF25-75% impairment might suggest earlier asthma recognition in symptomatic subjects even in the absence of other abnormal spirometry values.

OBJECTIVES

The study was designed in order to verify whether FEF25-75% impairment in a cohort of subjects with asthma-like symptoms could be associated with the risk of bronchial hyperresponsiveness (BHR) and with airway inflammation expressed as fractional exhaled nitric oxide (FeNO) and eosinophil counts in induced sputum.

METHODS

Four hundred adults with a history of asthma-like symptoms (10.5% allergic) underwent spirometry, determination of BHR to methacholine (PD20FEV1), FeNO analysis and sputum induction. FEF25-75% <65% of predicted or <-1.64 z-score was considered abnormal.

RESULTS

All subjects had normal FVC, FEV1 and FEV1/FVC, while FEF25-75% was abnormal in 27.5% of them. FEF25-75% (z-score) was associated with PD20FEV1 (p < 0.001), FeNO (p < 0.001) and sputum eosinophils (p < 0.001). Patients with abnormal FEF25-75% showed higher levels of FeNO and eosinophils in induced sputum than did patients with normal FEF25-75% (p < 0.01 and p < 0.01, respectively). Subjects with abnormal FEF25-75% had an increased probability of being BHR positive (OR = 13.38; 95% CI: 6.7-26.7; p < 0.001).

CONCLUSIONS

Our data show that abnormal FEF25-75% might be considered an early marker of airflow limitation associated with eosinophilic inflammation and BHR in subjects with asthma-like symptoms, indicating a role for FEF25-75% as a predictive marker of newly diagnosed asthma.