Exhaled nitric oxide correlates with airway eosinophils in childhood asthma

Clinical implications of airway inflammation in mild intermittent asthma

OBJECTIVE

To determine whether inhaled corticosteroids should be prescribed to patients with milder forms of asthma and whether markers of airway inflammation should be considered when making therapy decisions.

DATA SOURCES

A PubMed search was performed of the English-language literature published in the preceding 10 years (January 1, 1993, through December 31, 2003) concerning epidemiology, pathophysiology, therapy, and prognosis of mild intermittent asthma, with asthma, mild, and intermittent as indexing terms.

STUDY SELECTION

All relevant studies including author's expert opinions were selected.

RESULTS

Several studies have addressed the question of a possible benefit of maintenance therapy (ie, inhaled steroids) in patients with mild intermittent asthma. Although a diminishing effect on airway inflammation has been widely demonstrated, even in patients with mild disease, the impact of inhaled steroids on the long-term prognosis is much less clear. For patients with mild disease who are long-term inhaled steroid users, alternative therapy strategies, including low-dose inhaled steroids and leukotriene receptor antagonists, have been advocated.

CONCLUSIONS

Mild intermittent asthma is a disease characterized not only by infrequent symptoms and normal lung function but also by chronic airway inflammation, possibly resulting in irreversible airflow limitation if left unattended. Therefore, maintenance therapy, such as (low-dose) inhaled steroids or leukotriene receptor antagonists, should be considered in patients with mild disease. Future studies should give more insight into the impact of prolonged anti-inflammatory therapy on the long-term prognosis of mild intermittent asthma patients. Whether results from these studies will justify a more aggressive treatment for these patients remains to be answered.

Increased macrophage-derived chemokine in exhaled breath condensate and plasma from children with asthma

BACKGROUND

Type 2 helper T lymphocyte-specific chemokines including macrophage-derived chemokine (MDC), thymus and activation-regulated chemokine (TARC) and eotaxin are important mediators for allergic airway inflammation.

OBJECTIVE

We investigated whether these chemokines can be detected in exhaled breath condensate (EBC) and their relation to childhood asthma.

METHODS

Asthmatics recruited from paediatric clinics of a university teaching hospital were classified into intermittent asthma (IA) and persistent asthma (PA) according to Global Initiative for Asthma guidelines. EBC was collected by a disposable collection kit, whereas fractional exhaled nitric oxide (FENO) was measured by a chemiluminescence analyser. Concentrations of MDC, TARC and eotaxin in both EBC and plasma were measured using sandwich enzyme immunoassay. The intra-subject reproducibility of exhaled chemokine measurements was determined by co-efficients of variation (CV).

RESULTS

Forty-eight patients with PA, 36 children with IA and 18 controls were recruited. MDC and eotaxin were present in EBC from nearly all subjects, whereas TARC could be measured in EBC from 33 (32%) subjects only. The median MDC concentration in EBC was higher in PA (117 pg/mL) as compared with IA (106 pg/mL) and controls (105 pg/mL; P=0.003 for both). The median plasma MDC concentration in PA (648 pg/mL) was also higher than that in IA (520 pg/mL; P=0.002) and controls (490 pg/mL; P=0.008). The median plasma TARC concentration was also increased in PA as compared with IA (72 pg/mL vs. 35 pg/mL; P=0.004). MDC concentrations in EBC were lower in patients with PA who received high-dose inhaled corticosteroid (P=0.005). FENO was significantly higher in asthmatics than controls (P<0.0001), but it was not associated with chemokines in EBC or plasma. The mean (range) CV for measuring MDC, TARC and eotaxin in EBC (n=6) were 5.5 (2.0-7.2%), 8.8 (3.6-14.4%) and 5.2 (2.8-7.9%), respectively.

CONCLUSIONS

Our results suggest that MDC in EBC and MDC and TARC in plasma are increased in children with PA as compared with IA or control. MDC concentrations in EBC are suppressed in patients on high-dose inhaled corticosteroid treatment.

The relation between obesity and asthmatic airway inflammation

Epidemiologic studies suggest increased asthma prevalence in obese subjects. However, the relation between obesity and airway inflammation remains unclear. This cross-sectional study aims to investigate the relation between obesity indices and exhaled nitric oxide (ENO) and leukotriene B(4) (LTB(4)) in children with asthma. Asthmatic patients aged 7-18 yr old were recruited. Weight-for-height Z score was calculated from anthropometry. ENO was measured by online single-breath method using a chemiluminescence analyzer, whereas LTB(4) concentrations in exhaled breath condensate (EBC) were quantified using competitive enzyme immunoassay. Ninety-two asthmatics and 23 controls were recruited. The mean ENO and LTB(4) concentrations in EBC were higher in asthmatic patients (87 p.p.b. and 40.5 pg/ml) than controls (25 p.p.b. and 18.7 pg/ml) (p < 0.0001 for both). Obesity, as defined by weight >120% median weight-for-height, was not associated with any alteration in ENO or LTB(4) concentrations in patients with asthma. Besides, these inflammatory markers did not differ between asthmatics in the highest and lowest quartiles of weight-for-height Z score. On multivariate analysis, ENO showed significant correlation with age (beta = 0.511, p < 0.0001), peripheral blood eosinophil count (beta = 0.222, p = 0.019), plasma total IgE concentration (beta = 0.187, p = 0.050) and forced expiratory volume in 1-s (FEV(1); beta = -0.221, p = 0.014). None of the factors was associated with LTB(4) concentration in EBC. In conclusion, ENO and LTB(4) concentration in EBC are increased in childhood asthma. However, these inflammatory markers did not differ between obese and non-obese children with asthma.

Childhood asthma: exhaled markers of airway inflammation, asthma control score, and lung function tests

Exhaled markers of airway inflammation become increasingly important in the management of childhood asthma. The aims of the present study are: 1) to compare exhaled markers of inflammation (nitric oxide, carbon monoxide, and acidity of breath condensate) with conventional asthma measures (lung function tests and asthma control score) in childhood asthma; and 2) to investigate the detectability of albumin, CRP, IL-6, IL-8, TNF-alpha, sICAM-1, and sTNF-R75 in the exhaled breath condensate (EBC) of asthmatic children. Thirty-two children with mild to moderate persistent asthma and healthy controls aged 6-12 years were studied. We measured exhaled NO and CO, and subsequently EBC was collected. Inflammatory mediators in EBC were measured using an enzyme-linked immunosorbent assay. Respiratory symptoms and asthma control were assessed using the asthma control questionnaire (ACQ) of Juniper et al. (Eur Respir J 1999;14:902-907). Exhaled NO showed a significant correlation with exhaled CO (r = 0.59, P < 0.05) and FEV1 (r = -0.59, P < 0.05), but not with ACQ score (r = 0.48, P = 0.06). Exhaled CO was correlated with prebronchodilator FEV1 (r = -0.45, P < 0.05), but not with asthma control (r = 0.18, P = 0.35). Acidity of EBC was significantly lower in asthmatic children than in healthy controls (P < 0.05), but did not correlate with any of the conventional asthma measures. We were not able to demonstrate the presence of CRP, IL-6, IL-8, TNF-alpha, sICAM-1, and sTNF-R75 in EBC. Albumin was found in two EBC samples of asthmatic children. We conclude that exhaled NO had a better correlation with lung function parameters and asthma control than exhaled CO and acidity of EBC, in mild to moderate persistent childhood asthma. However, exhaled NO, CO, and deaerated pH of EBC did not differ between asthmatic children and controls, possibly because of a too homogeneous and well-controlled study population. To further evaluate the clinical utility of exhaled markers in monitoring childhood asthma, more studies are required on a wider range of asthma severity, and preferably with repeated measurements of markers and of asthma control.

Exhaled nitric oxide in the assessment of asthma

PURPOSE

Asthma is now defined as a TH2-mediated inflammatory disease involving both large and small airways. However, assessment of airways inflammation is limited by techniques that are time consuming and possibly distressing to the patient. Exhaled nitric oxide, an easily and rapidly obtained noninvasive study, is a potential surrogate for measuring airways inflammation, but its clinical utility remains to be determined. This review examines the role of exhaled nitric oxide in assessing and directing therapy of asthmatic airways inflammation.

RECENT FINDINGS

It is well established that exhaled nitric oxide is increased in patients with untreated asthma and decreases with corticosteroid treatment. Exhaled nitric oxide also generally correlates with eosinophilic inflammation in asthmatic patients. Recent studies show that this correlation is especially pronounced in atopic subjects with asthma when compared with nonatopic subgroups. Recent studies also show that exhaled nitric oxide may be useful in identifying subclinical inflammation, assessing the antiinflammatory effects of asthma medications other than inhaled or oral corticosteroids, and heralding an asthma exacerbation. A number of new studies assert the utility of exhaled nitric oxide as a diagnostic tool for asthma.

SUMMARY

Exhaled nitric oxide may be a useful parameter for monitoring asthmatic inflammation, adjusting therapy, and diagnosing asthma, although prospective longitudinal trials investigating the correlation between exhaled nitric oxide and clinical outcomes are necessary to determine its utility.

Heterogeneity of FeNO response to inhaled steroid in asthmatic children

BACKGROUND

Nitric oxide in exhaled air is regarded as an inflammation marker, and may be used to monitor the anti-inflammatory control from inhaled corticosteroids (ICSs). However, this response to ICSs exhibits a heterogeneous pattern.

OBJECTIVE

The study aimed to describe the independent variables associated with the heterogeneity in the response of exhaled nitric oxide to ICSs.

METHODS

Exhaled nitric oxide (FeNO), lung function, bronchial hyper-responsiveness (BHR), specific IgE to common inhalant allergens, blood eosinophils, other atopic manifestations and variants in nitric oxide synthethase 1 (NOS1) gene were studied in a double-blind, placebo-controlled crossover comparison of budesonide (BUD) Turbohaler 1600 mcg daily vs. placebo in asthmatic schoolchildren.

RESULTS

Forty children were included in the study from a screening of 184 asthmatic children with moderately persistent asthma, well controlled on regular BUD 400 mcg daily: 20 children with normal FeNO and 20 with raised FeNO. FeNO, BHR and forced expiratory volume in 1 s improved significantly after BUD 1600 mcg (BUD1600). However, FeNO after ICS treatment exhibited a Gaussian distribution and FeNO was significantly raised in 15 children. Allergy and BHR, but none of the other independent variables under study were significantly related to FeNO after BUD1600.

CONCLUSION

Exhaled nitric oxide exhibited a heterogeneous response to ICS in asthmatic schoolchildren. Allergy and BHR were driving FeNO level independently of high-dose steroid treatment. This should be considered when using FeNO for steroid dose titration and monitoring of ICS anti-inflammatory control in asthmatic children.

Correlation of nitrites in breath condensates and lung function in asthmatic children

We aimed to evaluate the value of exhaled breath condensates in monitoring airway inflammation in childhood asthma before and after high altitude climate therapy. Forty-eight asthmatic children on regular anti-asthma treatment with a normal FEV1 and positive skin prick test for house dust mites were recruited. All children had been referred to an alpine clinic for high altitude climate therapy, because of persistent asthmatic symptoms despite use of daily anti-inflammatory treatment. Subjects were assessed on their arrival and before departure from the alpine clinic. Spirometry, bronchial provocation tests and measurements of nitrites in breath condensates were performed. Median levels of nitrites were significantly higher before than after high altitude climate therapy (1.27 vs. 0.93 microm; p = 0.008). In addition, MEF50 improved significantly (p < 0.0005). There was a significant correlation between nitrites in breath condensates and MEF50 (r = -0.63, p < 0.0001), symptoms (r = 0.47, p = 0.0007) and airway hyper-reactivity (AHR) (r = -0.41, p = 0.004). In summary, we found a reduction in nitrites in breath condensates after a high altitude climate therapy. Significant correlations were found between nitrites and MEF50, AHR and symptoms. We conclude that the measurement of nitrites may be feasible to objectively assess airway inflammation in asthmatic children in order to detect ongoing inflammation in children with normal FEV1 but persistent symptoms.

Cough frequency in children with stable asthma: correlation with lung function, exhaled nitric oxide, and sputum eosinophil count

BACKGROUND

A study was undertaken to assess the correlation between cough frequency in asthmatic children with lung function and two non-invasive markers of airway inflammation.

METHODS

Thirty two children of median age 12.0 years (interquartile range (IQR) 9.5-13.4) with stable asthma were recruited. They underwent spirometric testing, exhaled nitric oxide (eNO) measurement, sputum induction for differential cell count, and ambulatory cough monitoring over 17 hours and 40 minutes. Coughing episodes were counted both as individual spikes and as clusters.

RESULTS

Complete cough frequency data were available in 29 children (90%) and their median forced expiratory volume in 1 second (FEV1) and eNO were 88.5% (IQR 79.5-98) and 23.9 ppb (IQR 11.4-41.5), respectively. The median number of cough episodes was 14 (IQR 7.0-24.0) which was significantly higher than that of normal children (6.7 (IQR 4.1-10.5), p<0.001). Sputum induction was successful in 61% of the subjects; the median induced sputum eosinophil count was 0.05% (IQR 0-9.0). Cough frequency was found to have a significant positive correlation with eNO (Spearman's r =0.781, p<0.001) but not with FEV1 or sputum eosinophil count (r =-0.270, p=0.157; r =0.173, p=0.508, respectively).

CONCLUSIONS

Children with stable asthma have increased cough frequency compared with normal controls and cough frequency was greater during the day than at night. Cough may be a more sensitive marker of airway inflammation than simple spirometry.

Comparisons of the complementary effect on exhaled nitric oxide of salmeterol vs montelukast in asthmatic children taking regular inhaled budesonide

BACKGROUND

Inhaled, long-acting beta2-agonists or antileukotrienes are alternatives as add-on therapy for asthmatic children taking regular inhaled steroids. Any complementary effects would be relevant to the choice between these alternatives. Exhaled nitric oxide (FeNO) may reflect these effects.

OBJECTIVE

To compare the control of FeNO provided by salmeterol or montelukast add-on therapy in asthmatic children undergoing regular maintenance treatment with a daily dose of 400 microg of budesonide.

METHODS

The study included children with increased FeNO despite regular treatment with budesonide, 400 microg/d, and normal lung function. Montelukast, 5 mg/d, salmeterol, 50 microg twice daily, or placebo was compared as add-on therapy to budesonide, 400 microg, in a randomized, double-blind, double-dummy, crossover study.

RESULTS

Twenty-two children completed the trial. The geometric mean FeNO level was 20 ppb (95% confidence interval [CI], 15-27 ppb) after salmeterol, which was significantly higher than after montelukast (mean, 15 ppb; 95% CI, 11-18 ppb; P = 0.002) and placebo (mean, 15 ppb; 95% CI, 10-21 ppb; P = 0.03). There was no difference in FeNO between the montelukast and placebo groups. Mean forced expiratory volume in 1 second (FEV1) was significantly increased after salmeterol (mean, 2.63 L; 95% CI, 2.34-2.91 L) compared with placebo (mean, 2.48 L; 95% CI, 2.19-2.77 L). Montelukast (mean, 2.57 L; 95% CI, 2.33-2.80 L) was no different than placebo.

CONCLUSIONS

The FeNO levels were significantly higher after salmeterol add-on treatment compared with both placebo and montelukast add-on treatment. Salmeterol significantly improved lung function (FEV1) compared with placebo and nonsignificantly compared with montelukast. Montelukast failed to reduce FeNO and improve lung function compared with placebo in this group of children taking regular budesonide, 400 microg.

Nitric oxide in allergic airway inflammation

PURPOSE OF REVIEW

Exhaled nitric oxide has been proposed as a useful noninvasive marker of airway inflammation in asthma. Great efforts have been made to standardize the methodology for exhaled nitric oxide measurement in both children and adults. As a consequence there is now an opportunity to establish the precise relationship between exhaled nitric oxide, atopy and airway inflammation, and to investigate whether or not there is a role for the measurement of exhaled nitric oxide in the management of patients with asthma.

RECENT FINDINGS

A number of recent studies have investigated the relationship between exhaled nitric oxide and airway inflammation in asthma measured directly, using sputum induction, bronchoalveolar lavage and endobronchial biopsy. These measurements suggest that exhaled nitric oxide reflects eosinophilic airway inflammation in asthma, although there is no evidence for any relationship between exhaled nitric oxide and other airway inflammatory cells. Exhaled nitric oxide levels were found to be higher in atopic compared with nonatopic groups. These levels, however, are further elevated in atopic patients with asthma, suggesting that exhaled nitric oxide is not simply a marker of atopy. Although there is little evidence to support the routine use of measurement of exhaled nitric oxide in the management of patients with asthma, it may prove to be useful in assessing adherence to treatment with inhaled corticosteroids, or in the identification of patients in whom respiratory symptoms are associated with eosinophilic airway inflammation.

SUMMARY

There is good evidence that exhaled nitric oxide reflects eosinophilic airway inflammation in asthma. Well designed, long-term studies are needed to evaluate whether the addition of exhaled nitric oxide measurements to clinical and lung function assessment results in improved asthma control.

Asthma remission: does it exist?

Subjects believed to have grown out of asthma often develop symptoms again later in life. Ongoing airway inflammation may determine the risk of relapse, although the mechanisms involved are still misunderstood. Additionally, patients with asthma during childhood may develop irreversible airflow obstruction ( airway remodeling) as a result of chronic airway inflammation. Recently, airway inflammation and remodeling could be demonstrated in bronchial biopsy specimens from young adults who considered themselves grown out of asthma. It is also shown that evidence of airway inflammation and remodeling can be obtained noninvasively, thereby providing the opportunity to monitor disease activity. If chronic airway inflammation and/or remodeling are consistent findings in asymptomatic subjects with a history of atopic asthma, the question arises whether natural history can be positively altered with prolonged antiinflammatory therapy. Benefits of long-term prognosis are, however, not yet shown. Since epidemiologic work has demonstrated that a certain percentage of subjects with apparently outgrown atopic asthma remains asymptomatic without needing therapy for the rest of their lives, it can be argued that "asthma remission does exist." The question is whether this percentage can be increased with prolonged antiinflammatory therapy and regular control.