Does bronchial hyperresponsiveness in asthma matter?

Should Airway Hyper-Responsiveness Be Included in the Definition of Clinical Remission With Biologic Therapy in Severe Asthma

Airway hyper-responsiveness (AHR) is a tenet of the persistent asthma phenotype along with reversible airway obstruction and type 2 (T2) inflammation. Indirect acting challenges such as mannitol are more closely related to the underlying T2 inflammatory process as compared with direct challenges. In this review article, we summarise the current literature and explore the future role of mannitol AHR in clinical remission with biologics.

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.

Asthma: are we monitoring the correct measures?

The prevalence of asthma, a common chronic inflammatory disease of the airways, has risen sharply over the past 25-30 years, with the biggest increase found in children. Currently, more than 22 million Americans have asthma. Asthma also is associated with significant morbidity and mortality worldwide. Each year, asthma is responsible for $16 billion in direct and indirect costs due to health care utilization and loss of productivity, with over 14 million missed workdays. Asthma also accounts for almost 1.8 million emergency room visits and almost 500,000 hospitalizations annually. Therefore, assessment and monitoring of disease activity is critical to improve clinical and economic outcomes for patients with asthma. To help in this endeavor, practitioners and payers rely on evidence-based guidelines to classify disease severity, to guide treatment decisions, and to assess the degree of asthma control. In August 2007, the National Asthma Education and Prevention Program (NAEPP) updated its guidelines based on greater knowledge of disease pathophysiology and the development of newer therapeutic agents. This includes an increased emphasis on the need to establish disease severity, including the components of impairment and risk, as well as on the level of asthma control. Despite the availability of the NAEPP and other guidelines, asthma control often remains suboptimal. While numerous clinical and patient-reported measures are available, it is clear that the optimal monitoring schema for patients with asthma remains undefined. To clearly establish whether asthma control is attained, multiple measures are required and should include clinical and patient-reported assessments.

Current and future use of the mannitol bronchial challenge in everyday clinical practice

OBJECTIVES

Asthma is a disease associated with inflammation, airway hyperresponsiveness (AHR) and airflow limitation. Clinical diagnosis and management of asthma often relies on assessment of lung function and symptom control, but these factors do not always correlate well with underlying inflammation. Bronchial challenge tests (BCTs) assess AHR, and can be used to assist in the diagnosis and management of asthma.

DATA SOURCE

Data presented at the symposium 'Use of inhaled mannitol for assessing airways disease' organised by the Allied Respiratory Professionals Assembly (9) of the European Respiratory Society (ERS) at the ERS Congress, Berlin 2008.

RESULTS

Indirect challenge tests such as exercise testing, hypertonic saline or adenosine 5'-monophosphate (AMP) are more specific though less sensitive than direct challenge tests (such as methacholine) for identifying patients with active asthma. Indirect BCTs may be used to diagnose exercise-induced bronchoconstriction or AHR consistent with active asthma, to evaluate AHR that will respond to treatment with anti-inflammatory drugs and to determine the effectiveness and optimal dosing of such therapy. An ideal indirect challenge test should be standardised and reproducible, and the test result should correlate with the degree of airway inflammation. The mannitol BCT provides a standardised and rapid point-of-need test to identify currently active asthma, and is clinically useful in the identification of patients with asthma who are likely to benefit from inhaled corticosteroid therapy.

CONCLUSION

In the future, mannitol BCT may be added to lung function and symptom assessment to aid in the everyday management of asthma.

Effects of asthma treatment: the present and future

The increasing burden of asthma in both primary and secondary care has led to extensive research into its genetics, pathophysiology and treatment over the past few decades. Inhaled corticosteroids remain an integral component in all but the mildest disease, although despite a low-to-moderate dose, many individuals remain symptomatic. In patients with persistent symptoms despite inhaled corticosteroids, a variety of different nonsteroidal second-line therapies are available as add-on therapy. In this review, existing and potential future pharmacological strategies involved in the management of asthma will be highlighted.

Relationship between bronchial hyperreactivity and asthma remission during adolescence

BACKGROUND

Many children with asthma outgrow this disease after the onset of puberty. However, the precise mechanism of outgrowing asthma in children is still unclear.

OBJECTIVE

To evaluate the characteristics of respiratory physiology during adolescence.

METHODS

The results of the lung function test and methacholine inhalation challenge were prospectively evaluated in adolescent patients with asthma with and without symptoms. One hundred sixty children with asthma participated. Twenty-eight children had symptom-free adolescent asthma (i.e., remission asthma) (boy to girl ratio, 16:12; mean age, 14.6 years), 25 had intermittent adolescent asthma (boy to girl ratio, 16:9; mean age, 14.9 years), and 47 had symptomatic adolescent asthma (boy to girl ratio, 27:20; mean age, 12.7 years). For comparison purposes, 60 younger children with symptomatic asthma participated. The parameters of bronchial hyperresponsiveness, baseline respiratory resistance, threshold of methacholine (Dmin) (bronchial sensitivity), and speed of bronchial constriction (Sm) (bronchial reactivity) were measured by methacholine inhalation challenge using the continuous oscillation method.

RESULTS

There was no significant difference in lung function results, such as forced vital capacity and forced expiratory volume in 1 second, between the intermittent asthma and the remission asthma groups. Also, there was no significant difference in baseline respiratory resistance and Dmin between the 2 groups. However, the value of Sm of the remission asthma group was significantly lower than that of the intermittent asthma group (P = .02) and the symptomatic asthma group (P = .02).

CONCLUSIONS

These data show that the adolescents with asthma remission showed a significant decrease of Sm, whereas Dmin was not changed. These results suggest one of the mechanisms by which asthma is outgrown in children and explain the common clinical aspects of adolescent asthma, such as symptom-free but bronchial hyperresponsive asthma.

Evaluation of glucose tolerance status in patients with asthma bronchiale

BACKGROUND

Asthma is characterized by inflammation and airway hyperesponsiveness, which results in episodic airflow obstruction. A relationship between inflammation and insulin resistance (IR) has been previously characterized, and asthma is known to correlate with increasing IR. Thus, we tested whether patients with asthma bronchiale exhibited abnormally low glucose tolerance. The aim of this study was to compare the occurrence of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), two precursors of type 2 diabetes mellitus (DM), in patients with asthma bronchiale and paired control patients.

PATIENTS AND METHODS

We examined patients diagnosed with asthma bronchiale. We excluded patients taking any medications other than inhaler broncodilators, patients with a history of other systemic illness, and patients with any diabetic risk factors. Age- and sex-matched healthy volunteers were included as the control group in this study. History, physical examination, and laboratory analyses were performed for both study and control groups.

RESULTS

Mean age of the study group was 40.3 +/- 7.8 (F/M: 32/19), and mean BMI of the study group was 26.7 +/- 2.2. Mean age of the control group was 39.5 +/- 6.7 (F/M: 25/15) and mean BMI of the control group was 26.0 +/- 2.1. Fasting blood glucose (FBG), Pg2hBG, Plasma insulin, Homeostasis Model Assessment-Insulin Resistance (HOMA IR), IFG, IGT, both IFG and IGT and (LDL) C levels were significantly higher in the asthmatic group, while HDL C levels were significantly higher in the control group.

CONCLUSION

Our results suggest that disturbance of the glucose metabolism caused by inflammation-induced insulin resistance may occur in asthmatic patients and that this phenomenon may increase the risk of diabetes mellitus in these individuals.

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.

Exercise and other indirect challenges to demonstrate asthma or exercise-induced bronchoconstriction in athletes

The prevalence of exercise-induced bronchoconstriction is reported to be high among recreational and elite athletes, yet diagnosis is often symptom-based. Indirect challenges such as the laboratory exercise challenge provide objective criteria for proper diagnosis and treatment. However, a standardized protocol using appropriate exercise intensity, duration, and dry air inhalation is often not implemented, and thus a false-negative test may result. This article reviews and describes the symptom-based diagnosis, the exercise challenge, and other indirect challenges such as eucapnic voluntary hyperpnea, hypertonic saline inhalation, and inhaled powdered mannitol as methods to diagnose and evaluate exercise-induced bronchoconstriction. Advantages and disadvantages of each diagnostic procedure are presented.

Acoustic analysis in asthmatics and the influence of inhaled corticosteroid therapy

The impact of sustained inhaled corticosteroid (ICS) therapy on the larynx and pharynx was assessed using a prospective, cross-sectional, and investigator-blinded study conducted at the University Hospital Aintree, Liverpool, UK. Forty-six adults recruited from two local general practices and from general ENT clinics at our University hospital were investigated for the study. Patients were allocated to three groups according to ICS use. Laryngeal effects were measured by correlating the results of a vocal performance questionnaire, a respiratory symptom questionnaire, and measurements obtained by computerized speech analysis. Sustained vowels and connected speech were analyzed in normal and asthmatic subjects. Acoustic analysis was correlated with cellular markers of inflammation after biopsy. Regular ICS users had significantly more pharyngeal inflammation and throat discomfort (P<0.0001). Vocal performance was also worse in this group (P<0.0001). They were more likely to have hoarseness, weakness of voice, aphonia, sore throat, throat irritation, and cough (P<0.0001). All these variables were directly related to one another (P<0.0001). Multiple linear regression analysis showed that jitter was a good objective measure of hoarseness (P<0.05). Regular ICS users were significantly more likely to have abnormal jitter, shimmer, and closed-phase quotient scores (P<0.0001). There was no difference between the groups in the observed parameters of inflammation (P>0.01). A higher pharyngitis score did not correlate with any of the histological markers of inflammation (P>0.01). Local side effects are more common in asthmatics that use ICS regularly. Measures of laryngeal function are significantly worse in regular ICS users. However, histological markers and oropharyngeal redness are not reliable measures of inflammation.

Reliability of a new hand-held device for the measurement of exhaled nitric oxide

BACKGROUND

Given the importance of airway inflammation in asthma, there has been an effort to incorporate inflammatory markers into its management. Measurement of fractional exhaled nitric oxide (FeNO) is a noninvasive marker of airway inflammation; however, the use of the available FeNO analyzer is limited by several factors including its cost and lack of transportability. The aim of this study was to compare the performance of a new hand-held FeNO measuring device (NIOX MINO) to the current clinical standard - the chemiluminescence FeNO analyzer (NIOX).

METHODS

Subjects 6 years and older presenting to an allergy and asthma clinic underwent FeNO evaluation by NIOX and each of three NIOX MINOs. The mean of two acceptable measurements from the NIOX and the first approved measurement from each NIOX MINO were used for analysis.

RESULTS

One hundred ten patients aged 6-86 years completed the study. Intrasubject FeNO levels obtained by each of the three NIOX MINOs revealed no significant difference between the measurements (P = 0.59). There was a very strong correlation between FeNO measurements by NIOX and by NIOX MINO (r = 0.98, P < 0.0001). The mean intrasubject FeNO difference between NIOX and NIOX MINO was -0.5 p.p.b. which was not statistically significantly different from zero (P = 0.21).

CONCLUSIONS

Fractional exhaled nitric oxide measurements by the NIOX MINO showed a strong correlation and a high degree of agreement with the current standard stationary device. The NIOX MINO may be reliably used in clinical practice.

Dosimetry counts: molecular hypersensitivity may not drive pulmonary hyperresponsiveness

Airway hyperresponsiveness is one measure of allergic asthma. One such test, the methacholine challenge, uses an inhaled aerosol to induce changes in resistance to breathing. The test is also used to test hyperresponsiveness in rodent models of asthma. For two varieties of mice, the B6C3F1 and the Balb/c, exposure to aerosolized methacholine demonstrates that the Balb/c is 12x more responsive based on the concentration of methacholine in the solution used to produce the inhaled aerosol (the normally accepted dose-metric). Here we show that the 12x difference in exposure disappears when measurements of airway dimensions of generations 1-6 are used first to calculate deposited mass of methacholine; and second to account for the physiology of airway constriction and pressure drop. These observations in mice provide one explanation of how some hyperresponsive subjects can have no underlying molecular sensitivity; and how constriction in the upper airways can have greater impact on breathing than constriction of airway generations 6-16.

Effect of aging on the relationship between asthma severity and bronchial hyperresponsiveness in children with asthma

An association between asthma and bronchial hyperresponsiveness (BHR) has been demonstrated. It is possible that the relationship between asthma severity and BHR in children with asthma is different in infants and in adolescents. The aim of this study is therefore to evaluate the effect of aging on the relationship between the severity of asthma and BHR in children with asthma. We measured BHR in 386 subjects ranging from 2 to 20 years of age. The subjects consisted of 323 children with asthma (boys:girls = 193:130, mean age 9.7 years) and 63 age-matched controls (boys:girls = 25:38, mean age 8.2 years). BHR was measured using the methacholine inhalation challenge by measuring the transcutaneous oxygen pressure (tcPO2) in children less than 6 years of age (Dmin-PO2) and by measuring the respiratory resistance (Rrs) in children 6 years of age and older (Dmin-Rrs). Throughout the whole age range, both the Dmin-PO2 and Dmin-Rrs in each asthma severity group were higher than those in the controls. In the asthmatics aged 2-5 years, the Dmin-PO2 levels in the mild asthma group were higher than those in the moderate and severe asthma groups (p < 0.001, p < 0.001, respectively), and the Dmin-PO2 levels in the moderate asthma group were also higher than those in the severe asthma group. This tendency was also found in the age ranges of 6-9 years and 10-13 years. In the asthmatics aged 14-20 years, the Dmin-Rrs levels were not significantly different among the three groups. Taken together, these data show that aging has an effect on the relationship between the severity of asthma and BHR during childhood and that BHR may not be the sole determinant for the severity of asthma in adolescence.

Revisiting asthma control: how should it best be defined?

Management guidelines for asthma emphasize a stepwise approach in treating this disease based on daytime symptoms, nighttime symptoms, and lung function assessed by peak expiratory flow or forced expiratory volume at 1s (FEV(1)). Although improvement of lung function is a key goal in managing asthma, clinicians often see patients who may have achieved a normal FEV(1) with guideline-recommended treatment but continue to experience limitations in their daily activities. In such situations, focusing the assessment solely on pulmonary function (e.g. FEV(1)) is often inadequate and may lead to undertreatment. Alternate assessment measures are therefore often needed to assess asthma control and achieve a successful treatment outcome. This review will provide practical guidance relevant to the clinical assessment of asthma control.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

Therapeutic modulation of allergic airways disease with leukotriene receptor antagonists

Although asthma is one of the most common chronic respiratory conditions, it often remains unrecognized and undertreated, while patients are often reluctant to comply with regular inhaled anti-inflammatory and bronchodilator therapy. Allergic rhinitis co-exists with asthma in as many as 40% of patients, and can be regarded as a continuum of the same inflammatory disease process. Corticosteroids are the 'gold standard' first-line treatment for both conditions, and have a significant impact upon underlying inflammation, symptoms and long-term outcome. Cysteinyl leukotrienes are potent airway inflammatory mediators, suggesting that treatment antagonizing their effects could play a role in disease management. In recent years, leukotriene receptor antagonists have provided a further therapeutic option in the management of allergic airways disease. These drugs are orally active, can be administered once daily, and provide a systemic approach to the management of patients with asthma and allergic rhinitis. We review the pharmacology of leukotriene receptor antagonists, their potential role in clinical practice in patients with allergic airways disease, and likely areas for further research.

Effects of dual therapy with corticosteroids plus long acting beta2-agonists in asthma

Asthma is a common condition characterised by inflammation, airway hyperresponsiveness and reversible airflow obstruction. Effective pharmacotherapy must therefore be aimed at attenuating these underlying hallmark features. Despite the use of regular low-to-moderate doses of inhaled corticosteroids, many patients remain symptomatic and require further 2nd line controller therapy. The addition of a concomitant long acting beta2-agonist provides an effective means in which to alleviate symptoms and reduce exacerbation frequency. Moreover, both agents can be combined in a single inhaler, and provide patients with a more convenient and effective way in which to deliver treatment to the endobronchial tree. This evidenced-based review article discusses the effects of such combination inhalers upon a variety of outcome parameters and their effects upon asthmatics across a range of severities.

Assessment of bronchial responsiveness following exposure to inhaled occupational and environmental agents

Inhalation of a range of agents can result in airway inflammation and/or irritation. This may result in occupational asthma or reactive airways dysfunction syndrome. Reactive airways dysfunction syndrome follows a single large exposure to a chemical agent but is now frequently embraced under the wider term of irritant-induced asthma, a term that also includes asthma due to persistent, lower dose irritant exposures. Bronchial hyperresponsiveness is a hallmark of both occupational asthma and reactive airways dysfunction syndrome, although some patients with occupational asthma may occasionally have typical clinical features without increased bronchial hyperresponsiveness. Following removal of the causal agent in occupational asthma, bronchial hyperresponsiveness generally returns towards normal over a 2-year period, although some individuals demonstrate increased bronchial hyperresponsiveness for longer. Measurement of specific bronchial hyperresponsiveness to the primary causal agent in occupational asthma is used diagnostically but not for assessing prognosis. Bronchial hyperresponsiveness to inhaled methacholine can be measured across individual workshifts to assess work-related change. It may also be measured at the end of a work period when exposure has occurred, and compared with values following a period away from work. There have been no direct, systematic comparisons of changes in methacholine responsiveness in the diagnosis of occupational asthma compared with the more frequently used serial peak flow measurements. Patients with reactive airways dysfunction syndrome classically exhibit non-specific bronchial hyperresponsiveness, which can be readily measured by evaluating responses to inhaled methacholine. Bronchial hyperresponsiveness in reactive airways dysfunction syndrome can persist for many years after initial exposure and serial changes can be used to assess recovery and subsequent disability over time.