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

Value of bronchial reversibility to salbutamol, exhaled nitric oxide and responsiveness to methacholine to corroborate the diagnosis of asthma in children

INTRODUCTION AND OBJECTIVES

Functional and inflammatory measures have been recommended to corroborate asthma diagnosis in schoolchildren, but the evidence in this regard is conflicting. We aimed to determine, in real-life clinical situation, the value of spirometry, spirometric bronchial reversibility to salbutamol (BDR), bronchial responsiveness to methacholine (MCT) and fractional exhaled nitric oxide (FENO), to corroborate the diagnosis of asthma in children on regular inhaled corticosteroids (ICS) referred from primary care.

METHODS

One hundred and seventy-seven schoolchildren with mild-moderate persistent asthma, on treatment with regular ICS, participated in the study. Abnormal tests were defined as FENO ≥ 27 ppb, BDR (FEV1 ≥ 12%) and methacholine PC20 ≤ 4 mg/mL.

RESULTS

The proportions of positive BDR, FENO and MCT, were 16.4%, 33.3%, and 87.0%, respectively. MCT was associated with FENO (p < 0.03) and BDR (p = 0.001); FENO was associated with BDR (p = 0.045), family history of asthma (p = 0.003) and use of asthma medication in the first two years of life (p = 0.004). BDR was significantly related with passive tobacco exposure (p = 0.003).

CONCLUSIONS

Spirometry, BDR and BDR had a poor performance for corroborating diagnosis in our asthmatic children on ICS treatment; on the contrary, MCT was positive in most of them, which agrees with previous reports. Although asthma tests are useful to corroborate asthma when positive, clinical diagnosis remains the best current approach for asthma diagnosis, at least while better objective and feasible measurements at the daily practice are available. At present, these tests may have a better role for assessing the management and progression of the condition.

Identifying uncontrolled asthma in children with the childhood asthma control test or exhaled nitric oxide measurement

BACKGROUND

International guidelines highlight the importance of assessing asthma control status in children with asthma, and research on practical and objective instruments for assessing asthma control is ongoing.

OBJECTIVE

To determine the role of the Childhood Asthma Control Test (C-ACT) and fractional concentration of exhaled nitric oxide (FeNO) in identifying children with not well-controlled asthma.

METHODS

Children 6 to 11 years of age with asthma were enrolled in the study. They completed C-ACT and underwent FeNO and spirometric measurements during the monthly clinic visits. An asthma specialist assessed asthma control according to the gold standard Global Initiative for Asthma guideline and decided the treatment of the patients.

RESULTS

Seventy-six children with a mean (SD) age of 8.7 (1.4) years were evaluated in the first visit, whereas 64 and 51 children were admitted for second and third visits, respectively. A C-ACT score of 22 or less had 69% sensitivity and 77% specificity in determining not well-controlled asthma, whereas an FeNO value of 19 ppb or higher had 61% sensitivity and 59% specificity in patients who completed 3 visits. Receiver operating characteristic curve analysis revealed that the C-ACT was better than FeNO for identifying patients with not well-controlled asthma (area under the curve, 0.79; P < .001 [C-ACT] vs .58, P = .10 [FeNO]) Results of multivariate generalized estimating equation analysis revealed that a C-ACT score of 22 or less (odds ratio, 8.75; 95% confidence interval, 4.35-17.59; P < .001) and an FeNO of 19 ppb or greater (odds ratio, 2.60; 95% confidence interval, 1.07-6.29; P = .03) were significant indicators for the presence of not well-controlled asthma.

CONCLUSION

The C-ACT is superior to FeNO in determining the control status of children with asthma and may be used as a complementary tool in clinical practice to detect children with not well-controlled asthma.

Ultrastructural immunogold localization of nitric oxide synthase isoforms in rat and human eosinophils

The involvement of nitric oxide (NO) as both pro and anti-inflammatory agent in allergic, airway inflammatory, and asthmatic diseases and the active participation of eosinophils in such ailments have been previously suggested. NO modulates eosinophil number, migration and their survival. The microenvironment of NO synthase (NOS) in subcellular organelles determines its rate and efficiency of catalysis, which in turn influences NO generation at distinct intracellular locales. The present study was undertaken to assess the intracellular distribution of NOS isoforms by transmission electron microscopy followed by morphometric analysis in human and rat eosinophils. Rat eosinophils were explored in parallel, and since they are widely used as model systems to mimic human diseases, a comparative study on NOS localization patterns might provide useful information in deciphering NO role in diverse aspects of eosinophil-related inflammatory ailments. The results demonstrated predominance of neuronal NOS (nNOS) in the eosinophilic granules and even distribution of inducible NOS (iNOS) and nNOS in the cytoplasm and nucleus of human eosinophils. In rat eosinophils, however, iNOS was mainly localized in the eosinophilic granules and nucleus, while nNOS was distributed evenly in cytoplasm and nucleus. Distribution of endothelial NOS (eNOS) in eosinophils was scanty. Differences in NOS isoforms and their localization in human and rat cells might have implications in differential mode of catalysis and functional contribution to eosinophil physiology and pathology, warranting detailed investigations. The present study highlights species-specific differences in the relative abundance and distribution pattern of NOS isoforms in rat and human eosinophils, which should be considered cautiously in interpreting the rat data to humans.

Effect of age on relationship between exhaled nitric oxide and airway hyperresponsiveness in asthmatic children

BACKGROUND

Numerous studies have examined the relationship between the fractional concentration of exhaled nitric oxide (Feno) and airway hyperresponsiveness (AHR). Our objective was to determine the effects of age on the relationship between Feno and AHR in asthmatic children.

METHODS

AHR was examined in 267 asthmatic patients (age range, 5 to 20 years). A challenge test was performed using acetylcholine chloride (Ach). We determined the provocative concentration of Ach producing a 20% decrease in FEV(1) from baseline (PC(20)). Feno was examined using the recommended online method before the Ach challenge test.

RESULTS

In children < 12 years of age (range, 5 to 11 years), decreasing AHR (PC(20)) was significantly related to higher Feno (r = -0.43; beta = -0.28; p < 0.001). In adolescents >or= 12 years of age (range, 12 to 20 years), decreasing PC(20) was associated with peripheral airway obstruction (FEV(1): r = 0.32; beta = 5.5; p = 0.002; forced expiratory flow at 50% of the FVC: r = 0.24; beta=8.4; p = 0.006; and forced expiratory flow at 25% of FVC: r = 0.28; beta=11.4; p = 0.002). AHR and Feno were weakly related (r = -0.18; beta = -0.14; p = 0.02).

CONCLUSIONS

In children with asthma, AHR is associated with airway inflammation. AHR in children with asthma may consist of variable components mainly reflecting airway inflammation. In contrast, in adolescents with asthma, AHR is associated with airway structural changes and weakly with airway inflammation. AHR in adolescents with asthma may consist of chronic components mainly reflecting airway remodeling.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Extended NO analysis in asthma

The discovery of the flow dependence of exhaled NO made it possible to model NO production in the lung. The linear model provides information about the maximal flux of NO from the airways and the alveolar concentrations of NO. Nonlinear models give additional flow-independent parameters such as airway diffusing capacity and airway wall concentrations of NO. When these models are applied to patients with asthma, a clear-cut increase in NO flux is found, and this is caused by an increase in both airway diffusing capacity and airway wall concentrations of NO. There is no difference in alveolar concentrations of NO compared to healthy subjects, except in severe asthma where an increase has been found. Inhaled corticosteroids are able to reduce the airway wall concentrations but not diffusing capacity or alveolar concentrations. Oral prednisone affects the alveolar concentration, suggesting that in severe asthma there is a systemic component. Steroids distributed by any route do not affect the airway diffusing capacity. Therefore, the airway diffusing capacity should be in focus in testing new drugs or in combination treatment for asthma. Exhaled NO analysis is a promising tool in characterizing asthma in both adults and children. However, there is a strong need to agree on the models and to standardize the flow rates to be used for the modelling in order to perform a systematic and robust analysis of NO production in the lung.